Phenotypic Characterisation Of Meatmaster Sheep Using Quantitative And Qualitative Trait Analysis

Dissertation

The aim of the study was to create a phenotypic analysis of the Meatmaster breed, utilizing linear body measurements, subjective assessments of body form, slaughter data and pedigree performance data (collected only from the ewes). The linear body measurements and pedigree performance data were collected from one hundred and eighty-seven rams (187) and two hundred and twenty-two ewes (222) of all age categories, measured both in incisor counts and number of days lived. Linear body measurements were used as the main instrument of measuring different body parts and the following means in both rams and ewes were measured: Body Weight (rams= 80.47±13.33 kg, ewes= 57.51±12.43 kg), Head Length (rams= 23.93±1.55 cm, ewes= 22.68±2.05 cm), Neck Length (rams= 28.35±5.16 cm, ewes= 29.61±3.82 cm), Chest Girth (rams= 102.45±8.42 cm, ewes= 92.95±8.08 cm) Tail Length (rams= 38.24±4.88 cm, ewes= 36.64±4.70 cm), Wither Height (rams= 63.91±4.04 cm, ewes= 58.99±4.86 cm), Chest Depth (rams= 37.51±2.97 cm, ewes= 34.47±2.97 cm), Chest Width (rams= 23.47±2.56 cm, ewes= 21.24±2.85 cm), Body Length (rams= 78.95±5.59 cm, ewes= 72.67±6.06 cm), Rump Length (rams= 21.82±3.29 cm, ewes= 20.77±1.93 cm) Rump Width (rams= 23.87±2.82 cm, ewes= 21.36±3.15 cm), Skin thickness (rams= 2.846±0.5 mm, ewes= 2.805±0.5 mm), Pelvis length (ewes= 7.66±.98 cm), Pelvis Width (ewes= 7.66±.90 cm), Pelvis Area (ewes= 46.69±10.62 cm²) and Scrotal Circumference (rams= 35.12±3.03 cm). All body measurements had a significant difference (P<0.001) between the genders, except for neck length (P>0.001) and tail length (P>0.001). The pedigree performance records of one hundred and seventy-seven (177) ewes showed the following means: Age at First Lambing (15.242±3.8 months), Number of Times Lambed (3.33±1.8), Number of Lambs Born (4.36±3.4), Number of Lambs Weaned (3.44±2.5) and Average Inter-lambing Period (258.64±151.3 days). Slaughtering data were compiled from two thousand two hundred and fifty one (2251) animals of different genders and ages the means are as follows: A0 (16.388±4.2 kg), A1 (16.098±3.1 kg), A2 (16.949±3.2 kg), A3 (18.138±3.5 kg), A4 (15.33±5.6 kg), A5 (14.80±0 kg), A6 (16.30±8.2 kg), Mean of A-grades (16.77±4.1 kg), AB1 (22.10±0 kg), AB2 (27.117±7.2 kg), AB3 (22.90±0 kg), Mean of AB-grades (24.039±13.8 kg), B1 (25.01±14.8 kg), B2 (26.656±5.2 kg), B3 (28.15±16.3kg), B4 (27.80±0 kg), Mean of B-grades (26.904±13.3 kg), C2 (25.127±4.3 kg), C3 (24.633±7.1 kg) and Mean of C-grades (24.88±4.9 kg). A stepwise regression was carried out using SPSS (Version 26) to determine the individual influence of body measurements on performance. An F to enter level of 0.05 was used to determine the significance of the partial contribution of each effect. Pearson correlations were conducted on the body measurements in both rams and ewes, following the guidelines of Field (2009). In order to investigate the difference between various age and area categories the Hochberg’s GT2 post hoc test was conducted. A Multiple Regression Analysis was conducted on five models using LBM as the variables. In the next step of the multiple regression analysis the tool of Model Summary boxes was used. The Durbin-Watson statistical test was used for the assumption to be made that the residuals are independent (or uncorrelated). A significant (P<0.01) correlation (89.5% for rams and 89.7% for ewes) were found between body weight and chest girth, this was the highest correlation found between all the body measurements and body weight. The only negative correlation to body weight was that of neck length (-8% for rams and -9% for ewes) and had no significant correlation (P>0.05). An interesting predictive value of R2= 0.140 was observed between the body measurement wither height and the performance trait average inter-lambing period as well as a predictive value of R2= 0.154 between the body measurement wither height and the performance trait number of lambs born. This seems to be a characteristic of the Afro-type sheep breeds which have a higher wither height and have a higher tendency to birth multiple lambs per lambing opportunity. Age has a significant influence (P<0.001) on all the body measurements of the Meatmaster, except for neck- and tail length. The environment has a significant influence (P<0.001) on all the body measurements of the Meatmaster, except for tail length.