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Abstract
Summary (1500 words)
EFFECT OF HEAT STRESS ON THE PERFORMANCE OF LOCAL CHICKEN
The present study was carried out at El-Sabahia Poultry Research Station in Alexandria, belonging to Animal Production Research Institute, throughout the period from March to May 2006. The chemical analyses were conducted at the laboratory of the same institute and the Laboratory of Animal and Fish Production Department, Faculty of Agriculture (Saba Basha), Alexandria University.
Ninety, Bandarah and Baheje layers in their 25th wks of age, were used in this study. The birds were selected on the basis of more than 50 % egg production rate after a two-week pretest period. Birds from each strain were randomly assigned to five comparable groups with nine females in each group. The present experiment was designed to evaluate the influence of supplementing laying hens’ diets with different levels of sodium bicarbonate on productive performance, egg quality and plasma blood constituents of two local strains (Bandarah and Baheje) raised in environmental controlled room under heat stress waves conditions, birds were exposed to a daily cyclic heat stress period (35º C) for 6 hours from 10 a.m to 4 p.m and then during one hour the temperature was back to the normal (25º C), and compare their response with the laying hens reared under normal conditions (thermoneutral condition, 25º C).
In each strain, the first group reared under normal ambient temperature (25º C) and received a basal corn-soybean diet. The second group received the same basal diet without supplementation and subjected to one week of normal temperature, followed by 72 daily cyclic heat stresses. The 3rd, 4th and 5th other experimental three groups were subjected to one week of normal temperature, followed by 72 daily cyclic heat stresses and given the basal diet with additional provision of 1.0, 1.5 or 2.0 % sodium bicarbonate, respectively.
The results can be summarized as follows:
1- Body weight of birds exposed to cyclic temperature and fed control diet without supplementation significantly decreased as compared to birds reared under normal conditions (25º C). Feeding birds diet containing 1 % NaHCO3 and exposed to cyclic temperature had the best body weight among all studied groups in comparison with the other experimental groups exposed to cyclic temperature.
2- Hen-day egg production was significantly decreased through all periods of the study for hens exposed to cyclic temperature compared with those reared under normal ambient temperature. Addition of sodium bicarbonate (NaHCO3) at 1 % level to the basal diet of laying hens resulted in improving laying rate of birds exposed to cyclic temperature during the experimental period.
3- Hens received basal diet and exposed to heat stress waves insignificantly produced smaller eggs as compared to the group reared under normal temperature. On the other hand, hens fed diet supplemented with 1 and 1.5 % NaHCO3 during 0-24 day of exposure to heat stress waves produced heavier (P ≤ 0.01) eggs comparing to the group of birds exposed to the same environmental conditions but fed basal diet only.
4- High ambient temperature waves caused a reduction in egg mass. Supplementing laying hens’ diet with 1 or 1.5 % NaHCO3 increased egg mass / hen comparing with those rose under the same conditions and fed basal diet, however, addition of 2 % NaHCO3 had negative effect on egg mass during all periods of the study.
5- Feed intake was significantly reduced in the group of birds exposed to cyclic temperature in comparison with those reared under normal conditions. Hens exposed to temperature waves and fed diets supplemented with 1 or 1.5 % NaHCO3 resulted in non significant increase in feed consumption as compared to the group reared under temperature waves and fed basal diet during 0-48 and 0-72 days and these groups not reached the amount of feed intake of laying hens under normal conditions.
Inferior feed conversion ratio was observed in the group reared under cyclic temperature waves during the study. Supplemented laying hens’ diets with 1 or 1.5 % NaHCO3 and exposed to temperature waves resulted in non significant