PhD

A detailed investigation involving two series of growth studies spread over a period of 24 weeks in Soviet Chinchilla and Cross Bred rabbits was carried out to establish the optimum energy and protein requirements for growth and to ascertain the optimum age for economic slaughter. One hundred and eight weanling Soviet Chinchilla and 108 weaning cross bred (SC X NZW) rabbits formed the experimental subjects. Rabbits of each breed were divided into nine identical groups and maintained factorially on three levels of crude protein (CP) viz., 12, 16 and 20 per cent and digestible energy viz., 2000, 2500 and 3000 kcal/kg for over a period of 168 days involving metabolism and slaughter studies during 8th, 16th and 24th week of experiment and production traits along with associated characters were studied and the salient results are presented.
Rabbits maintained on different energy protein combinations showed significant difference in growth rate (P < 0.01). Both dietary energy and crude protein were found to influence the average daily gain. The highest rate of gain was achieved in animals maintained on ration containing comparatively higher DE and CP while lowest rate of gain was noticed in animals maintained on low energy, low protein diet. On further scrutiny of the data, an appreciably better and identical growth response was observed in animals maintained on ration containing 3000 kcal DE/kg with 16 per cent CP and ration containing 2500 kcal DE/kg with 20 percent CP in both pure bred and cross bred rabbits. It is also noticed that for maximum growth rate a ration containing 2500 kcal. DE/kg need be sufficient as further increase in DE have not evinced any better response on ADG, which supports the view that for optimum biological response, a ration containing 2500 kcal DE/kg is sufficient for both pure bred and cross bred rabbits. As between the periods it was observed that the animals stained maximum ADG during the first 56 days of experiment and there after ADG gradually declines irrespective of the level of CP or DE in the ration.
Both dietary energy and crude protein significantly influenced (P < 0.01) the feed conversion efficiency of animals. Highest efficiency of feed conversion was noticed in rabbits maintained on Ration D containing 2500 kcal DE/kg and 20 per cent CP the values being 9.27 in SC and 8.85 in CB rabbits and further increase in DE from 2500 kcal/kg to the extent of 3000 kcal/kg did not contribute better feed efficiency. Data on feed efficiency further revealed that maximum efficiency was observed during the first eight weeks after weaning and there after there is a linear reduction in feed efficiency as the age advances, in all the nine dietary treatments.
With regard to cost of production the maximum biological and economical efficiency could be observed in animals maintained on ration containing 2500 kcal DE/kg with 20 per cent CP and when the cost of production was evaluated in between the periods viz., 0 – 56 days, 56 – 112 days and 112 – 168 days, the cost efficiency is seen maximum during 0 – 56 days of experiment.
Dry matter intake on percentage of body weight was found decreasing on increasing the dietary energy level. Haematological values were with in the normal range and were not significantly influenced by the dietary energy and protein levels. Digestibility of nutrients and percentage retention of nitrogen, calcium and phosphorus were significantly influenced by the dietary treatments with an increasing trend on increasing the dietary energy and protein level. From the metabolism studies carried out during 8th, 16th and 24th week of experiment, the percentage retention of nitrogen, calcium and phosphorus were found reduced on advancing the age of animals.
Slaughter studies conducted at 8th, 16th and 24th week of experiment revealed that dressing percentage is directly proportional to the pre – slaughter weight of the animals. Higher dressing percentage is recorded in animals having higher body weight and vice- versa. Carcass yield were higher at 16th and 24th week of experiment than that at eighth week of experiment.
Regarding the chemical composition of meat, the moisture and crude protein content on dry matter basis decreased on advancement of age, without any significant influence of dietary treatments, while the fat content progressively increased with increase in age and dietary energy content. Total ash content (dry basis) decreased with increase in age and dietary DE levels. An increase in liver protein percentage was observed with increase in dietary protein level. As the dietary energy level increased, liver fat content showed an increasing trend. Iodine number of the abdominal fat was not found influenced by the dietary energy – protein levels and age of the animal. Saponification value also was not influenced by the dietary CP and age of the animal.
Absence of appreciable quantities of abdominal fat during the 8th week indicates that for the production of lean meat, animals can be slaughtered during 8th week after weaning.
Evaluation of the data on slaughter studies indicate that broiler rabbits when slaughtered during 8 – 16 weeks after weaning yielded maximum profit, the profit accrued is seen inversely proportional to the increase in age of the animals with maximum profit obtained from slaughter during 8th week after weaning.
From a critical evaluation of the data gathered during the present investigation it can be reasonably concluded that broiler rabbits require a dietary level of 20 per cent crude protein and 2500 kcal DE/kg feed for evincing optimum growth and slaughtering rabbits during 8th week weaning is ideal for maximum profit.