<PAGE>

                                                                   Exhibit 10.82
                                                                   -------------

                            MANAGEMENT RETENTION PLAN

Synbiotics Corporation is implementing a "management retention plan" designed to
encourage you to remain an employee of the Company between now and the potential
sale of the Animal Health Business. The Management Retention Plan consists of a
cash or stock bonus and special treatment of outstanding stock options and
restricted stock. This Management Retention Plan does not alter or affect
existing Synbiotics employee benefit plans, the Special Payment Plan or existing
employee agreements.

To qualify for the Management Retention Plan, you must be an active employee,
who is employed on the day of the sale of the Animal Health Business, provided
that you have not notified the Company of your intent to resign your employment
with Synbiotics. This Management Retention Plan does not apply to:
                                                     ---

1)   Employees who voluntarily leave the Company prior to the sale of the Animal
     Health Business

2)   Employees whose employment is terminated prior to the sale of the Animal
     Health Business

3)   Employees of W3COMMERCE

4)   Active employees who are offered and accept continued employment with the
     Company following the sale of the Animal Health Business.

Cash Bonus

A cash bonus payment (or you can elect to receive the cash bonus in stock - see
below) will be made on the day following the sale of the Animal Health Business.
The bonus payment will depend on the ultimate sales price of the Animal Health
Business and will be paid as a percentage of annual base salary ("the
Percentage"). In no event will the Percentage payment be less than 25% of an
employee's annual base salary and there is no maximum percentage. The Percentage
will be calculated as 1.25 times the sales price of the Animal Health Business.

     Examples:

     If the sales price of the Animal Health Business were $35 million, then 35
times 1.25 would yield a Percentage of 43.75%. You would receive a cash bonus of
43.75% of your annual salary.

     If the sales price of the Animal Health Business were $60 million then 60
times 1.25 would yield a Percentage of 75%. You would receive a cash bonus of
75% of your annual salary.

<PAGE>

Stock Bonus In-lieu of Cash Bonus

You may elect to receive all or a part of the aforementioned cash bonus in
stock. Such election must be made within 30 days from the execution date of this
agreement. If you choose to receive part of your cash bonus in stock, then the
number of shares to be received will be determined by dividing the cash bonus by
$3.

     Example:

     If your cash bonus were $100, 000 and you elected to receive $60, 000 of it
in Stock, you would receive $40,000 in cash and 20,000 ($60.000/$3) shares of
Synbiotics stock.

Notwithstanding paragraph 4 above, if you are offered and accept employment with
the Company following the sale of the Animal Health Business you will receive
the equivalent of the cash bonus in "Synbiotics restricted stock" calculated by
dividing the cash bonus by $3.

Restricted Stock and Stock Options

All of your unvested restricted stock and stock options will become fully vested
on the day following the sale of the Animal Health Business and you will receive
two years following the sale of the Animal Health Business to exercise any
unexercised stock options.


/s/ Kenneth Cohen
----------------------
Kenneth Cohen
President and CEO
Synbiotics Corporation



I have read the above Management Retention Plan.
Acknowledged and accepted:

Serge Leterme                  /s/ Serge Leterme
----------------------         --------------------------
Print Name                     Employee Signature

July 7, 2000
------------
Date