Introduction

Rabbit farming, though a recent venture in India, has a promising scope for meat production in order to meet the growing global demand for quality animal protein. Despite of the beneficial attributes of rabbits, rabbit production has not yet become major segment of animal husbandry in our country due to lack of technical know-how, high prices of commercial rabbit feed and unorganised market for rabbit meat. About 72 per cent of the rabbit entrepreneurs reported that the feed prices were quite high when compared to output prices (Ashok Kumar et al., 2010). Protein is the most important component in the diet, which commonly depends on the traditional sources of protein such as soybean meal, groundnut cake and cotton seed cake which are costly pose a major problem. Under these circumstances, to make rabbit rearing more profitable as a small scale enterprise, there is a need for the development of cheap sources of feed as an alternative to replace or supplement cereal or other protein sources in the diet of rabbits. Various low cost protein sources such as moringa leaf meal were assessed in the past. Azolla is one of the locally available aquatic pteridophyte which is a good source of protein and almost all essential amino acids. Utilization of azolla was already enlightened in broiler chicken (Balaji et al., 2009), laying hens (Alalade et al., 2007), buffalo calves (Indira et al., 2009), pigs (Cherryl et al., 2014) and rabbits (Anitha et al., 2016). However, information on variations in various carcass traits of broiler rabbits due to feeding of azolla is scanty. Hence, the present study was undertaken to explore the effect on carcass traits of broiler rabbits by graded dietary levels of sun dried azolla as a substitute for conventional protein supplement.

Materials and Methods

The present work was undertaken at the Rabbitry unit of Livestock Farm Complex, College of Veterinary Science, Proddatur, Kadapa district in Andhra Pradesh.

Azolla was cultivated in two rectangular pits of dimensions 5m x 4m with a depth of 0.3m. Azolla was harvested at the end of week and was washed thoroughly in clean water, weighed and sun-dried for 2 to 3 days such that it becomes crispy while green colour is still retained in the dried azolla. The experiment was conducted in 24 New Zealand white rabbits divided into three groups (T₁, T₂ and T₃) with 8 rabbits in each group for 90 days. Conventional concentrate ration with CP 16% was formulated using maize, soybean meal, de-oiled rice bran, molasses, mineral mixture, salt, lysine and limestone to cover the nutrient requirements of rabbits according to NRC, 1977 recommendations. Three rations T₁ (conventional ration), T₂ and T₃ were prepared and fed after incorporation of sundried azolla as a protein replacement at 10 per cent in T₂ (900g of conventional ration + 74.41g of sundried azolla) and 20 per cent level in T₃ (800g of conventional ration + 148.82g of sundried azolla). The diets were compounded in mash form and fortified with vitamins and mineral supplements. Feeding was done thrice daily at 8.00AM, 1.00PM and 6.00PM. The concentrate ration and the required quantity of azolla to be fed were weighed and mixed thoroughly and fed accordingly. The daily feed left over was weighed daily and deducted from the feed supplied to know the amount of feed intake per day.

Slaughter of Rabbits

After 90 days 2 rabbits were chosen from each group at random for slaughter. The selected rabbits were fasted for 12 hours and then slaughtered by cutting the jugular vein and carotid arteries to allow thorough bleeding. After, decapitation and removal of feet, each carcass was de-skinned and the hot carcass weight was recorded. Then the carcass was opened by making an incision from lower part of the abdomen near the anus to the midpoint of the lowest ribs. The gut and the internal organs were removed. The carcass was drained under tap water and the dressed carcass weight was recorded. The weight of the pelt, gut, kidneys and pluck (lungs + heart + trachea) were recorded separately. Thereafter, each carcass was divided into 3 primal cuts namely fore cut (front portion of the carcass up to 7^th thoracic vertebrae), mid cut (portion of the carcass up to 7^thlumbar vertebrae) and the hind cut (portion of rump and hind limbs) and the weights of each cut were recorded separately. The data were subjected to one way ANOVA technique (Snedecor and Cochran, 1994) to arrive at the meaningful conclusions.

Results and Discussion

The carcass characteristics of rabbits fed with different rations were presented in Table 1.

Table 1: Carcass traits of New Zealand white rabbits under different feeding regimens

Means with different superscript differ significantly (P<0.01)

Perusal of the Table 1 revealed significant differences among the rabbits fed different rations for the various carcass characteristics. The head weight of rabbits from T_1, T₂ and T ₃ groups were 116.50 ± 0.50, 142.00 ± 1.00 and 105.50 ± 2.50 g, respectively and found to differ significantly (P<0.01) from each other. The pelt weight was found to be 81.00 ± 1.00, 93.00 ± 2.00 and 62.00 ± 2.00 g for T₁, T₂ and T₃ groups, respectively with significantly (P<0.01) higher pelt weight in rabbits of T₂ group followed by T₁ and T₃ groups. Sarin et al. (2015) reported an overall mean head weight and pelt weight of 196.50 ± 4.32 and 272.26 ± 9.33 g, respectively in APAU -Fawn and APAU-Black rabbits under conventional feeding system. The mean hot carcass weight recorded were 1182.50 ± 9.50, 1283.50 ± 0.50 and 860.50 ± 7.50 g for T₁, T₂ and T₃ groups, respectively. The hot carcass weight was observed to be significantly higher in rabbits of T₂group when compared to that of T₁ and T₃ groups. Significant difference (P<0.01) was also observed with regard to dressed carcass weight of rabbits among the three groups with significantly higher weight recorded in rabbits of T₂ group. The mean dressed carcass weight for T₁, T₂ and T₃ groups were found to be 817.00 ± 6.00, 895.00 ± 2.00 and 567.00 ± 5.00 g, respectively. Agrahar- Murugkar et al. (2000) reported slightly higher pre-slaughter weight and hot carcass weight of 1850 ± 3.19 and 965 ± 3.00, respectively while Rahman et al. (2013) findings revealed 1672 ± 277.20 and 940.7 ± 121.9 g for pre-slaughter weight and hot carcass weight, respectively in New Zealand white rabbit. The mean weight of fore cut for T₁, T₂ and T₃groups were 227.00 ± 1.00, 270.00 ± 2.00 and 145.00 ± 0.50 g, respectively and that of mid cut were 273.00 ± 3.00, 287.00 ± 1.00 and 180.50 ± 0.50 g for T₁, T₂ and T₃ groups, respectively. The hind cut weights recorded were 317.00 ± 2.00, 338.00 ± 1.00 and 241.00 ± 4.00 g for T₁, T₂and T₃ groups, respectively. The mean weights of fore cut, mid cut and hind cut differed significantly (P<0.01) among the three groups with highest weights in rabbits of T₂ group followed by T₁ and T₃ groups. The present findings were comparatively lower than the findings of Sarin et al. (2015) who reported average fore-cut, mid-cut and hind-cut weights of 451.09 ± 13.14, 325.85 ±11.15 and 459.48 ± 11.97g, respectively in APAU -Fawn and APAU-Black rabbits under traditional feeding system. The dressing percentage recorded for the rabbits fed with T₁, T₂and T₃ rations was 59.04 ± 0.01, 58.76 ± 0.06 and 54.96 ± 0.18, respectively. Significantly lower dressing percentage was found in rabbits fed with T₃ ration while the dressing percentage of T₁and T₂ groups did not differ significantly from each other. However, comparatively higher dressing percentage was found in rabbits of T₂ group. The dressing percentage was 57.29 and 54.8 per cent as reported by Agrahar-murugkar et al. (2000) and Rahman et al. (2013), respectively under conventional feeding systems which were slightly lower than the present findings. This variation among the carcass traits in rabbits as reported by different authors might be attributed to breed variation and different feeding practices followed in their studies.

The lower dressing percentage in T₃ group (20 % azolla replacement) is due to a lower pre-slaughter and dressed carcass weight when compared with the other two groups which in turn, might be ascribed to higher levels of fibre and tannins in azolla that may be responsible for decreased nutrient utilization/feed intake by the rabbits in T₃ group. No significant difference is observed in T₁ and T₂. Similarly Basak et al. (2002) reported that the dressing percentage of vencobb broiler chicken significantly improved with 5% replacement level of azolla to conventional protein. Wadhwani et al. (2010) observed that the average values of dressing percentage in lambs on live basis were 50.40, 59.63 and 58.51 in different groups fed with 0, 10 and 20 per cent azolla incorporated diets, respectively. Cherryl et al. (2014) reported no significant difference with inclusion of azolla on various carcass traits of pigs except for higher fat percentage in pigs fed basal diet without azolla.

Conclusion

Considering the results, it might be concluded that inclusion of azolla at 10% significantly improved the carcass parameters of New Zealand white rabbits. Hence, the scope for inclusion of sun dried azolla as an unconventional natural protein feed source in diets of rabbits is feasible up to 10 per cent and recommended without any negative harmful effects. Further proper utilisation of azolla in the system needs to be exploded through digestibility trials.

References

1. Agrahar-murugkar D, Gupta JJ, Yadav BPS and Das A (2000) Carcass evaluation and acceptability studies on rabbits in north eastern hill region of India. J of World Rabbit Sci Association 8: 547-551.
2. Alalade OA, Iyayi EA and Alalade TO (2007) The nutritive value of azolla (Azolla pinnata) meal in diets for growing pullets and subsequent effect on laying performance. The J of Poult Sci 44:273-277.
3. Anitha KC, Rajeshwari YB, Prabhu TM, Vivek patil M, Shilpa Shree J and Anupkumar PK (2016) Effect of supplementary feeding of Azolla on growth performance of Broiler Rabbits. ARPN J of Agric and Biological Sci 11(1):30-36.
4. Ashok Kumar, Atul Dogra, Guleria JS (2010) Problems and constraints of Rabbitry in India: A Study of Himachal Pradesh. Global J of Sci Frontier Research 10(8): 40-46.
5. Balaji K, Jalaludeen A, Churchil RR, Peethambaran PA and Sethilkumar S (2009) Efffect of dietary inclusion of azolla (Azolla pinnata) on production performance of broiler chicken. Indian J of Poult Sci 44:195-198.
6. Basak B, Md Ahsan Habib Pramank, Rahman MS, Tarahdar SU and Roy BC (2002) Azolla (Azolla pinnata) as a feed ingredient in broiler ration. Int J of Pout Sci 1:29-34.
7. Cherryl DM, Prasad RMV, Jagadeeswara Rao S, Jayalaxmi P and Srinivas Kumar D (2014) A study on the nutritive value of Azolla pinnata. Livestock Research Int 2(1): 13-15.
8. Indira D, Sarjan Rao K, Suresh J, Venugopal Naidu K and Ravi A, (2009) Azolla (Azolla pinnata) as feed supplement in buffalo calves on growth performance. Indian J of Animal Nutrition 26:345-348.
9. Nutrient Requirements of Rabbits (1977) 2^nd Revised Edition. National Academy Sciences, Washington. DC.
10. Rahman Hind A EI, Hind AA Elagib, SA Babiker and Khalidb M Elamin (2013) Meat production from Tropical and Temperate Rabbit Breeds in Sudan. Int J of Livestock Research 3:14-20.
11. Sarin K. Kunnath, Sakaram D, Gnanaprakash M and Sarat Chandra A (2015) Study on carcass traits of broiler rabbits. The Indian J of small ruminants 21(2):362-363.
12. Snedecor G W and Cochran W G (1994) Statistical Methods 8^th edn. The Iowa State University Press, Ames, Iowa. U.S.A.
13. Wadhwani K N, Parnerkar S, Saiyed LH and Pate A M. (2010). Feedlot performance of weaner lambs on conventional and non-conventional total mixed ration. Indian journal of Animal Research Vol. 44:16-21.