The Application of New Technology for the Protection of Amino Acids to Improve Wool Production and Body Growth in Sheep

Microspheres consisting of a central core of amino acid and binding agents which are coated with a pH sensitive (neutral stable/acid unstable) polymer have been developed by Rhone Poulenc. This new technology allows orally administered amino acids to avoid exposure to and degradation by, rumen microbes but allows bio-availability following release and absorption at the abomasum and distal gut sites. The microspheres can be mixed with grain supplements and fed to grazing sheep by using molasses as an adhesive. Three trials were conducted to evaluate the potential of rumen-protected DLmethionine (“Smartamine”, Rhone Poulenc Animal Nutrition) to achieve effective supplementation of sheep under a variety of physiological and nutritional conditions. Trial I assessed the effects on growth and wool production in weaner lambs. Trial 2 evaluated responses in breeding ewes which received medicated grain supplements in late pregnancy and early lactation while grazing summer pasture. The influence of diet was evaluated in Trial 3 by measuring responses in wethers maintained in an experimental feedlot on diets containing different types of grain and levels of roughage. Overall, the trials showed that an average daily dose of 2.0 gram of product per head (approximately 1.5 gram of methionine), given as a medicated grain supplement three times per week, increased the volume growth rate of wool during treatment by 6 to 27%. This was due to significant stimulation of both length growth and fibre diameter in all circumstances tested. Annual greasy fleece weights were increased by up to 7.8% (in weaners> from a ten week period of treatment. In trial 2, enrichment of supplements with protected methionine also resulted in a 7 to 10% increase in the tensile strength of wool grown by treated single or twin-bearing ewes when treatment was given during late pregnancy and early lactation. In trial 3, the stimulatory effects of the protected methionine treatment in mature wethers on near maintenance energy diets were independent of the type of grain (oats, wheat or lupins) and of the level of roughage in the diet (20,40 or 60% of ME), suggesting that protected methionine may be used effectively in a wide range of dietary circumstances. Treatment was also associated with a transient increase in the rate of live weight gain and condition score of merino weaners grazing good summer pasture. These trials illustrate the potential for the new protected formulations of methionine to provide a practical solution to methionine insufficiency and thus to at least partially overcome a common cause of sub-optimal performance of sheep in Australia.