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ABSTRACT: We conducted a retrospective meta-analysis based on individual cow data to assess the associations of parity, level of production, and pasture-based or intensively fed systems with fertility. Our goal was to provide understandings of the role of parity in risks for removal and reproductive failure. Multilevel models were used to evaluate the fixed effects of parity, milk, milk solids, milk fat and protein percentage and yield, and production system [intensively fed (n = 28,675) or predominantly pasture fed (n = 4,108)] on reproductive outcomes. The outcomes were the hazard of not being bred (HNBRED), hazard of pregnancy (HPREG), pregnancy to first breeding (PREG1), and odds of becoming pregnant in a lactation (OPAL). The 32,783 cows were in 13 studies conducted in Australia (14.6% of cows), Canada (2.4% of cows), and the United States (83.0% of cows). There were 38.5% of cows in the sample in parity 1, 27.3% in parity 2, 16.7% in parity 3, 9.0% in parity 4, and 8.6% in parity ≥5. Compared with cows of parity 1, parity ≥5 cows had a greater HNBRED [hazard ratio (HR) = 2.45], lesser HPREG (HR = 0.73), and reduced OPAL (odds ratio = 0.36). However, the parity ≥5 cows had similar PREG1 to other parities except for parity 1. This suggests the possibility of a higher proportion of subfertile parity ≥5 cows than for other parities. Associations between parity and reproductive measures were influenced by the different milk production measures, indicating that milk yield and milk component percentages and yields modified the odds or hazards of successful reproduction. All milk production measures had quadratic associations with OPAL, indicating that either low or high production or concentration of solids within a cohort reduced OPAL. This reduced OPAL reflected a greater HNBRED for lower milk yield and milk protein and fat yielding cows. Both milk yield and milk protein percentage had quadratic associations with HPREG. When centered milk yield was categorized into quartiles, small differences in HPREG existed. A more marked association of milk protein percentage occurred with HPREG, with optimal HPREG at approximately 0.5% above group mean milk protein percentage. Milk fat percentage (HR = 0.901), fat yield (kg/d; HR = 0.78), protein yield (kg/d; HR = 0.71), and milk solids yield (kg/d; HR = 0.84) were all linearly associated with reduced HPREG. Difference in production systems did not have substantive effects on PREG1 but did for HNBRED, HPREG, and OPAL. Estimates of associations of parity with reproductive outcomes HNBRED, HPREG, and OPAL were influenced by milk and milk solids yield; older cows had markedly lower reproductive outcomes. Interestingly, for PREG1, there were few differences among parities and differences were less influenced by milk yield and constituent measures. The marked associations of parity with removal for all reasons, deaths and culling, and reductions in HNBRED, HPREG, and OPAL indicate a need to focus on the physiological changes with parity to produce better strategies to support optimal longevity of cows.

ABSTRACT: Data were obtained from studies in Australia, Canada, and the United States using individual cow data from 28,230 Holstein cows to evaluate associations between parity and disease. Our goal was to develop understanding of disease risks for cows of differing parity. We hypothesized that there would be increased risks of disease and changes in metabolite concentrations with increased parity. Parity ≥5 represented 2,533 cows or 9.0%, parity 4 was 9.8% (2,778), parity 3 as 19.0% (5,355), parity 2 as 28.1% (7,925), and parity 1 was 34.1% (9,639) of the sample. Of these cows, 15.5% were in Australia, 14.7% in Canada, and 69.8% in the United States. Lactational incidence (LI) risk of clinical hypocalcemia increased with parity from 0.1% for parity 1 to 13% for parity ≥5 cows. The marked increase suggests profound differences in metabolism with increased parity. The LI of clinical mastitis was 17.4%. The odds of mastitis increased with parity to 2.5 times greater in parity ≥5 than in parity 1. The LI of lameness increased with parity; specifically, the odds of lameness was 5.6 times greater for parity ≥5 than parity 1. Dystocia incidence was 8.7% and greatest for parity 1 cows. The LI of retained placenta was 7.4% and increased with parity, with the odds for parity ≥5 2.3 times greater than for parity 1. The LI of metritis was 10% and of endometritis 14%, with the greatest odds in parity 1. The LI of clinical ketosis was 3.3% with a marked increase in odds with parity. The prevalence of subclinical ketosis was 26.8% with only cows in parity 1 having lower odds than other parities. Parity ≥5 cows had greater odds (odds ratio = 1.7) of respiratory disease than parity 1 cows, which were lesser than other parities. Metabolite concentrations were evaluated in 5,154 Holstein cows in the precalving, calving, and immediate postcalving data sets. Metabolic measures near peak lactation provided 1,906 observations. Concentrations of β-hydroxybutyrate (BHB) and nonesterified fatty acids increased with parity on d 1 to 3 of lactation and at peak lactation. On d 1 to 3 after calving differences in glucose, nonesterified fatty acids, and BHB indicated a greater reliance on mobilized lipid to export energy to peripheral tissues as BHB for greater parity cows. Differences in concentrations among parity groups were marked at times, for example >0.20 mM in Ca for parity 1 and 2 to parity ≥5 and >0.33 mM for all older parities compared with parity 1 for P on the day of calving. The marked increase suggests profound differences in metabolism with increased parity are probably influenced, in part, by increased production. We found marked differences in concentrations of metabolites with parity that are consistent with reduced reproduction, health, and body condition for higher parity cows. These unfavorable differences in metabolism in Ca, P, glucose, and cholesterol concentrations for higher parity cows also complement the often-substantial differences in disease risk with parity and suggest a need to carefully consider the parity structure in study design. Managers and advisors will need to consider methods to reduce risk of health disorders tailored to cows of different ages.

Body condition scoring (BCS) and body weight (BW) are observations associated with labile tissue reserves, health, and reproduction efficiency of dairy cows. The effect of parity (1 through to ≥5) and feeding system (pasture-based and TMR) on BCS and BW were evaluated utilizing raw data sets from 16 retrospective studies that totaled 24,807 Holstein cows across 3 nations (Australia, Canada, and the United States). Linear regression models were used to investigate the 5 outcome variables of precalving BCS, peak milk BCS, change in BCS from precalving to peak milk, and peak milk BW and their respective associations with parity and feeding system. To help control for the influence of calendar time, study treatment protocols when applicable, and genetic change, all outcome variables were center-transformed around each study group mean. Including feeding system as a covariate improved model fit for most outcome variables; however, the relative effect size of parity was generally much greater than feeding system effect size. Parity 2 cows had the lowest precalving BCS of −0.087 [95% confidence interval (CI): −0.107, −0.065] less than the mean, whereas parity 1 cows had the greatest, 0.068 (95% CI: 0.043, 0.092) above mean, regardless of feeding system. Peak milk BCS overall decreased with increasing parity (parity 1 to parity ≥5: −0.13, 95% CI: −0.19, −0.08) and BCS change during the transition period monotonically decreased with increasing parity (parity 1 to parity ≥5: −0.22, 95% CI: −0.26, −0.17). Peak milk BW monotonically increased with increased parity (parity 1 to parity ≥5: 114 kg, 95% CI: 104, 125). A waffle plot was used to present the proportions of cows, by parity, that were partitioned into “low BCS and low BW,” “low BCS and high BW,” “high BCS and low BW,” or “high BCS and high BW” groups. Cows were assigned either a high or low status by being above or below their specific centered study group means, respectively. Considering a null hypothesis of 25% per BCS-BW category, there was a striking change in category from parity 1 cows that were predominantly in the “high BCS and low BW” category (61.2%) to parity ≥5 cows that were predominantly in the “low BCS and high BW” category (55.5%). The study supports studies showing increased weight and change in BCS with increased parity. We highlight the associations among production system, BCS, BW, and parity.

Ketosis, evidenced by hyperketonemia with elevated blood β-hydroxybutyrate (BHB) levels, is a significant metabolic disorder of dairy cattle, typically diagnosed within the first 6 weeks post-calving when high energy levels are essential to milk production. Our study aimed to identify genetic markers linked to hyperketonemia (HYK) patterns in Holstein cows during early lactation and compare these to HYK-negative cows. We screened 964 cows for HYK using a threshold of BHB ≥1.2 mmol/L during the first 2 weeks postpartum (screening period, SP). Cows that tested negative initially were retested the following week. Cows were deemed HYK-negative (CON group) if BHB levels were below 1.2 mmol/L in both tests, while those with BHB levels exceeding this threshold at any test were treated and classified as HYK-positive (HYK+). Post-treatment, HYK+ cows were monitored for two-week follow-up period (FP) and classified based on their recovery: cured (CUR; consistently low BHB), recurrent (REC; fluctuating BHB levels), severe (SEV; high initial BHB that decreased), or chronic (CHR; persistently high BHB). Using 489 cows that were genotyped, a GWAS was conducted using GCTA software, revealing significant associations of several SNPs across different HYK patterns when compared to the CON group. These SNPs were primarily linked to genes affecting milk traits and were enriched in biological pathways relevant to protein glycosylation, inflammatory response, glucose homeostasis, and fatty acid synthesis. Our findings highlight genomic regions, potential candidate genes, and biological pathways related to ketosis, underscoring potential targets for improving health management in dairy cattle. These insights could lead to better strategies for managing ketosis through genetic selection, ultimately enhancing dairy cattle welfare and productivity. Further research with a larger number of cows is recommended to validate these findings and help confirm the implicated SNPs and genes., (© 2024 The Author(s). Journal of Animal Breeding and Genetics published by John Wiley & Sons Ltd.)

Introduction: Maintaining the welfare of cull dairy cows from the farm to slaughter is an ongoing challenge for the dairy industry. Recent research suggests that some cull dairy cows within the marketing system are in physical states that are below regulatory standards, and further research is required to determine why these unfit cows are found throughout the journey to abattoirs. Since dairy farms are the origin of these cows, decision making by dairy farmers has been identified as key to preventing cull cows that are considered unfit for transport from entering the marketing system. The objectives of this study were to understand dairy farmers' perspectives on their cull dairy cow management practices, recommendations and requirements of regulations, management tools, and welfare issues., Methods: Four focus groups with a total of 21 participants were each conducted virtually, video recorded, and transcribed verbatim, with dairy farmers from Ontario, Canada. A thematic analysis of focus group discussions was conducted utilizing deductive reasoning., Results: There were three themes identified including deciding to cull or not, management of cows being culled, and knowledge and perceptions of cull cow regulations. When making culling decisions, farmers utilize multiple sources of information including personal experiences and values and external referents like veterinarians, family members and other farmers. The welfare of their cows was a high priority but one that was often weighed against the financial outcomes of culling decisions. Finally, most participants considered recent regulatory changes for the management of cows before shipment to be of little importance on their farms., Discussion: In conclusion, the farmers from this study showed the diversity of considerations they make in culling decisions and the large contribution of animal productivity and economic factors. There was a general lack of knowledge of recent regulatory changes for the shipment of cull cows, and there is room for improving the uptake of new recommendations for culling only cows fit for transportation., Competing Interests: SR is employed by ACER Consulting Limited. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Marshall, Haley, Kelton, Miltenburg, Roche and Duffield.)

Background: The objectives of this study were to explore the level of shared decision making (SDM) between veterinarians and dairy and beef producers during on-farm interactions and to identify factors associated with veterinarians' use of SDM behaviours., Methods: A cross-sectional sample of food-animal veterinarians and their clients were recruited in Ontario, Canada. Their on-farm interactions were audio-video recorded. The recordings were analysed using the 'Observing Patient Involvement in Decision Making' (observer OPTION 5 ) instrument to determine the level of SDM utilised during preference-sensitive decisions. A logistic regression model was developed to assess factors associated with a preference-sensitive decision occurring. Meanwhile, a linear regression model was developed to identify factors associated with the level of SDM used., Results: Forty-one veterinarians participated, and 186 unique veterinarian-producer interactions were audio-video recorded and OPTION 5 score was calculated. SDM scores were low and comparable to other studies using the OPTION 5 instrument. The only factor associated with whether a preference-sensitive decision occurred was the length of the veterinarian and producer's relationship (in years). As the length of their relationship increased, a preference-sensitive decision was less likely to occur. The use of SDM behaviours was found to decrease as veterinarian burnout score increased. These findings demonstrate that SDM behaviours are being used by food-animal veterinarians, yet an opportunity exists to further implement more producer-centred SDM skills into on-farm interactions., Limitations: Small portions of veterinarian-producer conversation occurred outside of audio-video-recorded interactions and were not included in the analysis., Conclusion: The results of this study aid in further understanding on-farm interactions between veterinarians and producers and can help to further improve veterinary communication curricula., (© 2022 British Veterinary Association.)

A systematic review was conducted to assess the cost of ketosis in dairy cattle, and to elucidate how ketosis cost is estimated in each of the studies. Scientific papers addressing the economic impact of ketosis in dairy cows were identified through a search in 4 databases (Medline, ISI Web of Science, CAB Abstracts, and Agricola). The literature search was conducted with no restrictions on the date of study publication, publication type, or language. The methodological quality of the studies was assessed regarding study design, data collection, and analysis and interpretation of the study results. Of 531 identified records, 10 were selected, of which 9 were published from 2015 onward. Of the 10 studies reviewed, 9 report cost of a case of ketosis, and the estimates vary widely, with values ranging from €19 to €812. Two studies report ketosis cost at a farm level (€3.6-€29/cow per year). Among the studies, we observed great variation not only in the estimation models and inputs used (costs and losses associated with the disease) but also in the definition of ketosis and its prevalence or incidence figures. Moreover, the cost of ketosis was estimated for dairy farms in the United States, Canada, the Netherlands, Denmark, France, Germany, Spain, Sweden, Norway, and India. Consequently, there was great heterogeneity regarding herd characteristics, milk production, milk prices, culled cows' value, feed prices, and costs of veterinary services. Ketosis cost estimates vary as a consequence of all these aspects. Therefore, although most of the studies were well-designed and used high-quality data, the systematic approach review does not allow combination of the cost estimates of into a single figure. In conclusion, our review highlights an overall considerable economic impact of ketosis in dairy cattle. Economic prevention and mitigation strategies should be taken according to herd- and country-specific conditions. Ketosis cost figures reported in economic studies should always be considered carefully and interpreted with appropriate consideration of the inputs of the estimation, country context, and herd parameters., (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)