@conference {40769,
	title = {Reproductive efficiency in lactating dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {34-37},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Both genetic improvement and milk yield of dairy cows are dependent  on a high reproductive performance. Under normal situations, oocyte  fertilisation rates following insemination at the appropriate time are high  (>90\%) and gross genetic defects in embryos are estimated to be around  10\%. This means that the biological limit of conception rate should be  around 80\%. Such a performance has rarely been realised in practice, with  60\% being a normal target for lactating cows in New Zealand dairy herds.  At a herd level, reproductive performance is best measured by the  percentage of cows pregnant within a period after start of the breeding  season and this is determined by the combination of submission rate and  conception rate. Major factors that affect reproductive performance in New  Zealand dairy herds include anoestrus, errors in heat detection, fertilisation  failure and embryo mortality. Given adequate nutrition, herd management is  undoubtedly the major determinant of reproductive efficiency. The low  reproductive efficiency in dairy cows creates a bottleneck to genetic  improvement and is a major factor affecting milk production efficiency. },
	issn = {1176-5283},
	author = {Xu ZZ and Burton LJ}
}
