Fertility and behavioral responses of roosters to diets differing in protein and calcium

Diets differing in calcium (approximately 3.2 and .9%) and protein (15 and 12%) were fed to assess their effects on fertility, behavior, and physiological traits of White Leghorn males from lines selected for high (HA) and low (LA) antibody titers in response to the administration of sheep erythrocytes. Two trials, terminated when the males were 721 and 380 days of age, respectively, were conducted. In Trial 1, the HA males consumed significantly more feed than the LA males and those fed the low protein diets consumed more feed than those fed the high protein diets. No significant differences in feed intake were observed in Trial 2. Neither line, calcium level, nor protein level had a consistent effect on body weight in either trial. There were no significant first or second order interactions between main effects. Comparisons within ages and trials for percentage and duration of fertility revealed no significant differences between lines, protein level, or calcium level. Although the HA males produced significantly more antibodies to canine erythrocytes, dietary effects on antibody titers, heterophil: lymphocyte ratios, and plasma corticosterone were not significant. Thus, there was no indication that dietary treatments were inducing physiological adaptation. Behavioral adaptations, however, were observed; differences were significant for fear, territoriality, air pecking, and head shaking. It was concluded that behavioral responses symptomatic of nutrient deficiencies occur when no overt deficiency is present; this infers that an animal's well-being cannot be assessed strictly on the basis of behavioral consequences.