VOTING AGREEMENT

EXHIBIT 99.1

EXECUTION COPY

VOTING AGREEMENT

BY AND AMONG

SMITHFIELD FOODS, INC.,

CONTIGROUP COMPANIES, INC.

AND

(SOLELY FOR PURPOSES OF SECTION 5.2 HEREOF)

PREMIUM STANDARD FARMS, INC.

DATED AS OF SEPTEMBER 17, 2006

TABLE OF CONTENTS

i

INDEX OF DEFINED TERMS

ii

VOTING AGREEMENT

VOTING AGREEMENT, dated as of September 17, 2006 (this “ Agreement ”), by and among Smithfield Foods, Inc., a Virginia corporation (“ Parent ”), ContiGroup Companies, Inc., a Delaware corporation (“ Stockholder ”), and, solely for the purposes of Section 5.2 hereof, Premium Standard Farms, Inc., a Delaware corporation (the “ Company ”).

W I T N E S S E T H:

WHEREAS, concurrently with the execution of this Agreement, Parent, KC2 Merger Sub, Inc., a Delaware corporation and a wholly-owned subsidiary of Parent (“ Merger Sub ” ), and the Company are entering into an Agreement and Plan of Merger, dated as of the date hereof (as amended, supplemented, restated or otherwise modified from time to time, the “ Merger Agreement ”) pursuant to which, among other things, Merger Sub will merge with and into the Company (the “ Merger ”) and each outstanding share of the common stock, par value $0.01 per share, of the Company (the “ Common Stock ”) will be converted into the right to receive the merger consideration specified therein.

WHEREAS, as of the date hereof, the Stockholder is the record and beneficial owner, in the aggregate, of 12,428,592 outstanding shares of Common Stock, all of which such shares Stockholder controls the right to vote.

WHEREAS, as a material inducement to Parent entering into the Merger Agreement, Parent has required that the Stockholder agree, and the Stockholder has agreed, to enter into this agreement and abide by the covenants and obligations with respect to the Covered Shares (as hereinafter defined) set forth herein.

WHEREAS, simultaneously with the execution of this Agreement, Parent, the Company and the Stockholder have entered into the Missouri Sale Agreement.

NOW THEREFORE, in consideration of the foregoing and the mutual representations, warranties, covenants and agreements herein contained, and intending to be legally bound hereby, the parties hereto agree as follows:

ARTICLE I

GENERAL

1.1. Defined Terms . The following capitalized terms, as used in this Agreement, shall have the meanings set forth below. Capitalized terms used but not otherwise defined herein shall have the meanings ascribed thereto in the Merger Agreement.

“ Affiliate ” means, with respect to any Person, any other Person that directly, or indirectly through one or more intermediaries, controls, is controlled by or is under common control with, such specified Person.

“ Beneficial Ownership ” by a Person of any securities includes ownership by any Person who, directly or indirectly, through any contract, arrangement, understanding, relationship or otherwise, has or shares (i) voting power which includes the power to vote, or to direct the voting of, such security; and/or (ii) investment power which includes the power to dispose, or to direct the disposition, of such security; and shall otherwise be interpreted in accordance with the term “beneficial ownership” as defined in Rule 13d-3 adopted by the Securities and Exchange Commission under the Securities Exchange Act of 1934, as amended; provided that for purposes of determining Beneficial Ownership, a Person shall be deemed to be the Beneficial Owner of any securities which such Person has, at any time during the term of this Agreement, the right to acquire pursuant to any agreement, arrangement or understanding or upon the exercise of conversion rights, exchange rights, warrants or options, or otherwise (irrespective of whether the right to acquire such securities is exercisable immediately or only after the passage of time, including the passage of time in excess of 60 days, the satisfaction of any conditions, the occurrence of any event or any combination of the foregoing). The terms “ Beneficially Own ” and “ Beneficially Owned ” shall have a correlative meaning.

“ control ” (including the terms “ controlled by ” and “ under common control with ”), with respect to the relationship between or among two or more Persons, means the possession, directly or indirectly, of the power to direct or cause the direction of the affairs or management of a Person, whether through the ownership of voting securities, as trustee or executor, by contract or any other means.

“ Covered Shares ” means, with respect to the Stockholder, the Stockholder’s Existing Shares, together with any shares of Common Stock or other voting capital stock of the Company and any securities convertible into or exercisable or exchangeable for shares of Common Stock or other voting capital stock of the Company, in each case that the Stockholder acquires Beneficial Ownership of on or after the date hereof.

“ Encumbrance ” means any security interest, pledge, mortgage, lien (statutory or other), charge, option to purchase, lease or other right to acquire any interest or any claim, restriction, covenant, title defect, hypothecation, assignment, deposit arrangement or other encumbrance of any kind or any preference, priority or other security agreement or preferential arrangement of any kind or nature whatsoever (including any conditional sale or other title retention agreement), excluding restrictions under securities laws.

“ Existing Shares ” means, with respect to the Stockholder, the number of shares of Common Stock Beneficially Owned (and except as may be set forth on Schedule 1 hereto, owned of record) by the Stockholder, as set forth opposite the Stockholder’s name on Schedule 1 hereto.

“ Permitted Transfer ” means a Transfer by the Stockholder to a wholly owned Subsidiary of the Stockholder, provided that such transferee Subsidiary executes and delivers to Parent a written agreement, in form and substance acceptable to Parent, to assume all of Stockholder’s obligations hereunder in respect of the securities subject to such Transfer and to be bound by the terms of this Agreement, with respect to the securities subject to such Transfer, to the same extent as the Stockholder is bound hereunder and to make each of the representations and warranties hereunder in respect of the securities transferred as the Stockholder shall have made hereunder.

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“ Person ” means any individual, corporation, limited liability company, limited or general partnership, joint venture, association, joint-stock company, trust, unincorporated organization, government or any agency or political subdivision thereof or any other entity, or any group comprised of two or more of the foregoing.

“ Representatives ” means the officers, directors, employees, agents, advisors and Affiliates of a Person.

“ Subsidiary ” means, with respect to any Person, any corporation or other organization, whether incorporated or unincorporated, (i) of which such Person or any other Subsidiary of such Person is a general partner, or (ii) at least a majority of the securities or other interests of which having by their terms ordinary voting power to elect a majority of the board of directors or others performing similar functions with respect to such corporation or other organization is directly or indirectly owned or controlled by such Person or by any one or more of its Subsidiaries, or by such Person and one or more of its Subsidiaries.

“ Transfer ” means, directly or indirectly, to sell, transfer, assign, pledge, encumber, hypothecate or similarly dispose of (by merger (including by conversion into securities or other consideration), by tendering into any tender or exchange offer, by testamentary disposition, by operation of law or otherwise), either voluntarily or involuntarily, or to enter into any contract, option or other arrangement or understanding with respect to the voting of or sale, transfer, assignment, pledge, encumbrance, hypothecation or similar disposition of (by merger, by tendering into any tender or exchange offer, by testamentary disposition, by operation of law or otherwise).

ARTICLE II

VOTING

2.1. Agreement to Vote . The Stockholder hereby irrevocably and unconditionally agrees that during the term of this Agreement, at the Company Stockholders’ Meeting and at any other meeting of the stockholders of the Company, however called, including any adjournment or postponement thereof, and in connection with any written consent of the stockholders of the Company, the Stockholder shall, in each case to the fullest extent that such matters are submitted for the vote or written consent of the Stockholder and that the Covered Shares are entitled to vote thereon or consent thereto:

(a) appear at each such meeting or otherwise cause the Covered Shares as to which the Stockholder controls the right to vote to be counted as present thereat for purposes of calculating a quorum; and

(b) vote (or cause to be voted), in person or by proxy, or deliver (or cause to be delivered) a written consent covering, all of the Covered Shares as to which the Stockholder controls the right to vote (i) in favor of the adoption of the Merger Agreement and any related

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proposal in furtherance thereof, as reasonably requested by Parent, submitted for the vote or written consent of stockholders; (ii) against any action or agreement submitted for the vote or written consent of stockholders that is in opposition to, or competitive or materially inconsistent with, the Merger or that would result in a breach of any covenant, representation or warranty or any other obligation or agreement of the Company contained in the Merger Agreement, or of the Stockholder contained in this Agreement; and (iii) against any Takeover Proposal and against any other action, agreement or transaction submitted for the vote or written consent of stockholders that would reasonably be expected to impede, interfere with, delay, postpone, discourage, frustrate the purposes of or adversely affect the Merger or the other transactions contemplated by the Merger Agreement or this Agreement or the performance by the Company of its obligations under the Merger Agreement or by the Stockholder of its obligations under this Agreement. The obligations of the Stockholder specified in this Section 2.1(b) shall, subject to Section 2.1(c), apply whether or not the Merger or any action described above is recommended by the Board of Directors of the Company.

(c) Notwithstanding the foregoing, in the event of a Company Adverse Recommendation Change (as defined in the Merger Agreement) made in compliance with the Merger Agreement, other than a Company Adverse Recommendation Change not made in connection with a Superior Proposal, the obligation of the Stockholder to vote Covered Shares as to which the Stockholder controls the right to vote in the manner set forth in this Section 2.1 shall only apply to an aggregate number of Covered Shares entitled to vote in respect of such matter that is equal to thirty-two percent (32%) of the total number of shares of Common Stock entitled to vote in respect of such matter and the Stockholder shall cause all remaining Covered Shares so entitled to vote to be voted in a manner that is proportionate to the manner in which all shares of Common Stock (other than shares voted by the Stockholder) which are voted in respect of such matter, are voted.

2.2. No Inconsistent Agreements . The Stockholder hereby covenants and agrees that, except for this Agreement, the Stockholder (a) has not entered into, and shall not enter into at any time while this Agreement remains in effect, any voting agreement or voting trust with respect to the Covered Shares, (b) has not granted, and shall not grant at any time while this Agreement remains in effect, a proxy (except pursuant to Section 2.3 hereof), consent or power of attorney with respect to the Covered Shares and (c) has not taken and shall not knowingly take any action that would make any representation or warranty of the Stockholder contained herein untrue or incorrect or have the effect of preventing or disabling the Stockholder from performing any of its obligations under this Agreement.

2.3. Proxy . The Stockholder hereby irrevocably appoints as its proxy and attorney-in-fact, Michael Cole and Richard Poulson, in their respective capacities as officers of Parent, and any individual who shall hereafter succeed to any such officer of Parent, and any other Person designated in writing by Parent (collectively, the “ Grantees ”), each of them individually, with full power of substitution, to vote or execute written consents with respect to the Covered Shares as to which the Stockholder controls the right to vote in accordance with Section 2.1 hereof and, in the discretion of the Grantees, with respect to any proposed postponements or adjournments of any annual or special meeting of the stockholders of the Company at which any of the matters described in Section 2.1(a) was to be considered. This proxy is coupled with an interest and shall be irrevocable, and the Stockholder will take such further action or execute such other

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instruments as may be necessary to effectuate the intent of this proxy and hereby revokes any proxy previously granted by the Stockholder with respect to the Covered Shares. Parent may terminate this proxy with respect to the Stockholder at any time at its sole election by written notice provided to the Stockholder.

ARTICLE III

REPRESENTATIONS AND WARRANTIES

3.1. Representations and Warranties of the Stockholder . The Stockholder hereby represents and warrants to Parent as follows:

(a) Organization; Authorization; Validity of Agreement; Necessary Action . The Stockholder is duly organized and is validly existing and in good standing under the laws of the jurisdiction of its incorporation. The Stockholder has full power and authority to execute and deliver this Agreement, to perform its obligations hereunder and to consummate the transactions contemplated hereby. The execution and delivery by the Stockholder of this Agreement, the performance by it of its obligations hereunder and the consummation by it of the transactions contemplated hereby have been duly and validly authorized by the Stockholder and no other actions or proceedings on the part of the Stockholder or any stockholder thereof are necessary to authorize the execution and delivery by it of this Agreement, the performance by it of its obligations hereunder or the consummation by it of the transactions contemplated hereby. This Agreement has been duly executed and delivered by the Stockholder and, assuming this Agreement constitutes a valid and binding obligation of the other parties hereto, constitutes a legal, valid and binding obligation of the Stockholder, enforceable against it in accordance with its terms, subject to bankruptcy, insolvency, fraudulent transfer, moratorium, reorganization or similar laws affecting the rights of creditors generally and the availability of equitable remedies (regardless of whether such enforceability is considered in a proceeding in equity or at law).

(b) Ownership . The Stockholder’s Existing Shares are, and all of the Covered Shares owned by the Stockholder from the date hereof through and on the Closing Date will be, Beneficially Owned and owned of record by the Stockholder, except to the extent such Covered Shares are Transferred after the date hereof pursuant to a Permitted Transfer or constitute any warrants, options, conversion rights or similar rights with respect to Common Stock (collectively, “ Specified Rights ”) that expire after the date hereof. The Stockholder has good and marketable title to the Stockholder’s Existing Shares, free and clear of any Encumbrances. As of the date hereof, the Stockholder’s Existing Shares constitute all of the shares of Common Stock Beneficially Owned or owned of record by the Stockholder. Except (i) to the extent Covered Shares are transferred after the date hereof pursuant to a Permitted Transfer or constitute Specified Rights that expire after the date hereof or (ii) as set forth on Schedule 1, the Stockholder has and will have at all times through the Closing Date sole voting power (including the right to control such vote as contemplated herein), sole power of disposition, sole power to issue instructions with respect to the matters set forth in Article II hereof, and sole power to agree to all of the matters set forth in this Agreement, in each case with respect to all of the Stockholder’s Existing Shares and with respect to all of the Covered Shares owned by the Stockholder at all times through the Closing Date (subject, in the case of Covered Shares underlying Specified Rights acquired after the date hereof, to the terms of such Specified Rights).

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(c) No Violation . The execution and delivery of this Agreement by the Stockholder does not, and the performance by the Stockholder of its obligations under this Agreement will not, (i) conflict with or violate the certificate of incorporation, bylaws or other comparable governing documents, as applicable, of the Stockholder, (ii) conflict with or violate any law, ordinance or regulation of any Governmental Entity applicable to the Stockholder or by which any of its assets or properties is bound, or (iii) conflict with, result in any breach of or constitute a default (or an event that with notice or lapse of time or both would become a default) under, or give to others any rights of termination, amendment, acceleration or cancellation of, or result in the creation of any Encumbrance on the properties or assets of the Stockholder pursuant to, any note, bond, mortgage, indenture, contract, agreement, lease, license, permit, franchise or other instrument or obligation to which the Stockholder is a party or by which the Stockholder or any of its asse