FIRST AMENDMENT TO CREDIT AGREEMENT

                                                                   EXHIBIT 4.4.1
                                                                   -------------


                               FIRST AMENDMENT TO

                                CREDIT AGREEMENT


     This First Amendment to Credit Agreement (this "Amendment") is entered into
as of April 18, 2000, by and between IMPERIAL BANK, a California banking
corporation ("Bank") on the one hand, and Synbiotics Corporation ("Borrower") on
the other hand.

     WHEREAS, Borrower and Bank are parties to that certain Credit Agreement,
dated as of April 12, 2000 ( as otherwise amended, modified, revised,
supplemented or restated from time to time, the "Agreement"); and

     WHEREAS, the parties hereto desire to amend the Agreement in accordance
with the terms and conditions of this Amendment.

     NOW, THEREFORE, the parties agree as follows:

1.   Schedule 5.02 PERMITTED INDEBTEDNESS:

Add the following at the end of Schedule 5.02:

"Secured Promissory Note dated April 18, 2000 in the amount of One Million
Dollars ($1,000,000.00) from Synbiotics Corporation ("Maker") and Kirkegaard &
Perry Laboratories, Inc. ("Holder"), as secured by specific assets listed in
Exhibit B-1 to the Asset Purchase Agreement by and between Synbiotics
Corporation and Kirkegaard & Perry Laboratories, Inc. dated April 18, 2000."

2.   Schedule 5.03 PERMITTED LIENS:

Add the following at the end of Schedule 5.03:

"UCC Financing Statement, #_____________ to be filed on April 18, 2000 regarding
specific assets listed in Exhibit A to said financing statement and Exhibit B-1
to the Asset Purchase Agreement by and between Synbiotics Corporation and
Kirkegaard & Perry Laboratories, Inc. dated April 18, 2000

     Secured Party:  Kirkegaard & Perry Laboratories, Inc.
     Debtor:         Synbiotics Corporation "

3.   Section 5.05 ACQUISITION OR SALE OF BUSINESS; MERGER OR CONSOLIDATION:

In the third line of the second paragraph, delete "Exchange Agreement dated
April 14, 2000" and insert "Asset Purchase Agreement dated April 18, 2000"
therefor.

4.   Section 5.06 CAPITAL EXPENDITURES:

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In the second line of the second paragraph, delete "Exchange Agreement dated
April 14, 2000" and insert "Asset Purchase Agreement dated April 18, 2000"
therefor.

5.   Unless otherwise defined, all initially capitalized terms in this
Amendment shall be as defined in the Agreement. The Agreement, as amended
hereby, shall be and remain in full force and effect in accordance with its
respective terms and hereby is ratified and confirmed in all respects. Except as
expressly set forth herein, the execution, delivery, and performance of this
Amendment shall not operate as a waiver of, or as an amendment of, any right,
power, or remedy of Bank under the Agreement, as in effect prior to the date
hereof. Borrower ratifies and reaffirms the continuing effectiveness of all
promissory notes, guaranties, security agreements, mortgages, deeds of trust,
environmental agreements, and all other instruments, documents and agreements
entered into in connection with the Agreement.

6.   Borrower represents and warrants that the Representations and Warranties
contained in the Agreement are true and correct as of the date of this
Amendment, and that no Event of Default has occurred and is continuing.

7.   This Amendment may be executed in two or more counterparts, each of
which shall be deemed an original, but all of which together shall constitute
one instrument.

8.   As a condition to the effectiveness of this Amendment, Bank shall have
received, in form and substance satisfactory to Bank, the following:

     (a)  this Amendment, duly executed by Borrower;

     (b)  if requested by Bank, Bank shall have received a certified copy of the
          resolutions of Borrower's board of directors authorizing the execution
          and delivery of this Amendment and the execution and delivery of such
          other documents, instruments and agreements as Bank shall reasonably
          request; and

     (c)  such other documents, and completion of such other matters, as Bank
          may reasonably deem necessary or appropriate.

     IN WITNESS WHEREOF, the undersigned have executed this Amendment as of the
first date above written.

                                        SYNBIOTICS CORPORATION

                                        By: /s/ Xxxxxxx X. Xxxxx
                                           -----------------------------
                                                Xxxxxxx X Xxxxx

                                        Title:  Vice President - Finance


                                        IMPERIAL BANK

                                        By: /s/ Xxxxx X. Xxxxxx
                                           -----------------------------
                                                Xxxxx X. Xxxxxx

                                        Title:  Vice President

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