Responses of chickens to Streptococcus faecalis: genotype-housing interactions

Hens from lines selected for high and low juvenile body weight were maintained in single-bird wire cages or in litter-floor flocks and inoculated intravenously with Streptococcus faecalis. Responses to the inoculation, as measured by changes in body weight, plasma xanthophyll levels, heterophil/lymphocyte ratios, and mortality, were more severe in the high-body-weight line than the low-body-weight line. The effect of cage vs. floor housing varied according to genetic line. Responses of individuals to Str. faecalis could not be predicted from either plasma xanthophyll levels or numbers of heterophils and lymphocytes before inoculation. Diagnosis of field outbreaks would be difficult, because autopsies performed 14 days after inoculation revealed no lesions, and liver swabs positive for Str. faecalis were rare.     

实现家禽福利与生产性能之间的平衡

<正>1家禽育种和生产环境与动物福利相适应遗传改良与动物福利之间的平衡问题如同"先有鸡还是先有蛋"之争。近来,环境和管理调整成为满足动物福利需求的方法。满足农场动物的福利需要成为畜禽业生产的主要部分。近50年的遗传选育不仅改善了生长性能,提高了存活率和整体福利状况,同时也使代谢失调、某些疫病敏感性和骨骼问题等增多。