@conference {41876,
	title = {Development of new fertility breeding values in the dairy industry},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {66},
	year = {2006},
	month = {Jan},
	pages = {107-112},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Napier},
	abstract = {This paper provides the basis for a new method for calculating fertility breeding values. The objective of this study was to: firstly, investigate the data extract of mating and calving records from Livestock Improvement{\textquoteleft}s national database to identify improvements, secondly investigate the definition of the fertility trait from percent of calves born from artificial insemination (AI) to 42 day calving rate, and thirdly explore the inclusion of milk production and body condition score information. The overall aim was to improve the accuracy of the fertility breeding values available when a sire{\textquoteleft}s daughters have completed their first lactation (i.e., the time of the sire{\textquoteleft}s first proof). A new procedure for routine national evaluation of these traits is outlined. Results from the new system are given. Possible future enhancements to the new system are discussed. The new method improves the accuracy of the fertility breeding value for first crop sires with 80 daughters from 45\% to 52\%. The inclusion of body condition score and milk production in the calculation of the fertility breeding value improves the response to selection for fertility within breeding worth index by 34\% per annum. The improvement in response to selection is worth 0.18 $/cow/year or approximately $700,000 annually to the dairy industry. },
	issn = {1176-5283},
	author = {Harris BL and Pryce JE and Xu ZZ and Montgomerie WA}
}
@conference {41491,
	title = {Effect of timing of insemination of dairy cows with liquid semen relative to the observation of oestrus},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {64},
	year = {2004},
	month = {Jan},
	pages = {140-142},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {Many studies have confirmed that the best conception rates are obtained when cows are inseminated from mid to late oestrus. The conclusions of Trimberger, (1948) has led to the universally accepted AM - PM schedule for inseminating cows. The guideline suggests that cows found in oestrus during the AM period be inseminated at the following PM and the cows in oestrus at the PM be inseminated the following AM. Variations of this rule have been tested with single and multiple AI during oestrus periods and once daily AI after the AM milking with no adverse effect on conception rates. The objective of this study was to determine the effect of time of insemination on Non Return Rates (NRR{\textquoteright}s) in a sample of seasonal breeding New Zealand dairy cows submitted for insemination once a day after following the AM - PM guideline. Two hundred farms participated in this trial with over 12,000 animals representing Friesian, Jersey and Cross breeds were included in this dataset. The farmers were asked to keep accurate records on when cows were first detected in oestrus during the first two weeks of mating. There was no significant difference in 18 to 24 day non return rates for all cows observed in heat at the two time periods and inseminated the following AM (71.8\%, PM and 71.6\% AM respectively, p = 0.18). There was no effect of bulls or age of cows. A nominal effect of breed of cow was observed. In conclusion, there was no effect on NRR when cows were inseminated at the one time period after AM milking whether they were first observed in heat the previous PM or the AM just prior to insemination. },
	issn = {1176-5283},
	author = {Vishwanath R and Melis J and Johnson DL and Xu ZZ}
}
@conference {41283,
	title = {Relationship between bulk milk urea nitrogen and reproductive performance of New Zealand dairy herds},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {192-194},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {New Zealand dairy cows grazing lush spring pasture have relatively high plasma urea nitrogen levels as a consequence of the high soluble crude protein content of this rapidly growing pasture. The elevated plasma urea levels have been implicated as a cause of poor reproductive performance in dairy herds. The aim of this trial was to determine if the bulk milk urea nitrogen levels (BMUNs) collected during the period from calving and through mating were related to the reproductive performance of the herds. Bulk milk samples were collected twice a week from 127 farms during the spring of 1998. The farms were suppliers of the NZ Dairy Group and Kiwi co-operatives. Reproductive performance data was collected from all herds. BMUNs were determined spectrophotomically using Sigma blood urea nitrogen kits. The twice-weekly BMUNs were averaged for each farm and these weekly mean values were centred on the nominated week of mating (W=+1) for the individual farms. There were significant among-farm differences in BMUNs with individual weekly farm values ranging from 5.4 to 26.8 (mg/dl) and the mean (W-3 to W+5) value for farms ranging from 9.6 to 18.8 (mg/dl). There were significant between farm differences in reproductive performance. The percentage of cows submitted for AI in first 3 weeks of mating (\%SR21) ranged from 29.9 to 95.3\%. The percentage of SR21 cows conceiving to that AI (\%Preg1) ranged from 39 to 98.6\% and the percentage of all cows in the herd pregnant by the end of mating (\%Pregall) from 44.9 to 98.4\%. There was some indication of a relationship between reproductive performance and BMUNs in that the change in BMUN level from W-3 to W+5 was significantly correlated within geographic zones with \%SR21 and \%Pregall, correlation coefficients being 0.36 (P=0.013) and 0.37 (P=0.010) respectively. The corresponding correlation for \%Preg1 was only 0.21(P = 0.15). Thus farms for which BMUNs rose over the period W-3 to W+5 had higher reproductive performance than those in the same zone, which showed a fall. However, this accounted for very little of the overall variability. Farms were ranked on their reproductive performance and the average weekly BMUNs for the farms in each quartile calculated. There was no difference in the pattern of BMUNs for the different quartiles of each reproductive parameter. Thus, the measurement of BMUNs would appear to be of little value as an indicator or predictor of reproductive performance. },
	issn = {1176-5283},
	author = {Smith JF and Beaumont S and Hagemann L and McDonald RM and Peterson AJ and Xu ZZ and Duganzich DM}
}
@conference {41222,
	title = {Factors affecting the sex ratio of dairy cattle in New Zealand},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {60},
	year = {2000},
	month = {Jan},
	pages = {301-302},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {The sexes of calves born in 1996 (n = 319,539) and 1997 (n = 408,381) to artificial insemination in selected herds were analysed to study the effects of region, dam breed, dam age, semen type, semen breed, semen age, and sires on the sex ratio of calves. There was a significant (P < 0.001) effect of semen type on sex ratio; frozen semen resulted in 1.66\% and 1.24\% more male calves than fresh semen, respectively, in the 1996 and 1997 seasons. There was also significant (P < 0.01) variation among sires in sex ratio, but the heritability estimate for sex ratio was low (h2 = 0.02). No other effects were significant. Industry-wide use of fresh semen will result in more heifer calves from which future replacements can be selected. },
	issn = {1176-5283},
	author = {Xu ZZ and Johnson DI and Burton LJ}
}
@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}
}
@conference {40856,
	title = {Prospects for overcoming the physiological limits of dairy cow fertility},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {355-357},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Conception rates to a single first insemination in cycling dairy cows  often range between 55\% and 75\% . This paper outlines the physiological  processes that define this outcome and where possible gains could be made.  While herd management issues do influence the outcome of a reproduction  progamme quite significantly, the main impetus of this review is to identify  some opportunities that could raise the threshold level of fertility in New  Zealand dairy herds.},
	issn = {1176-5283},
	author = {Vishwanath R and Xu ZZ and Macmillan KL}
}
@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}
}
@conference {40724,
	title = {Reproductive performance of synchronised lactating dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {55},
	year = {1995},
	month = {Jan},
	pages = {242-244},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {The objective of this trial was to evaluate the reproductive performance  of lactating dairy cows following oestrous synchronisation with a  combination of progesterone, oestradiol and prostaglandin. Cycling cows in  11 herds were randomly divided, with restriction to age, calving date,  condition score and breed, into synchronised (n=1332) groups. Those in the  synchronised group were each treated with an EAZI-BREED},
	issn = {1176-5283},
	author = {Xu ZZ and Burton JR and Burton LJ and Macmillan KL}
}
@conference {40411,
	title = {Testis size and endocrine parameters in rams as predictors of aseasonality in their daughters},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {52},
	year = {1992},
	month = {Jan},
	pages = {195-198},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Overseas data suggest that feeding low energy/high protein diets  can increase carcass weight (and muscle mass) while reducing fat  content. The potential application of this technique to maximise the  returns from overfat lambs in New Zealand was studied. One hundred and  sixty ewe lambs, assessed as being overfat, were allocated on a  liveweight basis to one of seven treatment groups. These comprised an  initial slaughter group, 2 groups offered pasture at approximately  maintenance allowance, 2 groups offered pasture at approximately half  maintenance plus 200g/d of a high protein pellet and 2 groups held on a  bare paddock and offered ad lib straw plus 200g/d of a high  protein pellet. One group from each treatment was slaughtered after 3  weeks and the second after 5 weeks of controlled feeding. Liveweight  change, carcass weight and carcass fatness were monitored.   All groups lost liveweight (88-195 g/d) and estimated carcass weight  (37-89g/d) over the experiment. Corrected to a common carcass weight of  15.25kg decreased GR from 11.6mm for the initial slaughter group to 9.7  and 9.2mm after 3 and 5 weeks, respectively of maintenance pasture  feeding. Corresponding GR{\textquoteright}s of the supplemented groups were 9.3mm (both  groups) after 3 weeks and 8.1 and 7.5mm after 5 weeks for straw and  pasture based diets respectively.   Supplementation with a high protein diet was effective in reducing  carcass GR measurement after 3 weeks of supplementation with a further  decrease after 5 weeks. However, unsupplemented lambs also showed a  decrease in GR after 3 weeks, which was not significantly different from  supplemented lambs. The length of feeding required to effect a change  negated the advantage of decreased GR, although economic returns could  be achieved if the pellets were more readily accepted.  },
	issn = {1176-5283},
	author = {Xu ZZ and McDonald MF and McCutcheon SN and Blair HT}
}
@conference {40137,
	title = {The effect of exogenous melatonin, administered in summer, on wool growth and testis diameter of Romneys},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {49},
	year = {1989},
	month = {Jan},
	pages = {35-38},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {The expansion of molecular biology across most biological fields has meant an increasing application of this technology to agriculture. One of the most exciting new areas to emerge has been that of transgenic animal production. Genes, from a variety of sources, can be incorporated into the early embryo and therefore effectively alter the genotype, and even the physiology of an animal. Most of the work has been conducted using the laboratory mouse. Translation of the technology to the domestic animal has not met with great success, partly because of the genes and promoters chosen and partly because of the difficulty and expense in obtaining large numbers of suitable early embryos for gene incorporation. An efficient gene incorporation system is cow embryos ideally requires the development of a number of novel embryological techniques. They include in vitro maturation and fertilisation of bovine oocytes from abattoir- sourced ovaries, in-vitro culture to allow the development of fertilised embryos to readily transferable stages, satisfactory techniques for incorporating genes into the embryo and techniques such as embryonic cloning to exploit the transgenic cattle produced. The various techniques, their problems and successes are described in depth in this paper. A research programme has been initiated to link embryology, dairy science and molecular biology techniques with the aim of producing transgenic cattle with modified milk composition.},
	issn = {1176-5283},
	author = {Harris PM and Xu ZZ and Blair HT and Dellow DW and McCutcheon SN and Cockrem J}
}
