ALBERT

Description: Variations in the time of onset of the breeding season in Clun ewes have been studied during the four years 1962-65. Differences within seasons were studied in 1963 and 1964 by scattering the lambing over the first 7 months of the year. The date of first service then appears to be very highly dependent on the date of previous lambing. Time of previous weaning appears to be less important.Very highly significant differences have been found between seasonal means and these differences have been shown to be significantly related to the mean ambient temperature during a limited period between mid-summer and the mean date for the resumption of cyclic activity in the ewes. The higher this temperature the later the onset of breeding activity. Over the years individual ewes have tended to breed consistently either early or late.

Description: SUMMARYFifty Clun Forest ewe lambs with uniform birth dates were randomly stratified into two groups (A and B) of 25 each according to date of birth and body weight at 23 August 1971. On 26 August Group A (control) was joined with rams whilst Group B remained completely isolated from any contact with rams until 18 October.The sudden introduction of rams to ewe lambs in the transition from non-breeding to breeding activity resulted in a high degree of synchronization of first matings in Group B. However, it did not affect the mean date of onset of oestrous activity.

Description: SUMMARYSome aspects of sexual development and the attainment of puberty in Clun Forest ram lambs were studied during the two seasons 1970–1. Strong correlations existed between parameters of penial, scrotal and testicular development. Sexual development in general appeared to be more closely associated with the body growth than the chronological age of the ram lamb.Nevertheless, marked variation existed in both age and body weight at puberty. Although the majority of the lambs attained this stage of development at 4·5–5 months the age-range extended from 99 to 176 days. The mean body weight at puberty was 32·5 kg, ranging from 24·5 to 38·0 kg. There appeared to be an interaction between chronological age and general body development in relation to the appearance of sperm in the epididymides. Not only did it seem that a certain degree of body growth and testicular size was required before spermatozoa could be released, but also a limit of chronological age below which puberty was not attained. Large differences existed between individual lambs in both testicular and epididymal weights at puberty. There was a high degree of symmetry in growth between the left and the right testes and epididymides.Time of birth influenced the pattern and rate of body growth and sexual development. This seemed to be largely due to seasonal fluctuations in nutritional conditions during rearing but the results obtained do not preclude the possibility that other seasonal factors, such as the daylight environment experienced by the ram lamb, might have a certain limited influence on sexual development.

Description: SUMMARYCertain aspects of puberal development and reproductive performance in Clun Forest ewe lambs with a wide range of birth dates were investigated during the two seasons 1969–71. Of 33 ewe lambs born in the spring of 1969, 26 exhibited their first oestrus at a mean date of 8 November 1969 ± 2·5 days, the mean age being 228·3 ± 2·4 days and the mean body weight 36·3 ± 0·9 kg. The lambs which failed to breed in their first year, together with lambs born in the autumn of 1969, attained puberty during the autumn of 1970. Twenty-three ewe lambs carried foetuses to term in the spring of 1970 and had a mean lambing rate of 113·0 ± 7%. Of 84 ewe lambs born in the spring of 1970, 73 attained puberty in the first year of life at a mean date of 11 November 1970 ± 2·7 days, the mean age being 223·7 ± 3·0 days and the mean body weight 32·2 ± 0·5 kg. Cyclic activity of ewe lambs born in 1970 was recorded throughout their first breeding season. They experienced their last oestrus of the season at a mean date of 24 January 1971 ± 2·2 days, the mean age being 296·9 ±3·9 days and the mean body weight 32·4 ± 0·6 kg. The mid-breeding season was 18 December 1970, coinciding with the shortest days, and the mean number of heats exhibited throughout the season was 5·15 ± 0·24 per lamb.Marked individual variation existed in age and body weight at puberty and in breeding activity, largely due to differences in date of birth and growth rate during rearing. Ewe lambs born early tended to experience their first oestrus earlier in the season than late born lambs but they did so at a higher age and heavier body weight. Fast growth rate and earliness of puberty were associated with extended duration and enhanced regularity of cyclic activity. Time of birth was clearly of fundamental importance in relation to the onset and duration of breeding activity in the ewe lambs included in the present study.Adult rams of three breeds were found to vary consistently in the proportion of ewe lambs which they detected in oestrus, rams of the lambs' own breed being most efficient.

Description: SUMMARYSeventy-two Clun Forest ewe lambs were randomly stratified into three groups (I, II and III) of 24 each according to date of birth and body weight at 6 October 1970. The ewe lambs of Groups I and II were shorn on 15 and 30 October, respectively, and Group III acted as unshorn control. The ewe lambs were reared under natural field conditions but supplementary feeding and shelter were provided during the winter months.A large proportion (94%) of the ewe lambs attained puberty in their first year and differences between the three groups in the number of ewe lambs reaching this stage of development were small and not significant. Autumn shearing of ewe lambs was associated with a very slight but statistically wholly insignificant delay in the mean date of puberty whereas the duration of cyclic activity in these lambs was not affected by such treatments.