AMENDMENT NO. 4 TO CREDIT AGREEMENT

Exhibit 10.4

AMENDMENT NO. 4

TO

CREDIT AGREEMENT

THIS AMENDMENT NO. 4 TO CREDIT AGREEMENT (the “Amendment”) is made as of March 15, 2007 by and among Central Garden & Pet Company, a Delaware corporation (the “Company”), the institutions listed on the signature pages hereto and JPMorgan Chase Bank, National Association, as the administrative agent for the “Lenders” referred to below (the “Administrative Agent”). Capitalized terms used but not otherwise defined herein shall have the respective meanings given to them in the “Credit Agreement” referred to below.

WITNESSETH:

WHEREAS, the signatories hereto are parties to that certain Credit Agreement, dated as of February 28, 2006, among the Company, the Subsidiary Borrowers from time to time parties thereto, the financial institutions from time to time parties thereto (the “Lenders”) and the Administrative Agent (as amended by Amendment No. 1 thereto dated as of May 16, 2006, Amendment No. 2 thereto dated as of August 24, 2006, Amendment No. 3 thereto dated as of December 8, 2006 and as the same may from time to time be amended, restated, supplemented or otherwise modified, the “Credit Agreement”);

WHEREAS, the parties hereto have agreed to amend the Credit Agreement on the terms and conditions set forth herein;

NOW, THEREFORE, in consideration of the premises set forth above, the terms and conditions contained herein, and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Company, the Lenders and the Administrative Agent have agreed to the following amendment to the Credit Agreement.

1. Amendments. Effective as of the date hereof and subject to the satisfaction of the conditions precedent set forth in Section 2 below, the Credit Agreement is hereby amended as follows:

(a) Section 1.01 of the Credit Agreement is hereby amended to add the following new definitions in the appropriate alphabetical locations:

“Receivables Factoring Arrangement” has the meaning set forth in the defined term “Permitted Receivables Facility”.

“Receivables Securitization Facility” has the meaning set forth in the defined term “Permitted Receivables Facility”.

(b) Section 1.01 of the Credit Agreement is hereby amended to insert the words “, in the context of a Receivables Securitization Facility,” after the word “shall mean” in each of the definitions of “Receivables Entity” and “Standard Securitization Undertakings”.

(c) The definitions of “Permitted Receivables Facility” and “Permitted Receivables Facilities Assets” in Section 1.01 of the Credit Agreement are hereby amended and restated in their entirety as follows:

“Permitted Receivables Facility” shall mean a receivables facility or facilities created under Permitted Receivables Facility Documents, providing for:

(a) the sale or pledge by the Company and/or one or more other Receivables Sellers of Permitted Receivables Facility Assets (thereby providing financing to the Company and/or such Receivables Sellers) to the Receivables Entity (either directly or through another Receivables Seller), which in turn shall sell or pledge interests in the respective Permitted Receivables Facility Assets to third-party investors pursuant to the Permitted Receivables Facility Documents (with the Receivables Entity permitted to issue investor certificates, purchased interest certificates or other similar documentation evidencing interests in the Permitted Receivables Facility Assets) in return for the cash used by the Receivables Entity to purchase the Permitted Receivables Facility Assets from the Company and/or the respective Receivables Sellers, in each case as more fully set forth in the Permitted Receivables Facility Documents (a “Receivables Securitization Facility”); or

(b) the sale by the Company and/or one or more Receivables Sellers of Permitted Receivables Facility Assets (thereby providing financing to the Company and/or such Receivables Sellers) to a third party (other than an Affiliate) pursuant to arrangements under which such Permitted Receivables Facility Assets are factored on a non-recourse basis, as more fully set forth in the Permitted Receivables Facility Documents (a “Receivables Factoring Arrangement”);

provided, that (i) the maximum aggregate amount of Attributable Receivables Indebtedness permitted to be outstanding (and the actual amount outstanding) under all Receivables Securitization Facilities and Receivables Factoring Arrangements shall not exceed $100,000,000 at any time, and (ii) the investors or financiers party to any Receivables Securitization Facility or Receivables Factoring Arrangement shall have entered into an intercreditor agreement with the Administrative Agent, for itself and the Holders of Secured Obligations, in form and substance reasonably satisfactory to the Administrative Agent, providing for the treatment of Liens on the Permitted Receivables Facility Assets.

“Permitted Receivables Facility Assets” shall mean (i) Receivables (whether now existing or arising in the future) of the Company and its Subsidiaries which are transferred or pledged to the Receivables Entity, or transferred to a non-Affiliate third party, pursuant to the Permitted Receivables Facility, and any related assets that are customarily transferred or in respect of which security interests are customarily granted in connection with asset

securitization transactions or factoring arrangements involving receivables similar to Receivables and all proceeds and collections thereof, and (ii) loans to the Company and its Subsidiaries secured by Receivables (whether now existing or arising in the future) of the Company and its Subsidiaries which are made pursuant to a Receivables Securitization Facility.

(d) Section 6.04(e) of the Credit Agreement is hereby amended and restated in its entirety as follows:

(e) investments made in connection with a Permitted Receivables Facility that is a Receivables Securitization Facility;

(e) Clause (C) of Section 6.15(a) of the Credit Agreement is hereby amended and restated in its entirety and new clauses (D) and (E) are hereby inserted therein as follows:

(C) 2.75 to 1.00 commencing with and for the fiscal quarter ending in March 2007 through the fiscal quarter ending in June 2007;

(D) 3.00 to 1.00 commencing with and for the fiscal quarter ending in September 2007 through the fiscal quarter ending in June 2008; and

(E) 3.25 to 1.00 commencing with and for the fiscal quarter ending in September 2008 and for each fiscal quarter thereafter.

(f) Clauses (B), (C), (D) and (E) of Section 6.15(b) of the Credit Agreement are hereby amended and restated in their entirety and new clauses (F) and (G) are hereby inserted therein as follows:

(B) 4.50 to 1.00 for the fiscal quarter ending in December 2006;

(C) 4.75 to 1.00 commencing with and for the fiscal quarter ending in March 2007 through the fiscal quarter ending in June 2007;

(D) 4.25 to 1.00 commencing with and for the fiscal quarter ending in September 2007 through the fiscal quarter ending in June 2008;

(E) 4.00 to 1.00 commencing with and for the fiscal quarter ending in September 2008 through the fiscal quarter ending in June 2009;

(F) 3.75 to 1.00 for the fiscal quarter ending in September 2009; and

(G) 3.50 to 1.00 commencing with and for the fiscal quarter ending in December 2009 and for each fiscal quarter thereafter.

2. Conditions of Effectiveness. This Amendment shall become effective as of the date hereof if, and only if, the Administrative Agent shall have received: (a) executed copies of this Amendment from the Company and the Required Lenders; (b) executed copies of

the Reaffirmation attached hereto in the form of Exhibit A from the existing Subsidiary Guarantors; and (c) all fees agreed to be paid by the Company in connection with this Amendment.

3. Representations and Warranties of the Company. The Company hereby represents and warrants as follows:

(a) The Company has the power and authority and legal right to execute and deliver this Amendment and the Credit Agreement (as modified hereby) and to perform its obligations hereunder and thereunder. The execution and delivery by the Company of this Amendment and the performance of its obligations hereunder and under the Credit Agreement (as modified hereby) have been duly authorized by proper proceedings, and this Amendment and the Credit Agreement (as modified hereby) constitute legal, valid and binding obligations of the Company, enforceable against the Company in accordance with its terms, subject to applicable bankruptcy, insolvency, reorganization, moratorium or other laws affecting creditors’ rights generally and subject to general principles of equity, regardless of whether considered in a proceeding in equity or at law.

(b) Neither the execution and delivery by the Company of this Amendment, nor the consummation of the transactions herein contemplated, nor compliance with the provisions hereof or of the Credit Agreement (as modified hereby) (i) will require any consent or approval of, registration or filing with, or any other action by, any Governmental Authority, except such as have been obtained or made and are in full force and effect, (ii) will violate any applicable law or regulation or the charter, by-laws or other organizational documents of the Company or any of its Subsidiaries or any order of any Governmental Authority, (iii) will violate or result in a default under any indenture, agreement or other instrument binding upon the Company or any of its Subsidiaries or its assets (including, without limitation, the Senior Subordinated Note Indenture and the Senior Subordinated Notes), or give rise to a right thereunder to require any payment to be made by the Company or any of its Subsidiaries or (iv) will result in the creation or imposition of any Lien on any asset of the Company or any of its Subsidiaries.

(c) As of the date hereof and giving effect to the terms of this Amendment, (i) no Default has occurred and is continuing and (ii) the representations and warranties of the Company set forth in the Credit Agreement (as modified hereby) and the other Loan Documents are true and correct in all material respects (or, if any such representation or warranty is expressly stated to have been made as of a specific date, as of such specific date).

4. Reference to and Effect on the Credit Agreement and Loan Documents.

(a) Upon the effectiveness of this Amendment, each reference to the Credit Agreement in the Credit Agreement or any other Loan Document shall mean and be a reference to the Credit Agreement as modified hereby. This Amendment is a Loan Document pursuant to the Credit Agreement and shall (unless expressly indicated herein or therein) be construed, administered, and applied, in accordance with all of the terms and provisions of the Credit Agreement.

(b) The Company (i) agrees that this Amendment and the transactions contemplated hereby shall not limit or diminish the obligations of the Company arising under or pursuant to the Credit Agreement and the other Loan Documents to which it is a party, (ii) reaffirms its obligations under the Credit Agreement and each and every other Loan Document to which it is a party (including, without limitation, each applicable Collateral Document), (iii) reaffirms all Liens on the Collateral which have been granted by it in favor of the Administrative Agent (for itself and the other Holders of Secured Obligations) pursuant to any of the Loan Documents, and (iv) acknowledges and agrees that, except as specifically modified above, the Credit Agreement and all other Loan Documents executed and/or delivered in connection therewith shall remain in full force and effect and are hereby ratified and confirmed.

(c) The execution, delivery and effectiveness of this Amendment shall not, except as expressly provided herein, operate as a waiver of any right, power or remedy of the Administrative Agent or the Lenders, nor constitute a waiver of or consent to any modification of any provision of the Credit Agreement or any other Loan Documents executed and/or delivered in connection therewith.

5. Governing Law. This Amendment shall be construed in accordance with and governed by the law of the State of New York.

6. Headings. Section headings in this Amendment are included herein for convenience of reference only and shall not constitute a part of this Amendment for any other purpose.

7. Counterparts. This Amendment may be executed by one or more of the parties hereto on any number of separate counterparts (including by means of facsimile or electronic transmission), and all of said counterparts taken together shall be deemed to constitute one and the same instrument.

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IN WITNESS WHEREOF, this Amendment has been duly executed as of the day and year first above written.

EXHIBIT A

Reaffirmation

Each of the undersigned hereby acknowledges receipt of a copy of Amendment No. 4, dated as of March 15, 2007 (the “Amendment”), to the Credit Agreement, dated as of February 28, 2006, by and among Central Garden & Pet Company, a Delaware corporation (the “Company”), the subsidiary Borrowers from time to time parties thereto, the financial institutions from time to time parties thereto (the “Lenders”) and JPMorgan Chase Bank, National Association, as the administrative agent for the Lenders (the “Administrative Agent”) (as amended by Amendment No. 1 thereto dated as of May 16, 2006, Amendment No. 2 thereto dated as of August 24, 2006, Amendment No. 3 thereto dated as of December 8, 2006 and further amended by the Amendment, and as the same may from time to time hereafter be amended, restated, supplemented or otherwise modified, the “Credit Agreement”). Capitalized terms used in this Reaffirmation and not defined herein shall have the meanings given to them in the Credit Agreement.

Each of the undersigned, by its signature below, hereby (a) acknowledges and consents to the execution and delivery of the Amendment by the parties thereto, (b) agrees that the Amendment and the transactions contemplated thereby shall not limit or diminish the obligations of such Person arising under or pursuant to the Collateral Documents and the other Loan Documents to which it is a party, (c) reaffirms all of its obligations under the Loan Documents to which it is a party, (d) reaffirms all Liens on the Collateral which have been granted by it in favor of the Administrative Agent (for itself and the other Holders of Secured Obligations) pursuant to any of the Loan Documents, and (e) acknowledges and agrees that each Loan Document executed by it remains in full force and effect and is hereby reaffirmed, ratified and confirmed. All references to the Credit Agreement contained in any Loan Document shall be a reference to the Credit Agreement as so modified by the Amendment and as the same may from time to time hereafter be amended, restated, supplemented or otherwise modified. The Amendment is a Loan Document pursuant to the Credit Agreement and shall (unless expressly indicated therein) be construed, administered, and applied, in accordance with all of the terms and provisions of the Credit Agreement.

Dated as of March 15, 2007

IN WITNESS WHEREOF, this Reaffirmation has been duly executed as of the date first written above.