Document:

<PAGE>

                                                                     EXHIBIT 4.5

        FIRST AMENDMENT (this "Amendment"), dated as of November 20, 2001, to
the Vicar Operating, Inc. Senior Subordinated Notes Indenture (the "Company
Indenture"), dated as of September 20, 2000, by and among Vicar Operating, Inc.,
a Delaware corporation (the "Company"), the guarantors named therein and Chase
Manhattan Bank and Trust Company, National Association, a national banking
association organized under the federal laws of the United States, as trustee.
Capitalized terms used herein and not defined herein shall have the respective
meanings ascribed to such terms in the Company Indenture.

                                    RECITALS

        WHEREAS, the parties have agreed to amend the Company Indenture, but
only upon the terms and subject to the conditions set forth below,

        NOW, THEREFORE, in consideration of the premises and the mutual
agreements herein set forth, the parties hereto agree as follows:

1. Section 1.01 (Definitions). Section 1.01 of the Company Indenture shall be
amended by inserting the following terms with the following definitions thereof:

        "Company 144A Notes" shall mean the 9 7/8% Senior Subordinated Notes due
2009 to be issued by the Company pursuant to the Company 144A Notes Indenture in
an original aggregate principal amount of up to $175,000,000.

        "Company 144A Notes Indenture" shall mean the Indenture to be entered
into among the Company, the Guarantors (as defined therein) and the trustee
named therein, pursuant to which the Company 144A Notes shall be issued..

2.      Section 1.01 (Definitions).

        a. Clause (iii) of the definition of "Change of Control" in Section 1.01
of the Company Indenture shall be amended to read in its entirety as follows:

"(iii) the consummation of any transaction (including, without limitation, any
merger or consolidation), as a result of which, (x) prior to a Note
Registration, (1) the Principals, Management Investors and their Related Parties
beneficially own and control, directly or indirectly, less than 40% of the
aggregate voting interest attributable to all outstanding Capital Stock of
Holdings, or (2) GEI and its Affiliates beneficially own, directly or
indirectly, less than 20% of the aggregate voting interest attributable to all
outstanding Capital Stock of Holdings, or (y) Holdings ceases to own directly
100% of the outstanding Equity Interests of the Company or (z) any Person or
"group" (within the meaning of Rules 13d-3 and 13d-5 under the Exchange Act),
other than the Principals, Management Investors or their Related Parties, shall
have acquired, directly or indirectly, beneficial ownership of 35% or more on a
fully diluted basis of the aggregate voting interest attributable to all
outstanding Capital Stock of Holdings or the Company and the Principals,
Management Investors or their Related Parties have less voting power than such
Person or "group" or"

<PAGE>

        b. The definition of "Consolidated Interest Expense" in Section 1.01 of
the Company Indenture shall be amended to read in its entirety as follows:

        "Consolidated Interest Expense" means for the applicable period of
measurement of the Company and its Subsidiaries on a consolidated basis, the
aggregate interest expense (whether or not payable in cash) for such period
(including all commissions, discounts, fees and other charges in connection with
standby letters of credit and similar instruments) for the Company and its
Subsidiaries on a consolidated basis, but excluding all amortization of
financing fees and other charges incurred by the Company and its Subsidiaries in
connection with the issuance of the Notes, the Company 144A Notes and the
borrowings under the Credit Agreement, minus interest income of the Company and
its Subsidiaries for such period, on a consolidated basis.

        c. The definition of "Consolidated EBITDA" in Section 1.01 of the
Company Indenture shall be amended to read in its entirety as follows:

        "Consolidated EBITDA" means for the applicable period of measurement,
the Consolidated Net Income of the Company and its Subsidiaries on a
consolidated basis, plus, without duplication, the following to the extent
deducted in calculating such Consolidated Net Income: (i) Consolidated Interest
Expense for such period, plus (ii) provisions for taxes based on income, plus
(iii) total depreciation expense, plus (iv) total amortization expenses, plus
(v) other non-cash items reducing Consolidated Net Income (excluding any such
non-cash item to the extent that it represents an accrual or reserve for
potential cash items in any future period or amortization of a prepaid cash item
but, notwithstanding anything to the contrary herein, including without
limitation, reserves for lease expenses and charges and expenses related to the
closure of hospitals to the extent not paid in cash), plus (vi) non-recurring
costs incurred by Holdings and its Subsidiaries in 1999 relating to year 2000
computer matters, plus (vii) other one-time non-recurring charges incurred by
Holdings, the Company or any of its Subsidiaries associated with the
consummation of Holdings' initial public offering and the issuance of the
Company 144A Notes,, including, without limitation (A) any non-cash charges
incurred by Holdings and/or the Company; provided that such non-cash charges
shall not exceed $10,400,000 in the aggregate; (B) a one-time payment to GEI;
provided that such one-time payment to GEI shall not exceed $8,000,000; and (C)
underwriting discounts and commissions and other reasonable costs and expenses
associated therewith, including reasonable legal fees and expenses, less other
non-cash items increasing Consolidated Net Income (excluding any such non-cash
item to the extent it represents the reversal of an accrual or reserve for
potential cash item in any prior period).

        d. The definition of "Holdings" in Section 1.01 of the Company Indenture
shall be amended to read in its entirety as follows:

        "Holdings" means VCA Antech, Inc., a Delaware corporation (formerly
known as Veterinary Centers of America, Inc.).

        e. Clause (i) of the definition of "Permitted Partially Owned
Subsidiary" in Section 1.01 of the Company Indenture shall be amended to read in
its entirety as follows:

                                       2
<PAGE>

"(i) with respect to each Permitted Partially Owned Subsidiary other than the
Exempt Subsidiaries, Capital Stock representing 51% or more of the aggregate
voting and economic interests in such Subsidiary is directly or indirectly
owned, beneficially and of record, by the Company,"

        f. Clause (iv) of the definition of "Permitted Partially Owned
Subsidiary" in Section 1.01 of the Company Indenture shall be amended to read in
its entirety as follows:

"(iv) at the time of designation of any Permitted Partially Owned Subsidiary as
such, that portion of Consolidated EBITDA attributable to all Permitted
Partially Owned Subsidiaries (including the Subsidiary proposed to be designated
as such) does not represent more than 15% of the Consolidated EBITDA for the
four-Fiscal Quarter period most recently ended."

        g. The definition of "Seller Notes" in Section 1.01 of the Company
Indenture shall be amended to read in its entirety as follows:

        "Seller Notes" means, collectively, any unsecured promissory notes
issued by Holdings to any seller or sellers in connection with a Permitted
Acquisition which are permitted to be incurred under Section 5.04(b)(xi) of the
Holdings Indenture.

3. Section 5.04 (Incurrence of Indebtedness and Issuances of Disqualified
Capital Stock or Preferred Stock).

        The final proviso of the final sentence of Section 5.04(a) shall be
amended to read in its entirety as follows:

"provided, however, such calculations of Adjusted EBITDA with respect to
Permitted Acquisitions, the consideration for which constitutes $3,000,000 or
less, shall be based on reasonable estimations of such pre-acquisition Adjusted
EBITDA based on actual pre-acquisition revenues."

4. Company Indenture Remains in Effect. Except as expressly amended herein, the
Company Indenture shall continue to be, and shall remain, in full force and
effect. This Amendment shall not be deemed to be a waiver of, or consent to, or
a modification or amendment of, any other term or condition of the Company
Indenture or the Notes or to prejudice any other right or rights which the
holders of the Notes may now have or may have in the future under or in
connection with the Company Indenture or any of the instruments or agreements
referred to therein, as the same may be amended from time to time.

5. Counterparts. This Amendment may be executed by one or more of the parties
hereto in any number of separate counterparts (which may include counterparts
delivered by facsimile transmission) and all of said counterparts taken together
shall be deemed to constitute one and the same instrument.

                                       3
<PAGE>

6. GOVERNING LAW. THIS AMENDMENT SHALL BE GOVERNED BY, AND CONSTRUED IN
ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK BUT WITHOUT GIVING EFFECT TO
APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT THE APPLICATION OF
THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

7. Effectiveness. The effectiveness of this Amendment shall be contingent on the
execution of the Company 144A Notes Indenture, the sale of the Company 144A
Notes and the consummation of Holdings' initial public offering.

                                       4
<PAGE>

        IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed, as of the day and year first above written.

VICAR OPERATING, INC.

By:     /s/ Robert L. Antin
        Name:  Robert L. Antin
        Title: Chief Executive Officer and President

CHASE MANHATTAN BANK AND TRUST
COMPANY, NATIONAL ASSOCIATION

By:     /s/ Rose T. Maravilla
        Name:  Rose T. Maravilla
        Title:  Assistant Vice President

<PAGE>

GUARANTORS:

                      AAH MERGER CORPORATION
                      ACADEMY ANIMAL, INC.
                      ANDERSON ANIMAL HOSPITAL, INC.
                      ANIMAL CLINIC OF SANTA CRUZ, INC.
                      ANIMAL EMERGENCY CLINIC, P.C.
                      BEAUMONT VETERINARY ASSOCIATES, P.C.
                      BERLA, INC.
                      CACOOSING ANIMAL HOSPITAL, LTD.
                      CACOOSING PET CARE & NUTRITION CENTER, INC.
                      CLARMAR ANIMAL HOSPITAL, INC.
                      DETWILER VETERINARY CLINIC, INC.
                      DIAGNOSTIC VETERINARY SERVICE, INC.
                      EAGLE PARK ANIMAL CLINIC, INC.
                      EAGLE RIVER VETERINARY HOSPITAL, INC.
                      EDGEBROOK, INC.
                      FLORIDA VETERINARY LABORATORIES, INC.
                      FOX CHAPEL ANIMAL HOSPITAL, INC.
                      FREEHOLD, INC.
                      GLEN ANIMAL HOSPITAL, INC.
                      GOLDEN MERGER CORPORATION
                      H.B. ANIMAL CLINICS, INC.
                      HIGHLANDS ANIMAL HOSPITAL, , INC.
                      HOWELL BRANCH ANIMAL HOSPITAL, P.A.
                      LAKE JACKSON VETERINARY HOSPITAL, INC.
                      LAKEWOOD ANIMAL HOSPITAL, INC.
                      LAMMERS VETERINARY HOSPITAL, INC.
                      LEWELLING VETERINARY CLINIC, INC.
                      MILLER ANIMAL HOSPITAL
                      M.S. ANIMAL HOSPITALS, INC.
                      NEWARK ANIMAL HOSPITAL, INC.
                      NORTHERN ANIMAL HOSPITAL, INC.
                      NORTH ROCKVILLE VETERINARY HOSPITAL, INC.
                      NORTHSIDE ANIMAL HOSPITAL, P.C.
                      NOYES ANIMAL HOSPITAL, INC.
                      OAK HILL VETERINARY HOSPITAL, INC.
                      OLD TOWN VETERINARY ANIMAL HOSPITAL, INC.
                      PET PRACTICE (MASSACHUSETTS), INC.
                      PETS' RX, INC.
                      PETS' RX NEVADA, INC.
                      PPI OF PENNSYLVANIA, INC.
                      PRINCETON ANIMAL HOSPITAL, INC.
                      PROFESSIONAL VETERINARY SERVICES,  INC.
                      RIVIERA ANIMAL HOSPITAL, INC.

<PAGE>

                      ROBERTSON BLVD. ANIMAL HOSPITAL, INC.
                      ROSSMOOR CENTER ANIMAL CLINIC, INC.
                      ROSSMOOR - EL DORADO ANIMAL HOSPITAL, INC.
                      SAN VICENTE ANIMAL CLINIC
                      SILVER SPUR ANIMAL HOSPITAL, INC.
                      SOUTH COUNTY VETERINARY CLINIC, INC.
                      SPANISH RIVER ANIMAL HOSPITAL, INC.
                      TAMPA ANIMAL MEDICAL CENTER, INC.
                      THE PET PRACTICE (FLORIDA), INC.
                      THE PET PRACTICE (ILLINOIS), INC.
                      THE PET PRACTICE (MASSACHUSETTS), INC.
                      THE PET PRACTICE OF MICHIGAN, INC.
                      VCA ALABAMA, INC.
                      VCA ALBANY ANIMAL HOSPITAL, INC.
                      VCA ALBUQUERQUE, INC.
                      VCA ALL PETS ANIMAL COMPLEX, INC.
                      VCA ALPINE ANIMAL HOSPITAL, INC.
                      VCA ANDERSON OF CALIFORNIA ANIMAL HOSPITAL, INC.
                      VCA ANIMAL HOSPITALS, INC.
                      VCA ANIMAL HOSPITAL WEST, INC.
                      VCA APAC ANIMAL HOSPITAL, INC.
                      VCA - ASHER, INC.
                      VCA BAY AREA ANIMAL HOSPITAL, INC.
                      VCA CACOOSING ANIMAL HOSPITAL, INC.
                      VCA CASTLE SHANNON VETERINARY HOSPITAL, INC.
                      VCA CENTERS-TEXAS, INC.
                      VCA CENVET, INC.
                      VCA CLARMAR ANIMAL HOSPITAL, INC.
                      VCA CLINICAL VETERINARY LABS, INC.
                      VCA CLINIPATH LABS, INC.
                      VCA CLOSTER, INC.
                      VCA DETWILER ANIMAL HOSPITAL, INC.
                      VCA DOVER ANIMAL HOSPITAL, INC.
                      VCA EAGLE RIVER ANIMAL HOSPITAL, INC.
                      VCA EAST ANCHORAGE ANIMAL HOSPITAL, INC.
                      VCA GOLDEN COVE ANIMAL HOSPITAL, INC.
                      VCA GREATER SAVANNAH ANIMAL HOSPITAL, INC.
                      VCA HOWELL BRANCH ANIMAL HOSPITAL, INC.
                      VCA INFORMATION SYSTEMS, INC.
                      VCA KANEOHE ANIMAL HOSPITAL, INC.
                      VCA LAKESIDE ANIMAL HOSPITAL, INC.
                      VCA LAMB AND STEWART ANIMAL HOSPITAL, INC.
                      VCA LAMMERS ANIMAL HOSPITAL, INC.
                      VCA LEWIS ANIMAL HOSPITAL, INC.
                      VCA MARINA ANIMAL HOSPITAL, INC.

<PAGE>

                      VCA MILLER ANIMAL HOSPITAL, INC.
                      VCA - MISSION, INC.
                      VCA NORTHBORO ANIMAL HOSPITAL, INC.
                      VCA NORTHWEST VETERINARY  DIAGNOSTICS, INC.
                      VCA OF COLORADO-ANDERSON, INC.
                      VCA OF NEW YORK, INC.
                      VCA OF SAN JOSE, INC.
                      VCA OF TERESITA, INC.
                      VCA PROFESSIONAL ANIMAL LABORATORY, INC.
                      VCA REAL PROPERTY ACQUISITION CORPORATION
                      VCA REFERRAL ASSOCIATES ANIMAL HOSPITAL, INC.
                      VCA ROHRIG ANIMAL HOSPITAL, INC.
                      VCA - ROSSMOOR, INC.
                      VCA ST. PETERSBURG ANIMAL HOSPITAL, INC.
                      VCA SILVER SPUR ANIMAL HOSPITAL, INC.
                      VCA SOUTH SHORE ANIMAL HOSPITAL, INC.
                      VCA SPECIALTY PET PRODUCTS, INC.
                      VCA SQUIRE ANIMAL HOSPITAL, INC.
                      VCA TEXAS MANAGEMENT, INC.
                      VCA WYOMING ANIMAL HOSPITAL, INC.
                      VETERINARY HOSPITALS, INC.
                      WEST LOS ANGELES VETERINARY MEDICAL GROUP, INC.
                      WESTWOOD DOG & CAT HOSPITAL
                      W.E. ZUSCHLAG, D.V.M., WORTH ANIMAL HOSPITAL, CHARTERED
                      WILLIAM C. FOUTS, D.V.M., LTD.
                      WINGATE, INC.

                               By:  /s/ Robert L. Antin
                                    Name:  Robert L. Antin
                                    Title: Chief Executive Officer and President

                               By:  /s/ Tomas W. Fuller
                                    Name:  Tomas W. Fuller
                                    Title: Chief Financial Officer and Assistant
                                           Secretary

<PAGE>

VCA VILLA ANIMAL HOSPITAL, L.P.

By:     VCA Animal Hospitals, Inc.,
        General Partner

By:     /s/ Robert L. Antin
        Name:  Robert L. Antin
        Title: Chief Executive Officer and President

By:     /s/ Tomas W. Fuller
        Name:  Tomas W. Fuller
        Title: Chief Financial Officer and Assistant
               Secretary

VETERINARY CENTERS OF AMERICA - TEXAS, L.P.

By:  VCA Centers-Texas, Inc., General Partner

By:     /s/ Robert L. Antin
        Name:  Robert L. Antin
        Title: Chief Executive Officer and President

By:     /s/ Tomas W. Fuller
        Name:  Tomas W. Fuller
        Title: Chief Financial Officer and Assistant
               Secretary

<PAGE>

ANIMAL CENTER, INC.

By:     /s/ Robert L. Antin
        Name:
        Title:

ASSOCIATES IN PET CARE, S.C.

By:     /s/ Robert L. Antin
        Name:
        Title:

KIRKWOOD ANIMAL HOSPITAL - LEA
M.E. TAMMI, V.M.D., P.A.

By:     /s/ Robert L. Antin
        Name:
        Title:

MAIN STREET SMALL ANIMAL HOSPITAL, INC.

By:     /s/ Robert L. Antin
        Name:
        Title:

SOUTHEAST AREA VETERINARY MEDICAL
CENTER, P.C.

By:     /s/ Robert L. Antin
        Name:
        Title:

<PAGE>

VCA ASSOCIATE ANIMAL HOSPITAL, L.P.

By:     /s/ Robert L. Antin
        Name:
        Title:

VCA HERITAGE ANIMAL HOSPITAL, L.P.

By:     /s/ Robert L. Antin
        Name:
        Title:

TOMS RIVER VETERINARY HOSPITAL, P.A.

By:     /s/ Robert L. Antin
        Name:
        Title:

<PAGE>

Agreed to and accepted by:

GS MEZZANINE PARTNERS II, L.P.

By:     GS Mezzanine Advisors II, L.L.C.,
        its general partner

By:     /s/ Katherine L. Nissenbaum
        Name:  Katherine L. Nissenbaum
        Title:  Vice President

GS MEZZANINE PARTNERS II OFFSHORE, L.P.

By:     GS Mezzanine Advisors II, L.L.C.
        its general partner

By:     /s/ Katherine L. Nissenbaum
        Name:  Katherine L. Nissenbaum
        Title: Vice President

TCW LEVERAGED INCOME TRUST, L.P.

By:     TCW Advisers (Bermuda), Ltd.
        as its General Partner

By:     /s/ Mark D. Senkpiel
        Name:  Mark D. Senkpiel
        Title:  Managing Director

By:     TCW Investment Management Company
        as Investment Adviser

By:     /s/ Jean-Marc Chapus
        Name:  Jean-Marc Chapus
        Title:  Managing Director

<PAGE>

TCW LEVERAGED INCOME TRUST II, L.P.

By:     TCW (LINC II), L.P.
        as its General Partner

By:     TCW Advisers (Bermuda), Ltd.
        its General Partner

By:     /s/ Mark D. Senkpiel
        Name:  Mark D. Senkpiel
        Title:  Managing Director

By:     TCW Investment Management Company
        as Investment Adviser

By:     /s/ Jean-Marc Chapus
        Name:  Jean-Marc Chapus
        Title:  Managing Director

<PAGE>

TCW LEVERAGED INCOME TRUST IV, L.P.

By:     TCW Asset Management Company
        As its Investment Adviser

By:     /s/ Mark D. Senkpiel
        Name:  Mark D. Senkpiel
        Title:  Managing Director

By:     /s/ Jean-Marc Chapus
        Name:  Jean-Marc Chapus
        Title:  Managing Director

By:     TCW (LINC IV), L.L.C.
        As General Partner

By:     TCW Asset Management Company
        As its Managing Member

By:     /s/ Mark D. Senkpiel
        Name:  Mark D. Senkpiel
        Title:  Managing Director

By:     /s/ Jean-Marc Chapus
        Name:  Jean-Marc Chapus
        Title:  Managing Director

TCW/CRESCENT MEZZANINE PARTNERS II, L.P.

By:     TCW/Crescent Mezzanine II, L.P.
        its general partner or managing owner

By:     TCW/Crescent Mezzanine, L.L.C.
        its general partner

By:     /s/ Jean-Marc Chapus
        Name:  Jean-Marc Chapus
        Title:  Managing Director

<PAGE>

TCW/CRESCENT MEZZANINE TRUST II

By:     TCW/Crescent Mezzanine II, L.P.
        its general partner or managing owner

By:     TCW/Crescent Mezzanine, L.L.C.
        its general partner

By:     /s/ Jean-Marc Chapus
        Name:  Jean-Marc Chapus
        Title:  Managing Director

THE NORTHWESTERN MUTUAL LIFE INSURANCE COMPANY

By:     /s/ Richard A. Strait
        Name: Richard A. Strait
        Title: Its Authorized Representative<PAGE>

                                                                    EXHIBIT 4.7

        FIRST AMENDMENT (this "Amendment"), dated as of November 20, 2001, to
the VCA Antech, Inc. Senior Notes Indenture (the "Holdings Indenture"), dated as
of September 20, 2000, by and between VCA Antech, Inc., a Delaware corporation
(formerly known as Veterinary Centers of America, Inc.) ("Holdings"), and Chase
Manhattan Bank and Trust Company, National Association, a national banking
association organized under the federal laws of the United States, as trustee.
Capitalized terms used herein and not defined herein shall have the respective
meanings ascribed to such terms in the Holdings Indenture.

                                    RECITALS

        WHEREAS, the parties have agreed to amend the Holdings Indenture, but
only upon the terms and subject to the conditions set forth below,

        NOW, THEREFORE, in consideration of the premises and the mutual
agreements herein set forth, the parties hereto agree as follows:

1.      Section 1.01 (Definitions). Section 1.01 of the Holdings Indenture shall
be amended by inserting the following terms with the following definitions
thereof:

        "Company 144A Notes" means the 9 7/8% Senior Subordinated Notes due 2009
to be issued by the Company pursuant to the Company 144A Notes Indenture in an
original aggregate principal amount of up to $175,000,000.

        "Company 144A Notes Indenture" means the Indenture to be entered into
among the Company, the Guarantors (as defined therein) and the trustee named
therein, pursuant to which the Company 144A Notes shall be issued.

        "Company Purchase Agreement" means the Purchase Agreement, dated as of
the Closing Date, by and among the Company, the Guarantors and the Purchasers.

2.      Section 1.01 (Definitions).

        a. Clause (iii) of the definition of "Change of Control" in Section 1.01
of the Company Indenture shall be amended to read in its entirety as follows:

"(iii) the consummation of any transaction (including, without limitation, any
merger or consolidation), as a result of which, (x) prior to a Note
Registration, (1) the Principals, Management Investors and their Related Parties
beneficially own and control, directly or indirectly, less than 40% of the
aggregate voting interest attributable to all outstanding Capital Stock of
Holdings, or (2) GEI and its Affiliates beneficially own, directly or
indirectly, less than 20% of the aggregate voting interest attributable to all
outstanding Capital Stock of Holdings, or (y) Holdings ceases to own directly
100% of the outstanding Equity Interests of the Company or (z) any Person or
"group" (within the meaning of Rules 13d-3 and 13d-5 under the Exchange Act),
other than the Principals, Management Investors or their Related Parties, shall
have acquired, directly or indirectly, beneficial ownership of 35% or more on a
fully diluted basis of the aggregate voting interest attributable to all
outstanding Capital Stock of Holdings and the

<PAGE>

Principals, Management Investors or their Related Parties have less voting power
than such Person or "group" or"

        b. The definition of "Consolidated EBITDA" in Section 1.01 of the
Company Indenture shall be amended to read in its entirety as follows:

        "Consolidated EBITDA" means for the applicable period of measurement,
the Consolidated Net Income of Holdings and its Subsidiaries on a consolidated
basis, plus, without duplication, the following to the extent deducted in
calculating such Consolidated Net Income: (i) Consolidated Interest Expense for
such period, plus (ii) provisions for taxes based on income, plus (iii) total
depreciation expense, plus (iv) total amortization expense, plus (v) other
non-cash items reducing Consolidated Net Income (excluding any such non-cash
item to the extent that it represents an accrual or reserve for potential cash
items in any future period or amortization of a prepaid cash item but,
notwithstanding anything to the contrary herein, including, without limitation,
reserves for lease expenses and charges and expenses related to the closure of
hospitals to the extent not paid in cash), all fees and expenses incurred in
connection with the Merger and the financing thereof, including all non-compete
payments, employment contract termination payments, deferred payments for
restricted Capital Stock of Holdings and stay bonuses made in connection with
the Merger and identified on Schedule 1(q) to the Purchase Agreement; plus (vi)
non-recurring costs incurred by Holdings and its Subsidiaries in 1999 relating
to year 2000 computer matters; plus (vii) other one-time non-recurring charges
incurred by Holdings, the Company or any of its Subsidiaries associated with the
consummation of Holdings' initial public offering and the issuance of the
Company 144A Notes, including, without limitation (A) any non-cash charges
incurred by Holdings and/or the Company; provided that such non-cash charges
shall not exceed $10,400,000 in the aggregate; (B) a one-time payment to GEI;
provided that such one-time payment to GEI shall not exceed $8,000,000; and (C)
underwriting discounts and commissions and other reasonable costs and expenses
associated therewith, including reasonable legal fees and expenses, less other
non-cash items increasing Consolidated Net Income (excluding any such non-cash
item to the extent it represents the reversal of an accrual or reserve for
potential cash item in any prior period).

        c. The definition of "Consolidated Interest Expense" in Section 1.01 of
the Holdings Indenture shall be amended to read in its entirety as follows:

        "Consolidated Interest Expense" means for the applicable period of
measurement of Holdings and its Subsidiaries on a consolidated basis, the
aggregate interest expense (whether or not payable in cash) for such period
(including all commissions, discounts, fees and other charges in connection with
standby letters of credit and similar instruments) for Holdings and its
Subsidiaries on a consolidated basis, but excluding all amortization of
financing fees and other charges incurred by Holdings and its Subsidiaries in
connection with the issuance of the Notes, the issuance of the Company Notes,
the issuance of the Company 144A Notes and the borrowings under the Credit
Agreement, minus interest income of Holdings and its Subsidiaries for such
period, on a consolidated basis.

        d. Clause (i) of the definition of "Permitted Partially Owned
Subsidiary" in Section 1.01 of the Holdings Indenture shall be amended to read
in its entirety as follows:

                                       2
<PAGE>

"(i) with respect to each Permitted Partially Owned Subsidiary other than the
Exempt Subsidiaries, Capital Stock representing 51% or more of the aggregate
voting and economic interests in such Subsidiary is directly or indirectly
owned, beneficially and of record, by the Company,"

        e. Clause (iv) of the definition of "Permitted Partially Owned
Subsidiary" in Section 1.01 of the Holdings Indenture shall be amended to read
in its entirety as follows:

"(iv) at the time of designation of any Permitted Partially Owned Subsidiary as
such, that portion of Consolidated EBITDA attributable to all Permitted
Partially Owned Subsidiaries (including the Subsidiary proposed to be designated
as such) does not represent more than 15% of the Consolidated EBITDA for the
four-Fiscal Quarter period most recently ended."

3.      Section 5.02 (Restricted Payments).

        Section 5.02(a) of the Holdings Indenture shall be amended to read in
its entirety as follows:

        "(a) Holdings shall not, and shall not permit any of its Subsidiaries
to, (i) declare or make any dividend payment or other distribution of assets,
properties, cash, rights, obligations or securities on account of any shares of
any class of Capital Stock or other Equity Interests of, including any payment
in connection with a merger or consolidation involving Holdings or any of its
Subsidiaries, (ii) purchase, redeem or otherwise acquire for value any shares of
Capital Stock or other Equity Interests of Holdings or any of its Subsidiaries
now or hereafter outstanding, (iii) make any payment or prepayment of principal
of, premium, if any, interest, redemption, exchange, purchase, retirement,
defeasance, sinking fund or other payment with respect to, any Subordinated
Indebtedness or (iv) make any Restricted Investments (the items described in
clauses (i), (ii), (iii), and (iv) are referred to as "Restricted Payments");
except that Holdings, the Company or any Subsidiary of the Company may make a
Restricted Payment if at the time of and after giving effect to such Restricted
Payment;

                        (A) no Default or Event of Default shall have occurred
                and be continuing or would occur as a consequence thereof; and

                        (B) Holdings or the Company, as the case may be, would,
                at the time such Restricted Payment was made and after giving
                pro forma effect thereto as if such Restricted Payment had been
                made at the beginning of the applicable four-Fiscal Quarter
                period, have been permitted to incur at least $1.00 of
                additional Indebtedness pursuant to the Coverage Ratio Test set
                forth in Section 5.04(a) hereof;

                        (C) if being made by the Company or any of its
                Subsidiaries, such Restricted Payment, together with the
                aggregate of all other Restricted Payments made by the Company
                and its Subsidiaries after the date of this Indenture (excluding
                Restricted Payments permitted by the next succeeding paragraph
                (b)), is less than the sum of (1) 50% of the Consolidated Net
                Income of

                                       3
<PAGE>

                the Company for the period (taken as one accounting period) from
                the beginning of the first Fiscal Quarter commencing after the
                date of this Indenture to the end of the Company's most recently
                ended Fiscal Quarter for which internal financial statements are
                available at the time of such Restricted Payment (or, if such
                Consolidated Net Income for such period is a deficit, less 100%
                of such deficit), plus (2) 100% of the aggregate net cash
                proceeds received by the Company from contributions of capital
                from Holdings to the Company since the date of this Indenture or
                the issue or sale since the date of this Indenture of Equity
                Interests of the Company or of debt securities of the Company
                that have been converted into such Equity Interests (other than
                Equity Interests (or convertible debt securities) sold to a
                Subsidiary of the Company and other than Disqualified Capital
                Stock or debt securities that have been converted into
                Disqualified Capital Stock), plus (3) to the extent that any
                Restricted Investment that was made after the date of this
                Indenture is sold for cash or otherwise liquidated or repaid for
                cash, the lesser of (x) the cash return of capital with respect
                to such Restricted Investment (less the cost of disposition, if
                any) and (y) the initial amount of such Restricted Investment;
                and

                        (D) if being made by Holdings, such Restricted Payment,
                together with the aggregate of all other Restricted Payments
                made by Holdings, the Company and its Subsidiaries after the
                date of this Amendment (excluding Restricted Payments permitted
                by the next succeeding paragraph (b) and excluding Restricted
                Payments made to Holdings as permitted in Clause (C) above), is
                less than the sum of (1) 50% of the Consolidated Net Income of
                Holdings for the period (taken as one accounting period) from
                the beginning of the first Fiscal Quarter commencing after the
                date of this Amendment to the end of the Company's most recently
                ended Fiscal Quarter for which internal financial statements are
                available at the time of such Restricted Payment (or, if such
                Consolidated Net Income for such period is a deficit, less 100%
                of such deficit), plus (2) 100% of the aggregate net cash
                proceeds received by Holdings from the issue or sale since the
                date of this Amendment of Equity Interests of Holdings or of
                debt securities of Holdings that have been converted into such
                Equity Interests (other than Equity Interests (or convertible
                debt securities) sold to a Subsidiary of Holdings and other than
                Disqualified Capital Stock or debt securities that have been
                converted into Disqualified Capital Stock), plus (3) to the
                extent that any Restricted Investment that was made after the
                date of this Indenture is sold for cash or otherwise liquidated
                or repaid for cash, the lesser of (x) the cash return of capital
                with respect to such Restricted Investment (less the cost of
                disposition, if any) and (y) the initial amount of such
                Restricted Investment."

4.      Section 5.04 (Incurrence of Indebtedness and Issuances of Disqualified
Capital Stock or Preferred Stock).

        a. The final proviso of the final sentence of Section 5.04(a) shall be
amended to read in its entirety as follows:

                                       4
<PAGE>

"provided, however, such calculations of Adjusted EBITDA with respect to
Permitted Acquisitions, the consideration for which constitutes $3,000,000 or
less, shall be based on reasonable estimations of such pre-acquisition Adjusted
EBITDA based on actual pre-acquisition revenues."

        b. A new Section 5.04(b)(xxi) shall be added to the Holdings Indenture
to read in its entirety as follows:

        "(xxi) the Guarantee by Holdings of Indebtedness under the Company 144A
Notes and the Company 144A Notes Indenture, provided that such Guarantee shall
be subordinated to the Notes and the Guarantee by Holdings of Indebtedness under
the Credit Documents to the same extent the Company 144A Notes are subordinated
in right of payment to "Senior Indebtedness" (as such term is defined in the
Company 144A Notes Indenture)."

5.      Section 7.01 (Events of Default).

        A new Section 7.01(h) shall be added to the Holdings Indenture to read
in its entirety as follows:

        "(h) an Event of Default (as defined in the Company 144A Notes
Indenture) occurs under the Company 144A Notes Indenture."

6.      Holdings Indenture Remains in Effect. Except as expressly amended
herein, the Holdings Indenture shall continue to be, and shall remain, in full
force and effect. This Amendment shall not be deemed to be a waiver of, or
consent to, or a modification or amendment of, any other term or condition of
the Holdings Indenture or the Notes or to prejudice any other right or rights
which the holders of the Notes may now have or may have in the future under or
in connection with the Holdings Indenture or any of the instruments or
agreements referred to therein, as the same may be amended from time to time.

7.      Counterparts. This Amendment may be executed by one or more of the
parties hereto in any number of separate counterparts (which may include
counterparts delivered by facsimile transmission) and all of said counterparts
taken together shall be deemed to constitute one and the same instrument.

8.      GOVERNING LAW. THIS AMENDMENT SHALL BE GOVERNED BY, AND CONSTRUED IN
ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK BUT WITHOUT GIVING EFFECT TO
APPLICABLE PRINCIPLES OF CONFLICTS OF LAW TO THE EXTENT THAT THE APPLICATION OF
THE LAWS OF ANOTHER JURISDICTION WOULD BE REQUIRED THEREBY.

9.      Effectiveness. The effectiveness of this Amendment shall be contingent
on the execution of the Company 144A Notes Indenture, the sale of the Company
144A Notes and the consummation of Holdings' initial public offering.

                                       5
<PAGE>

        IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed, as of the day and year first above written.

VCA ANTECH, INC.

By:     /s/ Robert L. Antin
        Name:  Robert L. Antin
        Title: Chief Executive Officer and President

CHASE MANHATTAN BANK AND TRUST
COMPANY, NATIONAL ASSOCIATION

By:     /s/ Rose T. Maravilla
        Name:  Rose T. Maravilla
        Title: Assistant Vice President

<PAGE>

Agreed to and accepted by:

GS MEZZANINE PARTNERS II, L.P.

By:     GS Mezzanine Advisors II, L.L.C.,
        its general partner

By:     /s/ Katherine L. Nissenbaum
        Name:  Katherine L. Nissenbaum
        Title: Vice President

GS MEZZANINE PARTNERS II OFFSHORE, L.P.

By:     GS Mezzanine Advisors II, L.L.C.
        its general partner

By:     /s/ Katherine L. Nissenbaum
        Name:  Katherine L. Nissenbaum
        Title: Vice President

TCW LEVERAGED INCOME TRUST, L.P.

By:     TCW Advisers (Bermuda), Ltd.
        as its General Partner

By:     /s/ Darryl L. Schall
        Name:  Darryl L. Schall
        Title: Managing Director

By:     TCW Investment Management Company
        as Investment Adviser

By:     /s/ Darryl L. Schall
        Name:  Darryl L. Schall
        Title: Managing Director

<PAGE>

TCW LEVERAGED INCOME TRUST II, L.P.

By:     TCW (LINC II), L.P.
        as its General Partner

By:     TCW Advisers (Bermuda), Ltd.
        its General Partner

By:     /s/ Mark D. Senkpiel
        Name:  Mark D. Senkpiel
        Title: Managing Director

By:     TCW Investment Management Company
        as Investment Adviser

By:     /s/ Darryl L. Schall
        Name:  Darryl L. Schall
        Title: Managing Director

<PAGE>

TCW LEVERAGED INCOME TRUST IV, L.P.

By:     TCW Asset Management Company
        As its Investment Adviser

By:     /s/ Mark D. Senkpiel
        Name:  Mark D. Senkpiel
        Title: Managing Director

By:     /s/ Darryl L. Schall
        Name:  Darryl L. Schall
        Title: Managing Director

By:     TCW (LINC IV), L.L.C.
        As General Partner

By:     TCW Asset Management Company
        As its Managing Member

By:     /s/ Mark D. Senkpiel
        Name:  Mark D. Senkpiel
        Title: Managing Director

By:     /s/ Darryl L. Schall
        Name:  Darryl L. Schall
        Title: Managing Director

TCW/CRESCENT MEZZANINE PARTNERS II, L.P.

By:     TCW/Crescent Mezzanine II, L.P.
        its general partner or managing owner

By:     TCW/Crescent Mezzanine, L.L.C.
        its general partner

By:     /s/ Darryl L. Schall
        Name:  Darryl L. Schall
        Title: Managing Director

<PAGE>

TCW/CRESCENT MEZZANINE TRUST II

By:     TCW/Crescent Mezzanine II, L.P.
        its general partner or managing owner

By:     TCW/Crescent Mezzanine, L.L.C.
        its general partner

By:     /s/ Darryl L. Schall
        Name:  Darryl L. Schall
        Title: Managing Director

THE NORTHWESTERN MUTUAL LIFE INSURANCE COMPANY

By:     /s/ Richard A. Strait
        Name:  Richard A. Strait
        Title: Its Authorized Representative

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