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sur le développement des zones arides et semi-arides

Titre : Water intake, nutrient utilisation, and production efficiency of selected South African sheep breeds

Auteur : Mupfiga, Sandra

Université de soutenance : Stellenbosch University

Grade : Master of Science (MS) Animal Sciences 2021

Résumé partiel
The main objective of the current study was to compare nutrient intake, water intake, nutrient digestibility, nitrogen and water balance, growth performance and carcass attributes of six South African sheep breeds kept under feedlot conditions. Fifty-seven, 4 to 5 months old wether lambs of pure indigenous (Pedi and Damara), indigenous composite (Meatmaster and Dorper) and exotic composite (Merino and Dohne Merino) wethers were used for the digestibility and growth trials. They were fed a pelleted total mixed ration containing 143.5 g crude protein (CP)/ kg DM and 10.29 MJ/ kg DM metabolisable energy. The wethers were adapted to the diet for 21 days, followed by 7 days of sample collection for digestibility trial and 42 days for growth trial. Breed had an influence on nutrient intake with Meatmaster having the highest dry matter (DM), organic matter (OM), CP, ash-free neutral detergent fibre (aNDFom) and ether extract (EE) intake followed by Damara, with Pedi having the least values (P ≤ 0.05). Damara and Meatmaster had higher (P ≤ 0.05) DM digestibility than the rest of the breeds. The aNDFom digestibility was in the following order : Dorper ≥ Merino ≥ Meatmaster ≥ Damara ≥ Dohne Merino ≥ Pedi. Damara had higher (P ≤ 0.05) ether extract digestibility than the rest of the breeds. Meatmaster had the highest total N intake (feed + microbial N) and faecal N compared to other breeds (P ≤ 0.05). Relative to other breeds, Meatmaster and Damara had higher (P ≤ 0.05) N retention. Meatmaster, Dohne Merino, Damara and Dorper had higher (P ≤ 0.05) positive water balance than Merino and Pedi. Average daily gain was highest for the Meatmaster and Damara, moderate for Dorper and Pedi and lowest for the Merino and Dohne Merino (P ≤ 0.05). The feed conversion ratio was lowest for the Pedi with Dohne Merino having the highest ratio (P ≤ 0.05). The Pedi drank the least amount of water while Meatmaster drank the highest (P ≤ 0.05). Dohne Merino had the highest water to gain ratio while Pedi had the least (P ≤ 0.05). Hot and cold carcass weights and dressing percentage were lower (P ≤ 0.05) for the Damara and Pedi lambs compared to other breeds

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