FEED WITHDRAWAL CARCASS YIELD: SHRINK VS. GROWTH

Authors: Buhr, Richard - Jeff; Northcutt, Julie

Submitted to: Georgia Poultry Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/24/2003
Publication Date: 9/24/2003
Citation: Buhr, R.J., Northcutt, J.K. 2003. Feed withdrawl carcass yield: shrink vs. growth. Georgia Poultry Conference Proceedings. p.38-41.

Interpretive Summary: By definition feed withdrawal periods either 'precede' or are 'subsequent' to attaining a specific age or time of day. Feed withdrawal studies for broilers have almost exclusively used feed withdrawal periods that preceded the processing of the full fed controls. For example, broilers subjected to 24 hour feed withdrawal were on feed for a total of 41 days and were compared to full fed controls that were on feed for 42 days when they were processed. Obviously, broilers on feed for 42 days would have heavier slaughter and eviscerated carcass weights than those on feed for 41 days and then processed after a 24 hour feed withdrawal period. The additional weight (growth) associated with this extra one day on feed has been incorrectly interpreted to indicate shrink for the broilers subjected to the feed withdrawal. Therefore, to accurately determine carcass yield, the feed withdrawal period must be started after attaining the same age or time on feed as the full fed control broilers. Our experiments reevaluated the determination of carcass yield in broilers as influenced by both preceding and subsequent feed withdrawal periods of 6, 12, 18, or 24 hours. Comparisons were made to initial live weight (prior to initiation of withdrawal) for slaughter weight and eviscerated carcass weight. It was not until 18 hours off feed that eviscerated carcass weight was first detected to decline by 1%. Eviscerated carcass weight for broilers subjected to 12 hour feed withdrawal were numerically 0.3% heavier than the carcasses of full fed control broilers processed at the time the feed withdrawal period was initiated, 12 hours earlier. In contrast, if comparisons are made to the broilers that remained on feed for an additional 24 hours, there is a difference of 3.4% in eviscerated carcass weight after only 6 hours of feed withdrawal. Comparisons to the full fed control broilers after an additional 24 hours on feed resulted in consistent calculation errors of 4.2%.

Technical Abstract: By definition feed withdrawal periods either 'precede' or are 'subsequent' to attaining a specific age or time of day. Feed withdrawal studies for broilers have almost exclusively used feed withdrawal periods that preceded the processing of the full fed controls. For example, broilers subjected to 24 hour feed withdrawal were on feed for a total of 41 days and were compared to full fed controls that were on feed for 42 days when they were processed. Obviously, broilers on feed for 42 days would have heavier slaughter and eviscerated carcass weights than those on feed for 41 days and then processed after a 24 hour feed withdrawal period. The additional weight (growth) associated with this extra one day on feed has been incorrectly interpreted to indicate shrink for the broilers subjected to the feed withdrawal. Therefore, to accurately determine carcass yield, the feed withdrawal period must be started after attaining the same age or time on feed as the full fed control broilers. Our experiments reevaluated the determination of carcass yield in broilers as influenced by both preceding and subsequent feed withdrawal periods of 6, 12, 18, or 24 hours. Comparisons were made to initial live weight (prior to initiation of withdrawal) for slaughter weight and eviscerated carcass weight. It was not until 18 hours off feed that eviscerated carcass weight was first detected to decline by 1%. Eviscerated carcass weight for broilers subjected to 12 hour feed withdrawal were numerically 0.3% heavier than the carcasses of full fed control broilers processed at the time the feed withdrawal period was initiated, 12 hours earlier. In contrast, if comparisons are made to the broilers that remained on feed for an additional 24 hours, there is a difference of 3.4% in eviscerated carcass weight after only 6 hours of feed withdrawal. Comparisons to the full fed control broilers after an additional 24 hours on feed resulted in consistent calculation errors of 4.2%.