Response of coccidiostat- versus vaccination-protected broilers to gelatin inclusion in high and low crude protein diets.

Experimentation examined if Gly and Ser (Gly + Ser) and Pro from gelatin inclusion in low and high CP feeds would relieve impaired performance of broilers after vaccination for coccidiosis. Broilers in floor pens were fed 20-18-16% or 23-20-18% CP corn-soybean meal regimens from 0 to 8 wk of age such that 1 or more of the most limiting essential amino acid levels were similar across treatments and considered adequate respective of age. Gelatin was included in diets at 2%, which contributed Gly + Ser and Pro levels comparable to using 5% meat meal. Half of the chicks were spray-vaccinated with live oocysts before placement and received nonmedicated feed, whereas the other half received coccidiostat-medicated (salinomycin) feed to 6 wk of age. Vaccination adversely affected live performance in the first 3 wk, which could not be fully compensated to the level of birds receiving coccidiostat by the end of experimentation. Inclusion of gelatin mitigated vaccination response through the first 3 wk, while improving overall live performance of birds fed low CP diets. Gelatin had no effect on carcass composition, but the low CP regimen increased abdominal fat and reduced carcass and breast meat relative to high CP feeds. Vaccination also reduced overall carcass weight; however, part yields were not affected. Males were generally more sensitive to treatments than females. The conditionally essential amino acids Gly + Ser and Pro may be important factors in recovery from live anticoccidial vaccines.