Effects of heat stress on growth, carcass traits and blood components of New Zealand White rabbits fed various dietary energy-fibre levels, under Egyptian conditions

Eighty weaned male New Zealand white rabbits were offered diets with normal or high energy (NE, HE) and normal or high fibre (NF, HF) contents, to appetite. Rabbits reared in summer showed a reduction in final body weight, daily weight gain, feed intake, final margin (financial return), weights of carcass and kidney fat and all blood components compared to those reared in winter. Rabbits fed HE diet showed significantly higher final body weight, daily weight gain, final margin and carcass weight than those fed NE diet, while feed intake decreased. The dietary energy level did not have any significant effect on blood components, except the serum albumin which increased with increasing dietary energy. The HF diet gave significantly higher values in carcass weight, kidney fat weight and creatinine, and significantly lower values in serum total protein, globulin and SGOT when compared to the LF diet. Interaction between season and dietary energy level showed highly significant effects on final body weight, daily weight gain and serum total protein. Interaction between season and dietary fibre level showed significant effects on final body weight, daily weight gain and kidney fat weight. The interactions between dietary energy and fibre levels or between season, dietary energy and dietary fibre did not show any significant effect on the studied traits. Rabbits fed HE-HE diet in winter recorded the highest values in most of the growth performance and carcass traits when compared with the other winter and summer groups. In summer, rabbits fed HE-NE diet showed better body gain than other summer rabbits. (C) 1997 Academic Press Limited.