Amino acid requirements of South African Mutton Merino lambs 2. Essential amino acid composition of the whole empty body
The essential amino acid (EAA) composition of the whole empty body of South African Mutton Merino ram lambs fed a standard diet was investigated. The standard diet consisted (%) of 30 lucerne, 8 wheat straw, 56.25 maize meal, 3.5 molasses meal, 1 urea, 0.5 salt and 0.75 ammonium chloride. Twenty lambs were randomly allocated to four pre-assigned average target slaughter weights (30, 35, 40 and 45 kg live weight): The EAA composition of the carcass, blood, head and feet, skin & wool, liver, lungs, kidneys, heart, spleen, testis, digesta-free gastrointestinal tract (GIT) and whole empty body was determined. The composition of the whole empty body remained similar regardless of slaughter weight. The concentration of the following EAAs increased significantly (p < 0.05) with increasing live weight (30, 35, 40 and 45 kg): head & feet valine (3.87a,5.56ab, 5.68ab, 6.70b), spleen phenylalanine (4.96a, 5.00a, 5.07ab, 5.56b) and valine (5.31a, 5.50ab, 5.69ab, 6.03b) as well as GIT phenylalanine (5.00a, 6.50a, 11.10a, 18.78b). The amino acid composition of the carcass, skin and wool, and GIT plays a predominant role in regression equations used to predict the whole empty body EAA composition. The whole empty body EAA composition (g AA/100 g crude protein) was as follows: 7.72 arginine; 4.54 histidine; 3.06 isoleucine; 8.53 leucine; 6.46 lysine; 3.56 methionine; 5.22 phenylalanine; 4.65 threonine and 5.18 valine. This composition can serve as an example of the ideal EAA requirements for whole empty body growth between 30 and 45 kg live weight of South African Mutton Merino ram lambs.