Abstract
AbstractTen Scottish male castrated cashmere-yielding (C) and 10 Angora (A) goats with initial live weights of 38·2 (C) and 32·1 (A) kg respectively were used in a 112-day study in the time period August to December. The goats were blocked within genotypes according to live weight and randomly assigned to one of two treatments: either no supplementation (O) or dietary supplementation (S) with 2·5 g/kg dry matter (DM) intake of rumen-protected intestinally available methionine (Smartamine™ M, Rhone Poulenc, Animal Nutrition, Antony 92164, France) in a 2 × 2 factorial arrangement.The goats were offered a basal diet in the proportion of 0·6, grass hay and 0·4 concentrate according to their live weight. Diet metabolizable energy (ME) and crude protein (CP) concentration per kg DM were estimated as 9·9 MJ (ME) and 107 g (CP) and DM intake was restricted to 28 g/kg live weight daily. Apparent digestibility and nitrogen (N) balance studies were conducted from days 24 to 40 and 51 to 64. Measurements were made within three time periods of days 0 to 40, 41 to 75 and 76 to 112.Angora goats excreted less urinary N than cashmere-yielding goats and had lower values for plasma urea and glucose and greater overall retention ofN, associated with a two- to three-fold greater total fibre yield. Cashmere as a proportion of total fibre by weight, (guard hair plus cashmere) varied from 0·27 to 0·43.The main effects due to methionine supplementation were improvements in live-weight gain and food conversion ratio. Reductions in urinary N excretion and increases in N retention were recorded, which were generally greater for Angora than for cashmere-yielding goats, and were again associated with the larger responses in fibre production. Clear evidence was also obtained for methionine-induced increases in the weight of raw cashmere, although not guard hair up to day 58. This response was obtained in the absence of significant effects on cashmere diameter, although methionine supplementation consistently increased the average diameter of mohair fibres.
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