Crossbred sheep production I. Factors affecting production from the crossbred ewe flock

Abstract

Donald (1962) has recently pointed out the paucity of available data on production from British sheep, though some information is available for hill sheep (see for example Donald, 1958; Purser and Roberts, 1959; Purser and Young, 1959; Dalton, 1962). Most of these refer mainly to the Scottish Blackface and Welsh Mountain breeds. Hill sheep form approximately 40% of the national flock of over 11 million breeding ewes. Another 40% of ewes are found in crossbred flocks mainly kept on the lowlands; these produce fat lambs and hoggets with wool as a secondary product. Very little information has so far been published on these crossbred ewes, exceptions being work reported by Bywater (1945) and Rennie (1957). This is the first of three papers to be presented with the object of providing such information, and is based mainly on the work of Yalçin (1963). It is hoped that these papers will be of use on two counts:1. To provide a documentation of one specific cross, the Border Leicester × Cheviot ewe and her Suffolk-cross lambs under North of England grassland conditions.2. To analyse the usefulness of keeping production records within such flocks as aids to good commercial management, to culling and to selective breeding.In this paper the traits studied are body weight, fleece weight and litter size of the ewes, and the weights of the lambs between birth and slaughter or weaning. Estimates were obtained for the effects upon some of these traits of age and live-weight of ewe, and of sex, year and type of birth and rearing of the lambs. The usefulness of such correction factors is considered within recording schemes. In subsequent papers the effects on production of differences between crossbred ewes and between the rams used as fat lamb sires will be considered.

Reproductive performance and protein utilization in pregnancy of sheep conceiving at eight months of age

“…The mean litter size of 1-52 obtained with the young Finnish Landrace x Dorset Horn females in the present experiment is considerably higher than that reported for the more common breeds in use in this country (Williams, 1954;Yalcin and Bichard, 1964). The prolificacy appears to be a direct result of the inclusion of the highly prolific Finnish Landrace (Donald and Read, 1967) in the cross rather than to any effects of nutrition during the rearing and mating stages, since conventional management techniques were adopted during both those periods and nutritional flushing has been shown to have a negligible effect on the fertility of 'ewe lambs' (Williams, 1954).…”

Factors affecting production records of lambs from a flock of East African Blackheaded sheep

“…As correction factors for twinning and parity of ewe are likely to depend greatly on management, there is little point in comparing the factors used here with those arrived at by other workers under very different conditions, save to note that the weighted differences at birth and weaning between sexes, twins and singles, and lambs from gimmers and ewes, when expressed as percentages of lamb weight, fall within the considerable range found by other investigators and quoted by Yalcin & Bichard (1964).…”

“…If comparisons between groups of lambs can only be made by combining data from animals subjected to similar influences, it will not here be possible to obtain large enough subgroups, therefore the adjustment of lamb weights would appear essential. Donald (1962) and Yalcin & Bichard (1964) have discussed the problems of finding the most efficient correction factors with which to adjust raw data, and whether simple additive models are sufficient.…”

“…Weaning weight was taken as weight at 5 months of In the use of correction factors on production data, Donald (1962) stated that, whether it was better to adjust independently year by year, or use the means of the whole period, depended on the statistical resolution of the conflict between the advantage of either basing the corrections on more animals, or the advantage of treating each year's performance independently. Yalcin & Bichard (1964) concluded that within one flock where the total number of animals available was not large, and providing that no obvious changes of management occurred, then it might be more useful to combine data from several years in order to get more accurate estimates of environmental effects.…”

“…and twins from ewes 0-25 lb. Maximum birth weights of lambs have been reported as being achieved between the 3rd (Yalcin & Bichard (1964) in U.K.) and 6th parturitions (Starke, Smith & Joubert (1958) in South Africa), with the greatest increase between 1st and 2nd parturitions. The difference in birth weight between lambs from gimmers and lambs from ewes was 0-5 lb.…”