@conference {41213,
	title = {Comparison of selected reproductive characteristics in Overseas and New Zealand Holstein-Friesian cows grazing pasture or fed a total mixed ration},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {60},
	year = {2000},
	month = {Jan},
	pages = {270-274},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {Lactating overseas and NZ-derived Holstein-Friesian cows were fed either pasture or total mixed ration (NZGrass, n=14; NZ TMR, n=14; OSGrass, n=12; OS TMR, n=13). For cows ovulating before breeding began, mean postpartum anoestrous intervals (PPAI) were 39{\textpm}6, 29{\textpm}4, 27{\textpm}6 and 23{\textpm}2 d, respectively. Of 13 cows with PPAI 43d, four were NZGrass (P<0.02). Of seven with PPAI >43d, four were NZGrass (P<0.05). Growth of the first dominant follicle and corpus luteum through time, and day of emergence of the second follicle wave, measured by transrectal ultrasonography, did not differ between treatment groups. Feeding system affected mean plasma progesterone concentration at emergence of the second follicle wave and number of subordinate follicles recorded during the first follicle wave (4.5 {\textpm} 0.4 and 6.1 {\textpm} 0.5 ng/ml, P<0.02; 6.2 {\textpm} 0.6 and 4.1 {\textpm} 0.7 follicles/d, P<0.05; for grass and TMR, respectively). In summary, both genotype and feed system affected length of PPAI, while feed system influenced aspects of peripheral hormone profiles. },
	issn = {1176-5283},
	author = {Verkerk GA and Morgan S and Kolver ES}
}
@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 {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 {40998,
	title = {Some Effects of Using Progesterone and Gonadotrophin Releasing Hormone on the Reproductive Performance of Inseminated Cows},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {58},
	year = {1998},
	month = {Jan},
	pages = {92-94},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {The administration of progesterone (P4) within 3 days following insemination can reduce pregnancy rates. In contrast, an injection of gonadotrophin releasing hormone (GnRH) at about 12 or 13 days after insemination can increase them by around 10\%. This field trial tested the hypothesis that the negative effects reported for the P4 treatment on fertility could be eliminated by strategically injecting GnRH to convert the two ovarian follicle waves per cycle created by using P4, into three wave ones, with increased fertility. A total of 830 cows in 13 dairy herds received comparative treatments involving: (i) the insertion of a P4 intravaginal device 2 or 3 days after first insemination (1st insem.) for 10 days, with an injection of 10 mg of GnRH at device removal (P4 + GnRH); (ii) the same GnRH treatment but without P4 pre-treatment (GnRH); and, (iii) no post-insemination intervention (Control). Pregnancy status and conception date were confirmed by rectal palpation of uterine contents Calving data were recovered from 10 herds to monitor gestation length, dystocia and calf birth weight. The conception rates to 1st insem. were highest for the 255 cows treated with GnRH (64\%; p = 0.05), but similar in the other two groups of 273 and 302 cows (57\%). Second insemination results were not affected by the treatments; neither were final pregnancy rates. Birth weights were higher for bull than heifer calves (36.9 vs 33.0kg; p<0.01), but were not affected by treatment. The results of this trial showed that the P4 + GnRH treatment did have normal fertility and that GnRH injected 12 or 13 days after first insemination could increase conception rates. },
	issn = {1176-5283},
	author = {Taufa VK and Macmillan KL and Day AM and Ashcroft MJ and Morgan S}
}
