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                                                                    Exhibit 4(b)


                          REGISTRATION RIGHTS AGREEMENT

                  This REGISTRATION RIGHTS AGREEMENT (this "Agreement") is
entered into as of ___________, 2000, by and among Purina Mills, Inc., a
Delaware corporation (the "COMPANY"), and the Holders (as hereinafter defined)
of Registrable Securities (as hereinafter defined) who are parties to this
Agreement.

                              W I T N E S S E T H:
                               - - - - - - - - - -


         WHEREAS, certain Holders are acquiring Common Stock (as hereinafter
defined) pursuant to the Plan (as hereinafter defined); and

         WHEREAS, pursuant to the Plan, the Company is obligated to provide the
Holders with certain registration rights with respect to the Registrable
Securities and to take certain other actions with respect to the Registrable
Securities.

         NOW, THEREFORE, in consideration of the foregoing and of the mutual
premises and covenants contained herein and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
parties hereto hereby agree as follows:

1.       DEFINITIONS.

         Unless otherwise defined herein, capitalized terms used herein and in
the recitals above shall have the following meanings:

         "AFFILIATE" of a Person means any Person that directly or indirectly
through one or more intermediaries controls or is controlled by, or is under
common control with, such other Person. For purposes of this definition, the
term "control" (including the terms "controlling," "controlled by" and "under
common control with") means the possession, direct or indirect, of the power to
cause the direction of the management and policies of a Person, whether through
the ownership of voting securities, by contract or otherwise.

         "APPROVED UNDERWRITER" has the meaning assigned to such term in Section
2(d).

         "APPROVED UNDERWRITER AMOUNT" has the meaning assigned to such term in
Section 2(b).

         "BUSINESS DAY" means any day except a Saturday, Sunday or other day
that is a legal holiday or a day on which commercial banks in New York City
generally are authorized or required by law or other government actions to be
closed.

         "CLAIM" has the meaning assigned to such term in Section 7(a).

         "COMMON STOCK" means the Common Stock, $0.01 par value, of the Company
and includes any securities of the Company issued or issuable with respect to
such securities by way of a stock split, recapitalization, merger, consolidation
or other reorganization or otherwise.



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         "COMPANY UNDERWRITER" has the meaning assigned to such term in Section
3(a).

         "EFFECTIVE DATE" has the meaning assigned to such term in the Plan.

         "EXCHANGE ACT" means the Securities Exchange Act of 1934, as amended,
and the rules and regulations thereunder, or any similar or successor statute.

         "HOLDER" means (a) Koch Agriculture Company, (b) each Person entitled
to receive distributions pursuant to the Plan of Common Stock representing at
least ten percent (10%) of the aggregate Common Stock issuable pursuant to the
Plan, (c) each Person entitled to receive distributions of Common Stock pursuant
to the Plan, which Person is otherwise an Affiliate of the Company, and (d) any
permitted transferee of any of the Persons identified in clauses (a) through (c)
of this definition who after giving effect to such transfer is the beneficial
owner of three percent (3%) or more of the outstanding Common Stock and who has
agreed in writing to be bound by the terms of this Agreement; PROVIDED in the
case of clause (a) through (d) of this definition that such Person owns
Registrable Securities.

         "INDEMNIFIED PARTY" has the meaning assigned to such term in Section
7(c).

         "INDEMNIFYING PARTY" has the meaning assigned to such term in Section
7(c).

         "INSPECTORS" has the meaning assigned to such term in Section 5(a)(ii).

         "LOCK-UP PERIOD" has the meaning assigned to such term in Section 4(a).

         "LOSSES" has the meaning assigned to such term in Section 7(a).

         "NASD" means the National Association of Securities Dealers, Inc.


         "PARTICIPATING HOLDERS" means Holders participating, or requesting to
participate, as the case may be, in an underwritten offering of Registrable
Securities.

         "PERSON" means any individual, firm, corporation, company, partnership,
trust, incorporated or unincorporated association, limited liability company,
joint venture, joint stock company, government (or an agency or political
subdivision thereof) or other entity of any kind, and includes any successor (by
merger or otherwise) of any such entity.

         "PLAN" means the plan of reorganization of the Company and its debtor
subsidiaries under Chapter 11 of Title 11 of the United States Code, 11 U.S.C.
Sec. 101 et seq. filed with the United States Bankruptcy Court for the District
of Delaware and confirmed by such court on ________, 2000, as the same may be
amended, modified or supplemented from time to time in accordance with the terms
thereof.

         "REGISTRATION EXPENSES" means all expenses (other than underwriting
discounts and commissions) arising from or incident to the performance of, or
compliance with, this Agreement, regardless of whether any Registration
Statement filed in connection with this Agreement is declared effective,
including, without limitation, (a) SEC, stock exchange, NASD and other
registration and filing fees, (b) all fees and expenses incurred in connection
with



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complying with any securities or blue sky laws (including, without limitation,
fees, charges and disbursements of counsel in connection with blue sky
qualifications of the Registrable Securities), (c) all printing, messenger and
delivery expenses, (d) the fees, charges and disbursements of counsel to the
Company and of its independent public accountants and any other accounting and
legal fees, charges and expenses incurred by the Company (including, without
limitation, any expenses arising from any special audits or "comfort letters"
required in connection with or incident to any registration), (e) the fees,
charges and disbursements of any special experts retained by the Company in
connection with any registration pursuant to the terms of this Agreement, (f)
all internal expenses of the Company (including, without limitation, all
salaries and expenses of its officers and employees performing legal or
accounting duties), (g) the fees and expenses incurred in connection with the
listing of the Registrable Securities on any securities exchange or the Nasdaq
Stock Market and (h) Securities Act liability insurance (if the Company in its
sole discretion elects to obtain such insurance).

         "REGISTRABLE SECURITIES" means any and all shares of Common Stock
issued or issuable pursuant to or as otherwise contemplated by the Plan to the
Holders. For the purposes of this Agreement, Registrable Securities will cease
to be Registrable Securities when (a) a Registration Statement covering such
Registrable Securities has been declared effective under the Securities Act by
the SEC and such Registrable Securities have been disposed of pursuant to such
effective Registration Statement, (b) such Registrable Securities are
distributed to the public pursuant to Rule 144 under the Securities Act or (c)
such Registrable Securities cease to be outstanding.

         "REGISTRATION STATEMENT" means any Registration Statement of the
Company filed with the SEC on the appropriate form pursuant to the Securities
Act which covers any of the shares of Common Stock pursuant to the provisions of
this Agreement and all amendments and supplements to any such Registration
Statement, including post-effective amendments, in each case including the
prospectus contained therein, all exhibits thereto and all materials
incorporated by reference therein.

         "REQUISITE HOLDERS" has the meaning assigned to such term in Section
2(b).

         "RULE 144" means Rule 144 promulgated pursuant to the Securities Act or
any similar or successor rule.

         "SEC" means the Securities and Exchange Commission, or any other
successor thereto.

         "SECURITIES ACT" means the Securities Act of 1933, as amended, and the
rules and regulations promulgated by the SEC thereunder or any similar or
successor statute.

         "SELLING EXPENSES" means the underwriting fees, discounts, selling
commissions and stock transfer taxes applicable to all Registrable Securities
registered by the Holders and any and all fees of counsel to all or any of the
Participating Holders.

         "SHELF REGISTRATION" has the meaning assigned to such term in Section
2(a).


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         "SHELF REGISTRATION STATEMENT" has the meaning assigned to such term in
Section 2(a).

2.       SHELF REGISTRATION

         (a) FILING OBLIGATION. As promptly as practicable following the
Effective Date, the Company shall prepare and file with the SEC a "shelf"
registration statement for an offering to be made on a continuous basis pursuant
to Rule 415 under the Securities Act (a "SHELF REGISTRATION STATEMENT") on Form
S-1 or any other appropriate form under the Securities Act covering the
continuous resale of the Registrable Securities (the "SHELF REGISTRATION"). The
Company shall use its good faith, reasonable commercial efforts to cause the
Shelf Registration to be declared effective under the Securities Act as promptly
as practicable, but in no event later than ninety (90) days after the Effective
Date, and once effective, the Company shall use good faith reasonable commercial
efforts to cause such Shelf Registration to remain effective for a period ending
on the earlier of: (i) the date on which there are no Registrable Securities
outstanding; or (ii) subject to Section 5(c), the date that is the two-year
(2-year) anniversary of the Effective Date. The Company shall not include or
permit any other party to include any securities other than Registrable
Securities in the Shelf Registration. The Shelf Registration Statement shall
contain a broad-form plan of distribution (including permitting underwritten
offerings). The Company shall be permitted to file a post-effective amendment to
its Form S-1 Registration Statement on Form S-3 at such time as the Company
becomes eligible, in its sole discretion, to use Form S-3.

         (b) UNDERWRITING PROCEDURES. At any time, if Holders of at least a
majority of the Registrable Securities ("REQUISITE HOLDERS") so elect, an
offering of Registrable Securities only pursuant to such Shelf Registration
Statement may be effected on no more than two (2) occasions in the form of an
underwritten offering, with only one (1) such underwritten offering required to
be effected in any one (1) consecutive twelve-month period. Upon the receipt of
a written request for an underwritten offering meeting the foregoing
requirements, the Company shall promptly take such steps as are necessary or
appropriate to prepare for such offering. Promptly, but in no event later than
ten (10) days after the receipt of such written request for an underwritten
offering, the Company shall give written notice thereof to all other Holders and
include in such underwriting all Registrable Securities held by any Holder from
whom the Company has received a written request for inclusion therein.
Notwithstanding the foregoing, if the Approved Underwriter advises the Company
and the Participating Holders in writing that, in its opinion, the aggregate
amount of such Registrable Securities requested to be included in such offering
is sufficiently large so as to have an adverse effect on the success of such
offering, then such registration shall include only the aggregate amount of
Registrable Securities that in the opinion of the Approved Underwriter may be
sold without any such adverse effect on the success of such offering (the
"APPROVED UNDERWRITER AMOUNT") and if the number of Registrable Securities
requested to be included in such underwriting is greater than the Approved
Underwriter Amount, then each such Participating Holder shall be entitled to
have included in such underwriting Registrable Securities equal to its pro rata
portion of the Approved Underwriter Amount, based on the proportion of the
amount of Registrable Securities requested to be included in such underwritten
offering by each Participating Holder to the aggregate


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amount of Registrable Securities requested to be included in such underwritten
offering by all Participating Holders.

         If, after electing to participate in an underwritten offering of
Registrable Securities pursuant to this Agreement, any Participating Holder
disapproves of the terms of the underwriting, such Participating Holder may
elect to withdraw from such underwritten offering by written notice to the
Company, the managing underwriter and the other Participating Holders. The
Registrable Securities and/or other securities so withdrawn shall also be
withdrawn from such underwriting; PROVIDED, HOWEVER, that if by such withdrawal
a greater number of Registrable Securities held by other Participating Holders
may be included in such underwriting (up to the maximum of any limitation
imposed by the underwriters), then the Company shall offer to all Participating
Holders who have included Registrable Securities in such underwritten offering
the right to include additional Registrable Securities in the same proportion
used in determining the Approved Underwriter Amount in this Section 2(b).

         The Company shall cooperate with the Holders in order to facilitate
communications among Holders solely for the purpose of obtaining the consent of
sufficient Holders to request an underwritten offering pursuant to this Section
2(b), including, without limitation, by providing a list of stockholders of the
Company with their respective ownership of Registrable Securities and contact
information, which shall be used solely for purposes of this Agreement.

         (c) EFFECTIVE UNDERWRITTEN OFFERING. An underwritten offering requested
by the Holders pursuant to Section 2(b) shall not count as one of the two (2)
underwritten offerings to which the Holders are entitled under Section 2(b)
unless (i) all of the Registrable Securities requested by Participating Holders
to be included in the underwritten offering are so included and sold pursuant to
such underwritten offering or (ii) Registrable Securities requested by
Participating Holders to be included in such underwriting are so included and
sold pursuant to such underwritten offering in an amount that is both (A) equal
to or greater than the Approved Underwriter Amount and (B) not less than forty
percent (40%) of all Registrable Securities requested by Participating Holders
to be included in such underwritten offering.

         (d) SELECTION OF UNDERWRITERS. If any offering pursuant to a Shelf
Registration is in the form of an underwritten offering, (i) the Requisite
Holders shall select and obtain an investment banking firm of national
reputation to act as the managing underwriter of the offering (the "Approved
Underwriter"); provided, that such underwriter shall be reasonably satisfactory
to the Company, and (ii) the Company and the Participating Holders shall enter
into an underwriting agreement with the Approved Underwriter in a customary form
reasonably satisfactory to the Company.

     3.  PIGGY-BACK REGISTRATION

         (a) PIGGY-BACK RIGHTS. If the Company proposes to file a Registration
Statement (other than a Registration Statement on Form S-4 or S-8 or any
successor form) with respect to an offering under the Securities Act by the
Company for its own account or for the account of any selling stockholder of
Common Stock, then the Company shall give written notice of such proposed filing
to each of the Holders, which notice shall be delivered as soon as


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practicable (but in no event fewer than thirty (30) days before the anticipated
filing date) and shall describe in reasonable detail the proposed registration
and intended method of distribution and offer such Holders the opportunity to
register the number of Registrable Securities as each such Holder may request.
The Company shall use its good faith reasonable commercial efforts to permit the
Holders who have requested to participate in the registration for such offering
within twenty (20) days of the delivery of notice provided for in the preceding
sentence to include such Registrable Securities in such offering on the same
terms and conditions as the securities of the Company included therein.
Notwithstanding the foregoing, if such registration involves an underwritten
offering and the managing underwriter (or underwriters) selected by the Company
(the "COMPANY UNDERWRITER") advises the Company and the Participating Holders in
writing that, in its reasonable good faith opinion, the aggregate amount of
Registrable Securities requested to be included in such offering (including
those securities requested by the Company to be included in such registration)
is sufficiently large so as to have an adverse effect on the success of the
offering, then such registration shall include, first, all securities that the
Company proposed to register for its own account or for the account of such
selling stockholder, second, all Registrable Securities timely requested to be
registered by the Participating Holders, pro rata among such Participating
Holders (based upon the number of Registrable Securities which each such
Participating Holder requested to be included in such registration), and third,
all other securities proposed to be registered, in each case, to the extent of
the number of securities which the Company is so advised can be sold in (or
during the time of) such offering without having such adverse effect.

         (b) PRIORITY OF REGISTRATIONS. If the Company proposes to register
securities for its own account or for the account of any selling stockholder at
a time when Requisite Holders have requested an underwritten offering pursuant
to Section 2, then the Company shall take any action that an Approved
Underwriter, if already chosen pursuant to Section 2, or, in lieu thereof, the
Participating Holders in such underwritten offering pursuant to Section 2 may
reasonably demand be taken to give the underwritten offering pursuant to Section
2 full priority, including, without limitation, foregoing or delaying
registration pursuant to this Section 3.

         (c) CONDITIONS AND LIMITATIONS ON PIGGYBACK REGISTRATIONS. If, at any
time after giving written notice of its intention to register any securities and
prior to the effective date of the Registration Statement filed in connection
with such registration, the Company determines for any reason not to register or
to delay registration of such securities, the Company may, at its election, give
written notice of such determination to all Participating Holders of Registrable
Securities and, (i) in the case of a determination not to register, shall be
relieved of its obligation to register the Registrable Securities in connection
with such abandoned registration and, (ii) in the case of a determination to
delay registration, shall be permitted to delay the registration of such
Registrable Securities by not more than ninety (90) days; provided that such
right to delay registration shall be exercised by the Company not more than once
in any consecutive twelve (12) month period.

         Any Participating Holder shall have the right to withdraw its request
for inclusion of its Registrable Securities in any Registration Statement
pursuant to this Section 3 by giving written notice to the Company of its
request to withdraw; PROVIDED, HOWEVER, that (i) such request must be made in
writing prior to the earlier of the execution of the underwriting


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agreement or the execution of the custody agreement with respect to such
registration and (ii) such withdrawal shall be irrevocable and, after making
such withdrawal, such Participating Holder shall no longer have any right to
include Registrable Securities in such registration.

         The Company's obligations to include Registrable Securities of any
Holder who is not an Affiliate of the Company in any Registration Statement
pursuant to this Section 3 shall terminate on the two-year anniversary date of
the Effective Date.

     4.  HOLDBACK AGREEMENTS.

         (a) RESTRICTIONS ON PUBLIC SALE BY HOLDERS. Each Holder whose
Registrable Securities are covered by a Registration Statement involving an
underwritten offering pursuant to Section 2 or 3 agrees not to effect any public
sale or distribution (except as part of such offering) of any Registrable
Securities or of any securities convertible into or exchangeable or exercisable
for Registrable Securities, including a sale pursuant to Rule 144, during a
period as may be requested in good faith by the Approved Underwriter or the
Company Underwriter of not more than ninety (90) days (which period, in any
case, shall not exceed the applicable period under Section 4(b)) commencing on
the commencement of such underwritten offering pursuant to such registration
(the "LOCK-UP PERIOD"); PROVIDED, HOWEVER, that if any other selling stockholder
of the Company shall be subject to a shorter period of prohibition in connection
with any such registration or underwritten offering, then the Lock-Up Period
shall be such shorter period.

         (b) RESTRICTIONS ON PUBLIC SALE BY THE COMPANY. The Company agrees not
to effect any public sale or distribution of Common Stock or of any securities
convertible into or exchangeable or exercisable for Common Stock for its own
account or the account of any other selling stockholder (except pursuant to
registrations on Form S-4 or S-8 or any successor form under the Securities Act)
during any Lock-Up Period (except for Registrable Securities being sold by the
Company as part of such offering).

     5.  REGISTRATION PROCEDURES.

         (a) OBLIGATIONS OF THE COMPANY. Whenever registration of Registrable
Securities is required pursuant to Sections 2 or 3 of this Agreement, the
Company shall use its good faith reasonable commercial efforts to effect the
registration and sale of such Registrable Securities in accordance with the
intended method of distribution thereof as quickly as practicable, and in
connection with any such request, the Company shall, as expeditiously as
possible:

               (i) Preparation of Registration Statement. Prepare and
file with the SEC a Registration Statement on any form on which the Company then
qualifies that counsel for the Company deems appropriate and pursuant to which
such offering may be made in accordance with the intended method of distribution
thereof (except that the Registration Statement shall contain such information
as may reasonably be requested for marketing or other purposes by the Approved
Underwriter or the Company Underwriter), and use its good faith reasonable
commercial efforts to cause any registration required hereunder to become
effective as soon as practicable after the initial filing thereof (and in any
event not later than seventy-five (75) days thereafter);


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               (ii) Participation in Preparation. Provide any Participating
Holder of Registrable Securities, any underwriter participating in any
disposition pursuant to a Registration Statement, and any attorney, accountant
or other agent retained by any Participating Holder or underwriter (each, an
"Inspector" and, collectively, the "INSPECTORS"), the opportunity to
participate, including, but not limited to, reviewing, commenting on and
attending all meetings in the preparation of such Registration Statement, each
prospectus included therein or filed with the SEC and each amendment or
supplement thereto;

               (iii) Due Diligence. For a reasonable period prior to the filing
of any Registration Statement pursuant to this Agreement, make available for
inspection and copying by the Inspectors such financial and other information
and books and records, pertinent corporate documents and properties of the
Company and its subsidiaries and cause the officers, directors, employees,
counsel and independent certified public accountants of the Company and its
subsidiaries to respond to such inquiries and to supply all information
reasonably requested by any such Inspector in connection with such Registration
Statement, as shall be reasonably necessary, in the judgment of the respective
counsel referred to in Section 5(a)(ii), to conduct a reasonable investigation
within the meaning of the Securities Act;

               (iv) General Notifications. Promptly notify in writing the
Participating Holders, the sales or placement agent, if any, therefor and the
managing underwriter of the securities being sold, (A) when such Registration
Statement or the prospectus included therein or any prospectus amendment or
supplement or post-effective amendment has been filed, and, with respect to any
such Registration Statement or any post-effective amendment, when the same has
become effective, (B) when the SEC notifies the Company whether there will be a
"review" of such Registration Statement, (C) of any comments (oral or written)
by the SEC and by the blue sky or securities commissioner or regulator of any
state with respect thereto and (D) of any request by the SEC for any amendments
or supplements to such Registration Statement or the prospectus or for
additional information;

               (v) 10b-5 Notification. (A) Promptly notify in writing the
Participating Holders, the sales or placement agent, if any, therefor and the
managing underwriter of the securities being sold pursuant to any Registration
Statement at any time when a prospectus relating thereto is required to be
delivered under the Securities Act upon discovery that, or upon the happening of
any event as a result of which, any prospectus included in such Registration
Statement (or amendment or supplement thereto) contains an untrue statement of a
material fact or omits to state any material fact required to be stated therein
or necessary to make the statements therein not misleading in light of the
circumstances under which they were made and (B) promptly prepare a supplement
or amendment to such prospectus so that after delivery of such prospectus, as so
amended or supplemented, to the purchasers of such Registrable Securities, such
prospectus, as so amended or supplemented, shall not contain an untrue statement
of a material fact or omit to state any material fact required to be stated
therein or necessary to make the statements therein not misleading in light of
the circumstances under which they were made;

               (vi) Notification of Stop Orders; Suspensions of Qualifications
and Exemptions. (A) Promptly notify in writing the Participating Holders, the
sales or placement


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agent, if any, therefor and the managing underwriter of the securities being
sold of the (I) issuance or threatened issuance by the SEC or any state
securities regulator of any stop order or any notification with respect to the
suspension of the qualification or exemption from qualification of any of the
Registrable Securities for sale in any jurisdiction or (II) initiation or
threaten initiation of any proceeding for such purpose and (B) use its good
faith reasonable commercial efforts to (I) prevent the issuance of any such stop
order, and in the event of such issuance, to obtain the withdrawal of any such
stop order and (II) obtain the withdrawal of any order suspending or preventing
the use of any related prospectus or suspending the qualification of any
Registrable Securities included in such Registration Statement for sale in any
jurisdiction at the earliest practicable date;

               (vii) Amendments and Supplements. Prepare and file with the SEC
such amendments, including post-effective amendments to each Registration
Statement as may be necessary to keep such Registration Statement continuously
effective for the applicable time period required hereunder; cause the related
prospectus to be supplemented by any required prospectus supplement, and as so
supplemented to be filed pursuant to Rule 424 (or any similar provisions then in
force) promulgated under the Securities Act; and comply with the provisions of
the Securities Act and the Exchange Act with respect to the disposition of all
securities covered by such Registration Statement during such period in
accordance with the intended methods of disposition by the sellers thereof set
forth in such Registration Statement as so amended or in such prospectus as so
supplemented;

               (viii) Copies. Furnish as promptly as practicable to each
Inspector and Participating Holder prior to filing a Registration Statement or
any supplement or amendment thereto, copies of such Registration Statement,
supplement or amendment as it is proposed to be filed, and after such filing
such number of copies of such Registration Statement, each amendment and
supplement thereto (in each case including all exhibits thereto), the prospectus
included in such Registration Statement (including each preliminary prospectus)
and such other documents as each such Participating Holder or underwriter may
reasonably request in order to facilitate the disposition of the Registrable
Securities owned by such Participating Holder;

               (ix) Blue Sky. Use its good faith reasonable commercial efforts,
prior to any public offering of the Registrable Securities, to register or
qualify (or seek an exemption from registration or qualification) such
Registrable Securities under such other securities or blue sky laws of such
jurisdictions as any Participating Holder or underwriter may request, and to
continue such registration and qualification in effect in each such jurisdiction
for as long as is permissible pursuant to the laws of such jurisdiction, or for
as long as a Participating Holder or underwriter requests or until all of such
Registrable Securities are sold, whichever is shortest, and do any and take any
and all other actions that may be reasonably necessary or advisable to enable
any Participating Holder to consummate the disposition in such jurisdictions of
the Registrable Securities; PROVIDED, HOWEVER, that the Company shall not be
required to (A) qualify generally to do business in any jurisdiction where it
would not otherwise be required to qualify but for this Section 5(a)(ix), (B)
subject itself to material taxation in any such jurisdiction or (C) consent to
general service of process in any such jurisdiction;


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               (x) Other Approvals. Use its good faith reasonable commercial
efforts to obtain all other approvals, consents, exemptions or authorizations
from such governmental agencies or authorities as may be necessary to enable the
Participating Holders and underwriters to consummate the disposition of
Registrable Securities;

               (xi) Agreements. Enter into customary agreements (including any
underwriting agreements in customary form), and take such other actions as may
be reasonably required in order to expedite or facilitate the disposition of
Registrable Securities;

               (xii) "Cold Comfort" Letter. Obtain a "cold comfort" letter from
the Company's independent public accountants in customary form and covering such
matters of the type customarily covered by "cold comfort" letters as the
managing underwriter may reasonably request;

               (xiii) Legal Opinion. Furnish, at the request of any underwriter
of Registrable Securities on the date such securities are delivered to the
underwriters for sale pursuant to such registration, an opinion, dated such
date, of counsel representing the Company for the purposes of such registration,
addressed to the Holders, and the placement agent or sales agent, if any,
thereof and the underwriters, if any, thereof, covering such legal matters with
respect to such registration that such underwriter may reasonably request and
that are customarily included in such opinions;

               (xiv) SEC Compliance, Earnings Statement. Comply with all
applicable rules and regulations of the SEC, and make available to its
stockholders, as soon as reasonably practicable, but no later than fifteen (15)
months after the effective date of any Registration Statement, an earnings
statement covering a period of twelve (12) months beginning after the effective
date of such Registration Statement, in a manner that satisfies the provisions
of Section 11(a) of the Securities Act and Rule 158 thereunder;

               (xv) Certificates, Closing. Provide officers' certificates and
other customary closing documents that are required pursuant to any registration
and offerings of the Registrable Securities and the consummation of any sales
thereof;

               (xvi) NASD. Cooperate with each Participating Holder and each
underwriter participating in the disposition of such Registrable Securities and
underwriters' counsel in connection with any filings required to be made with
the NASD;

               (xvii) Road Show. With respect to an underwritten offering, cause
appropriate officers as are requested by an Approved Underwriter or a Company
Underwriter to participate in a "road show" or similar marketing effort being
conducted by such underwriter;

               (xviii) Listing. Use its good faith reasonable commercial efforts
to cause all such Registrable Securities to be listed on the Nasdaq National
Market and each securities exchange on which the Common Stock is then listed;
and


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               (xix) Good Faith Reasonable Commercial Efforts. Use its good
faith reasonable commercial efforts to take all other actions necessary to
effect the registration of the Registrable Securities as contemplated hereby.

         (b) SELLER INFORMATION. The Company may require each Participating
Holder to furnish to the Company such information regarding such Participating
Holder and such Participating Holder's method of distribution of such
Registrable Securities as the Company may from time to time reasonably request
in writing.

         (c) NOTICE TO DISCONTINUE. Upon the receipt by a Participating Holder
whose Registrable Securities are covered by a Registration Statement filed
pursuant to Sections 2 or 3 of any notice from the Company of the happening of
any event of the kind described in Section 5(a)(v), such Participating Holder
shall immediately discontinue disposition of Registrable Securities pursuant to
the Registration Statement covering such Registrable Securities until such
Participating Holder's receipt of the copies of the supplemented or amended
prospectus contemplated by Section 5(a)(v) and, if so directed by the Company in
the case of an event described in Section 5(a)(v), such Participating Holder
shall deliver to the Company (at the Company's expense) all copies, other than
permanent file copies then in such Participating Holder's possession, of the
prospectus covering such Registrable Securities that is current at the time of
receipt of such notice. If the Company gives any such notice, the Company shall
extend the period during which such Registration Statement is to be maintained
effective by the number of days during the period from and including the date of
the giving of such notice to and including the date when the Participating
Holder receives the copies of the supplemented or amended prospectus
contemplated by, and meeting the requirements of, Section 5(a)(v).

     6.  REGISTRATION AND SELLING EXPENSES.

         Except as otherwise expressly provided herein, the Company shall bear
and pay all Registration Expenses incurred in connection with any Shelf
Registration pursuant to Section 2, any registration pursuant to Section 3 and
any underwritten offering pursuant to Sections 2 and 3, regardless of whether
such Shelf Registration or other registration becomes effective or such
underwritten offering is consummated. All Selling Expenses relating to
Registrable Securities registered shall be borne by the Participating Holders of
such Registrable Securities pro rata on the basis of the number of shares so
registered.

     7.  INDEMNIFICATION; CONTRIBUTION.

         (a) INDEMNIFICATION BY THE COMPANY. Notwithstanding termination of this
Agreement, the Company shall indemnify and hold harmless to the fullest extent
permitted by law, each Holder, each of its directors, members, officers,
partners, employees, advisors and agents, their respective Affiliates and each
Person who controls (within the meaning of the Securities Act or the Exchange
Act) any of such Persons, and each underwriter and each Person who controls
(within the meaning of the Securities Act or the Exchange Act) any underwriter
from and against any and all losses, claims, damages, penalties, fines, expenses
(including, without limitation, reasonable costs of investigation and fees,
disbursements and other charges of counsel) and other liabilities (collectively,
"LOSSES") incurred in connection with any action, suit, investigation,
complaint, claim or other proceeding (collectively, a "CLAIM") commenced or


                                       11
<PAGE>   12

conducted by any Person, including, without limitation, any governmental agency
or body, arising out of or based upon any actual or alleged untrue statement of
a material fact contained in any Registration Statement, prospectus or
preliminary prospectus (as amended or supplemented) or any document incorporated
by reference in any of the foregoing or arising out of or based upon any actual
or alleged omission therein of a material fact required to be stated therein or
necessary to make the statements therein (in the case of a prospectus, in light
of the circumstances under which they were made) not misleading; PROVIDED,
HOWEVER, that the Company will not be liable in any such case to the extent that
any Losses arise out of or are based on any actual or alleged untrue statement
or omission made in reliance upon and in conformity with written information
furnished to the Company by such Indemnified Party expressly for use therein;
PROVIDED, FURTHER, HOWEVER, that the Company shall not be liable to any
Indemnified Party (as hereinafter defined) in any such case to the extent any
such Losses arise out of or are based upon the failure of such Indemnified Party
following its receipt from the Company of any amendment or supplement to a
Registration Statement which corrects any untrue statement or alleged untrue
statement or omission or alleged omission made in the Registration Statement to
which such amendment or supplement pertains to deliver such amendment or
supplement.

         (b) INDEMNIFICATION BY HOLDERS. Each Holder agrees to indemnify and
hold harmless the Company, any underwriter retained by the Company and their
respective directors, members, officers, partners, employees, advisors and
agents, their respective Affiliates and each Person who controls (within the
meaning of the Securities Act and the Exchange Act) any of such Persons from and
against any and all Losses incurred in connection with any Claim commenced or
conducted by any Person, including, without limitation, any governmental agency
or body, arising out of or based upon any actual or alleged untrue statement or
omission to state a material fact in any information furnished in writing by
such Holder expressly for use in any Registration Statement or prospectus or
preliminary prospectus to be used in connection with any registration pursuant
to Sections 2 and 3 (subject to the exceptions set forth in the foregoing
indemnity, the proviso to this sentence and applicable law); PROVIDED, HOWEVER,
that the liability of any Holder under this Section 7(b) shall be limited to the
amount of the net proceeds received by such Holder in the offering giving rise
to such liability.

         (c) CONDUCT OF INDEMNIFICATION PROCEEDINGS. Any Person entitled to
indemnification hereunder (the "INDEMNIFIED Party") agrees to give prompt
written notice to the indemnifying party (the "INDEMNIFYING PARTY") after the
receipt by the Indemnified Party of any written notice of the commencement or
threat of any Claim for which the Indemnified Party intends to claim
indemnification or contribution pursuant to this Agreement; PROVIDED that the
failure so to notify the Indemnifying Party shall not relieve the Indemnifying
Party of any liability that it may have to the Indemnified Party hereunder
unless such Indemnifying Party is materially prejudiced by such failure. The
Indemnifying Party shall be entitled to participate in and, to the extent it may
wish, including jointly with any other Indemnifying Party, to assume the defense
of such action at its own expense with counsel chosen by it and reasonably
satisfactory to such Indemnified Party except to the extent that the Indemnified
Party or Parties, as the case may be, retains separate counsel pursuant to the
following sentence. The Indemnified Party shall have the right to employ
separate counsel in connection with its defense of any such Claim, but the fees
and expenses of such counsel shall be paid by the Indemnified Party unless (i)
the


                                       12
<PAGE>   13

Indemnifying Party agrees to pay the same, (ii) the Indemnifying Party fails
to assume the defense of such action with counsel satisfactory to the
Indemnified Party in its reasonable judgment and such failure is not due to the
failure of the Indemnified Party to provide the notice required in this Section
7(c), or (iii) the named parties to any such action (including, but not limited
to, any impleaded parties) reasonably believe based upon written advice of
counsel that the representation of such Indemnified Party and the Indemnifying
Party by the same counsel would be inappropriate under applicable standards of
professional conduct; PROVIDED, HOWEVER, that the Indemnifying Party shall only
have to pay the fees and expenses of one firm of such separate counsel for all
Indemnified Parties in each jurisdiction. No Indemnifying Party shall be liable
for any settlement entered into without its written consent, which consent shall
not be unreasonably withheld. No Indemnifying Party shall, without the written
consent of the Indemnified Party, effect the settlement or compromise of, or
consent to the entry of any judgment with respect to, any pending or threatened
Claim in respect of which indemnification or contribution may be sought
hereunder (whether or not the Indemnified Party is an actual or potential party
to such Claim) unless such settlement, compromise or judgment (A) includes an
unconditional release of the Indemnified Party from all liability arising out of
such Claim and (B) does not include a statement or an admission of fault,
culpability or a failure to act by or on behalf of any Indemnified Party. The
rights afforded to any Indemnified Party hereunder shall be in addition to any
rights that such Indemnified Party may have at common law, by separate agreement
or otherwise.

         (d) CONTRIBUTION. If the indemnification provided for in this Section 7
is unavailable or insufficient to hold harmless an Indemnified Party in respect
of any Losses, then the Indemnifying Party, in lieu of indemnifying such
Indemnified Party, shall contribute to the amount paid or payable by such
Indemnified Party as a result of such uncovered Losses in such proportion as is
appropriate to reflect the relative fault of the Indemnifying Party and the
Indemnified Party, as well as any other relevant equitable considerations. The
relative faults of such Indemnifying Party and Indemnified Party shall be
determined by reference to, among other things, whether any action in question,
including any untrue or alleged untrue statement of a material fact or omission
or alleged omission to state a material fact, was made by, or relates to
information supplied by, such Indemnifying Party or Indemnified Party, and the
Indemnifying Party's and Indemnified Party's relative intent, knowledge, access
to information and opportunity to correct or prevent such action; PROVIDED,
HOWEVER, that the liability of any Holder under this Section 7(d) shall be
limited to the amount of the net proceeds received by such Holder in the
offering giving rise to such liability. The amount paid or payable by a party as
a result of the such Losses shall be subject to the limitations set forth in
Sections 7(a), 7(b) and 7(c).

         The parties hereto acknowledge that determining contribution pursuant
to this Section 7(d) by any method of allocation (including, without limitation,
a pro rata allocation based simply on the relative proportion of Registrable
Securities that the Indemnifying Party and Indemnified Party included in a
registration or offering) that does not take account the equitable
considerations referred to in the immediately preceding paragraph would be
neither just nor equitable.


                                       13
<PAGE>   14

         No person guilty of fraudulent misrepresentation (within the meaning of
Section 11(f) of the Securities Act) shall be entitled to contribution pursuant
to this Section 7(d).

     8.  RULE 144; OTHER EXEMPTIONS.

         With a view to making available to the Holders the benefits of Rule 144
and other rules and regulations of the SEC that may at any time permit a Holder
to sell securities of the Company to the public without registration, the
Company covenants that it shall (a) file in a timely manner all reports and
other documents required to be filed by it under the Securities Act and the
Exchange Act and the rules and regulations adopted by the SEC thereunder and (b)
take such further action as each Holder may reasonably request (including, but
not limited to, providing any information necessary to comply with Rule 144),
all to the extent required from time to time to enable such Holder to sell
Registrable Securities without registration under the Securities Act within the
limitation of the exemptions provided by (x) Rule 144 as such rule may be
amended from time to time or (y) any other similar rules or regulations now
existing or hereafter adopted by the SEC.

     9.  CERTAIN LIMITATIONS ON REGISTRATION RIGHTS.

         (a) In the case of (i) an underwritten offering under Section 2 or (ii)
a registration under Section 3, if the Company has determined to enter into an
underwriting agreement in connection therewith, no Holder may participate in
such registration unless such Holder (A) agrees to sell such Holder's
Registrable Securities on the basis provided therein and (B) completes and
executes all questionnaires, powers-of-attorney, custody agreements,
indemnities, lock-up agreements, underwriting agreements and other documents
required under the terms of such underwriting agreement, provided, HOWEVER,
that, notwithstanding the foregoing, the Company shall not enter into any such
underwriting agreement that conflicts with, or diminishes in any manner, the
rights and benefits provided to Holders pursuant to this Agreement, including,
without limitation, the performance of any obligations by the Company hereunder.

         (b) The Company may require each Holder of Registrable Securities to
furnish to the Company such information regarding the Holder of such securities,
the securities of the Company held by such Holder, the manner of acquisition of
such securities, and any information required by the rules and regulations of
the SEC, as the Company may from time to time reasonably request in writing.

     10. MISCELLANEOUS.

         (a) TERMINATION. This Agreement shall terminate upon the earlier of (i)
the written agreement of the Company and all Holders hereto and (ii) the date
upon which there are no Registrable Securities outstanding.

         (b) NO INCONSISTENT AGREEMENTS; OTHER REGISTRATION RIGHTS. The Company
shall not enter into any agreement with respect to its Common Stock that is
inconsistent with or has priority over the rights granted to the Holders in this
Agreement.



                                       14
<PAGE>   15

         (c) REMEDIES. The Holders, in addition to being entitled to exercise
all rights granted by law, including recovery of damages, shall be entitled to
specific performance of their rights under this Agreement. The Company
acknowledges that monetary damages would not be adequate compensation for any
loss incurred by reason of a breach by it of the provisions of this Agreement
and hereby agrees to waive in any action for specific performance the defense
that a remedy at law would be adequate.

         (d) AMENDMENTS AND WAIVERS. Except as otherwise provided herein, the
provisions of this Agreement may not be amended, modified or supplemented, and
waivers or consents to departures from such provisions may not be given, unless
the Company has obtained the prior written consent of seventy-five percent (75%)
of the Holders holding Registrable Securities.

         (e) NOTICES. All notices, demands and other communications provided for
or permitted hereunder shall be made in writing and shall be by registered or
certified first-class mail, return receipt requested, facsimile, courier service
or personal delivery:

             (i)      if to the Company:

                      Purina Mills, Inc.
                      1401 South Hanley Road
                      St. Louis, Missouri 63144
                      Attention:  David G. Kabbes
                      Telephone Number:    (314) 768-4157
                      Facsimile Number:     (314) 768-4582

                      with a copy to (which shall not constitute notice):

                      Jones, Day, Reavis & Pogue
                      North Point
                      901 Lakeside Avenue
                      Cleveland, Ohio 44114
                      Attention:  Sean M. McAvoy, Esq.
                      Telephone Number:   (216) 586-3939
                      Facsimile Number:    (216) 579-0212

             (ii)     if to Holders: at the address set forth in the
                      Company's records.

                      with a copy to (which shall not constitute notice):

                      Akin, Gump, Strauss, Hauer & Feld, L.L.P.
                      590 Madison Avenue
                      New York, New York 10022
                      Attention:       Daniel H. Golden, Esq.
                      Telephone Number:   (212) 872-1000
                      Facsimile Number:    (212) 872-1002

         Each such notice, request or other communication will be effective (a)
if given by certified mail, 96 hours after such communication is deposited in
the mails with certified postage


                                       15
<PAGE>   16

prepaid addressed as aforesaid, (b) one Business Day after being furnished to a
nationally recognized overnight courier for next Business Day delivery, and (c)
on the date sent if sent by electronic facsimile transmission, receipt confirmed
followed by a hard copy by mail.

         (f) SUCCESSORS AND ASSIGNS. This Agreement shall inure to the benefit
of and be binding upon the successors and assigns of the parties hereto;
PROVIDED, HOWEVER, that the registration rights of the Holders and the other
obligations of the Company contained in this Agreement shall, with respect to
any Registrable Securities, be automatically transferred from a Holder to any
subsequent holder of such Registrable Securities so long as such securities are
Registrable Securities. Notwithstanding any transfer of such rights, all of the
obligations of the Company hereunder shall survive any such transfer and shall
continue to inure to the benefit of all transferees.

         (g) COUNTERPARTS. This Agreement may be executed in any number of
counterparts and by the parties hereto in separate counterparts, each of which
when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement.

         (h) HEADINGS. The headings in this Agreement are for convenience of
reference only and shall not limit or otherwise affect the meaning hereof.

         (i) GOVERNING LAW. This Agreement shall be governed by and construed in
accordance with the laws of the State of New York, without regard to the
principles of conflicts of law of such State.

         (j) JURISDICTION. Any legal action or proceeding arising out of or
relating to this Agreement or any agreements or transactions contemplated hereby
shall be brought in the courts of the State of New York or of the United States
of America for the Southern District of New York and each party hereto hereby
expressly submits to the personal jurisdiction and venue of such courts for the
purposes thereof and expressly waives any claim of improper venue and any claim
that such courts are an inconvenient forum. Each party hereby irrevocably
consents to the service of process of any of the aforementioned courts in any
such suit, action or proceeding by the mailing of copies thereof by registered
or certified mail, postage prepaid, to the address set forth in Section 10(e),
such service to become effective ten (10) Business Days after such mailing.

         (k) SEVERABILITY. If any one or more of the provisions contained
herein, or the application thereof in any circumstance, is held invalid, illegal
or unenforceable in any respect for any reason, the validity, legality and
enforceability of any such provision in every other respect and of the remaining
provisions hereof shall not be in any way impaired.

         (l) RULES OF CONSTRUCTION. Unless the context otherwise requires, "or"
is not exclusive, and references to sections or subsections refer to sections or
subsections of this Agreement.

         (m) ENTIRE AGREEMENT. This Agreement is intended by the parties as a
final expression of their agreement and intended to be a complete and exclusive
statement of the


                                       16
<PAGE>   17

agreement and understanding of the parties hereto in respect of the subject
matter contained herein. There are no restrictions, promises, warranties or
undertakings in respect of the subject matter contained herein other than those
set forth or referred to herein. This Agreement supersedes all prior oral and
written agreements and understandings between the parties with respect to such
subject matter.

         (n) FURTHER ASSURANCES. Each of the parties shall execute such
documents and perform such further acts as may be reasonably required or
desirable to realize each party's benefits and rights under this Agreement and
to perform its obligations hereunder.

         (o) INTERPRETATION. This Agreement is the result of arms-length
negotiations between the parties hereto and has been prepared jointly by the
parties. In applying and interpreting the provisions of this Agreement, there
shall be no presumption that the Agreement was prepared by any one party or that
the Agreement should be construed in favor of or against any one party.

         (p) NO THIRD PARTY BENEFICIARIES. This Agreement is for the benefit of
the parties hereto and any Person who agrees to become bound by the terms hereof
and become a Holder for the purposes of this Agreement, and is not intended to
confer upon any other Person any rights or remedies.

                  [remainder of page intentionally left blank]





                                       17
<PAGE>   18



                  IN WITNESS WHEREOF, the parties hereto have executed this
Agreement as of the date first above written.

                                   PURINA MILLS, INC.

                                   By:____________________________________
                                      Name:
                                      Title:

                                   HOLDERS:

                                   KOCH AGRICULTURE COMPANY

                                   By:____________________________________
                                      Name:
                                      Title:

                                   GCP, INC.

                                   By:____________________________________
                                      Name:
                                      Title:

                                      [ADD OTHERS]










                                      18