The effect of dietary polyunsaturated fatty acid (PUFA) concentration on body fat deposition and composition in broiler chickens was studied. Twenty-day-old birds were fed five isocaloric diets supplemented with different combinations of tallow and vegetable oils. Contents of abdominal adipose tissue (AAT) as well as body fat were determined at 40 days of age. A significant linear effect was observed between dietary PUFA and feed utilization. Fatty acid (FA) profiles in AAT and total body fat were correlated to dietary PUFA content, with the main effect of higher dietary PUFA being a reduction in monoenoic FA (C16:1 and C18:1) and an increase in C18:2. The effect of dietary PUFA on the saturated FA (C16:0 and C18:0) was small and not statistically significant. Increased dietary PUFA modified FA composition such that C18:2, rather than C18:1 became the dominant FA in AAT. In that respect, greater changes were observed in FA composition of AAT, as compared with that on the whole carcass. The deposition of saturated and monoenoic FA in the whole carcass during the experimental period was related to dietary PUFA content in a quadratic manner. However, deposition of C18:2 and C18:3 was not affected by intake and their utilization (deposition:intake ratio) was reduced in a manner parallel to their dietary levels.

No abstract

1. The effect of egg weight on the subsequent performance of individual growing chicks was studied. Eggs from commercial broiler breeder hens were collected at 52, 55 and 57 weeks of age and incubated. The chicks were reared for 18 d. 2. Egg weight and hatched chick weight were not affected by the age of the hens during the 52 to 57-week period, but there was a close correlation between egg weight and hatching weight, irrespective of the age of the hens (r = 0.89). Chick:egg weight ratio at hatching was about 0.71 and independent of hen age. One d after hatching, chick weights had decreased by about 1.5 g. 3. The initial high correlation between egg weight and chick weight decreased markedly during post-hatching growth, becoming insignificant 5 d after hatching. At 18 d of age, however, chicks from eggs of older hens tended to be heavier than those from younger birds. The greater 18-d weights appeared to be associated more with higher food intake during that period, than with greater egg weight. 4. It was concluded that, in individual broiler chicks, the advantage of the initially higher weight attributable to a larger egg diminishes rapidly after hatching, and the main factor affecting final body weight is food intake.

Performance of broiler chicks fed low protein diets supplemented with several essential amino acids (EAA) is generally inferior to that of birds fed a higher protein diet composed primarily of intact protein. Two experiments were conducted to determine whether lowering the minimum requirements of the EAA in proportion to the lowered protein concentration or equalizing the dietary amino nitrogen content by use of glutamic acid would prevent the reduction in performance. Chicks were fed the experimental diets from 7 to 21 days of age, and body weight gain, feed consumption, and feed efficiency were determined. In the first experiment, the chicks were fed diets with 23, 20, or 17% CP with minimum EAA set at 100% of the 1984 National Research Council (NRC) suggested requirements. Other groups were fed the 20% CP diet with EAA set at 93.5% or the 17% CP diet set at either 93.5 or 87.5% of the NRC requirements. In the second experiment, the 23% and 17% CP diets were fed, and glutamic acid was added at 3, 6, or 9% to provide the amino nitrogen equivalent of 23% protein with the minimum EAA set at 100% of 1984 NRC requirements. In the first experiment, body weight gain and feed efficiency, but not feed intake, were depressed by lowering CP content. Reducing the minimum EAA requirements in proportion to the reduction in CP failed to correct the difference in performance between the high and low CP diets. In Experiment 2, body weight gain and feed intake were reduced as intact CP decreased and glutamic acid increased, but feed efficiency was unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

No abstract