Screening herds for cows with a history of twin calving
C.A. Morris
MAF Technology, Ruakura Agricultural Centre, Private Bag,
Hamilton, New Zealand
Proceedings of the New Zealand Society of Animal Production.
1991, 51: 447-452
Dairy and beef cows (n=349) which had calved at least two sets
of twins were identified in farmers' herds in 1982-85. Their calving
performance is summarised here, and an experimental herd was founded from
a sample of them. The calvings of 11 high twinning-rate dairy herds
identified from this publicity are also summarised. Repeat-twinning
cows were from factory-supply dairy herds (66%), town-supply dairy herds
(10%), beef herds (21%) and house cows (2%). The twin calving rate in
factory-supply survey herds with Friesians was 2.6%, greater than the
national average. There were, on average, 2.44 twin or triplet sets per
cow. Of all the multiple births, 1.3% were triplet sets. Data on sex
ratios of calves from the twinning cows suggested that probably all
their twins were the result of multiple ovulations. Perinatal calf
survival rates averaged 86%, with 80% of sets having both calves
surviving; 21% of twin calvings were associated with a retained
placenta, and 18% of twin calvings were assisted. Mean ages of cows at
first and later twin calvings were also summarised. The 11 'elite'
herds averaged a 4.1% twin calving rate (21 000 records), with 16% of
cows calving at least one set of twins. Subsequent twin calving
frequencies were summarised. The 69 foundation experimental cows
averaged 2.39 twin sets and a 50% twin calving rate/year at purchase,
and subsequently (1983-89) a twin calving rate of 10.3% (18 sets/174
calvings) compared with controls at 0.8% (1/121).
Keywords: NZSAPAB;
Cattle; twin calving; repeatability; calf survival; assisted
calvings; retained placenta
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Last Updated 25-01-1997
