Six nutritional regimes were applied to 134 Friesian heifers to determine the effects of differential rearing on productive and reproductive performance. Cycling animals were identified at 11.5 and 15 months by measuring progesterone in consecutive weekly blood plasma samples. Heifers were synchronised using CIDR devices and artificially inseminated for two cycles, followed by six weeks of natural mating. At 11.5 months, 95% of the high (268 kg LW), 65% of the medium (242 kg LW), and 2% of the low (186 kg LW) nutrition groups were cycling. At 15 months, all heifers in the four high groups were cycling compared to only 82% of heifers in the two low groups was probably enhanced by the CIDR progesterone treatment stimulating puberty in non-cycling heifers. Friesian heifers should average 300 kg to ensure all animals are cycling normally prior to the start of mating.
Proceedings of the New Zealand Society of Animal Production, Volume 55, , 39-41, 1995
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