ASSESSMENT OF SYNERGISTIC EFFECT OF ZINC AND VITAMIN A ON SOME PRODUCTIVE AND PHYSIOLOGICAL INDICES IN RABBITS

Abstract

The present study was carried out at the Rabbits Production Unit (RPU), Faculty of Agriculture, Ain Shams University, Cairo, Egypt. The aim of this study was to investigate the effects of supplemental vitamin A or zinc and their combinations on growth performance, nutrients digestibility coefficients, carcass traits, some blood constituents and economic evaluation of growing Rex rabbits. A total number of 135, unsexed Rex Rabbits, (5 weeks) with an average initial body weight of 645.46±77.85gm, were randomly allotted in a factorial design into nine experimental groups (3*3), there were three replicates of five rabbits for each experimental treatment. The experimental groups included three vitamin A levels (6000,1000 or 14000 IU/kg diet) and three Zn levels (50,100 and 150 ppm/kg) in factorial (3*3) design. The basal experimental diet was formulated and pelleted at Egyptian Canadian Company to cover the nutrient requirements of rabbits recommended by NRC (1977) and Lebas et al. (1997). The added premix in the growing rabbit diets was vitamin A and Zn free. The rabbits were housed in galvanized metal wire cages provided with feeders and automatic drinking system and were kept under the same managerial and hygienic conditions. The experimental period was extended for 8 weeks. Individual live body weight, feed consumption, feed conversion ratio and mortality rate were weekly recorded.

The main results could be summarized as follows: 1- Live body weights and body weight gain of rabbits were increased significantly throughout the experimental period in a linear manner due to supplemental vitamin A and Zn. 2- Zn supplementation at any level did not affect on feed consumption of growing rabbits, while vitamin A tended to reduce it, especially with the mid-level (10000 IU/kg). 3- Rabbits group received the control diet contained 50 ppm Zn plus 6000 IU vitamin A gave the worest overall feed conversion ratio as compared with those given the other experimental diets. 4- The interaction between Zn and vitamin A was highly significant during the whole experimental period indicating the presence of reciprocal positive synergism between both supplements. 5- No significant differences were observed in the digestibility coefficients of dry matter, organic matter and crude protein, ether extract, crude fiber, nitrogen free extract and nutritive values (TDN & DCP) among experimental diets. 6- There were insignificant improvements in most nutrients digestibility coefficients and nutritive values for rabbits fed diets containing 14000 IU vitamin A. The same trend was noted with rabbits received diet contained 50 ppm zinc. 7- No significant differences were observed in dressing percentage and relative weights of hot carcass, head, liver and heart due to feeding rabbits on different levels of zinc, regardless of vitamin A in the rabbit diets. 8- Dietary Zn levels did significantly affect (P<0.05 or 0.01) relative weights of kidneys, kidneys fat and spleen. 9- significant differences were noted in dressing percentage and relative weights of hot carcass, liver, kidneys fat and spleen for rabbit groups given diets containing different levels of vitamin A (6000, 10000 and 14000 IU). 10- Rabbits fed diet containing 10000 IU vitamin A gave the highest dressing percentage than those received 6000 and 14000 IU vitamin A diets. While head, heart and kidneys relative percentages were not significantly affected by vitamin A addition.