<PAGE>

                                                                   EXHIBIT 10.21

                                  AMENDMENT TO
                                CREDIT AGREEMENT

            THIS AMENDMENT TO CREDIT AGREEMENT, made and entered into as of the
30th day of December, 1999, by and between VIRBAC CORPORATION, a Delaware
corporation ("Virbac"), PM RESOURCES, INC., a Missouri corporation ("PM
Resources"), ST. JON LABORATORIES, INC., a California corporation ("St. JON"),
FRANCODEX LABORATORIES, INC., a Kansas corporation ("Francodex"), and VIRBAC AH,
INC., a Delaware corporation ("Virbac AH," and collectively with Virbac, PM
Resources, St. JON and Francodex referred to herein as the "Borrowers"), and
FIRST BANK, a Missouri state banking corporation ("Bank").

                                   WITNESSETH:

            WHEREAS, Borrowers heretofore jointly and severally executed and
delivered to Bank a Revolving Credit Note dated September 7, 1999, in the
principal amount of up to Ten Million Dollars ($10,000,000.00), payable to the
order of Bank as therein set forth (as amended and restated, the "Note"); and

            WHEREAS, the Note is described in a certain Credit Agreement dated
as of September 7, 1999 made by and among Borrowers and Bank (as amended, the
"Loan Agreement," all capitalized terms used and not otherwise defined herein
shall have the respective meanings ascribed to them in the Loan Agreement); and

            WHEREAS, Borrowers and Bank desire to amend the Loan Agreement and
the Note to increase the maximum available principal amount thereunder and to
make certain other amendments thereto on the terms and conditions set forth
herein;

            NOW, THEREFORE, in consideration of the premises and the mutual
provisions and agreements hereinafter set forth, the parties hereto do hereby
mutually promise and agree as follows:

            1.    The Note shall be amended and restated in the form of that
certain Revolving Credit Note attached hereto as Exhibit C, to increase the
maximum principal amount thereof to Twelve Million Three Hundred Fifty Thousand
Dollars ($12,350,000.00) for the period of time up to and including February 28,
2000, reducing automatically on February 29, 2000 to the new maximum amount of
Twelve Million Fifty Thousand Dollars ($12,050,000.00) for the period up to and
including March 30, 2000, reducing automatically on March 31, 2000 to the new
maximum amount of Eleven Million Eight Hundred Thousand Dollars ($11,800,000.00)
for the period up to and including April 29, 2000, reducing automatically on
April 30, 2000 to the new maximum amount of Eleven Million Four Hundred Fifty
Thousand Dollars ($11,450,000.00) for the period up to and including May 30,
2000, reducing automatically on May 31, 2000 to the new maximum amount of Ten
Million Eight Hundred Thousand Dollars ($10,800,000.00) for the period up to and
including June 29, 2000, reducing automatically on June 30, 2000 to the new
maximum amount of Ten Million Two Hundred Thousand Dollars ($10,200,000.00) for
the period up to and including July 30, 2000, reducing automatically on July 31,
2000 to the new maximum amount of Nine Million Five Hundred Fifty Thousand
Dollars ($9,550,000.00) and thereafter reducing as set forth in Section 3.1(b)
of the Loan Agreement, and to make certain amendments as set forth therein. All
references in the Loan Agreement to the "Note," the "Revolving Credit Note" and
other references of similar import shall hereafter be amended and deemed to
refer to the Note in the form of the Revolving Credit Note, as amended and
restated in the form attached hereto as Exhibit C. Borrowers hereby agree that
on or before 5:00 p.m. (St. Louis time) on the last day of each month from
February 29, 2000 up to and including July 31, 1999, Borrowers shall jointly

<PAGE>

and severally repay to Bank, without any requirement of demand or notice from
Bank, an amount equal to the amount by which the outstanding principal balance
of the Note exceeds the maximum principal amounts set forth above as of such
month-end dates, together with all other amounts then due under the terms of the
Loan Agreement and the Note.

            2.    The third paragraph beginning with the word "WHEREAS" on the
first page of the Loan Agreement shall be deleted in its entirety and in its
place shall be substituted the following:

                  WHEREAS, Borrowers, including Virbac AH and Francodex which
      have been added as parties to the credit facilities, have requested that
      the aggregate amount thereof be increased to an aggregate principal amount
      of up to Twelve Million Three Hundred Fifty Thousand Dollars
      ($12,350,000.00) and otherwise amended on the terms and conditions set
      forth herein, of which joint and several loan facility from Bank Seven
      Million Dollars ($7,000,000.00) shall be subject to a Borrowing Base (as
      set forth herein) ("Facility A"), and the remaining Five Million Three
      Hundred Fifty Thousand Dollars ($5,350,000.00) shall be a reducing
      revolving credit line from Bank ("Facility B"), that on February 29, 2000
      the maximum principal amount of such loan facility and Facility B shall
      reduce automatically as set forth in Section 3.1(b) herein, and reducing
      thereafter pursuant to Section 3.1(b) herein during the period of time
      from March 1, 2000 up to and including July 31, 2002; and

            3.    Section 3.1(b) of the Loan Agreement shall be deleted in its
entirety and in its place shall be substituted the following:

                  (b)   Facility B. Subject to the terms and conditions hereof,
      during the Term of this Agreement, Bank hereby agrees to make such loans
      (individually, a "Facility B Loan" and collectively, the "Facility B
      Loans") to Borrowers, jointly and severally, as any of the Borrowers may
      from time to time request pursuant to Section 3.2. The aggregate principal
      amount of Facility B Loans which Bank, cumulatively, shall be required to
      have outstanding hereunder at any one time shall not exceed Five Million
      Three Hundred Fifty Thousand Dollars ($5,350,000.00) from December 31,
      1999 until February 28, 2000 which amount shall be reduced on February 29,
      2000 to the new maximum Facility B amount of Five Million Fifty Thousand
      Dollars ($5,050,000.00) for the period up to and including March 30, 2000,
      further reducing on March 31, 2000 to the new maximum Facility B amount of
      Four Million Eight Hundred Thousand Dollars ($4,800,000.00) for the period
      up to and including April 29, 2000, further reducing on April 30, 2000 to
      the new maximum Facility B amount of Four Million Four Hundred Fifty
      Thousand Dollars ($4,450,000.00) for the period up to and including May
      30, 2000, further reducing on May 31, 2000 to the new maximum Facility B
      amount of Three Million Eight Hundred Thousand Dollars ($3,800,000.00) for
      the period up to and including June 29, 2000, further reducing on June 30,
      2000 to the new maximum Facility B amount of Three Million Two Hundred
      Thousand Dollars ($3,200,000.00) for the period up to and including July
      30, 2000, further reducing on July 31, 2000 to the new maximum Facility B
      amount of Two Million Five Hundred Fifty Thousand Dollars ($2,550,000.00),
      and thereafter such maximum Facility B amount shall be reduced by One
      Hundred Fifty Thousand Dollars ($150,000.00) on each February 28, May 31,
      August 31 and November 30, commencing with the next such reduction on
      August 31, 2000. This commitment of Bank as so reduced from time to time
      is herein sometimes referred to as the "Bank's Facility B Commitment."
      Subject to the terms and conditions hereof, Borrowers may jointly and
      severally borrow, repay and reborrow such sums from Bank, provided,
      however, that the aggregate principal amount of all Facility B Loans

                                     - 2 -
<PAGE>

      outstanding under Bank's Facility B Commitment at any one time shall not
      exceed Bank's Facility B Commitment then available hereunder. Bank and
      Borrowers agree that all Loans (but not including Letters of Credit which
      in all cases shall be issued under Facility A) outstanding under this
      Agreement shall first be made under Facility B up to the Bank's Facility B
      Commitment, and then shall be made under Facility A, and all principal
      payments shall be applied, first to the outstanding principal under
      Facility A until paid in full, and then to the outstanding principal under
      Facility B. The Facility B Loans may be either (a) a Prime Loan, (b) a
      LIBOR Loan or (c) any combination thereof, as determined by the Borrowers
      and notified to the Bank in accordance with Section 3.2 herein, provided,
      however, that the amount of any Loan under this Section 3.1(b) which is a
      LIBOR Loan shall be for an aggregate principal amount of at least
      $500,000.00 or any larger multiple of $100,000.00.

            4.    Section 3.1(f) of the Loan Agreement shall be deleted in its
entirety and in its place shall be substituted the following:

                  (f)   Mandatory Repayments - Facility B. Commencing with the
      next such principal reduction on February 29, 2000, and on each of March
      31, 2000, April 30, 2000, May 31, 2000, June 30, 2000 and July 31, 2000
      and on each August 31, November 30, February 28 and May 31 thereafter
      during the Term of this Agreement, Borrowers shall jointly and severally
      pay to Bank in immediately available funds an amount equal to the
      difference between Bank's Facility B Commitment (as reduced on such date
      pursuant to the terms of Section 3.1(b) above) and the aggregate principal
      amount of all Facility B Loans then outstanding. In the event any such
      mandatory repayment shall be due on a day which is not a Business Day,
      then such payment shall be due on the immediately preceding Business Day.
      Such mandatory payments shall be applied first to the outstanding Facility
      B Loans which are Prime Loans, and second to Facility B Loans which are
      LIBOR Loans, provided, however, that any such repayment of LIBOR Loans
      made on any date other than the last day of the applicable Interest Period
      for such LIBOR Loan shall be subject to payment jointly and severally by
      Borrowers of the amounts due under Section 3.8 below.

            5.    The last sentence of Section 3.2 of the Loan Agreement shall
be deleted in its entirety and in its place shall be substituted the following:

      Contemporaneously with the execution of that certain Amendment to Credit
      Agreement dated as of December ___, 1999 amending this Agreement,
      Borrowers shall execute and deliver to Bank a Note of Borrowers dated as
      of December ___, 1999 and payable jointly and severally to the order of
      Bank in the original principal amount of Twelve Million Three Hundred
      Fifty Thousand Dollars ($12,350,000.00) in the form attached as Exhibit C
      to such Amendment to Credit Agreement and incorporated herein by reference
      (as the same may from time to time be amended, modified, extended or
      renewed, the "Note").

            6.    Section 7.1(i)(i) of the Loan Agreement shall be deleted in
its entirety and in its place shall be substituted the following:

                  (i)   Maintain a ratio of Consolidated EBITDA minus permitted
      purchases by Borrowers of any of the outstanding capital stock of Virbac
      during any such period (determined on a consolidated basis for Borrowers
      and their Consolidated Subsidiaries and in accordance with Generally
      Accepted Accounting Principles

                                     - 3 -
<PAGE>

      consistently applied, for the applicable period ending on the date of any
      such calculation), to Consolidated Debt Service (which for any such
      calculations prior to January 1, 2000 shall be determined using Virbac's
      and its Consolidated Subsidiaries' actual principal reductions made or
      required on all long term borrowed money Indebtedness during the period
      included in any such calculation instead of scheduled principal payments
      during the period of equal length following the date of any such
      calculation) of at least (A) 1.25 to 1.0 for the two quarter period ending
      June 30, 1999, (B) 1.25 to 1.0 for the seven month period ending July 31,
      1999, (C) 1.25 to 1.0 for the eight month period ending August 31, 1999,
      (D) 1.50 to 1.0 for the three quarter period ending September 30, 1999,
      (E) 1.50 to 1.0 for the ten month period ending October 31, 1999, (F) 1.50
      to 1.0 for the eleven month period ending November 30, 1999, (G) 1.75 to
      1.0 for the four quarter period ending December 31, 1999, (H) 1.75 to 1.0
      for the four quarter period ending January 31, 2000, (I) 1.75 to 1.0 for
      the four quarter period ending February 29, 2000, (J) 1.75 to 1.0 for the
      four quarter period ending March 31, 2000, (K) 1.75 to 1.0 for the four
      quarter period ending April 30, 2000, (L) 1.75 to 1.0 for the four quarter
      period ending May 31, 2000, (M) 1.75 to 1.0 for the four quarter period
      ending June 30, 2000, and (N) 2.00 to 1.0 for the four quarter period
      ending at each month-end and fiscal year end thereafter during the Term
      hereof;

            7.    In consideration of Bank's agreement to amend the Loan
Agreement and Note as set forth herein and to amend the covenants as set forth
herein, Borrowers agree to jointly and severally pay to Bank an amendment fee in
the amount of $12,500.00, of which $6,250.00 was paid on December 29, 2000 and
the remaining $6,250.00 of which amendment fee is due and payable on the date
hereof and all of such amendment fee shall be fully earned on each date upon
which it is due and payable.

            8.    The agreements of Bank contained herein are expressly
conditioned upon deliver by Borrowers of the following:

                  (a)   the executed original of this Amendment to Credit
Agreement;

                  (b)   the executed original of the amended and restated Note;

                  (c)   a copy of resolutions of the Board of Directors of each
of the Borrowers, duly adopted, which authorize the execution, delivery and
performance of this Amendment to Credit Agreement and the amended and restated
Note and the other Transaction Documents, certified by the Secretary of each
such Borrower;

                  (d)   the written consent to these amendments signed by Ramon
Mulholland as holder of the subordinated debt, which consent shall be in form
and substance acceptable to Bank;

                  (e)   such other documents as Bank may reasonably request; and

                  (f)   payment by Borrowers of the amendment fee required under
paragraph 7 above.

            9.    Borrowers hereby represent and warrant to Bank that:

                  (a)   The execution, delivery and performance by Borrowers of
this Amendment to Credit Agreement and the amended and restated Revolving Credit
Note are within the corporate powers of Borrowers, have been duly authorized by
all necessary corporate action and require no action by or in respect of, or
filing with, any governmental or regulatory body, agency or official. The

                                     - 4 -
<PAGE>

execution, delivery and performance by Borrowers of this Amendment to Credit
Agreement and the amended and restated Revolving Credit Note do not conflict
with, or result in a breach of the terms, conditions or provisions of, or
constitute a default under or result in any violation of, and none of the
Borrowers is now in default under or in violation of, the terms of the Articles
of Incorporation or Bylaws of such Borrower, any applicable law, any rule,
regulation, order, writ, judgment or decree of any court or governmental or
regulatory agency or instrumentality, or any agreement or instrument to which
any of the Borrowers is a party or by which any of them is bound or to which any
of them is subject;

                  (b)   This Amendment to Credit Agreement and the amended and
restated Revolving Credit Note have been duly executed and delivered and
constitute the legal, valid and binding obligations of Borrowers enforceable in
accordance with their terms; and

                  (c)   As of the date hereof, all of the covenants,
representations and warranties of Borrowers set forth in the Loan Agreement are
true and correct and no "Event of Default" (as defined therein) under or within
the meaning of the Loan Agreement has occurred and is continuing.

            10.   All references in the Loan Agreement to "this Agreement" and
any other references of similar import shall henceforth mean the Loan Agreement
as amended by this Amendment to Credit Agreement.

            11.   This Amendment to Credit Agreement and the amended and
restated Revolving Credit Note shall be binding upon and inure to the benefit of
the parties hereto and their respective successors and assigns, except that
Borrowers may not assign, transfer or delegate any of their rights or
obligations hereunder.

            12.   This Amendment to Credit Agreement shall be governed by and
construed in accordance with the internal laws of the State of Missouri.

            13.   In the event of any inconsistency or conflict between this
Amendment to Credit Agreement and the Loan Agreement, the terms, provisions and
conditions of this Amendment to Credit Agreement shall govern and control.

            14.   The Loan Agreement, as hereby amended and modified, and the
amended and restated Revolving Credit Note, as hereby amended and restated, are
and shall remain the binding obligations of Borrowers and all of the provisions,
terms, stipulations, conditions, covenants and powers contained therein shall
stand and remain in full force and effect, except only as the same are herein
and hereby specifically varied or amended, and the same are hereby ratified and
confirmed. If any installment of principal or interest on the amended and
restated Revolving Credit Note shall not be paid when due as provided in the
amended and restated Revolving Credit Note, the holder of the amended and
restated Revolving Credit Note shall be entitled to and may exercise all rights
and remedies under the amended and restated Revolving Credit Note and the Loan
Agreement, as amended.

            15.   ORAL AGREEMENTS OR COMMITMENTS TO LOAN MONEY, EXTEND CREDIT OR
TO FOREBEAR FROM ENFORCING REPAYMENT OF A DEBT, INCLUDING PROMISES TO EXTEND OR
RENEW SUCH DEBT, ARE NOT ENFORCEABLE. TO PROTECT BORROWERS AND BANK FROM ANY
MISUNDERSTANDING OR DISAPPOINTMENT, ANY AGREEMENTS REACHED BY BORROWERS AND BANK
COVERING SUCH MATTERS ARE CONTAINED IN THE LOAN AGREEMENT, AS AMENDED BY THIS
AGREEMENT, WHICH CONSTITUTES A COMPLETE AND EXCLUSIVE STATEMENT OF THE
AGREEMENTS BETWEEN BORROWERS AND BANK EXCEPT AS BORROWERS AND BANK MAY LATER
AGREE IN WRITING TO MODIFY.

                                     - 5 -
<PAGE>

THE LOAN AGREEMENT, AS AMENDED BY THIS AGREEMENT, EMBODIES THE ENTIRE AGREEMENT
AND UNDERSTANDING BETWEEN THE PARTIES HERETO AND SUPERSEDES ALL PRIOR AGREEMENTS
AND UNDERSTANDINGS (ORAL OR WRITTEN) RELATING TO THE SUBJECT MATTER HEREOF.

            IN WITNESS WHEREOF, the parties hereto have executed this instrument
as of the date first written above on this _____ day of December, 1999.

                             VIRBAC CORPORATION

                             By: _______________________________________________
                                 Bruce G. Baker, Executive Vice President

                             PM RESOURCES, INC.

                             By: _______________________________________________
                                 Bruce G. Baker, Executive Vice President

                             ST. JON LABORATORIES, INC.

                             By: _______________________________________________
                                 Bruce G. Baker, Executive Vice President

                             VIRBAC AH, INC.

                             By: _______________________________________________
                                 Bruce G. Baker, Executive Vice President

                             FRANCODEX LABORATORIES, INC.

                             By: _______________________________________________
                                 Bruce G. Baker, Executive Vice President

                         FIRST BANK

                         By: ___________________________________________________
                             Traci L. Dodson, Vice President

                                     - 6 -
<PAGE>

                                    EXHIBIT C

                              Revolving Credit Note

$12,350,000.00                                               St. Louis, Missouri
                                                              December ___, 1999

            FOR VALUE RECEIVED, on July 31, 2002 (or such subsequent anniversary
thereof as determined pursuant to Section 3.16 of the Loan Agreement
(hereinafter identified)), the undersigned, VIRBAC CORPORATION, a Delaware
corporation (formerly known as Agri-Nutrition Group Limited), PM RESOURCES,
INC., a Missouri corporation, ST. JON LABORATORIES, INC., a California
corporation, FRANCODEX LABORATORIES, INC., a Kansas corporation and VIRBAC AH,
INC., a Delaware corporation (collectively, the "Borrowers"), hereby jointly and
severally promise to pay to the order of FIRST BANK, a Missouri state banking
corporation ("Bank"), the principal sum of Twelve Million Three Hundred Fifty
Thousand Dollars ($12,350,000.00), or such lesser sum as may then be outstanding
hereunder. The aggregate principal amount which Bank shall be committed to have
outstanding under Facility A hereunder at any one time shall not exceed the
lesser of (i) Seven Million Dollars ($7,000,000.00), or (ii) the "Borrowing
Base" (as defined in the Loan Agreement (as hereinafter defined)), which amount
may be borrowed, paid, reborrowed and repaid, in whole or in part, subject to
the terms and conditions hereof and of the Loan Agreement hereinafter
identified. The aggregate principal amount which Bank shall be committed to have
outstanding under Facility B hereunder at any one time shall not exceed Five
Million Three Hundred Fifty Thousand Dollars ($5,350,000.00) as reduced from
time to time pursuant to Section 3.1(b) of the Loan Agreement hereinafter
identified, which amount may be borrowed, paid, reborrowed and repaid, in whole
or in part, subject to the terms and conditions hereof and of the Loan Agreement
hereinafter identified.

            Borrowers further jointly and severally promise to pay to the order
of Bank interest on the principal amount from time to time outstanding hereunder
prior to maturity from the date disbursed until paid at the rate or rates per
annum required by the Loan Agreement or otherwise selected by any of the
Borrowers as set forth in the Loan Agreement. All accrued and unpaid interest
with respect to each principal disbursement made hereunder shall be payable on
the dates set forth in Section 3.6 of the Loan Agreement and at the maturity of
this Note, whether by reason of acceleration or otherwise. After the maturity of
this Note, whether by reason of acceleration or otherwise, interest shall accrue
and be payable on demand on the entire outstanding principal balance hereunder
until paid at a rate per annum equal to Three and One-Half Percent (3.50%) over
and above the Prime Rate, fluctuating as and when said Prime Rate shall change.
All payments hereunder (other than prepayments) shall be applied first to the
payment of all accrued and unpaid interest, with the balance, if any, to be
applied to the payment of principal. All prepayments hereunder shall be applied
solely to the payment of principal.

            All payments of principal and interest hereunder shall be made in
lawful currency of the United States in Federal or other immediately available
funds at the office of Bank situated at 1281 Graham Road, Florissant, Missouri
63031, or at such other place as the holder hereof shall designate in writing.
Interest shall be computed on an actual day, 360-day year basis.

            Bank may record the date and amount of all loans and all payments of
principal and interest hereunder in the records it maintains with respect
thereto. Bank's books and records showing the account between Bank and Borrowers
shall be admissible in evidence in any action or proceeding and shall constitute
prima facie proof of the items therein set forth.

                                     - 7 -
<PAGE>

            This Note is the Note referred to in that certain Credit Agreement
dated as of September 7, 1999 made by and between Borrowers and Bank (as the
same may from time to time be amended, the "Loan Agreement"), to which Loan
Agreement reference is hereby made for a statement of the terms and conditions
upon which the maturity of this Note may be accelerated, and for other terms and
conditions, including prepayment, which may affect this Note. All capitalized
terms used herein and not otherwise defined shall have the meanings assigned to
such terms in the Loan Agreement.

            This Note is secured by that certain Security Agreement dated as of
May 14, 1998 executed by Virbac Corporation in favor of Bank, by that certain
Security Agreement dated as of May 14, 1998 and executed by PM Resources, Inc.
in favor of Bank, by that certain Security Agreement dated as of May 14, 1998
executed by St. JON Laboratories, Inc. in favor of Bank, by that certain
Security Agreement dated as of September 7, 1999 and executed by Virbac AH, Inc.
in favor of Bank and by that certain Security Agreement dated as of September 7,
1999 executed by Francodex Laboratories, Inc. in favor of Bank (as the same may
from time to time be amended, the "Security Agreements"), to which Security
Agreements reference is hereby made for a description of the security and a
statement of the terms and conditions upon which this Note is secured.

            This Note is also secured by that certain Deed of Trust and Security
Agreement dated September 9, 1993 and executed by PM Resources, Inc. in favor of
Katherine D. Knocke, as trustee for Bank (as the same may from time to time be
amended, the "Deed of Trust"), to which Deed of Trust reference is hereby made
for a description of the security and a statement of the terms and conditions
upon which this Note is secured.

            This Note is also secured by that certain Agreement of Pledge dated
as of September 7, 1999 and executed by Virbac Corporation in favor of Bank and
by that certain Agreement of Pledge dated as of September 7, 1999 and executed
by Virbac AH, Inc. in favor of Bank (collectively, as the same may from time to
time be amended, the "Pledge Agreements"), to which Pledge Agreements reference
is hereby made for a description of the additional security and a statement of
the terms and conditions upon which this Note is further secured.

            If any of the Borrowers shall fail to make any payment of any
principal of or interest on this Note as and when the same shall become due and
payable, or if an "Event of Default" (as defined therein) shall occur under or
within the meaning of the Loan Agreement, any of the Security Agreements, the
Deed of Trust or any of the Pledge Agreements, Bank may, at its option,
terminate its obligation to make any additional loans under this Note and Bank
may further declare the entire outstanding principal balance of this Note and
all accrued and unpaid interest thereon to be immediately due and payable.

            In the event that any payment of any principal of or interest on
this Note shall not be paid when due, whether by reason of acceleration or
otherwise, and this Note shall be placed in the hands of an attorney or
attorneys for collection or for foreclosure of any of the Security Agreements,
the Deed of Trust or any of the Pledge Agreements securing payment hereof or for
representation of Bank in connection with bankruptcy or insolvency proceedings
relating hereto, Borrowers jointly and severally promise to pay, in addition to
all other amounts otherwise due hereon, the reasonable costs and expenses of
such collection, foreclosure and representation, including, without limitation,
reasonable attorneys' fees and expenses (whether or not litigation shall be
commenced in aid thereof). All parties hereto severally waive presentment for
payment, demand, protest, notice of protest and notice of dishonor.

                                     - 8 -
<PAGE>

            This Note shall be governed by and construed in accordance with the
internal laws of the State of Missouri.

                                VIRBAC CORPORATION

                                By: ____________________________________________
                                    Bruce G. Baker, Executive Vice President

                                PM RESOURCES, INC.

                                By: ____________________________________________
                                    Bruce G. Baker, Executive Vice President

                                ST. JON LABORATORIES, INC.

                                By: ____________________________________________
                                    Bruce G. Baker, Executive Vice President

                                VIRBAC AH, INC.

                                By: ____________________________________________
                                    Bruce G. Baker, Executive Vice President

                                FRANCODEX LABORATORIES, INC.

                                By: ____________________________________________
                                    Bruce G. Baker, Executive Vice President

                                     - 9 -