Effects of Feeding Different Sorghum Varieties on the Haematological Parameters and Carcass Measurements of Growing Rabbits

An eight-week feeding trial was conducted to investigate the effect of different sorghum varieties on the blood parameters and carcass measurements of cross-bred (Dutch x New Zealand) growing rabbits aged between five and seven weeks. Twenty five rabbits were randomly allocated to five dietary treatments; T1 (100% maize), T2 (50% maize and 50% “Chakalare” sorghum), T3 (100% Chakalare” sorghum), T4 (50% maize and 50% “Jigare” sorghum) and T5 (100% “Jigare” sorghum). The “Chakalare” and “Jigare” are low-tannin and hightannin sorghum varieties respectively. The haematological parameters were Packed Cell Volume (PCV), Haemoglobin (Hb), Red Blood Cell (RBC), White Blood Cell (WBC), Mean Corpuscular Volume (MCV), Mean Corpuscular Haemoglobin (MCH), Mean Corpuscular Haemoglobin Concentration (MCHC), Monocytes (%) basophils (%), Neutrophils (%), Eosinophils (%) and Lymphocytes (%). The carcass parameters were Slaughter weight (g), Dressed weight (g), Dressing percentage %, (As % of slaughter weight) of Shoulder/forelegs, Rack, Loin, Thighs/Hind legs, Skin/pelt, Tail, Head, Feet, Heart Liver, Lungs, Kidneys, Kidneys Caecum, Stomach, Large intestine, Small intestine, Caecum length (cm), Stomach length (cm), Small intestine length (cm) and Body length (cm). The response showed that most of the haematological parameters were significantly affected (P<0.05) by the different varieties of sorghum in the diets except packed cell volume, mean corpuscular volume, mean corpuscular haemoglobin concentration and basophils which were not significantly affected (P>0.05) by the different varieties of sorghum in the diets. However, most of the haematological values fell within the normal ranges PCV (37.33 to 40.67 %), Hb (13.37156.73 %), RBC (5.57-6.93%) and WBC (12.67-14.83) of growing rabbits. The carcass measurements and organs expressed as percentage of slaughter weight were not significantly (P>0.05) different among the treatment groups except slaughter weight, dressing percentage, rack, loin, liver, caecum weight and stomach length which were significantly (P<0.05) different. The study indicated that the two varieties of sorghum (“Chakalare” and “Jigare”) can be included in the diets of growing rabbits as replacement for maize without adverse effect on haematology and carcass parameters of growing rabbits.


INTRODUCTION
The level of performance in the livestock industries in Nigeria in recent years has fallen below expectation due to shortage of feed, escalating prices of feed ingredients and poor quality feed (Owen et al., 2009). Recent difficulties with animal production inputs in Nigeria, especially high cost of feed ingredients in particular, have brought about the need to look for alternatives to conventional feed resources. These led to the need to explore other locally In most developing countries the search for non-conventional feed ingredients to replace the expensive conventional ones appears to occupy the attention of the animal nutritionists. It is to reduce the cost of production, thus making it possible for people to afford animal protein in their menu (Ojebiyi et al., 2006). The objectives of this study is to determine the effect of feeding different varieties of sorghum on the haematology and carcass measurements of growing rabbits.

Location of the study
The study was conducted at the Livestock Teaching and Research Farm, Department of Animal Science, University of Maiduguri, Maiduguri, Borno State, Nigeria. Maiduguri is located on latitude 11 o 15' North and longitude 30 o 05' East and on an altitude of 345 m above sea level (Ugherughe and Ekedolum, 1986). The relative humidity ranges from 30 to 50%. The area experiences for 3 to 4 months from June to September and gets between 500 to 600 mm and followed by long period of dry season of 8 months (Encarta, 2007).

Experimental animals and management.
A total of twenty-five (25) Dutch x New Zealand white rabbits, between five and seven weeks of age were used for the feeding trial which lasted for 8 weeks. Before the commencement of the experiment, a one-week adjustment period was observed. The rabbits were individually weighed and divided into five groups with average weight of 569.4 g. The groups were randomly assigned to five dietary treatments. Each rabbit was individually housed in a wire cage measuring 38 x 33 x 45 cm. The cages, in rows, were raised 45 cm above the ground to facilitate cleaning. Each cage cell was equipped with plastic drinker and metal feeding trough. The experimental diets (in mash form) and clean drinking water were provided ad libitum throughout the experimental period.

Haematological parameters
At week 8 of the experiment, blood samples were collected randomly from three (3) rabbits per treatment for the determination of the haematological indices. Samples were collected from the ear vein of the rabbits by venipunture using disposable needle (21-gauge needle) and syringes. The rabbits were fasted overnight (12 hrs) and normally bled in the morning (7.00-8.00 am) to avoid excessive bleeding. The collection site was cleaned with alcohol and xylene to dilate the veins. Sterile cotton was used to cover the punctured vein after collection.
The blood samples were collected in sample bottles containing dipotassium salt of ethylene  (Schalm et al., 1975;Encarta, 2007). The haematological indices determined were packed cell volume (PCV), haemoglobin concentration (Hb), red blood cell (RBC) counts and white blood cell (WBC) counts and differential counts. Mean corpuscular haemoglobin (MCH), mean corpuscular volume (MCV) and mean corpuscular haemoglobin concentration (MCHC) were obtained by calculation according to standard formulae (Jain, 1986).

Carcass measurements
At the end of the experiment, three rabbits from each treatment were selected for slaughter based on average weight of the group. They were deprived of feed for 12 hours as recommended by Jain (1986) but drinking water was provided. Withholding feed for 12 hours before slaughter reduced the volume of gut contents and hence bacteria, and therefore reduced the risk of carcass contamination during dressing without adversely affecting meat yield and quality (Jain, 1986;FAO. 1991). The rabbits were weighed in the morning and slaughtered by cutting transversely across the trachea, oesophagus, large carotid arteries and jugular veins to ensure maximum bleeding (Mann, 1960). They were later opened and dressed as described by (Blasco et al., 1993). The dressed carcass is the portion of the rabbit remaining after the removal of the head, feet, skin (pelt), tail and visceral organs including kidneys. The dressed carcasses were split into retail cuts such as shoulder/forelegs, thigh/hind leg, rack and loin as described by (Blasco et al., 1993). The dressed carcass and the retail cuts were weighed and expressed as percentage of slaughter weight.

Statistical analysis
All the data collected were subjected to analysis of variance (ANOVA) using the randomized complete block design (Steel and Torrie, 1980). Means were separated where applicable using the Duncan's multiple range test (Duncan, 1955). A computer package (Statistix 9.0) was used for the analysis.

Carcass parameters
The carcass parameters in table 3 showed that dressed weight, shoulder, thighs, head, skin, feet, tail, small intestine, large intestine, stomach, heart, kidneys, lungs, caecum length, small intestine length, large intestine length and body length were not significantly (P>0.05) different among the treatment groups. This is an indication that body and organ developments of the growing rabbits were not compromised by the different varieties of sorghum included in their diets. The slaughter weight, dressing percentage, rack, loin, liver, caecum weight and stomach length were significantly (P<0.05) different among the treatment groups. Rabbits fed T5 (100% "Jigare" sorghum) and T4 (50% "Jigare" sorghum) diets had significantly (P<0.05) heavier slaughter weight than those fed T1 (100% maize) and T2 (50% "Chakalare" sorghum) diets. There were no significant difference in slaughter weight among the rabbits fed the T3 (100% "Chakalare" sorghum) diet and the other diets. Rabbits fed T2 (50% "Chakalare" sorghum) and T3 (100% "Chakalare" sorghum) diets had significantly better dressing percentage than those on T5 (100% "Jigare"sorghum) diet but was similar to other treatment groups.
Rabbits fed the control (100% maize) diet had significantly (P<0.05) heavier weight of rack compared to other treatment groups with similar values. Loin of rabbits fed T4 (50% "Jigare" sorghum) diet had significantly (P<0.05) heavier weight than those fed control (100% maize) diet but did not differ from rabbits fed T2 (50% "Chakalare" sorghum), T3 (100% "Chakalare" sorghum) and T5 (100% "Jigare" sorghum) diets. The loin weight expressed as percentage of slaughter weight followed the same trend as the slaughter weight. The shoulder, loin and thigh constitute over 90% of the carcass weight and thus rabbits with heavier shoulders, loins and thighs often have heavier carcasses (Igwebuike et al., 2007). The liver of rabbits fed T3 (100% "Chakalare" sorghum), T4 (50% "Jigare" sorghum) and T5 (100% "Jigare" sorghum) diets were superior to T2 (50% "Chakalare" sorghum) diet but was similar to rabbits fed control (100% maize) diet. Rabbits fed control (100% maize), T4 (50% "Jigare" sorghum) and T5 (100% "Jigare" sorghum) diets had significantly (P<0.05) heavier caecum weight than those fed T3 (100% "Chakalare" sorghum) diet but similar to rabbits fed T2 (50% "Chakalare" sorghum) diet. The stomach lengths of all the treatments with the exception of control (100% maize) were similar. The carcass measurements of rabbits in this study compared favourably with the values reported by Mohammed et al. (2010) who slaughtered rabbits of similar weight and ages in the same environment. This suggested that complete replacement of maize with the two varieties of sorghum in the diet of growing rabbits had no adverse effect on carcass and organ developments.

CONCLUSION
Based on the haematological findings and carcass measurements of the rabbits, different varieties of sorghum ("Chakalare" and "Jigare") can replace 100% of the maize in the diets of growing rabbits. This is a good indication that different varieties of sorghum irrespective of