Document:

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                                                                     Exhibit 4.1

                               PURINA MILLS, INC.
                             1401 SOUTH HANLEY ROAD
                               ST. LOUIS, MO 63144

                                  June 17, 2001

Wells Fargo Bank Minnesota, N.A.
Corporate Trust Services
Sixth and Marquette, N9303-120
Minneapolis, MN   55479
Attention:  Cory Branden

                     Re: AMENDMENT NO. 3 TO RIGHTS AGREEMENT

Ladies and Gentlemen:

                 Pursuant to Section 27 of the Rights Agreement, dated as of
June 29, 2000, between Purina Mills, Inc. (the "Company"), and Wells Fargo Bank
Minnesota, N.A. (f/k/a Norwest Bank Minnesota, N.A.), as rights agent, as
amended on December 1, 2000 and May 29, 2001 (as amended, the "Rights
Agreement"), the Company, by resolution adopted by its Board of Directors,
hereby amends the Rights Agreement as follows:

                 1. Section 1(a) of the Rights Agreement is hereby amended and
restated in its entirety as follows:

                           "(a) "ACQUIRING PERSON" means any Person (other than
                  the Company, any Related Person or GSCP (unless and until GSCP
                  shall have become the Beneficial Owner of a percentage of
                  Common Shares then outstanding that exceeds the GSCP
                  Percentage, at which time GSCP shall be an Acquiring Person))
                  who or which, together with all Affiliates and Associates of
                  such Person, is the Beneficial Owner of 10% or more of the
                  then-outstanding Common Shares; PROVIDED, HOWEVER, that a
                  Person (other than the Company, any Related Person or GSCP)
                  who or which, together with all Affiliates and Associates of
                  such Person, is the Beneficial Owner of 10% or more of the
                  then-outstanding Common Shares as of, and immediately prior
                  to, the first date of public announcement of the execution of
                  the Merger Agreement, will not be deemed to have become an
                  Acquiring Person unless and until such time as (i) such Person
                  or any Affiliate or Associate of such Person thereafter
                  becomes the Beneficial Owner of additional Common Shares,
                  other than as a result of a stock dividend, stock split or
                  similar transaction effected by the Company in which all
                  holders of Common Shares are treated equally, or (ii) any
                  other Person who is the Beneficial Owner of Common Shares
                  thereafter becomes an Affiliate or Associate of such Person;
                  PROVIDED

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<PAGE>   2

                  FURTHER, HOWEVER, that a Person will not be deemed to have
                  become an Acquiring Person solely as a result of a reduction
                  in the number of Common Shares outstanding unless and until
                  such time as (i) such Person or any Affiliate or Associate of
                  such Person thereafter becomes the Beneficial Owner of
                  additional Common Shares representing 1% or more of the
                  then-outstanding Common Shares, other than as a result of a
                  stock dividend, stock split or similar transaction effected by
                  the Company in which all holders of Common Shares are treated
                  equally, or (ii) any other Person who is the Beneficial Owner
                  of Common Shares representing 1% or more of the
                  then-outstanding Common Shares thereafter becomes an Affiliate
                  or Associate of such Person. Notwithstanding the foregoing, if
                  the Board of Directors of the Company determines in good faith
                  that a Person who would otherwise be an "Acquiring Person" as
                  defined pursuant to the foregoing provisions of this paragraph
                  (a), has become such inadvertently, and such Person divests as
                  promptly as practicable a sufficient number of Common Shares
                  so that such Person would no longer be an "Acquiring Person"
                  as defined pursuant to the foregoing provisions of this
                  paragraph (a), then such Person shall not be deemed to be an
                  "Acquiring Person" for any purposes of this Agreement."

                 2. Section 1(b) of the Rights Agreement is hereby amended and
restated in its entirely as follows:

                           "(b) "AFFILIATE" and "ASSOCIATE" will have the
                  respective meanings ascribed to such terms in Rule 12b-2 of
                  the General Rules and Regulations under the Exchange Act, as
                  in effect on the date of this Agreement; PROVIDED, HOWEVER,
                  that a Person will not be deemed to be the Affiliate or
                  Associate or another Person solely because either or both
                  Persons (i) are or were Directors of the Company, or (ii) are,
                  as of the execution date of the Merger Agreement, parties to
                  the Voting Agreement, as in effect on the execution date of
                  the Merger Agreement, without giving effect to any amendment,
                  modification or supplement to such Voting Agreement that takes
                  effect after the execution date of the Merger Agreement."

                 3. Section 1(c)(iii) of the Rights Agreement is hereby amended
and restated in its entirety as follows:

                           "(iii) of which any other Person is the Beneficial
                  Owner, if such Person or any of such Person's Affiliates or
                  Associates has any agreement, arrangement or understanding
                  (whether or not in writing) with such other Person (or any of
                  such other Person's Affiliates or Associates) with respect to
                  acquiring, holding, voting or disposing of any securities of
                  the Company; PROVIDED, HOWEVER, that a Person will not be
                  deemed to be the Beneficial Owner of, or to Beneficially Own
                  any securities Beneficially Owned by another Person solely
                  because both Persons are, as of the execution date of the
                  Merger Agreement, parties to the Voting Agreement, as in
                  effect on the execution date of the Merger Agreement, without
                  giving effect to any amendment, modification or supplement to
                  such Voting Agreement that takes effect after the execution
                  date of the Merger Agreement; PROVIDED FURTHER, HOWEVER, that
                  a Person will not be deemed the Beneficial Owner

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<PAGE>   3

                  of, or to Beneficially Own, any security (A) if such Person
                  has the right to vote such security pursuant to an agreement,
                  arrangement or understanding (whether or not in writing),
                  which (1) arises solely from a revocable proxy given to such
                  Person in response to a public proxy or consent solicitation
                  made pursuant to, and in accordance with, the applicable rules
                  and regulations of the Exchange Act and (2) is not also then
                  reportable on Schedule 13D under the Exchange Act (or any
                  comparable or successor report), or (B) if such beneficial
                  ownership arises solely as a result of such Person's status as
                  a "clearing agency," as defined in Section 3(a)(23) of the
                  Exchange Act; PROVIDED FURTHER, HOWEVER, that nothing in this
                  paragraph (c) will cause a Person engaged in business as an
                  underwriter of securities to be the Beneficial Owner of, or to
                  Beneficially Own, any securities acquired through such
                  Person's participation in good faith in an underwriting
                  syndicate until the expiration of 40 calendar days after the
                  date of such acquisition, or such later date as the Directors
                  of the Company may determine in any specific case."

                 4. Section 1(k) of the Rights Agreement is hereby amended and
restated in its entirety as follows:

                           (k) "EXPIRATION DATE" means the earliest of (i) the
                  Close of Business on the Final Expiration Date, (ii) the time
                  at which the Rights are redeemed as provided in Section 23,
                  (iii) the time at which all exercisable Rights are exchanged
                  as provided in Section 24, and (iv) the Effective Time of the
                  Merger (each as defined in the Merger Agreement).

                 5. Section 1 of the Rights Agreement is hereby amended by
adding the following new Section 1(ff) immediately after Section 1(ee):

                           "(ff) "MERGER AGREEMENT" means the Agreement and Plan
                  of Merger, dated as of June 17, 2001, by and among Purina
                  Mills, Inc., a Delaware corporation, Land O'Lakes, Inc., a
                  Minnesota cooperative corporation, LOL Holdings II, Inc., a
                  Delaware corporation and a wholly owned subsidiary of Land
                  O'Lakes, Inc., and LOL Holdings III, Inc., a Delaware
                  corporation and a wholly owned subsidiary of LOL Holdings II,
                  Inc."

                 6. Section 1 of the Rights Agreement is hereby amended by
adding the following new Section 1(gg) immediately after Section 1(ff):

                          "(gg) "VOTING AGREEMENT" means the Voting Agreement,
                  dated as of June 17, 2001, by and between GSCP and Land
                  O'Lakes, Inc., a Minnesota cooperative corporation, as in
                  effect on the execution date of the Merger Agreement, without
                  giving effect to any amendment, modification or supplement to
                  such agreement that takes effect after the execution date of
                  the Merger Agreement."

                 7. Section 1 of the Rights Agreement is hereby amended by
adding the following new paragraph at the end of that Section:

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<PAGE>   4

                           "Notwithstanding anything in this Agreement to the
                  contrary, none of Land O'Lakes, Inc., a Minnesota cooperative
                  corporation, LOL Holdings II, Inc., a Delaware corporation and
                  wholly owned subsidiary of Land O'Lakes, Inc. and LOL Holdings
                  III, Inc., a Delaware corporation and wholly-owned subsidiary
                  of LOL Holdings II, Inc., any of their Affiliates or
                  Associates or any of their permitted assignees or successors
                  (as contemplated in Section 8.07 of the Merger Agreement)
                  shall be deemed an Acquiring Person and none of a Distribution
                  Date, a Share Acquisition Date, or a Triggering Event
                  (including a Flip-in Event or Flip-over Event) shall be deemed
                  to occur or to have occurred, and that the Rights will not
                  become separable, distributable, unredeemable or exercisable,
                  in each such case, by reason or as a result of the approval,
                  execution or delivery of the Merger Agreement, execution or
                  delivery of the Voting Agreement, the grant of the irrevocable
                  proxy under the Voting Agreement, the consummation of the
                  Merger (as defined in the Merger Agreement) or the
                  consummation of the other transactions contemplated by the
                  Merger Agreement."

                 8. Section 26(b) of the Rights Agreement is hereby amended and
restated in its entirety as follows:

                           "(b) Subject to the provisions of Section 21 hereof,
                  any notice or demand authorized by this Agreement to be given
                  or made by the Company or by the holder of any Right
                  Certificate to or on the Rights Agent will be sufficiently
                  given or made if sent by first-class mail, postage prepaid,
                  addressed (until another address is filed in writing with the
                  Company) as follows:

                                    Wells Fargo Bank Minnesota, N.A.
                                    Corporate Trust Services
                                    Sixth and Marquette, N9303-120
                                    Minneapolis, MN 55479
                                    Attention:  Cory Branden"

                 9. The Rights Agreement shall not otherwise be supplemented or
amended by virtue of this Amendment No. 3 to the Rights Agreement, but shall
remain in full force and effect.

                 10. Capitalized terms used without other definition in this
Amendment No. 3 to the Rights Agreement shall be used as defined in the Rights
Agreement.

                 11. This Amendment No. 3 to the Rights Agreement shall be
deemed to be a contract made under the laws of the State of Delaware and for all
purposes will be governed by and construed in accordance with the laws of such
State applicable to contracts to be made and performed entirely within such
State.

                 12. This Amendment No. 3 to the Rights Agreement may be
executed in any number of counterparts and each of such counterparts shall for
all purposes be deemed to be an original, and all such counterparts shall
together constitute but one and the same instrument.

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<PAGE>   5

                 13. This Amendment No. 3 to the Rights Agreement shall be
effective as of, and immediately prior to, the execution and delivery of the
Merger Agreement, and all references to the Rights Agreement shall, from and
after such time, be deemed to be references to the Rights Agreement as amended
hereby.

                 14. Exhibits B and C to the Rights Agreement shall be deemed
amended in a manner consistent with this Amendment No. 3 to the Rights
Agreement.

                                    * * * * *

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<PAGE>   6

                                   Very truly yours,

                                   PURINA MILLS, INC.

                                        By: /s/ DARRELL D. SWANK
                                            -----------------------------------
                                            Name:    Darrell D. Swank
                                            Title:   Executive Vice President,
                                                     Chief Financial Officer
                                                     and Secretary

Accepted and agreed to as of the effective time specified above:

WELLS FARGO BANK MINNESOTA, N.A.

By:      ----------------------------
         Name:
         Title:

                                       10<PAGE>   1

                                                                     Exhibit 4.1

                               PURINA MILLS, INC.
                             1401 SOUTH HANLEY ROAD
                               ST. LOUIS, MO 63144

                                  June 17, 2001

Wells Fargo Bank Minnesota, N.A.
Corporate Trust Services
Sixth and Marquette, N9303-120
Minneapolis, MN   55479
Attention:  Cory Branden

                     Re: Amendment No. 3 to Rights Agreement
                         -----------------------------------

Ladies and Gentlemen:
                  Pursuant to Section 27 of the Rights Agreement, dated as of
June 29, 2000, between Purina Mills, Inc. (the "Company"), and Wells Fargo Bank
Minnesota, N.A. (f/k/a Norwest Bank Minnesota, N.A.), as rights agent, as
amended on December 1, 2000 and May 29, 2001 (as amended, the "Rights
Agreement"), the Company, by resolution adopted by its Board of Directors,
hereby amends the Rights Agreement as follows:

1.       Section 1(a) of the Rights Agreement is hereby amended and restated in
         its entirety as follows:

                           "(a)    "ACQUIRING PERSON" means any Person (other
                  than the Company, any Related Person or GSCP (unless and until
                  GSCP shall have become the Beneficial Owner of a percentage of
                  Common Shares then outstanding that exceeds the GSCP
                  Percentage, at which time GSCP shall be an Acquiring Person))
                  who or which, together with all Affiliates and Associates of
                  such Person, is the Beneficial Owner of 10% or more of the
                  then-outstanding Common Shares; PROVIDED, HOWEVER, that a
                  Person (other than the Company, any Related Person or GSCP)
                  who or which, together with all Affiliates and Associates of
                  such Person, is the Beneficial Owner of 10% or more of the
                  then-outstanding Common Shares as of, and immediately prior
                  to, the first date of public announcement of the execution of
                  the Merger Agreement, will not be deemed to have become an
                  Acquiring Person unless and until such time as (i) such Person
                  or any Affiliate or Associate of such Person thereafter
                  becomes the Beneficial Owner of additional Common Shares,
                  other than as a result of a stock dividend, stock split or
                  similar transaction effected by the Company in which all
                  holders of Common Shares are treated equally, or (ii) any
                  other Person who is the Beneficial Owner of Common Shares
                  thereafter becomes an Affiliate or Associate of such Person;
                  PROVIDED

<PAGE>   2

                  FURTHER, HOWEVER, that a Person will not be deemed to have
                  become an Acquiring Person solely as a result of a reduction
                  in the number of Common Shares outstanding unless and until
                  such time as (i) such Person or any Affiliate or Associate of
                  such Person thereafter becomes the Beneficial Owner of
                  additional Common Shares representing 1% or more of the
                  then-outstanding Common Shares, other than as a result of a
                  stock dividend, stock split or similar transaction effected by
                  the Company in which all holders of Common Shares are treated
                  equally, or (ii) any other Person who is the Beneficial Owner
                  of Common Shares representing 1% or more of the
                  then-outstanding Common Shares thereafter becomes an Affiliate
                  or Associate of such Person. Notwithstanding the foregoing, if
                  the Board of Directors of the Company determines in good faith
                  that a Person who would otherwise be an "Acquiring Person" as
                  defined pursuant to the foregoing provisions of this paragraph
                  (a), has become such inadvertently, and such Person divests as
                  promptly as practicable a sufficient number of Common Shares
                  so that such Person would no longer be an "Acquiring Person"
                  as defined pursuant to the foregoing provisions of this
                  paragraph (a), then such Person shall not be deemed to be an
                  "Acquiring Person" for any purposes of this Agreement."

2.       Section 1(b) of the Rights Agreement is hereby amended and restated in
         its entirely as follows:

                           "(b)    "AFFILIATE" and "ASSOCIATE" will have the
                  respective meanings ascribed to such terms in Rule 12b-2 of
                  the General Rules and Regulations under the Exchange Act, as
                  in effect on the date of this Agreement; PROVIDED, HOWEVER,
                  that a Person will not be deemed to be the Affiliate or
                  Associate or another Person solely because either or both
                  Persons (i) are or were Directors of the Company, or (ii) are,
                  as of the execution date of the Merger Agreement, parties to
                  the Voting Agreement, as in effect on the execution date of
                  the Merger Agreement, without giving effect to any amendment,
                  modification or supplement to such Voting Agreement that takes
                  effect after the execution date of the Merger Agreement."

3.       Section 1(c)(iii) of the Rights Agreement is hereby amended and
         restated in its entirety as follows:

                           "(iii) of which any other Person is the Beneficial
                  Owner, if such Person or any of such Person's Affiliates or
                  Associates has any agreement, arrangement or understanding
                  (whether or not in writing) with such other Person (or any of
                  such other Person's Affiliates or Associates) with respect to
                  acquiring, holding, voting or disposing of any securities of
                  the Company; PROVIDED, HOWEVER, that a Person will not be
                  deemed to be the Beneficial Owner of, or to Beneficially Own
                  any securities Beneficially Owned by another Person solely
                  because both Persons are, as of the execution date of the
                  Merger Agreement, parties to the Voting Agreement, as in
                  effect on the execution date of the Merger Agreement, without
                  giving effect to any amendment, modification or supplement to
                  such Voting Agreement that takes effect after the execution
                  date of the Merger Agreement; PROVIDED FURTHER, HOWEVER, that
                  a Person will not be deemed the Beneficial Owner of, or to
                  Beneficially Own, any security (A) if such Person has the
                  right to vote

<PAGE>   3

                  such security pursuant to an agreement, arrangement or
                  understanding (whether or not in writing), which (1) arises
                  solely from a revocable proxy given to such Person in response
                  to a public proxy or consent solicitation made pursuant to,
                  and in accordance with, the applicable rules and regulations
                  of the Exchange Act and (2) is not also then reportable on
                  Schedule 13D under the Exchange Act (or any comparable or
                  successor report), or (B) if such beneficial ownership arises
                  solely as a result of such Person's status as a "clearing
                  agency," as defined in Section 3(a)(23) of the Exchange Act;
                  PROVIDED FURTHER, HOWEVER, that nothing in this paragraph (c)
                  will cause a Person engaged in business as an underwriter of
                  securities to be the Beneficial Owner of, or to Beneficially
                  Own, any securities acquired through such Person's
                  participation in good faith in an underwriting syndicate until
                  the expiration of 40 calendar days after the date of such
                  acquisition, or such later date as the Directors of the
                  Company may determine in any specific case."

4.       Section 1(k) of the Rights Agreement is hereby amended and restated in
         its entirety as follows:

                           (k) "EXPIRATION DATE" means the earliest of (i) the
                  Close of Business on the Final Expiration Date, (ii) the time
                  at which the Rights are redeemed as provided in Section 23,
                  (iii) the time at which all exercisable Rights are exchanged
                  as provided in Section 24, and (iv) the Effective Time of the
                  Merger (each as defined in the Merger Agreement).

5.       Section 1 of the Rights Agreement is hereby amended by adding the
         following new Section 1(ff) immediately after Section 1(ee):

                           "(ff) "MERGER AGREEMENT" means the Agreement and Plan
                  of Merger, dated as of June 17, 2001, by and among Purina
                  Mills, Inc., a Delaware corporation, Land O'Lakes, Inc., a
                  Minnesota cooperative corporation, LOL Holdings II, Inc., a
                  Delaware corporation and a wholly owned subsidiary of Land
                  O'Lakes, Inc., and LOL Holdings III, Inc., a Delaware
                  corporation and a wholly owned subsidiary of LOL Holdings II,
                  Inc."

6.       Section 1 of the Rights Agreement is hereby amended by adding the
         following new Section 1(gg) immediately after Section 1(ff):

                           "(gg) "VOTING AGREEMENT" means the Voting Agreement,
                  dated as of June 17, 2001, by and between GSCP and Land
                  O'Lakes, Inc., a Minnesota cooperative corporation, as in
                  effect on the execution date of the Merger Agreement, without
                  giving effect to any amendment, modification or supplement to
                  such agreement that takes effect after the execution date of
                  the Merger Agreement."

7.       Section 1 of the Rights Agreement is hereby amended by adding the
         following new paragraph at the end of that Section:

<PAGE>   4

                           "Notwithstanding anything in this Agreement to the
                  contrary, none of Land O'Lakes, Inc., a Minnesota cooperative
                  corporation, LOL Holdings II, Inc., a Delaware corporation and
                  wholly owned subsidiary of Land O'Lakes, Inc. and LOL Holdings
                  III, Inc., a Delaware corporation and wholly-owned subsidiary
                  of LOL Holdings II, Inc., any of their Affiliates or
                  Associates or any of their permitted assignees or successors
                  (as contemplated in Section 8.07 of the Merger Agreement)
                  shall be deemed an Acquiring Person and none of a Distribution
                  Date, a Share Acquisition Date, or a Triggering Event
                  (including a Flip-in Event or Flip-over Event) shall be deemed
                  to occur or to have occurred, and that the Rights will not
                  become separable, distributable, unredeemable or exercisable,
                  in each such case, by reason or as a result of the approval,
                  execution or delivery of the Merger Agreement, execution or
                  delivery of the Voting Agreement, the grant of the irrevocable
                  proxy under the Voting Agreement, the consummation of the
                  Merger (as defined in the Merger Agreement) or the
                  consummation of the other transactions contemplated by the
                  Merger Agreement."

8.       Section 26(b) of the Rights Agreement is hereby amended and restated in
         its entirety as follows:

                           "(b)    Subject to the provisions of Section 21
                  hereof, any notice or demand authorized by this Agreement to
                  be given or made by the Company or by the holder of any Right
                  Certificate to or on the Rights Agent will be sufficiently
                  given or made if sent by first-class mail, postage prepaid,
                  addressed (until another address is filed in writing with the
                  Company) as follows:

                                    Wells Fargo Bank Minnesota, N.A.
                                    Corporate Trust Services
                                    Sixth and Marquette, N9303-120
                                    Minneapolis, MN 55479
                                    Attention:  Cory Branden"

9.       The Rights Agreement shall not otherwise be supplemented or amended by
         virtue of this Amendment No. 3 to the Rights Agreement, but shall
         remain in full force and effect.

10.      Capitalized terms used without other definition in this Amendment No. 3
         to the Rights Agreement shall be used as defined in the Rights
         Agreement.

11.      This Amendment No. 3 to the Rights Agreement shall be deemed to be a
         contract made under the laws of the State of Delaware and for all
         purposes will be governed by and construed in accordance with the laws
         of such State applicable to contracts to be made and performed entirely
         within such State.

12.      This Amendment No. 3 to the Rights Agreement may be executed in any
         number of counterparts and each of such counterparts shall for all
         purposes be deemed to be an original, and all such counterparts shall
         together constitute but one and the same instrument.

<PAGE>   5

13.      This Amendment No. 3 to the Rights Agreement shall be effective as of,
         and immediately prior to, the execution and delivery of the Merger
         Agreement, and all references to the Rights Agreement shall, from and
         after such time, be deemed to be references to the Rights Agreement as
         amended hereby.

14.      Exhibits B and C to the Rights Agreement shall be deemed amended in a
         manner consistent with this Amendment No. 3 to the Rights Agreement.

                                        Very truly yours,

                                        PURINA MILLS, INC.

                                        By: /s/ Darrell D. Swank
                                            ------------------------------------
                                            Name:    Darrell D. Swank
                                            Title:   Executive Vice President,
                                                     Chief Financial Officer
                                                     and Secretary

Accepted and agreed to as of the
effective time specified above:

WELLS FARGO BANK MINNESOTA, N.A.

By:  _______________________________
     Name:
     Title:

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