@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 {41122,
	title = {Milk production and production worth of anoestrous dairy cows compared with their cycling herd mates},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {59},
	year = {1999},
	month = {Jan},
	pages = {208-210},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {The primary aim of this study was to determine whether the milk production and production worth (PW) of anoestrous (AA) cows differed from that of their cycling (CYC) herd mates. In addition, a pilot survey was carried out to examine between herd factors, which may influence the percentage of cows diagnosed anoestrous. Individual production records were collated from 7786 cows in 26 herds, in which AA cows were identified following veterinary examination seven days before the planned start of mating. Milk production and PW did not differ between AA and CYC cows, after adjusting for herd, age and days in milk (P>0.05). The percentage of cows diagnosed AA varied from 13.4\% to 51.5\% among herds. Completed questionnaires were obtained from 19 herd owners regarding management factors in these herds. Stocking rates were higher in herds with a low percentage of anoestrous cows (<30\%AA) compared with those with a high percentage (>=30\%AA; p=0.05), but level of supplementary feeding was higher in herds with a low level of anoestrous (p=0.01). It is concluded that milk production and PW do not differ between AA and CYC cows. Nutritional supplementation after calving may influence the percentage of a herd still anoestrus before the start of mating. },
	issn = {1176-5283},
	author = {Rhodes FM and Morgan S}
}
@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 {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 {40996,
	title = {Ovarian volume is a predictor of the resumption of spontaneous oestrous cycles but not the response to the treatment of anoestrus.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {58},
	year = {1998},
	month = {Jan},
	pages = {88},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {This study examined the use of a classification system for ovarian activity as a predictor for both the spontaneous resumption of oestrous cycles and for reproductive per-formance after treatment for anoestrus.},
	issn = {1176-5283},
	author = {Nation DP and Rhodes FM and Day AM 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 {40944,
	title = {Effect of hormonal environment at emergence on persistence of ovarian follicles in cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {57},
	year = {1997},
	month = {Jan},
	pages = {239-240},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {Reduced fertility often occurs when progestins are used to control the timing of oestrus in cattle and is espe-cially evident when a corpus luteum (CL) is not present in the ovary (Kinder et al., 1996). The lowered conception rates at the synchronised oestrus are associated with the development of abnormally large, {\textquotedblleft}persistent{\textquotedblright} ovarian fol-licles as a result of increased secretion of LH. An under-standing of the endocrine regulation of persistent follicles is essential for development of methods to prevent ovula-tion of this aberrant structure in progestin-based oestrous control systems. The influence of time of luteal regression relative to follicle emergence on persistence of dominant follicles was evaluated in progestin-treated cows.},
	issn = {1176-5283},
	author = {Day ML and Burke CR and Nation DP and Rhodes FM and Macmillan KL}
}
@conference {40863,
	title = {Predicting the onset of nutritional anoestrus in Brahman heifers},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {56},
	year = {1996},
	month = {Jan},
	pages = {378-380},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {The objectives of this study were to monitor the physiological events  associated with decreasing liveweight in Bos indicus heifers and to  determine the characteristics which best predicted the onset of nutritional  anoestrus. Eleven post-pubertal Brahman heifers received a diet resulting in  a liveweight loss of 0.7 kg/day. Changes in ovarian morphology were  monitored using daily transrectal ultrasonography. Liveweight was recorded  twice weekly. Heifers became anoestrus after 98 },
	issn = {1176-5283},
	author = {Rhodes FM}
}
