پردیس کشاورزى و منابع طبیعى دانشگاه تهران
عنوان مقاله [English]
Increase in feed intake of broiler breeder hens, results to incidence of metabolic and hormonal changes and finally leads to poor reproductive performance. An experiment was conducted to evaluate responses of feed-satiated and feed-restricted laying breeder hens to daily injection of an acute dose of progesterone (P4). A total of 64 Cobb 500 hens were fed either restricted or ad libitum from 27 to 38 wk of age. Fourteen laying hens from each group were selected to conduct P4 injection assay. Each P4 injection were 2.5 mg P4/kg BW subcutaneously, at the base of the neck, daily for 21 days. Each treatment had 7 replicates. Settable and abnormal eggs were recorded daily. Blood sample were taken just before initiation of injections, 10-d and 20-d after initiation of injection. Plasma samples were analyzed for glucose, cholesterol, triacylglycerol, P4, estradiol (E2), testosterone, T3 and T4 concentrations. Progesterone injection in feed-satiated and feed-restricted birds resulted in ovary regression; the ovary of these birds had no hierarchical follicle (p>0.05). Progesterone injection increased incidence of holding hard-shelled eggs in the uterus (p>0.05). Our results revealed that whereas injecting an acute dose of P4 induced frequent ovulation early in the injection period in both feed-satiated and feed-restricted breeder hens (p>0.05); however this higher ovulation rate did not result in more settable egg production. Restricted fed and ad libitum fed laying breeder hens respond in a similar way to an acute dose of P4 injection.