Hill country sheep production

Abstract

Factors associated with mortality in 7,727 lambs born to 7,091 twoto five-year-old ewes over the 9 years 1959-67 were studied. The lambs were from two Romney flocks and first-, second-, third-, and fourthcross Border Leicester x Romney flocks. Lamb survival rate (lambs weaned as a percentage of all lambs born) increased with increasing age of dam for both single-and multipleborn lambs. Variation in survival rate between flocks and between female and male lambs was large. In 60% of the dead lambs, 44.6% of single-born lambs died of dystokia and 15.1 % from physiological starvation. Of the multiple-born lambs autopsied, 16% died from dystokia and 41.7% from starvation. Infections accounted for 11.6% and pre-natal deaths for 10.3% of the remaining deaths. Most of the deaths occurred within 3 days of birth, and relatively more single-than multiple-born lambs died at birth. Analysis of variance of birth weight showed that first-cross lambs were the heaviest and that birth weights decreased with interbreeding, to the fourth-cross lambs. Male lambs were 0.5 Ib heavier than females and singles 2.3 Ib heavier than twins. Lamb birth weight increased from two-year-old to five-year-old dams. Survival rate was related to birth weight. In single-born lambs survival rate was highest in lambs of about average birth weight and decreased with lambs of lower or higher birth weights. In multipleborn lambs survival rate was lowest with lambs of low birth weight and increased with increasing birth weight. Lamb mortality was highest in the earliest-born lambs.

Risk factors for perinatal and postnatal mortality in lambs

“…The high preweaning mortality recorded is consistent with estimates of mortality from major sheep producing countries, for example 5 to 25 per cent in New Zealand (Hight and Jury 1970), 22 per cent in Australia (Haughey 1983) and 10 to 35 per cent in the USA (Rook and others 1990). As in most flocks, there were constant attempts to improve lamb survival with the success being limited by the continually changing health status of the flock.…”

Body composition of cull ewes from New Zealand hill country

“…The BR, which had the heaviest live and carcass weights of the breeds in this trial, was shown by Hight & Jury (1969, 1970a to be superior to the straightbred RR in some aspects of production. According to Parker & Wiggins (1969), Pd hoggets grow better than RR, and Pd 2-tooths are also heavier.…”

Relationship Between Pelvic Dimensions, Other Body Measurements and Dystocia in Dorset Horn Ewes

“…Breed differences in lamb mortality due to dystocia have been reported (Hight and Jury 1970), and may, to some extent, be independent of birthweight (Gum 1968). Australian Dorset ewes have a high incidence of dystocia (Fogarty 1971) which is negligible in Border Leicester ewes, although birthweights in both breeds are similar (Fogarty, unpublished data).…”

“…High birthweights have been associated with increased dystocia in sheep (Dennis 1970;Hight and Jury 1970) and account for the higher incidence of dystocia in ewes bearing single lambs.…”

“…Dystocia is an important cause of perinatal lamb mortality (Hight and Jury 1970;Haughey 1973). High birthweights have been associated with increased dystocia in sheep (Dennis 1970;Hight and Jury 1970) and account for the higher incidence of dystocia in ewes bearing single lambs.…”