Selenium and formaldehyde treated sunflower seed as supplements for lactating ewes at pasture.

Abstract

SELENIUM AND FORMALDEHYDE-TREATED SUNFLOWER SEED AS SUPPLEMENTS FOR LACTATING EWES AT PASTURE J.P. LANGLANDS*, G.E. DONALD*, D.R. PAULL*, J.R. ASHES**, and G.S. SIDHU SUMMARY Thirty-five Merino ewes with wether lambs at foot grazed pasture with a low Se concentration and were given 0, 500 or 1000 g/week of a protected fat supplement containing 61% linoleic acid; 17 of the ewes had earlier been dosed with Se pellets. Growth rates, milk production, Se concentration and creatine phosphokinase activity in blood, and the composition of liver, and of milk and carcass fat were determined. Milk and tissue composition were modified but growth rates and milk production were not affected. INTRODUCTION Unsaturated fats in the diet can induce nutritional muscular dystrophy (NMD) and related disorders. This is attributed to breakdown products of lipid peroxides produced as a result of polyunsaturated fat autoxidation, which impair the function of cellular membranes. Both Vitamin E and selenium (Se) can protect animals from peroxide-induced disorders, and ruminants have additional protection because rumen microbes hydrogenate unsaturated fats (Garton 1960). Animal fats containing elevated levels of unsaturated fatty acids may be preferred by consumers for health reasons, and Scott et al. (1970) described a technique for the protection of unsaturated fats from hydrogenation which increases the proportion of unsaturated fatty acids in ruminant fat but may also increase the incidence of NMD particularly when Se and Vitamin E status are low. Lactating ewes with lambs at foot were given a protected unsaturated fat supplement while grazing a pasture on which both lambs and weaner cattle had previously responded to Se supplementation; Se pellets containing 0.5 g elemental selenium (Kuchel and Godwin 1976) had earlier been given to approximately half the ewes. MATERIALS AND METHODS Thirty-five fine wool Merino ewes mated to Merino rams, which gave birth to single male lambs between October 3 and 7 were selected; the lambs were weighed and castrated at birth and the ewes were prepared with rumen fistulae on October 6 and 9 by the technique of Hecker (1969); All grazed an improved pasture, fertilized annually with 125 kg superphosphate/ha, and dominated by Festuca amndinacea. and TrCfoZiwn spp. From October 17, three groups of six ewes that had not received a Se pellet were given 0 or 100 or 200 g formaldehydetreated sunflower seed daily f,or five days each week directly into the rumen. Six, five and six ewes that had received Se, were allocated to the 0, 100 or 200 g treatments respectively. The supplement contained 90.9% OM, 44.8% ether extractables (61% linoleic acid), 4.73% N and 0.186 pg Se/g on a dry matter basis. Selenium content of the available green pasture averaged 0.019 pg Se/g OM. . * CSIRO Pastoral Research Laboratory, Armidale, N.S.W. 2350. ** CSIRO Ian Clunies Ross Laboratory, Prospect, N.S.W. 2149. 269 Animal Production in Australia Lambs were weighed on Oct. 17, Nov. 20 and Dec.21; daily milk production was estimated on Nov. 21 and Dec. 21 by the technique of Corbett (1968). Milk fat, Se concentration (Brown and Watkinson 1977) and fatty acid composition (Jones and Davison 1965) were determined. Whole blood samples, taken from the ewes and lambs at milking, were analysed for Se; plasma from lambs was assayed for creatine phosphokinase (CPK) activity (Rosalki 1967). Ewes and lambs were slaughtered on Dec. 21; livers were removed, weighed, freeze dried and analysed for Se. The lamb carcasses were minced, and fat content and individual' fatty acids were determined. RESULTS Mean growth rate, milk production and its fat and Se concentrations and CPK activity in lamb's plasma (Table 1) did not differ significantly between treatments. Se concentrations in blood and liver were increased by Se supplementation, and sunflower seed'increased Se concentration in ewe's blood and in livers from both ewes and lambs. TABLE 1 Least squares means for live weight, liveweight gain, milk production and blood and liver composition 270 Animal production in Australia Variability between animals in fatty acid composition of milk and lamb's carcasses (Table 2) was large and a number of trends suggested by the results were not statistically significant. There were significant differences in the 14~0, 16:0 and 18:2 fractions of milk fat and in the 18:0 fraction in carcass fat after supplementation with sunflower seed. Supplementation decreased 14:0 and 16:O and increased 18:2 particularly at the Nov. 21 milking. Se increased TABLE 2 Least squares means for fatty acid composition of milk and carcass fats 18:O l2:O 12:0 than not in the carcass fat and there was a Se x sunflower seed 'interaction in the fraction of milk on Nov. 21; this resulted from a lower proportion of in milk from animals supplemented with Se but not sunflower seed (mean 3.0) in the group which did not receive either (mean 4.4). The difference was observed in milk from ewes which received sunflower seed. Animal production in Australia DISCUSSION There was no evidence of depressed productivity or NMD or any disorder which elevated CPK activity, in lambs of ewes not receiving Se or receiving sunflower seed. Milk and carcass fat compositions were affected by sunflower seed, and the changes were consistent with the results of Scott et al. (1970) and others; in brief the proportion of linoleic acid (18:2) in milk was increased and fatty acids with chain lengths ,<16:0 were depressed when ewes were given supplement. The ability of lambs with a low Se status to consume milk with elevated levels of unsaturated fatty acids without ill effects, may be attributable to the high Se content of sunflower seed. The supplement contained 10 times more Se than the available pasture and increased hepatic Se in both ewes and lambs. Higher concentrations would be associated with increased glutathione peroxidase activity, and peroxides formed during the autoxidation of unsaturated fats could be detoxicated by this enzyme. It is not known whether the observed concentration of Se in the protected sunflower seed is representative of the material available commercially. Se supplementation of the ewes increased Se concentration in blood and liver of both ewes and lambs, and there was a small but not significant increas in milk. Blood Se concentrations in lambs whose dams did not receive Se, were greater than in the previous year when responses in growth rate to Se supplementation were observed, and this may explain our failure to observe a response here. Changes in fatty acid composition of milk and carcass fats following Se supplementation were small, consistent with the results of Pendell et al. (1969). Larger changes would be anticipated if lambs had suffered from NMD. ACKNOWLEDGEMENTS We thank Messrs J.E. Bowles and A.J. Smith for skilled technical assistance, and the Rural Credits Development Fund of the Reserve Bank of Australia for financial assistance. REFERENCES BROWN, M.W. and WATKINSON, J.H. (1977). Analytica Chim. Acta 89: 2% CORBETT, J.L. (1968). Aust. J. Agric. Res. 19: 283. GARTON, G.A. (1960). Nutr. Abstr. Rev. 30: 1. HECKER, J.F. (1969). Aust. Vet. J. &: 293. JONES, E.P. and DAVISON, V.L. (1965). J. Am. Oil Chem. Soc. 42: 121. KUCHEL, R.E. and GODWIN, K.O. (1976). Proc. Aust. Soc. Anim. 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