@conference {40767,
	title = {Assessment of female traits for genetic improvement of fertility in dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {27-31},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = { The objective of the present study was to investigate the suitability of  various fertility traits for describing the reproductive performance of dairy  cows in New Zealand. Using a data set from herds participating in the  Livestock Improvement Sire Proving Scheme over the 1986/87 to 1992/93  seasons, the following female fertility traits have been investigated. Based  on the start of mating (STOM) in a particular herd, the intervals from STOM  to first mating (SMFM) and to the successful mating (SMCO) were  calculated and compared to the internationally used traits that are based on  the calving date, such as, calving to first mating (CFM) and calving to  successful mating (days open, DO). Further traits considered are age at  calving (AC), number of matings per conception (NS), first to successful  mating (FMCO), calving interval (CI) and two traits that indicate whether a  cow became pregnant within 21 or 42 days of STOM (PR21, PR42). The  traits defined for the unique conditions in New Zealand, SMFM, SMCO,  PR21 and PR42 emphasize the economic importance of reproduction to  dairy production. The comparison to overseas studies using DO, FMCO and  CI showed that New Zealand dairy cows had a better fertility performance  than overseas cows.},
	issn = {1176-5283},
	author = {Grosshans T and Xu ZZ and Burton LJ}
}
@conference {40770,
	title = {Genetic parameters for fertility traits in seasonal dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {38-41},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Genetic parameters for female fertility traits in New Zealand dairy  cattle have been estimated using a data set of herds participating in the  Livestock Improvement Sire Proving Scheme. In total, 66294 records of  both pure and crossbred Friesian, Jersey and Ayrshire cows in their first  lactation were used. The highest heritability estimates were .134, .058, .037, .037, .029 for age at  calving (AC), interval from start of mating (STOM) to first mating (SMFM),  interval from STOM to conception (SMCO), pregnancy rate at day 21 or 42  after STOM (PR21) or (PR42), respectively. Low heritabilities were  obtained for first mating to conception (FMCO), calving interval (CI) and  number of services (NS) (<.017). Genetic correlations between CI and either  SMFM or SMCO where high (.920 or .957). Genetic correlation between  SMCO and PR21 or PR42 is close to one. Therefore the later three traits are  identical from the selection point of view. For AC, genetic and phenotypic  correlations with milk production traits were high and unfavourable.  Antagonistic genetic correlations also existed between milk yield and the  fertility traits and between SMFM, SMCO, FMCO or NS and fat or protein  yield. The unfavourable genetic correlations between milk production and fertility  traits strongly suggest that fertility performance should be incorporated into  the breeding objectives of New Zealand dairy cattle. Based on their  heritability estimates, their genetic coefficients of variation and their genetic  correlations with production and other fertility traits, it is recommended that  SMFM and PR21 (or its more easily obtainable equivalent trait 2-to-24-day  non-return rate, 2-24NRR) should be used as selection criteria. In addition,  the incidence of use of treatment programmes for overcoming fertility  problems, such as induction of calving and anoestrus treatment, should also  be incorporated into the selection index.},
	issn = {1176-5283},
	author = {Grosshans T and Xu ZZ and Burton LJ and Johnson DL}
}
