Efficiency of wool production of grazing sheep. 3. The use of sulphur-containing amino acids to stimulate wool growth

Abstract

Merino sheep grazing native and improved pastures were given up to 2.2 g DL-methionine each day through an abomasal cannula. Wool growth of sheep grazing improved and native pastures was increased significantly by up to 30 and 41 per cent respectively. Nine sheep with abomasal camulae were maintained in pens, and were infused into the abomasum with 7 g DL-methionine per week given on either one, two, or seven days each week. Wool growth was significantly increased by daily infusions of DL-methionine but the response was less when the methionine was given on only one or two days each week. Dorset Horn wethers were given single injections of up to 50 g DL-methionine or L-cystine subcutaneously or into the peritoneal cavity. The rate of excretion of urinary sulphur was recorded following the injection. DL-methionine was rapidly excreted but L-cystine was excreted more slowly. In a series of trials quantities of DL-methionine, methionine hydroxy analogue (MHA) or L-cystine were injected subcutaneously or intra-peritoneally into grazing Merino sheep. DL-methionine did not increase wool growth and MHA was toxic. Twenty-eight g L-cystine given as two compressed pellets each month into the peritoneal cavity increased wool growth by approximately 22 per cent over the 8-week experim6ntal period.