A randomised controlled study to assess the effects of an extension programme on the 6 week in-calf rate of seasonal calving, pasture-based dairy herds in New Zealand

A pilot monitoring strategy for post-partum disease in an Australian dairy herd

AIMS

To design a monitoring strategy that could be applied to regular veterinary visits to dairy farms to assess the prevalence and association between health conditions (uterine disease, hyperketonaemia and suboptimal body condition score) when diagnosed and treated at 1-7 days post-calving (DPC) and then re-examined at 28-35 DPC.

METHODS

This study evaluated data from 187 high-yielding dairy cows (21 primiparous, 166 multiparous) on one South Australian dairy farm on two occasions; Visit A which was 1-7 DPC and Visit B which was 28-35 DPC. On each visit, the nature of vaginal discharge, concentration of beta-hydroxybutyrate (BOH) in blood and BCS were recorded and assigned a clinical score. This was converted to a categorical outcome denoting the presence or absence of an abnormal health event, namely metritis or endometritis, hyperketonaemia (BOH concentration ≥1.2 mm/L) and suboptimal body condition score (>0.5 from optimum score). Cows with uterine disease or hyperketonaemia at either visit were treated. The prevalence of abnormal health events at each visit was determined and the association between the prevalence of disease at Visit A and Visit B (following appropriate treatment at Visit A) was measured using regression analysis.

RESULTS

The prevalence of abnormal vaginal discharge, hyperketonaemia and suboptimal BCS at Visits A and B were 26%, 7%, 35% and 25%,16%, 33% respectively. A higher proportion of primiparous cows (Visit A: 0.86 (95% CI = 0.70-1.00); Visit B: 0.95 (95% CI = 0.86-1.00)) were found to have suboptimal BCS at both visits compared to multiparous cows (Visit A: 0.28 (95% CI = 0.20-0.35); Visit B: 0.24 (95% CI = 0.17-0.32)). A higher prevalence of hyperketonaemia at Visit B for multiparous compared to primiparous cows (19 (95% CI = 12-25)% vs. 0 (95% CI = 0-17) respectively) was identified. An increase in clinical discharge score at Visit A increased the odds of purulent vaginal discharge at Visit B (OR = 1.77 (95% CI = 1.31-2.40)). Failing to calve at target BCS was strongly associated with cows missing target BCS at Visit B (OR = 5.77 (95% CI = 2.35-13.11)) and for every unit increase in BCS at Visit A, BCS at Visit B increased by 0.40 (95% CI = 0.26-0.53).

CONCLUSIONS AND CLINICAL RELEVANCE

This study describes a pilot monitoring strategy for clinical parameters indicative of post-partum disease at 1-7 and 28-35 DPC. Determining the herd prevalence of these conditions will enable tracking of herd disease status over time.Abbreviations: BCS: Body condition score; BOH: Beta-hydroxybutyrate; DPC: Days post-calving; NEFA: Non-esterified fatty acids; SCHK: Subclinical hyperketonaemia.

Herd manager attitudes and intentions regarding the selection of high-fertility EBV sires in Australia

Reproductive performance in dairy cattle has declined over the last 50 years as an unintended consequence of selection for high milk yield. Since the early 2000s, dairy geneticists have released successive versions of fertility estimated breeding values (EBV) to assist in reversing this trend. At the herd level, fertility EBV can help managers accelerate improvements in reproductive performance by acting as a second selection criteria when used in tandem with a breeding index. However, use of the fertility EBV in sire selection currently varies between herd managers. The aim of this study was to better understand the reasons why herd managers choose or do not choose to select high-fertility EBV sires, using the Theory of Planned Behavior (TPB) as a social research framework. Thirty-five Victorian dairy herd managers were recruited as part of a larger study investigating the daughter fertility Australian Breeding Value and interviewed using a series of questions examining TPB constructs. The interviews were recorded and transcribed using template analysis. A wide range of herd manager types were enrolled into the study, with representation from diverse systems. Out of the 35 herd managers, 27 included fertility in their list of high-priority breeding objectives. A wide variation in results was consistent with previous studies that have demonstrated marked heterogeneity in herd manager attitudes toward bull selection. Herd manager-perceived barriers to selection of sires with high daughter fertility EBV included a lack of high daughter fertility bulls with other desirable traits, a lack of trust in the fertility EBV or in the Australian EBV system, difficulty in interpreting international proofs, information overload, semen prices, low bull reliability, and difficulty in understanding bull catalogs. Not all herd managers found the process problematic, however, particularly if a breeding consultant was employed to select all or most of the sires. Herd manager-perceived barriers for choosing to select daughter fertility as a breeding objective include a lack of awareness of the EBV, a lack of interest in genetics in general, low confidence in the impact of genetic selection for fertility, and a feeling that fertility was not important for their production system. The results of this study suggest that animal geneticists and on-farm service providers need to work together to allow the opportunities arising from appropriate use of fertility EBV to be realized more broadly across the dairy industry.

The effect of participation in a regular reproductive herd health program on 80-day submission rate and 100-day in-calf rate in year-round calving dairy farms

Herd health management programs are commonly implemented on dairy farms to improve farm reproductive performance. In year-round calving systems, herd health programs can be supported by extension programs such as InCalf, which focus on improving the 100-day in-calf rate (100DICR) as a key reproductive performance indicator. The effect of implementing a herd health program was evaluated by analysing the 80-day submission rate (80DSR) and 100DICR during the initial 18-month period following commencement of regular herd health visits at 11 year-round calving dairy farms. The mean 80DSR and 100DICR was calculated for each of six consecutive three-month intervals following the initial herd health visit at 11 dairy farms distributed across the north and south coasts of New South Wales (NSW). On the 11 study farms 80DSR increased from 36.9% (95% confidence interval [CI] 36.7-37.2) at 0-3 months to 61.9% (95% CI 61.4-62.4) and 100DICR increased from 19.1% (95% CI 18.9-19.3) at 0-3 months to 28.5% (95% CI 28.0-29.0) at 15-18 months. 80DSR increased at similar rates on north coast farms compared to south coast farms; however, north coast farms had a lower 100DICR at 0-3 months which increased at a greater rate compared to south coast farms. 100DICR on north coast farms increased from 12.8% (95% CI 12.5-13.2) at 0-3 months to 27.6% (95% CI 26.8-28.4) at 15-18 months, whereas 100DICR on south coast farms increased from 26.7% (95% CI 26.3-27.0) at 0-3 months to 29.6% (95% CI 28.8-30.5) at 15-18 months. Participation in a regular herd health program resulted in an increased 80DSR and 100DICR.

Applying animal-based welfare assessments on New Zealand dairy farms: feasibility and a comparison with United Kingdom data

AIMS

To assess the feasibility of applying animal-based welfare assessments developed for use in Europe on New Zealand dairy farms; in particular, to identify measures which could be evaluated during a single visit at milking time alongside whole herd locomotion scoring.

METHODS

A protocol for animal welfare assessment, developed in the United Kingdom (UK), was evaluated. Measures that were suitable for use on pasture-based dairy farms in New Zealand were then assessed for practicability on 59 farms across New Zealand, during and immediately after milking, alongside whole herd locomotion scoring. Where data were collected the results were compared to those from a UK study of 53 dairy farms.

RESULTS

Thirteen observations of the physical condition of cows were considered suitable for measurement, excluding observations related to hock lesions as they are rarely observed on pasture-based farms. Five of these measures were not assessed as there was not time to do so during milking alongside whole herd locomotion scoring. Thus, the prevalence of dirty flanks, hind limbs and udders, dull coat, thick hairy coat, significant hair loss, very fat cows (body condition score (BCS) ≥7 on 1-10 scale) and very thin cows (BCS≤3), were recorded. Three measures of behaviour were considered suitable for measurement on-farm, but only locomotion score was practicable and was measured. Farmer-estimates for the incidence of mastitis, lameness, sudden death, milk fever and other diseases were also obtained.Overall, dirty flanks, dirty udders and estimated milk fever incidence were more prevalent in this study than in the UK. The prevalence of thin and fat cows, lame cows and estimated mastitis incidence were much lower in the present study than on UK farms.

CONCLUSIONS AND CLINICAL RELEVANCE

Animal-based assessments can be used on dairy farms in New Zealand, but need to be modified from those developed for housed cows.Welfare on these farms was generally good compared to those in the UK, but these results need to be confirmed on more farms using a wider range of assessments than proved practicable in this study.