-Feed withdrawal during the warmest part of the day (09:00 to 16:00 h) was compared with the distribution of ground corn and commercial feed consumed ad libitum by control broilers from 28 to 42 d exposed to tropical climatic conditions (averaged Ta = 25 °C; Relative Humidity (RH) = 72%). From 16:00 to 09:00 h, a continuous illumination was in the poultry shed and the chickens received a commercial diet. Each diet was supplied to 7 pens of 14 unsexed broilers. Both feed withdrawal and corn distribution during the day period reduced growth (P < 0.01) and deteriorated feed conversion (P < 0.01) compared to the ad libitum control. At the age of 41 d, the average body temperature (Tb) at 14:00 h in the control group was 42.56 °C. It was higher (P < 0.002) than that recorded in the corn fed group (42.27 °C) and the feed withdrawal chickens (42.11 °C). These effects measured in 4-6 week-old broilers exposed to a moderate tropical climate, illustrate the limitation of feed restriction and sequential feeding under practical conditions. Further research is needed to study the diurnal distribution of corn or feed withdrawal coupled with a balanced diet richer in essential amino acids than the commercial diet during the nocturnal period. les phases les plus chaudes de la journée (09:00 à 16:00 h) a été comparé à la distribution ad libitum de maïs broyé ou d'un aliment commercial pendant la même période, chez des poulets de chair élevés en milieu tropical (Température moyenne = 25 °C ; HR moyenne = 72 %) entre 28 et 42 jours d'âge. Entre 16:00 et 09:00 h tous les poulets recevaient l'aliment commercial ad libitum et le poulailler était continuellement éclairé. Chaque régime expérimental a été distribué à 7 parquets de 14 poulets non sexés. Le retrait d'aliment comme la distribution de maïs ont réduit la croissance (P < 0,01) et détérioré l'indice de consommation (P < 0,01) par rapport aux témoins nourris ad libitum. A l'âge de 41 jours, la température corporelle moyenne mesurée à 14:00 h était de 42,56 °C chez les témoins. Elle était supérieure (P < 0,002) à celle mesurée chez les poulets recevant du maïs (42,27 °C) ou mis à jeun (42,11 °C). Ces effets mesurés entre 4 et 6 semaines d'âge chez des poulets exposés à un climat tropical modéré, illustrent les limites du retrait de l'aliment ou l'alimentation séquentielle dans des conditions pratiques. Des recherches complémentaires associant à la distribution de maïs ou au jeûne diurne, un régime complémentaire nocturne plus riche en acides aminés indispensables que le régime commercial sont souhaitables.poulet de chair / température corporelle / alimentation séquentielle / rythme / climat chaud
A stochastic model was developed to simulate the egg production of broiler breeders in response to changes in BW. The first step involved the construction of a diagram incorporating dependent and independent variables and their relationships to ovulation rate and egg production from 8 equations based on experimental results. The model was based on existing experimental data, and stochastic processes were invoked for 4 input parameters. Egg production curves and total egg production were simulated using inputs from a management manual, commercial trial data, and experimental results and were compared with actual rates of lay. The correlations between observed and predicted egg production were high (R(2) = 0.93 to 0.98). The assumptions made in developing the model were described and gaps in biological knowledge were identified.
1. Egg production, body weight, feed intake and mortality were recorded in over 78 000 broiler breeder hens in 4 commercial flocks housed in 16 houses from early lay though 40 weeks of lay. A total of 420 hens were sampled at regular intervals throughout the laying period to determine the changes in body weight and the numbers of yellow follicles, paired follicles and hierarchical positions with time in the ovary throughout lay to relate ovarian function to productivity. Average egg weight was recorded weekly from one flock. 2. A quadratic equation fitted the changes in time for the number of yellow follicles, body weight, feed intake and mortality; a linear equation described the decline in the number positions in the hierarchy and there was a linear decline in the logistic scale of the proportions of yellow follicles developing as pairs of similar weight. Egg production was described by a cubic equation and egg weight by a line plus exponential model. 3. The average number of yellow follicles declined from 7·2 to 5·4 and the number of hierarchical positions from 6 to 5 from 4 to 40 weeks after photostimulation. The proportion of follicles developing as pairs of similar weight was over 25% at the onset of lay and declined to less than 10% from 20 weeks after photostimulation, representing a substantial loss of potential productivity. 4. Body weight and egg production were similar to the breeder's targets whereas average egg weight and mortality were higher than expected. 5. The relationship defining ovarian function will facilitate the development of an improved model of egg production in broiler breeder hens.
1. A model that simulates the total production of eggs (TEP) in broiler breeders was used to predict the optimum initial (20 week) body weight (IBWexp), daily weight gains from 20 to 30 (DWGexp(20-30)) and 31 to 62 weeks of age (DWGexp(31-62)), age at photostimulation (affecting age at first egg, AFEexp), coefficients of variation of initial body weight (CV-IBWexp) and age at first egg (CV-AFEexp), and the effect of genetically increasing the numbers of yellow follicles at the onset of lay. 2. The results suggest that TEP in broiler breeders is very sensitive to changes in body weight gain during the first 10 weeks of the production period and body weight at the start of egg production, whereas changes in body weight gain after peak rate of lay showed only minor effects on TEP. Increasing CV-IBWexp was associated with a linear decrease in the mean and increased variability of TEP. 3. Decreasing AFEexp was negatively associated with TEP, whereas higher CV-AFEexp increased variability of TEP and had a trivial affect on the mean. 4. Results of the simulation suggested that reducing ovarian yellow follicle numbers by means of genetic selection could reduce the degree of feed restriction currently used in broiler breeder commercial stocks while maintaining total egg production. Higher numbers of yellow follicles associated with selection for higher growth rate would not result in lower egg production if the body weight target was maintained at the currently recommended commercial level and the effect on TEP of increasing the target in proportion to potential body weight may be relatively small.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.