9 CFR § 201.55 - Purchases, sales, acquisitions, payments and settlements to be made on actual weights.
(a) Except as provided in paragraph (b) of this section, whenever livestock or live poultry is bought, sold, acquired, paid, or settled on a weight basis, or whenever the weight of feed is a factor in determining payment or settlement to a livestock grower or poultry grower by a stockyard owner, market agency, dealer, packer, or live poultry dealer when livestock or poultry is produced under a growing arrangement, payment or settlement shall be on the basis of the actual weight of the livestock, live poultry, and/or feed shown on the scale ticket. If the actual weight used is not obtained on the date and at the place of transfer of possession, this information shall be disclosed with the date and location of the weighing on the accountings, bills, or statements issued. Any adjustment to the actual weight shall be fully and accurately explained on the accountings, bills, or statements issued, and records shall be maintained to support such adjustment.
(b) Whenever the weight of feed is a factor in determining payment or settlement to such livestock grower or poultry grower when the livestock or poultry is produced under a livestock or poultry growing arrangement, any feed that is picked up from or returned by a livestock grower or poultry grower must be weighed or its weight must be reasonably determined. When feed is picked up or returned and not weighed, the stockyard owner, market agency, dealer, packer, or live poultry dealer must document that the method used reasonably determines weight and is mutually acceptable to it and the livestock grower or poultry grower. The stockyard owner, market agency, dealer, packer, or live poultry dealer must document and account for the picked up or returned feed weight.