Subjectively assessed body condition scores, determined on the live animal, were related to the percentages of chemical fat in the fleece-free empty bodies of 30 adult Scottish Blackface ewes. The results show that body condition scores can provide an acceptable and useful estimate of the proportion of fat in the live animal, and that the level of prediction is superior to that afforded by live weight.

SummaryThree techniques, lamb-suckling and test-weighing, hand- or machine-milking following administration of oxytocin, and measurements of body-water turnover, used for the estimation of milk yield in suckled sheep are discussed in relation to sources of error and comparability of estimates.Results are presented from an experiment in which the lamb-suckling and the oxytocin techniques were compared. The mean daily milk production of Scottish Blackface and East Friesland × Scottish Blackface ewes suckling single and twin lambs was measured by both methods at weekly intervals for 6 weeks. All ewes were well nourished to ensure full expression of milking capacity. Additional information from a similar experiment on Merino ewes is also presented.The oxytocin method gave higher estimates of mean daily milk yield in the first week of lactation, especially in the groups of ewes rearing single lambs and in the Blackface breed. By the second week in most groups and the third week in all groups there were no significant differences between estimates made by the two methods and the relative values of the estimates were not affected by level of milk production, number of lambs suckled or genotype of ewe and lamb.

1. Fifty-one Scottish Blackface ewes were divided into three groups and individually fed throughout the latter half of pregnancy: (I) in excess of nutrient requirements, (II) to produce a uniformly moderate degree of undernourishment during the last 6 weeks of pregnancy, and (III) to produce a uniformly severe degree of undernourishment during the last 6 weeks of pregnancy,2. The prescribed levels of undernourishment were maintained by weekly adjustments of feed intake based on plasma FFA levels (group II) and plasma ketone levels (group III). The use of the technique is discussed.3. Undernourishment during the latter half of pregnancy reduced birth weights of single and twin lambs after adjustment for weight of the dams to the same extent. In the moderately undernourished ewes the reduction was approximately 10%, and, in the severely undernourished ewes, approximately 25%.

Two-hundred-and-seventy-three Scottish Blackface ewes in three ages (5, 4 and 2 years) were differentially group fed over 6 weeks in such a manner that at 6 weeks before mating there were approximately equal numbers in each of six subjectively assessed body condition groups ranging from score 1 (lean) to score 3£ (moderately fat). Over the 6 weeks prior to mating these groups were either well fed, fed at about maintenance, or underfed so that at mating the maj ority of ewes were in either condition 1$ or 3.A predetermined random sample of mature ewes from each of the six original condition groups was killed 2-3 days post-mating for ovulation counts. Surviving ewes were fed above maintenance post-mating and the number of lambs recorded at birth.Condition at mating had a significant, positive effect on both ovulation and lambing rates but had no effect on infertility measured as the difference between them.The level of food intake prior to and at mating had no effect on either ovulation or lambing rates of moderately fat ewes (condition 3) but the results can be interpreted as indicating that the level of food intake had a positive effect on both ovulation and lambing rates of lean ewes (condition 1£).

Live weight of 180 free-grazing Blackface ewes was measured approxim-ately every two weeks throughout a 12-month period. Mean live weight was at a maximum (47 kg) in late autumn prior to mating and declined progressively to 39 kg at about the time of parturition.Six ewes were slaughtered in November before mating, six at about the 16th week of pregnancy, and a further 11 in April during the final week of pregnancy. The loss of weight of maternal tissues (i.e. live weight less the weight of fleece and contents of the gastrointestinal tract and gravid uterus) during this period was more than 20% (7·5 kg) and comprised 51% of the fat, 14% of the water, and 20% of the protein plus ash present at maximum live weight. During the earlier stages of pregnancy there was an appreciable loss of water from the maternal tissues, but in late pregnancy the rate of water loss decreased and that of fat increased considerably.The distribution of fat throughout the maternal tissues at different levels of total fat content and the pattern of fat mobilization from various depots are described. The largest single contribution to fat loss during the pregnancy period was that of the subcutaneous reserves, which were depleted by 86%, most of this being lost during the first four months. At the other end of the scale bone fat reserves were reduced by only 25%, almost all of this occurring during the final month.