SUMMARYLuteinizing hormone (LH) and testosterone were measured in the peripheral plasma of two bulls by radioimmunoassay and competitive protein binding techniques. Samples were collected from an indwelling jugular catheter once an hour for 24 h, and then at more frequent intervals after a number of experimental procedures.Each bull showed its own characteristic pattern of cyclic LH changes, with 5\p=n-\10 peaks during 24 h that were apparently unrelated to daylight, feeding or sleep. Each LH peak was associated with a testosterone peak; the LH concentrations ranged from 5 to 50 ng/ml, and those of testosterone from 2 to 20 ng/ml.Sexual stimulation, such as the sight of a cow, or 'teasing', or on one occasion the act of ejaculation itself, caused an immediate release of a large amount of LH. If the testosterone levels were low at the time, the LH peak was followed by a testosterone peak. But when the testosterone levels were high at the time of LH discharge, the testis seemed to be unable to respond any further. An intravenous injection of 500 i.u. human chorionic gonadotrophin was associated with LH release and caused the testosterone levels to rise to maximal values of 22 ng/ml within 1\ m=1/ 2\ h.It is concluded that the cyclical pattern of LH release is due to some inherent central rhythm, and that each transient LH peak results in transient maximal stimulation of testicular testosterone secretion.

Summary. Testosterone was measured in the peripheral blood plasma of eleven male Asiatic elephants, using a competitive protein-binding assay. When the animals showed no signs of musth, the testosterone levels were low (<0\m=.\2 to 1\m=.\4 ng/ml) ; as they began to come into musth and the temporal glands started to enlarge, the testosterone levels rose (4\m=.\3 to 13\m=.\7ng/ml), and when the animals were in full musth, with discharging temporal glands and an aggressive temperament, the levels were extremely high (29\m=.\6 to 65\m=.\4 ng/ml). Musth may therefore be comparable to the rutting behaviour of some seasonally breeding mammals, although, in the elephant, there is some indication that it may be induced by sexual activity.

SUMMARY Three adult Suffolk rams were bled at weekly intervals for 14 months, and at hourly intervals for 24 h during the summer (one ram) and autumn (two rams). Luteinizing hormone (LH) was measured by radioimmunoassay, and testosterone by a competitive protein binding assay. There were episodic bursts of LH secretion during the 24 h period in both the summer and the autumn; the frequency of discharge was lower in the summer, but the amplitude (0·1–8·0 ng/ml) did not appear to change. It was not always possible to detect seasonal changes in LH concentration in single blood samples taken once a week throughout the year. The blood testosterone levels also showed marked fluctuations throughout the 24 h, and the frequency of the peaks was lower in the summer. But in contrast to LH, the magnitude of the testosterone peaks also changed throughout the year; from January to September the testosterone concentration ranged from 0·5 to 10 ng/ml plasma, whereas from October to December it ranged from 3 to 28 ng/ml. Thus in temperate regions the ram, like the ewe, shows seasonal changes in gonadal endocrine activity, although some degree of spermatogenesis continues throughout the whole year.

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This study identified the indigenous criteria used by livestock farmers in urban and peri-urban areas of Kampala to assess the nutritional quality of available feed resources. Focus group discussions and questionnaire interviews (with a total of 120 livestock farming households) were conducted. The findings showed that banana peels, leftover food and own-mixed feeds were the most commonly used feed resources for cattle, pigs and chickens, respectively. Farmers use several indigenous criteria to judge the nutritional quality of the available feed resources. These included perceived effects on disease resistance, feed intake, growth/body condition, hair coat appearance, faecal output, faecal texture and level of production, among others. According to farmers, animals offered with a feed resource of good nutritional quality are more resistant to diseases, ingest much of the feed, gain weight with well-filled bodies, have smooth hair coats, produce large quantities of faeces that are not too firm or watery and exhibit good performance (lactating cows produce more milk, sows produce piglets of good body size, hens lay more eggs of normal size, etc.). Although this indigenous knowledge exists, farmers put more importance on availability and cost as opposed to nutritional quality when choosing feed resources. This explains why banana peels were among the feed resources perceived to be of low nutritional quality but, at the same time, were found to be the most commonly used. Hence, there is a need to sensitise farmers on the importance of nutritional quality in ensuring better and efficient utilisation of the available feed resources.