Studies on the adaptability of three breeds of sheep to a tropical environment modified by altitude VII. Sexual activity in relation to age of ram

Abstract

The effect of age on attainment of puberty and on seminal characteristics in yearling and mature rams was studied in German Merino, Persian Blackhead and indigenous Native rams living on Rhodesian highveld.1. Puberty occurred at age and live weight proportional to mature live weight. Well-grown Native lambs ejaculated first at 169 days of age and 46 lb. live weight; Merino lambs when 250 days old and 79 lb. live weight and Persians were intermediate. Onset of sexual maturity was related more closely to live weight than to age, since runts ejaculated first at live weights close to those of well-grown lambs.

Some aspects of reproduction in fat‐tailed sheep in Subtropics IV. Puberty and sexual maturity

“…This is in accordance with the findings of DUN (1955), WArSON et a\. (1956); SYMINGTON (1961), PRETORIUS and MARINCOWITZ (1968), ORTAVANT et al (1969) and I~YRLJMDSSON and LEES (1972).…”

“…The poor quality of semen ejaculated by pubescent rams in the present work is substantiated by previous observations o f D U N (1955), SYMINGTON (1961), LOUW and ~O U B E R T (1964) and ELWISHY and ELSAWAF (1971). The high incidence of morphologically abnormal spermatozoa is accounted for mainly by immature forms with protoplasmic droplets and coiled tails (WILLIAM and SAVAGE 1925;STARKE 19.59).…”

“…Nevertheless, ejaculate volume, concentration of spermatozoa and consequently total sperm per ejaculate increased at a steady rate up to the fourth year. As TERRILL (1938) and SYMINGTON (1961) observed that maximum sperm concentration was attained in 2 year old rams, it could be concluded that in the slow maturing fat-tailed sheep full sexual maturity is not attained before the fourth year o f life. Hence it could be recommended that fewer number o f ewes should be allocated to younger rams if high conception were to be achieved.…”

A study of sexual development in ram lambs

“…These observations support the concept that physiological age is more important than chronological age in the determination of maturing behaviour (Symington, 1961;Dyrmundsson and Lees, 1972b), as demonstrated by the highly significant correlation (r=0-38) between body weight and number of ejaculations at 8 months of age. Moreover, although NR lambs displayed heterosexual interest at a later age, they did so at a heavier body weight, and their libido was somewhat better than that of AR ram lambs, suggesting that the heavier the lambs are when they attain puberty the higher their subsequent libido.…”

Sperm counts in semen of farm animals 1932–1995

“…Only values from apparently normal animals were included (e.g. in seasonal studies or from control groups in nutritional or other studies) and only values from mature animals [boars at least 8 months old (Lagerlof & Carlquist, 1959;Swierstra, 1973;Slechta, 1981;Michalski & Polanska, 1983), rams at least 12 months old (Symington, 1961;Louw & Joubert, 1964) and bulls at least 18 months old (Herman & Swanson, 1941;Flipse & Almquist, 1963;Almquist & Cunningham, 1967;Hahn et al, 1969;Stalhammar et al, 1989), ages at which sperm counts should have reached adult values]. Values were only included from animals from which collections were being made regularly, but not at a frequency which would lead to a reduction in sperm counts [less than once per day for rams (Salamon, 1962;Sharma et al, 1969;Kastyak, 1970), and less than twice weekly for bulls (Dukelow et al, 1960;Almquist & Cunningham, 1967;Almquist, 1982) and boars (Radford, 1961;Konjuhova, 1966;Swierstra & Rahnefeld, 1967;Swierstra, 1973)], if the frequency of collection was made clear in the article or abstract.…”