ASSESSMENT OF HUNGER IN GROWING BROILER BREEDERS IN RELATION TO A COMMERCIAL RESTRICTED FEEDING PROGRAM

From two weeks of age female broiler breeder chickens were fed either on a commercial daily ration (R), twice that amount (2R), or ad libitum (AL). Motivation to eat in R and 2R birds was compared every third week with that of AL birds subjected to 3-72h food deprivation. AL and 2R birds grew three and two times faster than R birds to 20 weeks, and AL birds ate two to four times as much per day as R birds, depending on age and on whether birds of the same age or weight were compared. When feeding motivation was measured in 16min tests with an operant procedure, numbers of responses by R and 2R birds were not related in a consistent way to the time since their daily meal ended. Responses by AL birds were correlated consistently with the preceding period of food deprivation, but it was not possible to express hunger in R and 2R birds in terms of equivalent deprivation in AL birds, as intended, because feeding motivation in the two situations differed in magnitude. Instead, it was calculated that motivation to eat in R and 2R birds, from 8 to 20 weeks, was 3.6 and 1.9 times greater than that of maximally (72h) deprived AL birds. Another measure of feeding motivation with different birds, rate of eating in 10min tests, produced a similar index of hunger with 2R but not R birds. It is concluded that broiler breeders fed on the commercial ration eat only a quarter to a half as much as they would with free access to food, and that they are highly motivated to eat at all times. The modern broiler breeder industry is caught in a welfare dilemma, since on the one hand stock appear to be chronically hungry, while on the other hand less severe food restriction leads to reduced fertility and health problems.