@conference {3672, title = {Calf and heifer development and the onset of puberty in dairy cows with divergent genetic merit for fertility}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {77}, year = {2017}, month = {06/2017}, pages = {205-210}, address = {Rotorua}, abstract = {A research herd with divergent genetic merit for fertility was established to better understand the underlying drivers of fertility in dairy cattle. This paper describes the establishment of this herd, heifer growth and development, and the effect of divergence in fertility breeding value (FBV) on the timing of puberty. The average FBV of the high and low fertility groups of heifers was +5.6 and -4.6, respectively. The heifers were weighed fortnightly, with body condition score (BCS) and stature recorded at six, nine, 12 and 15 months of age. Weight and age at puberty were defined as the first day when plasma progesterone was >1 ng/ml in two of three consecutive once weekly samples. There was no effect of FBV on live weight (LWT), BCS, nor stature by age as the heifers matured. High-fertility heifers attained puberty at a lighter LWT (271 vs. 296 kg; SED 4.3 kg), an earlier age (358 vs. 379 days; SED 6.0 days) and a lower proportion of estimated mature LWT (51 vs. 55\%; SED 0.7\%), compared with Low-fertility heifers. Therefore, the premise that high genetic merit for fertility is positively associated with reaching puberty earlier is supported. Further work is required to support and assess the value of incorporating a puberty trait into the FBV.}, issn = {1176-5283}, author = {Meier S and Fisher B and Eketone K and McNaughton LR and Amer PR and Beatson P and Bryant JR and Dodds KG and Spelman R and Roche JR and Burke CR} } @conference {3672, title = {Oocyte maturation and quality in dairy heifers with diverse genetic merit for fertility}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {77}, year = {2017}, month = {06/2017}, pages = {29-33}, address = {Rotorua}, abstract = {Oestrous behaviour, cumulus cell-oocyte complex (COC) quality, and steroid concentrations were characterised in dairy heifers of high and low values for fertility breeding value (FBV). The hypothesis was that the greater FBV is partly mediated through improved oocyte quality. Ovum pick-up (OPU) was used to collect COCs from the preovulatory follicle of 40 heifers observed in oestrus. Multiplex Taqman qPCR was used to investigate gene expression in cumulus cells (eight genes) and oocytes (three genes) of the recovered healthy COCs (n=9 per group). Plasma and follicular fluid steroid concentrations were measured using high-performance liquid chromatography. Low-FBV heifers were more active in the first eight hours of oestrus (P<0.05), leading to earlier detection and OPU (P<0.05). Consequently, COCs recovered from low-FBV heifers were morphologically less mature (P<0.05) and tended to have lower expression of genes regulating maturation compared with high-FBV heifers. Our findings suggest COC development is retarded in low-FBV heifers relative to the timing of visually observed oestrus, which may result in a poorly developed oocyte at ovulation. }, issn = {1176-5283}, author = {Reed CB and Meier S and Pitman JL and Burke CR} } @conference {3672, title = {Uncovering genetic variation in cow fertility using simulation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {75}, year = {2015}, month = {07/2015}, pages = {42-47}, address = {Dunedin}, abstract = { Dairy cow fertility is currently measured using two traits: the proportion of cows mated within 21 days of the start of mating (PM21) and the proportion of cows that calve within 42 days of the start of calving (CR42). These traits indirectly measure a cow{\textquoteright}s genetic propensity to return to a fertile state after calving. Both PM21 and CR42 have low heritability (0.05 and 0.03, respectively) and fertility is suspected to have much stronger genetic drivers than indicated by these lowly heritable components. The purpose of this study was to explore genetic and environmental factors that contribute to dairy cow fertility using a stochastic simulation model. The model traces the reproductive life of cows from birth until their second calving date using environmental and genetic variables to simulate fertility phenotypes. The model demonstrated that even when significant genetic variation was simulated in underlying fertility traits, this variation appears only weakly as genetic effects using the current fertility traits evaluated for genetic selection purposes. Potential alternative traits (e.g. gestation length, heifer puberty trait, strength of oestrus expression or post-partum anoestrous interval) were shown to have potential to add value when identifying sires whose daughters calve earlier in the season.}, issn = {1176-5283}, author = {Dennis NA and Stachowicz K and Visser B and Hely FS and Amer PR and Meier S and Burke CR} } @conference {3678, title = {BRIEF COMMUNICATION: Predicting the impact of climate change on the risk of facial eczema outbreaks throughout New Zealand}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {74}, year = {2014}, month = {06/2014}, pages = {161-163}, address = {Napier}, abstract = {Facial eczema (FE) is caused by the sporidesmin toxin, which is produced by the spores of the fungus, Pithomyces chartarum (PC). Sporidesmin causes damage to the gut, liver and bile ducts in ruminants. This can result in weight loss, decreased production and skin photosensitivity which characterise clinical FE cases (Sheath et al. 1987; Towers \& Smith 1978). Production losses also occur in sub-clinical cases, which may go undetected under normal farm management.}, issn = {1176-5283}, author = {Dennis NA and Amer PR and Meier S} } @conference {78982, title = {An evaluation of a progesterone-based diagnostic as an aid to re-insemination decisions in a seasonal, pasture-grazed dairy cow herd}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {72}, year = {2012}, month = {Jan}, pages = {35-37}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {

Progesterone-based diagnostic tests are commercially available to predict pregnancy status 19 to 23 days following an insemination, thus providing decision-making support for artificial breeding. The study objective was to evaluate the likely performance of such a test in a pasture-grazed, seasonal dairy farm. Progesterone was determined in milk samples collected twice weekly from 553 cows at the Lincoln University Dairy Farm. Receiver operating characteristic analysis was applied to these data to determine sensitivity, false positive rate and the positive predictive value using a range of progesterone threshold values for detecting non-pregnant cows. The gold standard was non-pregnancy as measured by ultrasonography. At an optimised threshold of 4.1 ng/mL, the sensitivity, false positive rate and positive prediction rate were 78\%, 2.6\% and 96\% for detecting non-pregnant cows on Days 19 to 23. A major source of inaccuracy was the 28 cows with elevated levels of progesterone in milk on Days 19 to 23 after first insemination that were subsequently diagnosed non-pregnant. Another source of error was the inherent variance in progesterone concentration profiles among individuals. At a current cost of about $5 per test, this technology would have limited appeal for detecting non-pregnant cows in dairy systems where a satisfactory level of oestrus detection performance can be achieved.

}, issn = {1176-5283}, author = {Burke CR and Kamphuis C and Meier S and Pellow R} } @conference {78984, title = {Use of progesterone profiling to investigate factors affecting conception rates in a large, pasture-grazed dairy herd}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {72}, year = {2012}, month = {Jan}, pages = {45-50}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {

A study was conducted at the Lincoln University Dairy Farm to investigate factors influencing conception rate (CR). Relative to the planned start of mating date (Day 0), milk progesterone (MP4) concentrations were determined weekly from Day -20 to 0, twice weekly from Day 0 to 42, and then weekly to Day 70 in 666 cows. Trough-like patterns among individual profiles were identified and defined as periovulatory events. Pre-mating ovulatory status was a predictor (P \< 0.01) of first service CR (FSCR), with anovulatory cows having a lower FSCR (37.4\%) compared with {\textquoteleft}late{\textquoteright} (47.3\%) and {\textquoteleft}early{\textquoteright} (56.4\%) ovulating cows. In turn, interval from calving to Day 0 was a significant determinant for pre-mating ovulatory status. Oestrus detection was performed to a high standard, even though 5\% of the 850 artificial inseminations were coincident with a lack of ovulation. MP4 profiles also indicated that 4\% of cows that conceived during the 37-day artificial breeding period subsequently lost these pregnancies. A 2.6\% error rate for diagnosing pregnancies on Day 78 was detected, mostly due to incorrectly attributing pregnancies following artificial breeding. Findings indicate the critical importance of managerial strategies that promote a high prevalence of cows having ovulated at least 21 days before mating starts.

}, issn = {1176-5283}, author = {Burke CR and Meier S and Pellow R} } @conference {60934, title = {The effect of feed restriction during peak lactation on milk production parameters : Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {69}, year = {2009}, month = {Jun}, pages = {24-26}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Adverse weather conditions that reduce pasture growth and/or quality can place the lactating dairy cow under periods of transitory nutritional stress. Previous research that has focused on the effects of feed restrictions in a pasture-based dairy system have imposed feed deficits either pre-calving (Roche, 2007), immediately post-calving for five to six weeks (Bryant \& Trigg, 1979; Roche, 2007) or up to a 23\% restriction in dry matter intake (DMI) (Bryant \& Trigg, 1979). All experiments reported an immediate reduction in milk production; however, the longer-term effects varied depending on... Continued }, issn = {1176-5283}, author = {Kay JK and Phyn CVC and Williams YJ and Roche JR and Burke CR and Meier S} } @conference {41681, title = {Effect of dairy cow breed on the metabolic adaptation to lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {66}, year = {2006}, month = {Jan}, pages = {390-396}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Napier}, abstract = {Three breeds (20 Friesian, 20 Jersey and 20 Jersey/Friesian crossbred multiparous cows) were used to determine the effect of breed on indicators of metabolic status and the post partum anovulatory interval (PPAI). Effect of breed on circulating concentrations of metabolites and hormones, liver mRNA levels and PPAI was established. Weekly blood samples were taken for the first 6 weeks of lactation. Liver biopsy samples were taken from a sub-sample of cows of each breed between 23-33 days post partum, to determine levels of expression of T-GHR, GHR-1A and IGF-1 receptors using RT-PCR. Milk progesterone analysis was used to determine PPAI. There was a significant breed effect on circulating concentrations of {\^a}-hydroxy butyrate (P<0.01), non-esterfied fatty acids (P<0.001), triacylglycerols (P<0.001) and leptin (P<0.01), with Jersey cows having higher concentrations of these hormones and metabolites than Friesian or crossbred cows. Despite the concentration differences between breeds, only leptin showed a significant difference (P<0.01) in the rate of change in concentration across time between the breeds. Jersey cows were observed to have shorter PPAI (34 vs 42 and 44 days for Friesian and crossbred cows respectively: SED 6 days) but this was not statistically significant (P=0.18). There was no difference in the expression of mRNA levels of TGHR, GHR-1A and IGF-1 receptors in the liver. It appears that grazing Jersey cows have a different fat metabolism, which affects the regulation of circulating leptin concentrations and this may have contributed to their apparent ability to return to cyclicity earlier. }, issn = {1176-5283}, author = {Back PJ and Meier S and Barnett CME and Cursons RT and Thomson NA} } @conference {41668, title = {Supplementing mature cows with either cereal or lipid-based supplements had no effect on the post-partum anoestrous interval}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {66}, year = {2006}, month = {Jan}, pages = {329-333}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Napier}, abstract = {A large scale retrospective study was undertaken in2005 on the impact of the policies for induction of early calving (either undertaken during study period, stopped in previous 2 seasons, or continuing to induce) and other factors on herd reproductive performance. Data was gathered from whole-herd pregnancy testing data and farm visit records, and electronic records from the LIC database. Data analysed included records from 3 consecutive seasons from 82 herds, and included 34,729 cows, 72,593 calvings, 237,884 individual herd test records and summary pregnancy test results for each herd for 3 seasons. Factors that significantly influenced herd reproductive performance were herd induction policy, season, herd predominant breed, 4 week submission rate, average milk protein percent at herd test within 60 days following the start of the breeding programme, and length of breeding programme (all P< 0.01). Induction usage was found to be declining over time, implemented at a later stage of the calving programme and unlikely to meet Code of Practice requirements, and under-reported to the LIC database. This large-scale epidemiologic study provides important information for herd owners, their advisors, and other scientists on herd reproductive performance.}, issn = {1176-5283}, author = {Meier S and Gore P and Minnee E and Thomson N} } @conference {41221, title = {The effect of supplementation with 3-omega fatty acids on plasma metabolites and ovarian function of dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {60}, year = {2000}, month = {Jan}, pages = {297-300}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {Two- year- old Holstein Friesian dairy cows (n=20) were allocated to receive either a rumen- protected fish oil supplement (omega group, n=10), starting between 5-6 weeks post-partum, or pasture only (control group, n=10). .Serum metabolites, including cholesterol, urea, glucose and beta-hydroxybutyrate (BOH) were measured weekly from calving through to week 11-12 post-partum. Within 2 weeks of the commencement of treatment, serum cholesterol concentrations had increased significantly in the omega group vs the control group, and continued to increase through to weeks 11-12 post-partum. None of the other serum metabolites measured showed any differences with treatment. However, levels of serum urea, BOH and plasma glucose showed significant variations from week to week . The size of the dominant follicles and corpus luteum were measured, using transrectal ultrasonography, on days 8 to 16 of both oestrous cycles. The corpus luteum of the second cycle was significantly larger in the omega group. The second oestrous cycle was interrupted through an oxytocin challenge carried out to measure prostaglandin synthesis, on day 16 of the cycle. After the oxytocin challenge, the omega group exhibited a longer interval to the next observed oestrus. These results suggest that supplementing dairy cows with 3-omega fatty acids will result in changes at the site of the ovary and uterus.}, issn = {1176-5283}, author = {Meier S} }