Fertility of norgestomet treated suckler cows
Drew, S.B.; Wishart, D.F.; Young, I.M.
Veterinary Record 104(23): 523-525
1979
ISSN/ISBN: 0042-4900 PMID: 582487 Document Number: 145451
Four studies are described involving 3050 single-suckled, mainly Hereford X Friesian, beef cows treated with norgestomet and oestradiol valerate to control the ovarian cycle. In study 1, the effect of insemination timing on pregnancy rate was studied. A greater proportion of cows inseminated twice, 48 and 72 h after treatment, became pregnant (61.1%) than after a single insemination at 48 h (44.4%). In study 2, large variations in fertility among farms were recorded in field trials of norgestomet and oestradiol valerate. In study 3 the effect on fertility of nutrition, weight and body condition was examined. For 79 cows treated with norgestomet and oestradiol, and fed a diet considered by the farmer to be adequate, and 82 treated cows fed an additional 20 megajoules metabolisable energy/day, the pregnancy rate was 37.9 and 59.7% resp. to 2 inseminations, 48 and 72 h after treatment. Body weight had a significant effect on pregnancy rate on 1 of the 3 farms. The effect of body condition score was not significant on any farm. In study 4, cows were fed a balanced ration designed to provide for a predicted daily milk yield of 9.0 kg for a 12-wk period starting 6 wk before insemination. The pregnancy rate for 1113 cows treated with norgestomet and oestradiol, inseminated twice, 48 and 72 h after treatment, was 57.9%.