O Instituto de Investigação e Tecnologia da Agronomia e Meio Ambiente (IITAA) desenvolve trabalho de investigação com o objetivo de perseguir estudos em diversas áreas, como a caracterização / previsão do clima insular e os efeitos das mudanças globais em comunidades do oceano para os to... Ler mais »
Many aspects of the conditions required to maximize the ewe's response to ram introduction in the late anoestrous season remain unclear. The aim of this research was to determine whether space allowances could influence the efficacy of the ram effect. In August 1995, at Reading (latitude 51˚ 27' N), following a three month isolation period from rams, two groups of nulliparous Mule ewes, aged 15 months, were introduced to 4 rams in a low (12 ewes/ hectare, treatment L, n=124) or in a high stocking rate (84 ewes/hectare, treatment H, n=126). From the beginning of August until the end of August oestrus behaviour was recorded by daily checks of mating marks on ewes. Afterwards rams were removed and in October all ewes were scanned for pregnancy. No significant diferences were found in the parameters investigated. Eighty two per cent of L and 75.4% of H ewes exhibited oestrus, with a pronounced peak on day 23 following ram introduction and a compact concentration in the 21 to 25 day period. The oestrous synchronization rate in this 5 day period was 69.4% and 68.3% respectively for L and H. The mean interval from ram introduction to oestrus was 23.17 2.4 days in L and 23.0 2.2 days in the H group. Conception rates were 84.3% and 87.4% for L and H groups respectively. These results suggest that the response of anoestrous ewes to the introduction of rams was not affected by space allowances and that earling Mule ewes respond well to the ram effect in the late anoestrus season.
Quarta, 31 Dezembro, 2003