The Effect of Gelatin and Dietary Crude Protein Level on Broilers Vaccinated for Coccidiosis

Abstract

Vaccinating for coccidiosis has been shown to adversely affect live performance of broilers compared to those given a dietary anticoccidial. Feeding diets with higher crude protein alleviates negative response to vaccination, presumably by providing the bird with the amino acids essential for recovery. Alternate means of providing nonessential amino acids for vaccination recovery have yet to be explored. Experiments were conducted to evaluate whether gelatin, as a source of proline and glycine, aided in recovery of vaccinated birds compared to coccidiostat-protected birds fed low and high crude protein diets; and to estimate a crude protein level where use of gelatin is optimized in diets of vaccinated broilers. In the first experiment, male and female broiler chicks were fed either a low or high crude protein (CP) diet from 0-8 weeks of age with limiting EAA levels meeting or exceeding NRC (1994) recommendations. Gelatin was included in half of the diets at 2% to increase proline and glycine. Half of the birds were vaccinated and the rest were protected with a dietary coccidiostat. Vaccination adversely affected performance during the first 3 weeks. Addition of gelatin reduced the early negative response of vaccinated birds, but by 8 weeks, vaccinated birds still had reduced gain and carcass weight compared to coccidiostat-protected birds. Addition of gelatin to low CP diets improved feed conversion to that of birds fed the high CP diets; however carcass yield of low CP diets was not improved with addition of gelatin. The second experiment was performed to estimate the optimal levels of crude protein and NEAA of vaccinated male broilers. Diets with graded levels of crude protein: 20, 21, 22, or 23% from 0-3 weeks; 19, 20, 21, or 22% from 3-6 weeks; and 18, 19, 20, or 21% from 6-8 weeks, respectively, were administered from 0-8 weeks of age, half of which contained 2% gelatin to increase proline and glycine. Increasing CP improved body weight gain while gelatin inclusion generally improved feed conversion. Carcass yield was increased and abdominal fat decreased with CP, but gelatin resulted in greater abdominal fat without affecting meat yield of the carcass. Additional NEAA, provided by gelatin and CP, generally improve performance of vaccinated birds, although specific estimates could not be determined.