Energy requirement of feed-restricted broiler breeder pullets

Energy partitioning by broiler breeder pullets in skip-a-day and precision feeding systems

An empirical nonlinear mixed model was derived to describe metabolizable energy (ME) partitioning in Ross 308 broiler breeder pullets. Its coefficients described ME used for total heat production (HP) and growth. A total of 630 pullets were randomly and equally assigned to 2 treatments: precision feeding (PF) and conventional skip-a-day feeding (CON) from 10 to 23 wk of age. The PF system allowed birds to enter voluntarily at any time, weighed them, and provided access to feed for 60 s if their BW was less than the target BW. Birds in the CON treatment were fed as a group on alternate days. Energetic efficiency of pullets was evaluated using residual total heat production (RHP), defined as the difference between observed and predicted total HP. Additionally, ME intake (MEI), ADG, HP, and cumulative feed conversion ratio (FCR) were calculated for the entire experimental period. The energy partitioning model (P < 0.05) predicted MEI = (120+u)BW0.68 + 1.52(ADG) + ε. Total HP was (120 kcal/kg0.68 + u); the energy requirement for each g of BW gain was 1.52 kcal/d. The random variable u ∼ N (0, σu2) indicated a pen level HP standard deviation σu = 12.1 kcal/kg0.68. Over the experimental period, for CON and PF treatments, respectively, MEI was 194 and 174 kcal/d (P < 0.001); ADG was 15.3 and 15.4 g/d (P = 0.94); HP was 129 and 111 kcal/kg0.68 (P < 0.001); FCR was 4.888 and 4.057 (P < 0.001); and RHP was 0.12 and -0.12 kcal/kg0.68 (P = 0.73). The CON pullets had similar ADG, but higher MEI relative to PF, consistent with levels of heat production predicted by RHP. The PF pullets had lower cumulative FCR compared to CON pullets. The PF pullets lost less energy as heat, likely because they were fed continuously, reducing the need to store and mobilize nutrients compared to CON pullets. Thus, increased feeding frequency likely increased PF pullet efficiency.

Broiler chick responses to anorectic agents: 1. Dietary acetic and propionic acids and the digestive system

The effects of various levels of acetic or propionic acid supplementation on feed intake and the gastrointestinal tract were studied in female broiler chicks. Voluntary feed intake and body weight gain decreased with the inclusion of the acids. Results indicate that acetic and propionic acids exert a similar anorectic effect on chicks fed diets differing in energy content. The inhibitory effect of these acids on voluntary feed intake could not be attributed to alterations in feed utilization, to differences in pancreatic alpha-amylase activity, or to differences in the acid-base balance. The increase in cecal capacity and volatile fatty acid (VFA) content is probably due to increased utilization of nonstarch polysaccharides at that site, the latter compensating for feed inhibition. This reflects a slight adaptive response of the cecum to anorectic agents.

Dietary supplementation with xanthophyll as an effective way of identifying low-producing broiler breeder hens

The relationship between dietary levels of xanthophyll, the degree of pigmentation in the hen, and egg production rate was studied in commercial broiler breeders (Anak 2000). In the first study, the degree of shank and beak coloration, measured with a 15-grade Roche yolk color fan, was determined in broiler breeder pullets until 34 wk of age. Although overall body coloration decreased with age following initiation of egg production, the degree of shank coloration was two- to threefold higher than that of the beak. In the second study, Roche Carophyll-red (canthaxanthin, 10%) was supplemented at levels of 0, 10, and 20 mg/kg in a corn and soybean diet containing xanthophyll, and given to hens for a period of 4 wk beginning at 55 wk of age. Increasing dietary canthaxanthin levels increased pigmentation of beak and egg yolk in a quadratic manner, whereas pigmentation increased linearly in the shank. The production rate was inversely related to the degree of shank and beak pigmentation. In a third study, the relationship between hen pigmentation (using Carophyll-red, 30 mg/kg of diet) and production rate was examined in a commercial flock of broiler breeder hens. Hens were sampled according to shank coloration (Grades 1 to 3) and egg production was monitored. The production rate of hens with high coloration was significantly lower (by approximately 33%) than the flock average. At peak production, shank pigmentation was too low to differentiate visually between degrees of coloration. Dietary supplementation of 5% corn gluten meal increased shank pigmentation and enabled efficient identification of the nonlaying hens.