The essential amino acid requirements of springbok, blesbok and impala for optimal growth

[摘要] ENGLISH ABSTRACT:Regardless of the extensive game eradication during most of the previous century, thegame farming industry in South Africa has shown dynamic growth over the past fewdecades. Currently the approximately 8 000 game farms have a total income of morethan R850 million per annum. Although there are various game species included inthese farming enterprises, three of the most important species for commercial farmingand meat marketing are springbok iAntidorcas marsupialisï, blesbok (Damaliscusdorcas phillipsiï and impala (Aepyceros melampus).Since nutrition is a key factor in the productivity of animals, any information on thissubject is essential for the successful management of a game farm. However, apartfrom the general lack in applied research on game animals (due to the differentapproaches by biologists and agricultural researchers), there is also only limitedinformation available on the nutritional requirements of game species or any of theaspects affected by nutrition.In order to address the above shortcomings in game animal nutrition, two separatestudies were conducted. The purpose of the first study was to determine the physicalbody component and nitrogen (N) distribution in the springbok, blesbok and impala.The chemical composition of the three-rib cut was also compared with that of thecarcass. Amino acid requirements for growth of the three game species wereinvestigated in the second study according to the ideal protein concept. The essentialamino acid (EAA) profile of the whole empty body of the three game species wascompared with the EAA profile of the duodenal digesta in order to detect anyimbalances for optimal growth.The same animals were used in both studies, namely eight of each of the three gamespecies. Characterization of the physical body composition revealed that the dressingpercentages (% of body weight; % of empty body weight) for the three game specieswere: springbok (57.1 ± 2.4 %; 64.0 ± 2.5 %), blesbok (50.2 ± 2.1 %; 62.8 ± 1.4 %)and impala (57.4 ± 2.2 %; 65.6 ± 2.0 %). The proportional distribution ofN betweenthe carcass, external offal and internal offal was also determined. The mean carcass Nconcentration of the impala was higher (P<0.05) than that of the springbok andblesbok on a dry matter basis. According to the carcass chemical composition, thethree game species seem to have a better potential for lean meat production (fatcontent of carcass 4.7-5.2 %) than domestic sheep (17-25 % fat). Male animals had alower (P<0.05) fat and higher (P<0.05) moisture percentage in the carcass and threeribcut than the females. The fat correlation between the three-rib cut and the carcasson both an as-is and dry matter basis was significant across species and sexes. Theprotein content of the same cuts did, however, not yield a significant correlation on anas-is basis, and only the protein content of the springbok three-rib cut related (P<0.05)to that in the carcass on a dry matter basis.The second study concentrated on the nutritional requirements of springbok, blesbokand impala, and more specifically the EAA requirements. Differences (P<0.05) werefound between the whole empty body EAA composition of the three game species.These differences were present whether protein quantity was included in thecalculations (g AA/100 g crude protein) or not (expressed as % of lysine). Thechemical scores indicated that the four most limiting amino acids (three for impala) inthe duodenal digesta for whole empty body growth were: arginine, histidine,threonine and methionine (springbok); methionine, arginine, histidine and lysine(blesbok); and methionine, histidine and arginine (impala). Further disproportion ofthe amino acids in the duodenal digesta was present in excess levels of isoleucine(blesbok) and lysine, valine, leucine, threonine, isoleucine and phenylalanine(impala). The EAA:Lysine ratios of the whole empty body indicated a similar trendfor the three game species.

[发布机构] Stellenbosch University