Methionine hydroxy analogue as a dietary supplement for sheep.

Abstract

Proc. Aust. Soc. Anim. Prod. (1972) 9: 321 METHIONINE HYDROXY ANALOGUE* AS A DIETARY SUPPLEMENT FOR SHEEP J. P. LANGLANDS** Summary Three experiments are described in which methionine hydroxy analogue (MHA) was given to sheep. In experiment (1) penned sheep maintained on lucerne chaff received 2.6 g MHA daily by mouth or through an abomasal cannula. Wool production increased by 15 and 32 per cent respectively. In experiment (2) grazing sheep were given up to 5.2 g MHA daily by mouth in gelatine capsules, and wool production increased by up to 35 per cent. In the last experiment MHA equivalent to 2.8 g/day was mixed in a survival ration of barley, and the response in wool production averaged 10 per cent. I. INTRODUCTION Wool production is frequently increased when sulphur containing amino acids or some of their derivatives are infused into the abomasum (Reis 1967)) injected subcutaneously (Marston 1935) or given as an intra-peritoneal implant (Langlands 1970). Methionine hydroxy analogue (MHA), like methionine, is a precursor for cystine but is less soluble and less readily degraded in vitro in rumen fluid than is methionine (Salsbury et al. 197 1) ; it is also commercially available at relatively low cost, and has been shown to increase wool production if given per abomasum (Reis 1967). In the three experiments reported, MHA was given by mouth or per abomasum, and responses in wool production were recorded. II. MATERIALS, METHODS AND RESULTS (a) Experiment 1 (i) Experimental Six fine wool Merino wethers with abomasal cannulae were held in metabolism cages for six months and received 500 g lucerne chaff daily. In each period of two months, two sheep received daily either (A) two empty gelatine capsules by mouth; (B) two gelatine capsules containing 2.6 g MHA by mouth, or (C) two gelatine capsules containing 2.6 g MHA through the abomasal cannula. In each period, the sheep received a different treatment, the allocation of treatments being randomized to form two 3 x 3 Latin squares. *Calcium DL-2-hydroxy-4-methylthiobutryrate. **CSIRO Pastoral Research Laboratory, Armidale, N.S.W., 2350. At the start of the experiment and at the end of each period, dyebands (Chapman and Wheeler 1963) were applied to staples on the flank, midside and shoulder regions of each sheep. At the termination of the experiment, the sheep were shorn, fleece weights were recorded, the dyebands were scoured, cut and weighed, and clean wool production per day was calculatetd. A similar procedure was followed in all experimentts. Wool production was increased by 32 per cent when MHA was given per abomasum and by 15 per cent when given by mouth. Mean daily wool production averaged over all sites was 4.50, 5.16 and 5.93 g/day for treatments A, B and C respectively; the mean values differed significantly (P < 0.001) . (b) Experiment 2 ( ii) Results Sixty adult Merino wethers grazed a Phalaris tuberosa-Trifolium repens pasture for four months from May to August. During the first month, no treatments were given but dyebands were applied to the midside and flank regions of each sheep at the beginning and end of the month. The sheep were then randomized into five treatment groups of 12 sheep, and each group received daily either 0, 1.3, 2.6, 3.9 or 5.2 g MHA/day by mouth in gelatine capsules for three months. (i) Experimental TABLE 1 Mean daily clean wool production (g) in months (2), (3) and (4) of Experiment 2 adjusted by covariance analysis for wool production in month (I), expressed in albsolute terms and as a ratio of the wool production of the group receiving no MHA 322 (ii) Results Estimates of wool production in the flank and midside region were averaged. Wool growth in months (2)) (3) and (4) were adjusted by covariance analysis for production in month ( 1). Differences between treatments were significant in months (2) and (3)) but not in month (4). The adjusted means are given in Table 1. Wool production averaged over months (2), (3) and (4) increased by 0.15 g (P < 0.05) /g MHA given. Liveweight change was not signmcantly affected by treatmtent, and averaged - 81 g, + 23 g and - 13 1 g/day in months (2), (3) and (4) respectively. Mean liveweights in these months were 39.3, 38.5 and 37.0 kg respectively. (c) Experhmzt 3 (i) Experimental Eighty Merino wethers were held in yards for several weeks and were accustomed to a diet of rolled barley. They were then allocated at random to 16 yards each containing five sheep for four periods of 28 days. During the first month, all sheep received the equivalent of 350 g rolled barley containing 1 per cent ground limestone and 0.5 per cent salt per head/day given twice weekly; the sheep were weighed and dyebanded at the start and end of each month. In the second, third and fourth months, the 16 groups were allocated at random to eight dietary treatments arranged in a replicated 23 factorial design. The basal diet was that given in the tist month, and the three factors were 8 g MHA/kg barley, 20 g urea/kg barley, and formaldehyde treatment of the barley. In all cases the first level of each factor was either no additive or no treatment. The formaldehyde treatment was achieved by misting 500 ml of 5 per cent formalin into 10 kg barley while it rotated in a cement mixer, and the barley was then stored in a sealed polythene bag for 21 days. It was fed without drying, and the urea and MHA were mixed with the barley after the formaldehyde treatment. Wool production in months (2), (3) and (4) was adjusted by covariance analysis for wool production during month ( 1 ), statistical analyses being undertaken on group means. The only significant treatment effects or interactions were a response to MHA in months (3) (P< 0.05) and (4) (P< 0.1). TABLE 2 (ii) Results Mean daily clean wool production (g) for the MHA treatments in months (2)) (3) and (4) of experiment (3) adjusted by covariance analysis for wool production in month (1) 323 The adjusted mean values for the MHA treatments are given in Table 2. The average response to MHA represented an increase in wool production of 10 per cent. Liveweight change was not significantly affected by any treatment. III. DISCUSSION Wool growth was increased by 15 per cent and 10 per cent in Experiments ( 1) and (3) when the equivalents of 2.6 and 2.8 g MHA respectively were given daily by mouth, and by 20 per cent when grazing sheep received 2.6 g MHA. The response was greater when MHA was given per abomasum (Experiment 1) or when greater quantities of MHA were given (Experiment 2), which suggests that it was partially degraded in the rumen, and that more MHA escaped degradation as the dose was increased. Reis ( 1967) had also observed an increased wool growth when MHA was given per abomasum, but when Reis ( 1970) gave 2, 4 or 8 g MHA/day in the diet, he found a response of less than 6 per cent and concluded that MHA did not influence the rate of wool growth when given in this way. This conflicts with the results of Experiment 2 in which wool growth of grazing sheep was increased by 35 per cent in response to daily dosing with 3.9 g MHA/day. Differences in the retention time of MHA in the rumen or in the activity of rumen microbes capable of degrading MHA may be explanations for this anomaly, but no information is available. Although MHA will stimulate wool growth when given in the diet, the response was insufficient to justify its use in commercial practice at present prices for wool and MHA. A greater response may be achieved if MHA was completely protected from microbial degradation in the rumen. Carrico et all ( 1970) mixed MHA and casein in the proportions 1:5, and protected the casein with formalin, but obtained no response in wool growth when the equivalent of 1 g MHA was fed daily. Wickham ( 1970) tried to bypass the rumen, and every second day grazing ewes were given a drench of 10 ml of 10 per cent sodium bicarbonate to close the oesophageal groove followed by 5 g MHA. in 20 ml water. Wool production was increased by 15 per cent. This response was less than observed in Experiment (1) when MHA was infused into the abomasum, and may indicate that closure of the oesophageal groove was not complete. Langlands ( 1970) also attempted to bypass the rumen by establishing a depot of MHA in the peritoneal cavity from which the MHA could be slowly released, but was unsuccessful because MHA is toxic when given by this route. IV. ACKNOWLEDGMENTS I would like to thank Messrs. I. L. Bennett, J. E. Bowles, G. E. Donald and C. R. Holmes for skilled technical assistance. V. REFERENCES Carrico, R. G., Cockrem, F. R. M., Haden, D. D., and Wickham, G. A. (1970). New Chapman, R. E., and Wheeler, J. L. (1963). Australian Journal of Science, 26:' 53. 324 Zealand Journal of agricultural Research, 13: 631. Langlands, J. P. (1970). Australian Journal of experimental Agriculture and Animal Husbandry, 10: 665. Marston, H. R. (1935). Journal of Agricultural Science, Cambridge, 25: 113. Reis, P. J. (1967). Australian Journal of Biological Science, 20: 809. Reis, P. J. (1970). Australian Journal of Biological Science, 23: 441. Salsbury, R. L., Marvil, D. K., Woodmansee, C. W., and Haenlein, G. F. W. ( 1971). Journal Wickham, G. A. (1970). Proceedings of the New Zealand Society of Animal Production, 30: 209. of Dairy Science, 54: 390. 325