Study On The Relationship Among Early Feed Restriction, Pulmonary Arterioles Remodeling And Pulmonary Hypertension Syndrome In Broilers

Undergoing large-scale field trials, a set of early feed restriction regimes were established to reduce the pulmonary hypertension syndrome (PHS) morbidity without negative influence on the performance characteristics and carcass traits of broiler. Based on these facts, the cytochemistry staining techniques, immunohistochemical staining techniques etc were used to investigate the differences on the micro morphological changes and percentages of different types of pulmonary arterioles in broiler as well as differences on the nitric oxide (NO), oxygen free radicals concentration and enzymatic antioxidant activity in vivo between feed restricted and unrestricted broilers. The technique of cell culture and immunocytochemical staining method etc were employed to investigate the xanthine/ xanthine oxidase oxygen free radical generating system and the sodium nitroprosside (SNP), a NO donor on the proliferation and apoptosis of cultured pulmonary artery endothelial cells and smooth muscle cells of broiler in vitro. These works clarified the relationship between early feed restriction, pulmonary arterioles remodeling and pulmonary hypertension in broilers and provided theoretical basis of the feed restriction technique for controlling the PHS incidence.Test I Effects of early feed restriction on the pulmonary hypertension syndrome morbidity, performance and abdominal fat pad ratio in commercial broilers. Broilers were exposed to low ambient temperature to induce PHS. Experiments were conducted to investigate the effects of different early feed restriction regimes on the PHS morbidity, performance characteristics and meat quality of commercial broilers under normal or low ambient temperature. In experiment 1, the restricted chicks were fed 8 hours per day either from day 7 to day 14 or from day 7 to day 21, while the controlled chicks were fed ad libitum. In experiment 2, the restricted chicks were fed 80% or 60% of previous 24 hourfeed consumption of full-fed controls for 7 days from day 7 to day 14, while the full-fed controls were fed ad libitum all through the experiment. The results showed that early feed restriction treatments reduced PHS morbidity, which was more significant under low temperature. Feed conversion ratios were lower in fed restricted broilers than in full fed controls. Early feed restriction had no obvious effects on abdominal fat pad ratio, and proper feed restriction did not affect the final body weight of broiler on market age. These results indicated that early feed restriction was an effective method to control the incidence of PHS in broiler.Test II Study on the mechanism of early feed restriction reducing the incidence of PHS in broiler: I. Effects on the pulmonary vascular remodeling in broilers.Experiments were conducted to investigate the effects of early feed restriction on the incidence of PHS and microstructure of pulmonary arterioles in broiler under normal and low ambient temperature. Lung samples were taken continuously and stained for elastin. The vessel wall area to vessel total area ratio (WA/TA) and mean media thickness in pulmonary arterioles (mMTPA) were measured using microscopic image analysis software. The muscular arterioles (MA), partially muscular arterioles (PMA) and non- muscular arterioles (NMA) were counted and the percentages of thick-walled peripheral lung vessels (%TWPV) were calculated. The PHS morbidity were significantly increased in low temperature treated broiler. Early feed restriction markedly reduced the PHS morbidity compared with the ad libitum feeding chicks. Low ambient temperature significantly increased the WA/TA, mMTPA and %TWPV in pulmonary arterioles, while early time feed restriction markedly decreased the WA/TA, mMTPA and %TWPV. It was concluded that feed restriction during the early period was of benefit to reduce PHS morbidity in broiler, and the attenuated pulmonary vascular remodeling characterized by pulmonary arterioles hypertrophy and muscularization might be involved in the underlying mechanisms.Test III Study on the mechanism of early...