1970). Photoperiodism in the ewe: 2. The effects of various patterns of decreasing daylength on the onset of oestrus in clun forest ewes. SUMMARYIn six light-proofed buildings experiments were conducted with Clun Forest ewes to determine whether the date of first oestrus was affected by the absolute size of reduction in the case of an abrupt decrease in daylength and by the rate of reduction in the case of a given total decrease in daylength. The mean number of days from the onset of the light treatments to first oestrus (the reaction interval) for ewes receiving gradual decreases in daylength of 3-5, 7-2 or 10-9 min/day from 1 July were 66-4, 53-7 or 33-6 days, respectively. The reaction interval for ewes receiving abrupt decreases in daylength of 3-75, 7-75 or 11-75 hr on 1 July were 59-5, 44-8 or 33-6 days, respectively. A control group of ewes at pasture on natural daylength had a mean reaction interval of 66-2 days. It is concluded that the various light treatments applied significantly affected the date of onset of oestrus in Clun Forest ewes.

A series of trials was conducted to measure the extent of individual variation in feedblock intake for ewes on upland/hill farms. From 15 flocks on nine farms 4284 ewes were selected with a range of environmental conditions and levels of performance. Ewes were given either Rumevite, Norbloc or Wintawell feedblocks containing chromic oxide. Faecal grab samples were taken per rectum from individual ewes and analysed for their chromium content to obtain estimates of feedblock consumption.The results showed that provision of feedblocks does not ensure a uniform intake of supplementary nutrients by sheep in upland/hill situations. On average, 19% of the 2931 ewes sampled had not eaten the feedblock on offer. The proportion of ewes not consuming feedblock varied from flock to flock (0 to 67%). The coefficient of variation of faecal chromium concentrations varied between flocks (46 to 231%). The reasons for the large variation in intakes observed are discussed. Feedblock intake was significantly affected by the grazing area per ewe (P<0·01) and the age of ewes (P<0·05 to P< 0·001).

Link to this article: http://journals.cambridge.org/abstract_S0003356100011880How to cite this article: M. J. Ducker and J. S. Boyd (1977). The effect of body size and body condition on the ovulation rate of ewes. SUMMARYBody size was estimated for 255 Greyface ewes using five linear body dimensions. On the basis of this calculated measure combined with a subjective measure of body size 50 small and 50 large ewes were selected for use in the experiment. Precise ovulation data were obtained by endoscopy and this technique allowed the ewes to be mated subsequently. Body size did not affect the mean ovulation rate of the ewes although, at the same level of body condition, the large ewes were 25 % heavier than the small ewes. The ovulation rates and the numbers of lambs born were influenced by changes in live weight and body condition. For these reasons live weight per se was not a good indicator of ovulation rate as ewe live weight was a combination of both body size and body condition. At the same live weight small ewes in improving body condition had a significantly higher ovulation rate than large ewes in reducing body condition. The onset of the breeding season of the ewes was not affected by their body size. The mean date of onset of oestrous activity for both large and small ewes was 17 October 1972 at a latitude 55° 52' N.

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