New Zealand Journal of Agricultural Research abstracts

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A note on the pregnancy statistics of cows, and perinatal survival and birth weight of calves, in two herds selected for high or low susceptibility to bloat

C. A. MORRIS
N. G. CULLEN

AgResearch
Ruakura Agricultural Research Centre
Private Bag 3123
Hamilton, New Zealand

V. R. CARRUTHERS

Dairying Research Corporation
Private Bag 3123
Hamilton, New Zealand

Abstract  Pregnancy rates (PR) over 20 years were compared in two herds of Friesian x Jersey crossbred dairy cattle bred for high (HS) or low susceptibility (LS) to pasture bloat. Beginning in 1974, yearling heifers were naturally mated to yearling or 2-year-old bulls in single-sire groups (average PR = 91%; range of year means, 77-100%), while cows were naturally mated from 1975 to 1984 (average PR = 91%; range of year means, 79-98%) and artificially inseminated from 1985 to 1993 (average PR = 91%; range of year means, 84-99%). PR data on 467 yearling heifers, and 974 subsequent PR records on these animals as cows, were analysed. There was no significant herd effect on PR in either yearling heifers, or in milking cows, and average calving dates did not differ significantly between herds. Perinatal survival of calves was not significantly affected by herd. However, calf birth weights differed between herds (P < 0.001). Beginning with the 1973 calf crop, the LS herd mean increased above the HS herd mean by an average of 0.20 +/- 0.04 kg/year or 0.7% (P < 0.001). By the mid-point of the experiment, LS birth weights were greater than those in the HS herd by 2.2 +/- 0.3 kg or 7.9% (P < 0.001).

Keywords  pasture bloat; selection; pregnancy rate; calving date; perinatal survival; birth weight

New Zealand Journal of Agricultural Research, 1995, Vol. 38: 205-209

0028-8233/95/3802-0 205 $2.50/0 (c) The Royal Society of New Zealand 1995

PDF file of entire paper: medium quality (354K); (scanned from paper original: notes about this process)

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