@conference {41399,
	title = {Metabolic responses to glucose challenge in New Zealand and overseas Holstein-Friesian dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {63},
	year = {2003},
	month = {Jan},
	pages = {31-34},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Queenstown},
	abstract = {North American and Dutch Holstein-Friesian (HF) cattle have undergone genetic selection for increased milk production, however, at the same time, reproductive efficiency has decreased. Overseas HF also have greater propensity to mobilise body reserves during early lactation than New Zealand HF cows. It is possible that reproductive differences are a consequence of metabolic and endocrine differences between the strains. This trial was designed to investigate effects of genotype and diet on endocrine response to a challenge of intravenous glucose in HF cows. Twenty-five HF cows of New Zealand (NZ; n=13) and Overseas (OS; n=12) origin, were fed either pasture (Grass; n=12) or a total mixed ration (TMR; n=13) in a 2x2 factorial design. At two weeks postpartum, they were challenged with 300mg of glucose/kg live weight. Data were analysed for effects of genotype and diet. Following glucose challenge, the NZ TMR cows had higher plasma insulin concentrations than the NZ Grass, resulting in a significant interaction between diet and genotype in the area under the response curve; but the OS groups had similar patterns. Mean plasma leptin concentration was higher in NZ TMR than in NZ Grass, OS TMR or OS Grass. Plasma concentrations of glucose and IGF-I were not affected by genotype or feed regime. These results demonstrated metabolic differences between the strains and also diets. A better understanding of the genetic and nutritional basis of hormonal regulation of nutrient partitioning will be important to develop nutritional strategies to meet the requirements of lactating cows with different genotypes, and to find ways to improve reproductive efficiency. },
	issn = {1176-5283},
	author = {Chagas LM and Clark BA and Rhodes FM and Blache D and Kolver ES and Verkerk GA}
}
@conference {41282,
	title = {Postpartum anoestrous interval and metabolic changes in heifers supplemented with pasture prepartum},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {188-191},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {The aim of this study was to determine whether supplementation with pasture from 6 weeks before calving would alter the postpartum anoestrous interval (PPAI) in heifers calving with low body condition score (BCS). Metabolic hormones and metabolites were measured during the pre- and postpartum period. Forty Friesian heifers were managed during the last five months of gestation to achieve a BCS (1-10) of 4.0 (restricted; R; n=27) or 5.0 (fully fed; FF; n=13) by 6 weeks prepartum. One group with low BCS then received pasture ad libitum until calving (restricted + fully fed; R+FF; n=12). Live weight (LW) and BCS were assessed weekly. Blood samples were collected weekly from 10 weeks prepartum to 10 weeks postpartum to measure glucose, urea, non-esterified fatty acids (NEFA), betahydroxybutyrate (BOH) and cholesterol content. The patterns of metabolites measured differed between groups at different times, future work to investigate the relationship these profiles and PPAI would be of value. The percentage of cows cycling as measured by an elevated milk progesterone concentration was 69\%, 75\% and 8\% for FF, R+FF and R groups, respectively. Fully feeding heifers, with low condition score, 6 weeks before calving decreased PPAI when compared to heifers receiving restricted feeding. },
	issn = {1176-5283},
	author = {Chagas LM and Morgan SR and Gore PJS and Clark BA and Verkerk GA}
}
@conference {41284,
	title = {Relationships between, milk production, nutrition and reproduction in benchmark herds},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {195-198},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Inter-relationships between nutrition, milk production and reproduction in dairy cows were investigated in dairy herds with previous high reproductive performance. Ten herds were selected as {\textquoteleft}benchmark{\textquoteleft} farms from one area of the Waikato. Pasture and supplement intakes, and milk production were monitored on a herd basis. Bulk milk samples were taken weekly from calving through to the first three weeks of mating and assayed for levels of progesterone, urea nitrogen and b-hydroxybutyrate (BOH). Pre-mating oestrus, mating (AI) and pregnancy data were recorded. All data was expressed in relation to the planned date of mating (PSM) for each farm. Significant between farm differences were detected in all the reproductive parameters but there was no effect of supplement feeding. The mean proportion of cows cycling at PSM was 65.6 {\textpm} 3.3\% (range 50.5 to 81\%).The mean proportion of cows pregnant to AI at PSM + 3 weeks was 51.3 {\textpm} 2.1\% (range 43 to 61.5\%); at PSM + 6 weeks the mean was 74.5 {\textpm} 3.3\% (61 to 89.5\%); at PSM + 9 weeks it was 84.7 {\textpm} 2.2\% (74.9 to 91.6\%) and at PSM + 12 weeks it was 91.3 {\textpm} 1.2\% (85.6 to 95.4\%). Bulk milk progesterone rose linearly from a mean of 0.5 ng/ml at 8 weeks before PSM to 5.0 ng/ml at PSM and to 6.0 ng/ml three weeks later. The difference between farms at PSM ranged from (2.1 to 7.1 ng/ml). While the pattern of increase in bulk milk progesterone tended to mimic the overall pattern of oestrus activity, there was no relationship in the ranking of farms for these parameters at any time. Bulk milk BOH showed no consistent pattern over the period of measurement and levels ranged between farms in any one week from 0.01 to 0.05 mM. Bulk milk urea nitrogen concentration also showed little change on average (7.25 mM) over the pre-mating and mating periods. The significant between-farm differences in these bulk milk parameters did not appear to be related to reproductive performance. Metabolic indicators measured in bulk milk samples appear of little value for predicting reproductive performance at herd level. },
	issn = {1176-5283},
	author = {Smith JF and Verkerk GA and Clark BA and McKay BJ and Duganzich DM}
}
@conference {41148,
	title = {Prediction of post-partum anovulatory interval in dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {60},
	year = {2000},
	month = {Jan},
	pages = {15-18},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {Changes in a range of metabolites and body condition parameters in lactating cows were measured during early lactation to determine if any key indicators or combination of key indicators could be used as a predictor of length of post-partum anovulatory interval (PPAI). Fifty-three cows in a range of body condition scores were involved in the trial which ran from calving to 10 weeks post-calving. Plasma non-esterified fatty acids (NEFA) and serum cholesterol, glucose, betahyroxybutyrate (BOH) and urea content were measured in weekly samples. Live weight and body condition score (BCS) were measured weekly.Cows were categorised into four groups. Three groups were based on the post-partum anovulatory interval (PPAI). PPAI was defined as the interval between calving and the first evidence of oestrus behaviour. The fourth group contained all the two-year-old cows only. There was a calving interval of 31 days from the first to the last cow to calve. The nadir for live weight for all groups occurred one week after calving. Animals with a shorter PPAI had higher live weights on all occasions, with live weight at week 5 having the strongest association with length of PPAI (P<0.001). Mean BCS was higher for animals with a PPAI<60 days. Plasma urea concentrations were associated with PPAI at weeks 3 and 4 (P<0.01). NEFA and glucose were correlated with PPAI at weeks 3 and 4 only, respectively. There was no association between cholesterol or BOH with PPAI. These results demonstrate that the selected variables do not contribute greatly to prediction of PPAI. Those measures which give the closest association with PPAI are live weight, BCS and age. },
	issn = {1176-5283},
	author = {Clark BA and Chagas LM and Gore PM and Dow B and Verkerk GA}
}
@conference {41072,
	title = {Separate grazing as a breeding management strategy for anoestrous cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {59},
	year = {1999},
	month = {Jan},
	pages = {55-57},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {The aim of this study was to compare the rate of resumption of oestrous cycles and fertility to first insemination between anoestrous cows grazed separately (Split) or grazed in the main herd (Control) for 28 days and untreated or treated with progesterone (CIDR) and ODB from 7 days before the planned start of mating. Oestrus was detected in 54.7\%, 46.3\%, 93.5\% and 86.8\% of cows (Control, Split, CIDR and Split+CIDR, respectively) by 28 days after start of treatment (P<0.05). Compared to controls conception to first insemination was no different in Split and CIDR groups, but was reduced in the Split+CIDR group (P<0.05). The percentage of cows pregnant by 28 days after examination was 26.4\%, 18.9\%, 42.1\% and 31.4\% for Control, Split, CIDR and Split+CIDR groups, respectively (P<0.05). There was no overall effect of separate grazing on milksolids production or cow liveweights, but milksolids did vary between herds (P<0.001). Separate grazing did not enhance the reproductive performance of anoestrous cows. },
	issn = {1176-5283},
	author = {Clark BA and Rhodes FM and McDougall S}
}
@conference {40997,
	title = {Effect of luteolysis on control of ovarian follicles using oestradiol benzoate and progesterone in cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {58},
	year = {1998},
	month = {Jan},
	pages = {89-91},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {This study aimed to determine whether progesterone from intravaginal insertion of a CIDR device could substitute for luteal progesterone and facilitate oestradiol benzoate (ODB)-induced control of ovarian follicle waves in the event of luteolysis. Luteolysis was induced by an injection of prostaglandin-F2a on Day 13 of the oestrous cycle in 24 lactating dairy heifers. Concurrent treatments on Day 13 were: i) 1 mg ODB i.m. (ODB1); ii) CIDR for 6 days (CIDR); iii) 1 mg ODB i.m. plus CIDR for 6 days (ODB1/CIDR); or, iv) 2 mg ODB i.m. plus a CIDR for 6 days (ODB2/CIDR). Examination of the ovaries using ultrasonography showed that oestrous cycles comprising 2 follicle waves predominated among ODB1 and CIDR groups; whereas combination treatments produced mostly 3-wave cycles (p<0.05). Day of ovulation was 15.4 {\textpm} 0.3, 21.2 {\textpm} 0.2 and 22.5 {\textpm} 0.2 for ODB only, CIDR only and 1 or 2 mg ODB plus CIDR cows, respectively (p<0.01). The interval from day of emergence to ovulation of the ovulatory follicle was less (p<0.01) in cows treated with ODB only (6.0 {\textpm} 0.3 days), or ODB plus a CIDR (7.2 {\textpm} 0.6 days), compared to a longer interval in those receiving a CIDR only (11.0 {\textpm} 0.8 days). These results showed that progesterone from a CIDR device was able to facilitate ODB-induced follicle wave turnover at the time of luteolysis in lactating dairy heifers. },
	issn = {1176-5283},
	author = {Burke CR and Morgan S and Clark BA and Rhodes FM}
}
@conference {40994,
	title = {Effects of oestradiol benzoate by injection at CIDR insertion for the treatment of postpartum anovulatory anoestrus in dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {58},
	year = {1998},
	month = {Jan},
	pages = {82-84},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {The effect of an intramuscular (im) injection of oestradiol benzoate (ODB) at insertion of an intravaginal progesterone-releasing device (CIDRTM, InterAg, NZ) during hormonal treatment for postpartum anoestrum in dairy cattle was investigated. Inclusion of injected ODB at CIDRTM insertion in synchronisation programmes for cycling cows can increase fertility, possibly by initiating an emergence of a new ovarian follicle wave with resultant improved oocyte competence. A total of 882 cows, of mixed age and breed from 18 herds, were examined and diagnosed as anoestrous during the week preceding each herd{\textquoteright}s planned start of mating. Cows were allocated randomly as controls or to receive 0.5 or 1 mg ODB (Oestradiol Benzoate Inj., Intervet, Netherlands) by im injection at CIDRTM insertion. The device was removed after 7 days, and any cow which was not observed in spontaneous oestrus within 48 h received 1 mg ODB im (CIDIROLTM Injection, InterAg, NZ). Cows with an observed heat within 12 days of CIDRTM removal were defined as responders, and returns to service in the subsequent 30 days were recorded. There were no significant differences between the control, 0.5 and 1 mg ODB treatments for either the proportion responding (89.5\%, 89.4\% and 90.9\%, respectively) or returning (52.3\%, 50.3\% and 55.4\%, respectively); however the proportions of cows observed in spontaneous oestrus varied by treatment (P<0.01; 28.5\%, 22.9\% and 17.2\% for control, 0.5 and 1 mg ODB treatments, respectively). Conception rates were not significantly affected by treatment (35.9\%, 42.5\% and 43.2\% for control, 0.5 and 1 mg ODB treatments, respectively). Of cows which did not become pregnant to the induced oestrus, 21.7\%, 20.7\% and 29.9\% for control, 0.5 and 1 mg ODB treatments respectively, returned to service with an interval of more than 24 days. These observations suggest that an injection of ODB at CIDRTM insertion may alter follicle wave patterns in cows with PPA, but that this may not result in increased conception rate, and might be detrimental to ovarian activity in a proportion of cows. },
	issn = {1176-5283},
	author = {Verkerk GA and Taufa VK and Morgan S and Clark BA and Macmillan KL}
}
@conference {40993,
	title = {Factors influencing the prevalence of postpartum anoestrus in New Zealand dairy cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {58},
	year = {1998},
	month = {Jan},
	pages = {79-81},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {The aim of this study was to determine the association between age, interval from calving (PPI) and breeding worth (BW) and prevalence of postpartum anoestrus (AA), as well their effect on response to hormonal treatment by anoestrous dairy cows. Individual cow details were collated from 6649 cycling and 2446 AA animals in 29 herds. Probability of AA was influenced by herd and was negatively related to PPI and age (p<0.001); but was not related to BW (p>0.05). Response of AA cows to treatment with progesterone and oestradiol benzoate was evaluated using a subset of 1482 anoestrous cows. Within 7 days of treatment, oestrus was detected in 87.1\% cows and conception rate to insemination during this period was 42.2\%. Oestrous response varied between herds but was not influenced by BW, PPI or age (p>0.1). Conception rate was positively related to PPI (p<0.001), but was not influenced by BW or age (p>0.1). It is concluded that in commercial dairy herds the likelihood of a cow being AA is greatest in young and recently calved animals, but is not influenced by breeding worth.},
	issn = {1176-5283},
	author = {Rhodes FM and Clark BA and Nation DP and Taufa VK and Macmillan KL and Day ML and Day AM and McDougall S}
}
@conference {40995,
	title = {Manipulating patterns of ovarian follicle development in cattle with progesterone and gonadotrophin releasing hormone to produce oestrous cycles with two or three follicle waves},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {58},
	year = {1998},
	month = {Jan},
	pages = {85-87},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {This study tested the hypothesis that oestrous cycles with two follicle waves created using progesterone, could be converted to oestrous cycles with three follicle waves using gonadotrophin releasing hormone (GnRH). Oestrus (Day 0) was synchronised in 24 Friesian cows. On Day 2, a progesterone containing device (CIDR) was inserted into the vagina of 16 cows for 10 days. Eight of these animals received 8{\textmu}g of buserelin (GnRH) at device removal. Eight untreated animals formed the Control group. Daily transrectal ultrasonography showed that the oestrous cycles of the cows treated only with a CIDR device had two ovarian follicle waves compared to 1/8 in CIDR+GnRH and 3/8 in Control groups (p<0.01). The average length of the oestrous cycle was shorter in the CIDR-only group (19.3 {\textpm} 0.5 days), compared to the CIDR+GnRH (20.9 {\textpm} 0.2 days) and Control (22.3 {\textpm} 1.1 days) groups (p<0.05). These results demonstrate that strategic administration of GnRH can convert progesterone induced two-wave oestrous cycles into a three-wave pattern. },
	issn = {1176-5283},
	author = {Clark BA and Rhodes FM and Burke CR and Morgan SR and Macmillan KL}
}
@conference {40982,
	title = {Use of once daily milking compared with treatment with progesterone and oestradiol benzoate (ODB) in anoestrous cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {58},
	year = {1998},
	month = {Jan},
	pages = {44-46},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {The aim of this study was to compare the rate of resumption of oestrous cycles and fertility to first insemination of anoestrous cows examined 7 days before the planned start of mating (PSM), which were milked once (OAD) or twice daily (TAD) for at least 28 days and untreated or treated with progesterone and oestradiol benzoate (ODB; CIDR). By 28 days after the start of treatment, oestrus was detected in 65.8\%, 76.6\%, 93.5\% and 97.9\% of cows (TAD, OAD, TAD+CIDR and OAD+CIDR, respectively) (p<0.001). Conception rates to first insemination were lower in CIDR treated than untreated cows (40.4\% vs 50.3\%; p<0.05), but were not affected by milking frequency. The mean ({\textpm} sem) interval from PSM to conception was shorter in CIDR treated than untreated cows (12.8 {\textpm} 1.2 vs 19.0 {\textpm} 1.3 days; p<0.001). Daily milk yield decreased by 6.1 {\textpm} 0.2 and 2.2 {\textpm} 0.2 litres; and milk solids by 0.46 {\textpm} 0.02 and 0.19 {\textpm} 0.02 kg (p<0.001) in cows milked OAD and TAD, respectively, over the treatment period. Once daily milking increased the rate of spontaneous resumption of oestrous cycles in anoestrous cows compared with TAD, but was associated with a significant decrease in milk production. Compared to treatment with progesterone and ODB, OAD resulted in a longer interval from PSM to conception. },
	issn = {1176-5283},
	author = {Rhodes FM and Clark BA and Macmillan KL and McDougall S}
}
@conference {40655,
	title = {Effects of induced parturition on mammary function},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {55},
	year = {1995},
	month = {Jan},
	pages = {21-22},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Four 6.4 ha farmlets each stocked with 24 high genetic merit  Friesian cows were used to determine the effect of nitrogen fertiliser  (N), and a long summer grazing rotation on pasture and milk production  in summer. Treatments were 0 )-N) or 50 kg N/ha (+N) in December,  January and March and a 16 day (16) or 40 day (40) rotation. Treatments  started 15 December, following a two week uniformity period, and ran  until 29 April.    On the 16 and 40 day rotations N increased net herbage accumulation by  0.8 t DM/ha, and milksolids (MS) production by 92 and 38 kg/ha  respectively. Across both nitrogen treatments, the 40 day rotation  increased net herbage accumulation by 1.7 t DM/ha. The MS production  was 39kg/ha greater on the -N40 than the -N16 treatment whereas that of  the +N16 and +N40 did not differ significantly.    The N and long rotation treatments also resulted in higher average  herbage mass and cow condition at the end of the experimental period.  It is concluded that N in early summer and a long summer rotation are  useful management practices to reduce the effects of summer dry periods.   },
	issn = {1176-5283},
	author = {McFadden TB and Verkerk GA and Clark BA and Hovey RC and Macmillan KL}
}
