A study of the effects of a high, in contrast with a very low, planc of nutrition prior to calving, on the performance of hill-country beef cows and their calves, is described. On 8 June 1964, 122 three-to eight-year-old pregnant Aberdeen Angus cows were allocated to two equal groups. Thereafter, one group was maintained on a high plane of nutrition and the other group on a low plane of nutrition for, on average, 90 and 83 days rcspectively, until calving. All cows were offered a high plane of nutrition after calving. Low plane cows lost on average 155 lb, and high plane cows 38 Ib, betwecn initial liveweight and post-partum. After calving low plane cows rapidly recovered in liveweight, and, by weaning five months later, had compensated for their previous livewcight loss. The number of calves present at weaning as a percentage of the number of cows at the start of the experiment was 93.4% and 75.4% for the high and low pre-calving treatments respectively. Low plane calves were 121b or 20% lighter than high plane calves at birth. The mean difference in calf liveweights between treatments was 36.4 lb at weaning.
A study of the effects of relatively high and very low planes of nutrition in late pregnancy, together with high and low levels of feeding from calving to weaning, on the performance of hill-country beef cows and their calves, is described.
1079Four trials are described in which the liveweight gains of hoggets grazing different types of pasture over the autumn period were compared.In the first trial, hoggets grazed on white clover (Trifolium repens L.) had a greater liveweight gain (2.9Ib per week) from 26 February to 4 June 1963, compared with a 2.0 lb gain of those on mature perennial ryegrass (Lolium perenne L.) plus white clover, l.Ilb on short (1-2 in.) perennial ryegrass plus white clover, and 0.61b on short perennial ryegrass.In the second trial, hoggets grazed on white clover-dominant pasture from II
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.
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