A comparison of the body size, fleece weight and maternal performance of five breeds of sheep kept in one environment

Abstract

THE purpose of this paper is to compare female sheep of five breeds (Scottish Blackface, Cheviot, Welsh Mountain, Lincoln Longwool and Southdown) which were maintained together as a single grassland flock. Particular interest in this situation is derived from the fact that breed differences are not confounded with differences of farm environment, at least from the age of six months when the sheep were brought together. In Great Britain, different breeds-and especially hill breeds-are, as a rule, kept in separate regions not merely on separate farms.Female sheep were purchased as lambs in September 1955. At that time the Welsh Mountain sheep were five months old. Birth dates were not known for the Scottish Blackface and the Cheviot lambs but they were born during the lambing period normal for the district, which would make them the same age as the Welsh, viz. five months old. The Southdowns were, on average, about three weeks older and the Lincolns five weeks older.In order to make the sheep as representative as possible of their respective breeds and to obtain, as far as possible, unrelated sheep for the experimental flock, the lambs of each breed were chosen from flocks which were large, using many rams and were 'typical' of their breeds. The Blackfaces and Cheviots were bought in open market and each breed was drawn from four sources, the Welsh were obtained from two flocks in Merionethshire (one belonging to the Animal Breeding Research Organisation), the Lincolns came from two flocks in Lincolnshire and the Southdowns from two flocks in Sussex. The Blackfaces represented an admixture of the Lanark and Newton Stewart strains. The Cheviots were the South Country type.The sheep were brought together to Blythbank, Peeblesshire, a grassland farm at an elevation of around 800-1000 feet. They were run and managed as a single flock throughout their life. They grazed fenced fields and were moved between fields as management required. Supplementary feed (hay and concentrates) was offered only during periods of prolonged snow and for about six weeks prior to lambing. It was observed that all the breeds availed themselves of these supplements. Hardly any segregation of the 177

Genetic relationships of reproduction with growth and with carcass traits in British pigs

“…Within species, positive relationships have been observed between breeds for litter size and mature weight in dogs (Kaiser, 1971), rabbits (for example, Gregory, 1932) and mice (for example , Falconer, 1967). In sheep, Donald and Russell (1970) found a positive relationship between weight of ewe at mating and litter weight at birth across 15 breeds, although the same relationship does not apply to litter size (for example, Wiener, 1967).…”

Curvas de crescimento de ovinos Bergamácia criados no Distrito Federal

“…Resultados similares foram relatados por Bathaei & Leroy (1996, 1998, os quais constataram que ano de nascimento, sexo, idade da mãe e tipo de nascimento influenciaram as características das curvas de crescimento de ovinos, no Irã. Influência de sexo e tipo de nascimento no peso adulto também foram relatados por Weiner (1967) e Pitchford (1993.…”

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

“…(Donald, Read & Russell, 1968) compared to 1-9 for the Blackface (Wiener, 1967). The indication that the correlation between the duration of oestrus and subse¬ quent litter size is mediated through ovulation rate rather than differential embryonic mortality, however, suggests that the longer oestrous period of the ewe which subsequently produces a large litter is due to an increase in the output of ovarian steroids and not to the greater sensitivity of those ewes to steroids.…”