Morphological Indices and Carcass Measurements of Indigenous Breeds of Rams Intensively Fattened

Growth rate assessment is an important husbandry practice often carried out in livestock breeding and fattening. Meat production is the most important trait in the breeding objectives of sheep production. Useful information on the suitability of the animals for meat production could be evaluated on a morphological basis. The aim of this study was to investigate breed differences in liveweight, carcass traits and muscle distribution for meat characteristics among Balami (BA), Uda (UD), Yankasa (YK) and West African Dwarf rams (WAD). A total of forty-eight rams were randomly assigned into four groups of twelve rams per breed in a completely randomized design. Body linear measurements were obtained weekly during the fattening period. At the end of the feeding trial, animals were subjected to an 18-hours fast and slaughtered for carcass measurements and muscle distribution. Results showed that BA and UD had higher values for body length (115.75±4.25 and110.25±1.89cm), withers height (70.50±5.57and69.00±2.16cm) and heartgirth (92.00±2.94and84.00±1.41cm), than YK (96.50±3.87, 60.75±3.30 and 76.75±0.96cm), respectively which in turn had higher values than WAD (86.50±5.20, 53.25±5.32 and 75.25±3.30cm). Carcass length, pistol length, and leg length were75.75±4.79,60.75±7.14 and 88.00±2.16; 75.50±4.66, 56.00±5.00 and 80.25±5.80; 59.00±7.79, 56.00±10.62 and 71.50±2.65; 60.50±3.11, 53.75±5.91 and 61.00±2.94cm for BA, UD, YK and WAD rams, respectively. BA and UD had higher proportion of muscle distribution and were generally better than the YK and WAD breeds. This may boost their potential for large scale meat production under fattening conditions.


1.Introduction
Nigeria's livestock industry is small and slow-growing relative to the population relying on it for meat [1]. Farmers need to invest in breeds that have traits for good carcass quality.The breed that can deliver good quality meat should be selected or bred for important and desirable traits. The commercial value of meat animals is determined by the carcass weight, proportion, and distribution of carcass muscle [2]. The use of specialized meat breeds to improve animal productivity and economic results is desirable in intensive sheep production. The quality of rams of local breeds is an important instrument to promote the consumption of meat in the local population [3]. Morphometric measurements have been used to evaluate the characteristics of various breeds of animals and could provide first-hand information on the suitability of animals for selection [4]. Based on body conformation, meat production can better be estimated than other production properties, making body measurements important selection criteria [5]. Muscularity indicates the amount of muscle tissue, determined by muscle to bone ratio and fatness describes the external and internal deposition of Breeds of Rams Intensively Fattened fat in the carcass. According to Srivastava et al. [6], body measurements are indices of skeletal development and indirectly help to determine carcass composition. Another parameter that has been used over the years to estimate the amount of meat that could be obtained from slaughtered animals is carcass measurement. Carcass composition assessment assigns value, sorting of carcasses for further processing and transfers information back to the production sector, ensuring that carcasses meet consumer demand. The objectives of the present study were to analyze the interrelationships between weights and measurements of carcasses; compare various measurements of the body, carcass, and tissue distribution for BA, UD, YK and WAD breeds of ram under intensive management.

Location of Experiment
The study was conducted at the Sheep and Goat unit of the Teaching and Research Farm, University of Ibadan, located on Latitude 7 o 26'N and 3 o 54'E and on an elevation of 330m above sea level. The area is characterized by humid tropical climate with an annual rainfall of 1540 mm and an average temperature of 22.1°C to30.8°C for ten-hours per day

Animal Management
Forty-eight rams of Balami (BA), Uda (UD), Yankasa (YK) and West African Dwarf (WAD) breeds. Weighing 17.00±0.39-19.38±0.39 (12-18months of age). The age of the animals was estimated by visual observation, interviewing the owners and by dentition. Four breeds of rams (Twelve replicate per breed) were raised intensively. The rams were dewormed (300mg albendazole bolus for internal and with acarimic spray for external parasites, respectively), dipped and vaccinated against known parasites and diseases during the period of twenty-one days and were adapted for 15 days followed by ninety days feeding period. Experimental animals were fattened for ninety days, during which time each pen of rams was supplied with concentrate (14% crude protein and 2.00 Mcal/kg digestible energy) and hay at the rate 5% (60:40) of the body weight per ram and adlibtum access to salt lick and fresh, clean and cool water. At the end of the ninety days, four rams in each group whose weights were the closest to the average final weight of the rams of respective breeds were chosen for subsequent carcass analysis.

Linear Body Measurements
The six morphometric traits measured were wither height, pelvis height, body length, heart girth, chest width, and chest depth. Measurement was done using a graduated measuring stick. To achieve this, animals were placed on flat ground and held by two field assistants. The length measurements were done using a Dalton's weighing band tape rule while the width measurements were taken using a calibrated wooden caliper [7]. The following body measurements were estimated: 1) Body length: the distance between the point of shoulder and the pin-bone. 2) Height at withers: vertical distance from the withers to the floor. 3) Heart girth: circumference of the body just behind the fore legs 4) Chest depth: vertical distance from the withers to the chest bottom, 5) Chest width: width of the body at the withers. 6) Height at Pelvic: hind leg length between malleolus and perineeum

Slaughter Procedure
The selected rams (four rams per breed) were transported to the slaughter house of the Department of Animal Science, University of Ibadan where pre-slaughter liveweight was recorded after twelve-hours of fasting but free access to water. Exsanguination was carried out by an incision on the jugular furrow at the occipital-atlantal junction close to the head, severing the carotid arteries, jugular veins, trachea, oesophagus, and the spinal cord. The head was removed and the carcass was hung by the hindlegs using a pulley and then skinned [8].

The Evisceration of Carcasses and Carcass Evaluation
Evisceration was carried out and hot carcass weight was taken on the slaughter floor within ten minutes post-mortem. The carcass was chilled for twenty-four hours at 3 o C-4 o Cusing cold room and reweighed to get chilled carcass weight, allowed to thaw for twelve hours at room temperature and dimensional measurements: carcass length, length of hindquarters, length of fore-quarters, and depth of chest according to the procedures of De Boer et al. [7].Dissection of carcasses commenced after thawing. The left sides were separated as outlined by Fisher and De Boer [7]. The lengths of the pistol were obtained following quartering of the carcass side.

Dissection of Muscles
The abdominal muscles were freed where they join the pelvic limb and the side was cut along the edge of Iliocostalis lumborum muscle through the ribs to the earlier cut between the 5 th and6th thoracic vertebrae [9] and then the cut was continued along the caudal edge of the 5 th rib. This divided the side into a pistol hindquarter and a pistol forequarter. The right pistol hindquarter and pistol forequarter were weighed and dissected into individual lmuscles (semimembranosus, semitendinosus, bicepsfemoris, adductor, gluteus medius, deltoideus, supraspinatus, infraspinatus, subscapularis, and deltodius), bones and fat following the procedures of Robelin and Geay [10]. Values were expressed as a percentage of the pistol weight.

Derived Indexes
Body measurements to liveweight (cm/100g), hot carcass weight to carcass measurements (cm/100g), and the proportion of individual muscles to pistol weight were recorded based on standard procedure [11]. Also proportion of bone distribution to pistol weight, Proportion of fat distribution to pistol weight, relationship between hot carcass weight and percentage proportion of individual muscles were obtained according to Purchas et al. [12].

Statistical Analyses
Data were statistically analyzed using one-way analysis of variance, the procedure of the Statistical Analysis System [13]. The LSD procedure was applied for mean comparison at 5%. Simple correlation coefficients of hot carcass weight and proportional weight of tissues of the proximal hindquarter and proximal forequarter of the carcasses were carried out using Pearson's correlations.

Body Measurements
Linear measurements of Balami, Ouda, Yakansa and West African Dwarf rams intensively fattened are shown in Table1 [14] observed that chest girth and rump width were suitable factors for predicting hot carcass weight in each of Afshari and Zandi sheep, respectively. Also, body measurements are important data sources in terms of reflecting the breed standards [15], and giving information about the morphological structure and development ability of the animals.  hindquarters, forequarters, and Pistola lengths did not differ (P>0.05) between the breeds but the lowest were recorded (P<0.05) for WAD. All the four breeds differed significantly for lengths of hindquarters and forequarters relative to carcass weight, which was greatest for BA (0.47±0.04; 0.33±0.01) and least for WAD (0.34±0.02; 0.28±0.01). Carcass measurements and indexes are used as indicators of carcass conformation and size [16]. The results of the current study indicate a significant effect of breed on carcass measurements and conformation indexes, which could be explained by breed specific morphologic characteristics of Breeds of Rams Intensively Fattened BA rams.

Meat to Bone Ratio
Weight to length ratio has been proposed as an objective measure of the carcass index. This index describes the amount of meat and fat which a carcass carries relative to its length and affords a quick and accurate description of its meatiness [17]. Proportions of tissues in the carcass of the four breeds of rams intensively fattened are shown in Table3. The meat to bone ratio as determined by dissection of the proximal hindquarter and proximal forequarter of the left half of the carcass were 8.92 and 12.90 in BA and 5.81 and 12.64 in UD, respectively and the corresponding ratio for YK and WAD were 5.46; 7.92 and 4.88; 10.10, respectively. BA had the highest (P<0.05) meat to bone ratio due to its lowest fat proportion. UD, YK, and WAD yielded similar meat to the bone ratio (P>0.05) while BA, UD, and WAD breeds had similar meat to fat ratios. Differences in carcass were primarily due to the distribution of fat and to variation in the thickness of muscles but not differences in muscle distribution. The sequence of growth illustrates the importance of each fat depot in animals and the market value of the carcass [18]. Cloete et al. [19] observed differences in the fat deposition of mutton breeds which suggests that different breeds would deposit fat at different levels. Early matured breeds would render a fatter carcass at slaughter, after a constant number of days in the feed [20], which in turn would affect the value of the carcass. It is therefore important to determine the maturation rate of the major carcass tissues of various breeds of sheep to accurately predict a slaughter weight for ideal grading of the carcass. Using a commercial dissection procedure, Colomer-Rocheret al. [21] found that hindquarter cuts had more muscle and a higher muscle-to-bone ratio than those in forequarter cuts.

Relationship Between Hot Carcass Weight and Muscle Distribution
Significant positive correlations (P<0.05) were obtained between hot carcass weight and Semitendinosus muscle (0.89) and Supraspinatus muscle (0.56), whereas a high negative correlation (P<0.05) was obtained with Subscapularis muscle (0.34). Significant positive correlations were obtained between Semitendinosus muscle and Bicep femoris muscle (0.58), Adductor muscle (0.88), Gluteus medius (0.83), Infraspinatus (0.67) and Deltodius (0.66), whereas significant negative correlations were obtained with Subscapularis muscle and Bicep femoris muscle (0.50), Semimembranosus muscle (0.37), Adductor muscle (0.97), Deep pectoralis muscle (0.54) and Supraspinatus muscle (0.73) proportions. Correlation coefficients between Semimembranosus muscle and Bicep femoris muscle (0.84), Adductor muscle (0.68) and Gluteus medius (0.64) were in the same direction of those obtained from Bicep femoris muscle with Adductor muscle (0.61) and Gluteus medius (0.71) value. Correlations between the muscles of the carcass appear more dependent upon hindlegs and forelegs rather than an absolute hot carcass weight. This is evidenced by the fact that the highest correlations were seen between the muscles of the foreleg (supraspinatus and infraspinatus, Deep pectoralis and Deltoideus muscles) and the hindleg (semimembranosus and semitendinosus, Adductor and Gluteus medius muscles). The relationship between hot carcass weight and the distribution of muscles suggests that an increase in one could lead to a corresponding increase in the other muscles [23,24].

4.Conclusions
Differences between breeds were observed in the morphology of the carcass and muscles of four breeds of rams intensively fattened. Yankasa and West African Dwarf breeds of rams had lower carcass measurements than Balami and Ouda breeds. The combination of morphological traits and distribution of muscles found in the carcasses for the Balami breeds of rams in this study indicated that this breed would most likely produce the best carcass under similar agricultural conditions. The study also concludes that the measurements of the muscles of the hindlegs and forelegs could be used satisfactorily for prediction of hot carcass weight.