@conference {40348,
	title = {Wool sulphur concentration in fleeceweight-selected and control Romney hoggets},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {51},
	year = {1991},
	month = {Jan},
	pages = {395-400},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Dairy and beef cows (n=349) which had calved at least two sets  of twins were identified in farmers{\textquoteright} 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 {\textquoteright}elite{\textquoteright}  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).  },
	issn = {1176-5283},
	author = {Sun YX and Koolaard JP and Blair HT and Lee J and McCutcheon SN}
}
