<PAGE>   1
                                                           Exhibit 10.6


                                                           STRICTLY CONFIDENTIAL

                               FIRST AMENDMENT TO
                              EMPLOYMENT AGREEMENT
                                     BETWEEN
                             DOANE PET CARE COMPANY
                                       AND
                                 DAVID L. HORTON


      THIS EMPLOYMENT AGREEMENT (this "Amendment") dated as of January 1, 2001
is made between Doane Pet Care Company (the "Company"), a Delaware corporation,
and David L. Horton (the "Executive"). This Agreement is made with reference to
the following facts and objectives:

                                    RECITALS

      A. The Company and Executive are parties to that certain Employment
Agreement dated January 1, 1998 (the "Original Agreement").

      B. The Company and Executive desire to amend the Original Agreement to
extend the non-compete period and the severance period for termination without
cause from one year to two years, in accordance with the provisions set forth
below.

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

                                    AGREEMENT

      1. Section 6 of the Original Agreement is hereby amended by deleting the
words "first anniversary" in the fourth line of Section 6 and replacing them
with the words "second anniversary".

      2. Section 9(c)(2) of the Original Agreement is hereby amended by deleting
the words "first anniversary" in the eighth line of subsection (2) and replacing
them with the words "second anniversary".

      3. The Company and Executive hereby ratify, confirm, adopt and approve the
terms of the Original Agreement, except as amended by the terms of this
Amendment.

             - The remainder of this page is intentionally left blank -

<PAGE>   2
      PLEASE NOTE: BY SIGNING THIS AMENDMENT, THE EXECUTIVE IS HEREBY CERTIFYING
THAT THE EXECUTIVE (A) RECEIVED A COPY OF THIS AMENDMENT FOR REVIEW AND STUDY
BEFORE EXECUTING IT; (B) READ THIS AMENDMENT CAREFULLY BEFORE SIGNING IT; (C)
HAD SUFFICIENT OPPORTUNITY BEFORE SIGNING THIS AMENDMENT TO ASK ANY QUESTIONS
THE EXECUTIVE HAD ABOUT THIS AMENDMENT AND RECEIVED SATISFACTORY ANSWERS TO ALL
SUCH QUESTIONS; (D) UNDERSTANDS THE EXECUTIVE'S RIGHTS AND OBLIGATIONS UNDER
THIS AMENDMENT; AND (E) EXECUTED AND DELIVERED THIS AMENDMENT AT THE OFFICES OF
THE COMPANY IN BRENTWOOD, TENNESSEE.

           EXECUTED AND EFFECTIVE as of the date first written above.

WITNESS:                                  DOANE PET CARE COMPANY


----------------------------------        ------------------------------
                                          Douglas J. Cahill
                                          President & CEO


WITNESS:                                  EXECUTIVE:


----------------------------------        ------------------------------
                                          David L. Horton