Sheep on a sole diet of Leucaena glauca Benth. shed their fleece. The amino acid mimosine has been shown to be the depilatory agent. The depilatory effect of L. glauca was influenced by level and method of feeding.Small quantities of mimosine were excreted by sheep consuming L. glauca, but the major metabolite in the urine was identified as 3,4-dihydroxypyridine (DHP). It was established from the results of intravenous, intra-abomasal, and intraruminal administration of mimosine that sheep cannot detoxicate mimosine after absorption, but extensive degradation of mimosine to DHP takes place in the rumen.The absence of toxic symptoms in a sheep conditioned to L. glauca appeared to be due to increased detoxication in the rumen rather than to the development of an adaptive tolerance after absorption.The histological changes in the skin are described, and reasons for conflicting reports on the toxicity of L. glauca are discussed.A simple method for the isolation of mimosine from the seed of L. glauca is described in the Appendix.The possibility that Leucaena glauca Benth., a tropical leguminous shrub, could make a substantial contribution to the protein requirements of cattle over large areas of tropical Australia has led to an intensive research programme being carried out on this legume at the Division of Tropical Pastures, Brisbane. Hutton and Gray (1959) have stated that the reported toxicity of L. glauca to animals may be a problem in its utilization as a forage crop. Owen (1958) has summarized the extensive literature on the depilatory and other toxic effects resulting from ingestion of L. glauca leaves and seeds by ruminants and non-ruminants. Various investigators (see Owen 1958) have shown conclusively that these adverse effects in horses, pigs, and small laboratory animals were caused by the amino acid mimosine, which occurs in both the leaves and the seeds of L. glauca. The chemistry of mimosine, which has the structure P-[N-(3-hydroxy-4-pyridone)) a-aminopropionic acid, has been reviewed by Wibaut (1953).Published evidence on the toxicity of L. glauca to ruminants is conflicting. Takahashi and Ripperton (1949) and Hutton and Gray (1959) reported that beef and dairy cattle showed no toxic effects when fed on L. glauca, except in rare cases

The effect of high and lox- levels of feed intake during pregnancy in ewes, and from birth to 4 months of age in their lambs, on adult body weight and wool production has been studied. As compared with the corresponding high intake groups, lambs from the low intake ewes were 34% smaller at birth and 9% smaller at maturity. They also had c. 15% fewer wool follicles per sheep, and produced c. 8.5% less wool as adults. Low levels of feed intake between birth and 4 months resulted in a slower growth rate and a reduction (c. 10%) in mature body weight. The maturation of the follicle population was delayed by a low feed intake in this period but no permanent reduction in numbers was observed. The post-natal low intake group produced c. 12% less wool as adults, owing to a smaller (c. 10.5%) fibre weight. The major effect on wool growth potential of low levels of nutrient supply during pre-natal life was a restriction of body size and total number of follicles, while restriction of nutrient intake during early post-natal life reduced the capacity of the individual follicles to produce fibre.

Observations were made on the effect of the presence of the ram when introduced to Merino ewes in the transition from the "non-breeding" to the "breeding" season in the Roseworthy environment. These observations showed that the primary effect was to stimulate ovulation without oestrus ("silent heat") in the majority of those ewes which had not already commenced cyclic breeding activity. This effect occurred within 6 days of joining the rams with the ewes. It is concluded that this mechanism explains the "lag and peak" incidence of oestrus previously observed under these conditions (Underwood, Shier, and Davenport 1944; Thompson and Schinckel 1952; Schinckel 1954).

The utilization of nitrogen was examined in sheep fed several diets; in some experiments the diet was supplemented with soluble casein given directly into the abomasum through a fistula. Casein supplements per abomasum were almost completely digested and absorbed. At the highest level of casein supplementation (55 g casein nitrogen per day) 95% of the casein was digested and absorbed. An increase in nitrogen intake resulted in an immediate increase in nitrogen balance, followed by a gradual return towards a stable level. There was also an immediate response of faecal and urinary nitrogen excretion to a change in nitrogen intake. Most of the adjustment in urinary nitrogen excretion occurred within 4 days, this period being followed by a gradual change towards a stable level of excretion during the next 6 weeks. Much higher levels of nitrogen retention were obtained from casein administered per abomasum than from similar levels of nitrogen given per os. Changes in wool production also occurred following changes in the nitrogen intake per 0s. The observed changes were variable, depending on the sheep and the feed change involved, and periods of up to 10 weeks were required before the rate of wool production became stable following a change in nutrition. Casein supplementation per abomasum resulted in a substantial increase in wool production and in a rapid increase in wool fibre diameter; most of the increase in fibre diameter occurred in the first week of supplementation. The efficiency of conversion of dietary nitrogen into wool nitrogen was much higher in experiments where a casein supplement was administered per abomasum than in experiments involving normal feeding; possible reasons for this difference are discussed.

The effect on wool growth and the sulphur content of wool of supplements of L-oyswine, DL-methionine, and casein, given per abomasum a�s a continuous infusion, has been examined.