PSX-19 - Influence of grease trap waste level supplementation on growth performance in finishing lamb

Forty-eight (37.66±3.41 kg) hairy lambs were used (two lambs per pen with 6 repetitions per treatment) in a growth-performance experiment lasting 61 days in order to evaluate a cooked grease recovered from rinse-trap water lines included in different levels (0, 2, 4, and 6%) in a corn-based diet. Inclusion levels of grease trap (GT) was replacing cracked corn. The GT used was obtained from an oil recycling company and its chemical composition was: moisture=16.48%, impurities=3.05%, and total fatty acids=79.80%. Increasing GT level in diets did not affect DMI and ADG, but due to numerically differences on DMI or in ADG, increasing GT level, linearly increased (P < 0.01) gain-to-feed ratio. Observed dietary NE was linearly increased as GT inclusion increased, but the magnitude of this effect did not correspond to was expected; thus, observed-to-expected diet NE ratio was linearly decreased. Kidney-pelvic-hearth fat was linearly increased as GT increased in diet, but the other carcass characteristics evaluated, nor tissue shoulder composition were affected by GT inclusion. Using the replacement equation, estimated NE of maintenance and gain (Mcal/kg) of supplemental GT were 5.83 and 4.70, 5.86 and 4.72, and 4.99 and 3.97, for 2, 4, and 6% supplementation level, respectively. These values represent an average of 0.88 of the NE value for supplemental fats indicated in current standards. The slightly lower NE value observed at moderated supplemental levels (up to 4%) was mainly by low contains of total fatty acids and high moisture content. At higher supplementation level, the negative effect on net energy of GT became most evident.GT supplementation up to 4% can be considered as a suitable source of energy to finishing lambs; however, its chemical composition (total fatty acids content) must be considered. In this case, GT at 4% level showed 7% lower NE content than conventional supplemental fats.