Sex Behaviour of Purebred and Crossbred Merino and Blackhead Persian Ewes

Abstract

Data are presented on a number of aspects of the sex behaviour of four breeds of sheep in South Africa. In crossbred Dorset Horn : Persian ewes, puberty was reached at an average age of 399-7 days. Autumn-born lambs, however, showed their first signs of oestrus 67-2 days later than those born in winter. Ewes generally exhibited a seasonal pattern in their sex activity with a peak in autumn and the lowest level in spring. This was most pronounced in the Merino and least so in Blackhead Persians. Crossbred ewes by Dorset Horn sires occupied an intermediate position. The mean length of the oestrous cycle was 16-9 days, oestrus lasting 29-2 hr. Significant differences between breeds were found for the duration of oestrus, the period being shorter in purebred than in crossbred ewes. Dorset Horn : Persian lambs were born after a gestation period of 146-5 days. It was also observed that the males were being carried slightly longer than the female lambs. A period of lactation anoestrus was observed in all the breeds, but in crossbred Dorset Horn : Merino and Dorset Horn : Persian ewes, oestrus was first recorded at respectively 42 and 51 days post partum, as compared with 90-1 days for purebred Blackhead Persians and 103-3 days in the case of Merino ewes.

A note on annual reproductive rhythm in Marwari sheep of the Rajasthan Desert in India

“…Its average length of 36 h (range 24 to 48 h) was similar to that found for the Dorset Horn, Suffolk and fat-tailed ewes (Hafez, 1952;Joubert, 1962;Sefidbakht, Mostafavi and Farid, 1978). Its average length of 36 h (range 24 to 48 h) was similar to that found for the Dorset Horn, Suffolk and fat-tailed ewes (Hafez, 1952;Joubert, 1962;Sefidbakht, Mostafavi and Farid, 1978).…”

A Relationship Between the Duration of Oestrus, Ovulation Rate and Litter Size of Sheep

“…The duration of oestrus in the sheep has been found to differ from one breed to another (Hafez, 1952;Joubert, 1962), but Asdell (1964) concluded that "the mean heat period (of the sheep) is from 30 to 36 hours, with little differences between breeds". The Finnish Landrace, however, has been found by Donald & Read (1967) to have an oestrous period of 48 to 72 hr, much longer than that of British breeds.…”

Effect of the Ram on Duration of Oestrus in the Ewe

“…Considerable variation is to be found in the published estimates of the length of heat in sheep (Quinlan & Mare, 1931; Grant, 1934;McKenzie & Terrill, 1937;Hulet, Blackwell, Ercanbrack, Price & Wilson, 1962;Hunter, 1962;Joubert, 1962;Joubert & Louw, 1964;and others). Since overt characteristics accompanying oestrus are almost completely absent in the ewe, these reports have been based on observations of mating behaviour during continuous or, more commonly, intermittent periods of association of the sexes.…”