With One Text-figure)The sexual performance of the male is assessed by measuring semen characteristics, by studying the histology of the testis, and by measuring sexual libido (sex drive). There is always a physiological interaction between the testis, accessory sexual organs and anterior pituitary gland. Moreover, the output of the anterior pituitary is controlled by complex factors, mainly season, breed, age and nutrition. Seasonal variations in climatic conditions differ greatly with the locality (latitude). In the subtropics there is more seasonal fluctuation in atmospheric temperature and less variation in daylength than in the temperate zones.The common practice for sheep breeding in Egypt is to arrange the mating season in the summer so that lambing coincides with the winter months when climatic conditions are favourable for vegetation. Some farmers, however, do not follow this practice but permit continuous association of the two sexes, and consequently lambs are dropped throughout the year. Other breeders arrange two mating seasons a year; spring and autumn. Knowledge concerning the breeding season of fat-tailed sheep should provide the necessary background for the successful application of artificial insemination, which may be of special value in fat-tailed sheep where the fat tail handicaps free coitus.This work was an attempt to evaluate semen characteristics in Egyptian fat-tailed sheep under natural conditions. It was also hoped to find out the seasonal variation in semen quality for both Ossimi and Rahmani breeds which are widely distributed in the Delta. MATERIALS AND METHODS (1) Experimental animals and managementTwelve fat-tailed rams of two breeds (nine Ossimi and three Rahmani) were available. The rams of each breed were derived from flocks inbred for over 12 years and kept at the Animal Breeding Research Farm, Giza, Egypt (30° N.). They were from 1-5 to 2-5 years old at the beginning of the experiment which started on 1 March 1951 and lasted for 12 months. The rams were housed in semi-open sheds all in one group. They were allowed to graze 6 hr. a day (from 8 a.m. to 2 p.m.) in the neighbouring fields. During the summer months, they were allowed to graze early in the morning and late in the afternoon so as to avoid the hot weather during midday. On the day of semen collection they were not sent for grazing and were kept near the laboratory.The experimental animals were fed ad lib. on green clover (Trifolium alexandrinum) starting from January until May. During summer months the diet was supplemented with hay ad lib. and 1 lb. of a mixture made of bran, barley, rice polish, horse beans and cottonseed cake in equal parts. A shaded water supply was available all the day long. The animals were shorn twice yearly during May and September.The different seasons were defined as follows(2) Semen tests Semen was collected from all the rams by an artificial vagina (A.V.) every 10 days throughout the experimental period (12 months). The temperature of the A.V. at collection ranged from 40 to 45° C. Colle...

The comparative studies on the rate of exhaustion of spermatozoa after successive ejaculation, in different species, are of significance in reproductive physiology. In the course of vertebrate evolution, patterns of increasing complexity have arisen, the main tendency of which has been to ensure better maturation and viability of spermatozoa in the male genitalia. This involves the interaction of anatomical, physiochemical and neuro-muscular mechanisms of sperm transport and accessory glands secretion. A rest period is usually required to restore the number of sperm to normal and to eliminate the high proportion of non-viable spermatozoa (immature, non-motile or abnormals). The depression in the physiological characteristics of semen as a result of excessive ejaculations is not necessarily associated with biochemical changes in the seminal plasma. This has been demonstrated for the fructose concentration in bull semen (Mann, 1948). In the Indian buffalo bull, when two successive ejaculates are collected weekly, the second one has better semen quality than the first (Prabhu & Bhattacharya, 1951). On the other hand, in stallions a prolonged sexual rest results in the first ejaculate being of lower fertility (Perry, 1947).This study was undertaken to find out the effect of successive ejaculations on semen characteristics in the domestic buffalo, Bos (Bubalus) bubalis L. MATERIALS AND METHODSSemen samples were collected from four buffalo bulls by an artificial vagina at intervals of 24, 12, 8 and 2 hr.; four consecutive ejaculates were collected for each bull in every treatment. A period of some 10 days elapsed from one treatment (comprising four consecutive collections) to another to eliminate the effect of exhaustion. In some cases, the buffalo bulls refused to react to the artificial vagina, and it was necessary to change the buffalocow teaser to accelerate the service behaviour.Semen evaluation was carried out within 10 min. from collection. Sperm concentration was measured in fresh semen, and a portion of each sample was gradually cooled and stored undiluted at 4° C. for 48 hr. Initial motility, percentage of live sperm and percentage of abnormals were recorded, whilst the types of abnormals were examined in both fresh and stored semen. Initial motility was measured at 37-5° C, while the percentage of live sperm was determined by using the eosin-phosphate buffer solution stain (Hafez, Badreldin & Darwish, 1955). RESULTS Mating behaviourThe sex drive of the experimental males was affected during the period of observation. The time elapsing from exploring the female genitalia to ejaculation was prolonged when the interval between ejaculations was curtailed. The copulatory pattern in the buffalo under natural mating conditions was similar to that when using the artificial vagina. In one case, buffalo-bull no. 2, which was the youngest (just maturing), refused to react to the artificial vagina when the interval was 2 hr.; this was excluded from the averages. Fresh semenThe initial values for all semen characteristic...