Short communication: Temporal profiles of colostrum and milk haptoglobin and substance P in early lactation multiparous Holstein cows.

Milk markers have the potential to aid in the detection of cow disease in early lactation if the automation of milk analysis becomes commonplace. Characterising temporal profiles of milk markers in dairy cows will improve the understanding of basal concentrations in clinically healthy cows. The objective of this observational study was to characterise the variation and temporal profiles of colostrum and milk haptoglobin (Hp) and substance P concentrations within 21 days postcalving in clinically healthy multiparous Holstein dairy cows. Ninety Holstein dairy cows from a commercial dairy herd were included. Milk samples were collected on the day of calving (day 0), and on days 1 to 4, 7, 14, and 21 postcalving and concentrations of Hp and substance P in colostrum (days 0 to 3) and milk (days 4, 7, 14, and 21) were determined using Enzyme Linked Immunosorbent assay. Haptoglobin and substance P concentrations were, on average (raw means ± SD), 0.40 ± 0.26 µg/ml and 56.2 ± 38.7 pg/ml in colostrum, respectively, and 0.23 ± 0.23 µg/ml and 37.1 ± 27.8 pg/ml in milk, respectively. Haptoglobin and substance P were elevated and greatest 1 day postcalving (least squares mean ± SE of the mean; 0.53 ± 0.05 µg/ml and 46.5 ± 3.64 pg/ml, respectively) and substance P varied widely within 21 days postcalving. The presence of substance P in dairy cow colostrum was not documented previously. Elevated concentrations of Hp and substance P immediately postcalving may be due to physiological roles these inflammatory markers have in the dairy cow or neonate or may simply represent an accumulation in colostrum before the first milk is removed.

Animal- and herd-level factors associated with onset of puberty in grazing dairy heifers.

AIMS: To explore animal- and herd-level risk factors influencing age at puberty in predominantly Holstein-Friesian dairy heifers managed in seasonal, pasture-based systems. METHODS: Heifers born in spring 2018 (n = 5,010) from 54 commercial dairy herds in New Zealand were visited on three occasions when the mean heifer age, within herd, was 10 (visit 1; V1), 11 (V2) and 12 (V3) months old. Blood samples were collected on each visit and liveweight, stature and anogenital distance (AGD) were measured at V2. Heifers were defined as having reached puberty at the first visit where blood progesterone was elevated (≥ 1 ng/mL). Animal-level response variables included pubertal status by V1, V2 and V3, and age at puberty (or age at V3 plus 31 days for those that had not attained puberty by V3). To explore herd-level management factors, farmers answered a questionnaire relating to animal location, land type, health, feeding, and management between weaning and mating. A partial least squares regression was undertaken to identify herd-level factors associated with the greatest influence on puberty rate within herd. RESULTS: The mean age at puberty was 352 (SD 34.9) days. Heavier animals at a greater proportion of expected mature liveweight based on their breeding value for liveweight, or animals with a higher breed proportion of Jersey and lower breed proportion of Holstein, were associated with earlier puberty. Herd puberty rates varied widely among enrolled herds, and averaged 20%, 39% and 56% by V1, V2 and V3, respectively. Liveweight, followed by breed and land type, had the greatest influence on the herd puberty rate. Heifer herds with a greater mean liveweight (absolute and proportion of expected mature weight) or greater Jersey proportion had more animals that reached puberty at any visit, whereas herds located on steep land or with greater Holstein breed proportions had lower puberty rates. Management-related factors such as vaccinations, provision of feed supplements, and weighing frequency were also herd-level risk factors of puberty but had less influence. CONCLUSIONS AND CLINICAL RELEVANCE: This study highlights the importance of having well-grown heifers for increasing the chances of earlier puberty onset and the effect of breed and youngstock management to achieve growth targets. These outcomes have important implications for the optimal management of heifers to achieve puberty before their maiden breeding and for the timing of measurements to potentially incorporate a puberty trait in genetic evaluations.

Associations between peripartum lying and activity behaviour and blood non-esterified fatty acids and ß-hydroxybutyrate in grazing dairy cows.

During early lactation, most dairy cows experience negative energy balance (NEB). Failure to cope with this NEB, however, can place cows at greater risk of developing metabolic disease. Our objective was to characterise, retrospectively, lying behaviour and activity of grazing dairy cows grouped according to blood non-esterified fatty acids (NEFAs) and ß-hydroxybutyrate (BHB) as indicators of postpartum metabolic state. Blood was sampled weekly for up to 4 weeks precalving, on the day of calving (day 0), daily between 1 and 4 days postcalving, and then at least weekly between week 1 and week 5 postcalving for analysis of plasma NEFAs and BHB concentrations. Two hundred and forty-four multiparous Holstein-Friesian and Holstein-Friesian × Jersey cows were classified into one of three metabolic status groups based on maximum blood NEFAs and BHB concentrations during week 1 and 2 postcalving. A cow was classified as having either: (1) low NEFAs and low BHB (Lo-Lo; n = 78), when all blood samples were <1.0 mmol/L for NEFAs and ≤1.0 mmol/L for BHB during the first 2 weeks postcalving; (2) high NEFAs and low BHB (Hi-Lo; n = 134), when blood NEFAs were ≥1.0 mmol/L and blood BHB was ≤1.0 mmol/L at the same sampling time point during the first 2 weeks postcalving; or (3) high NEFAs and high BHB (Hi-Hi; n = 32), when blood NEFAs were ≥1.0 mmol/L and blood BHB was ≥1.2 mmol/L at the same sampling time point during the first 2 weeks postcalving. Accelerometers (IceTag or IceQube devices; IceRobotics Ltd.) were used to monitor lying and activity behaviours peripartum (-21 to +35 days relative to calving). Changes in lying behaviour and activity occurred before the mean day that cows were classified Hi-Hi and Hi-Lo (2.2 and 3.5 d postcalving, respectively). Up to 3 weeks preceding calving, Hi-Hi cows were more active, had fewer daily lying bouts (LBs), and spent less time lying than Lo-Lo cows. In addition, Hi-Hi cows had fewer daily LBs and were less active up to 4 weeks postcalving than Lo-Lo cows, but these differences were biologically small. Groups of grazing cows classified as experiencing a more severe metabolic challenge behave differently up to 3 weeks precalving than their herdmates with lower blood NEFAs and BHB postcalving. These altered behaviours may allow identification of individual cows at risk of a metabolic challenge, but further research is required.

Supplementation of urea to a basal pasture diet fed to dairy cows to model N-partitioning relationships.

The main objective of this study was to investigate whether altering dietary crude protein (CP) through the supplementation of urea to a basal pasture diet fed to dairy cows accurately modeled N-partitioning relationships. To test this, we first needed to establish safe tolerance levels for urea in this setting. Fifteen multiparous, rumen-fistulated, mid-lactation Holstein-Friesian dairy cows were offered spring pasture (~20 kg of dry matter/cow per day) and allocated to 1 of 3 urea supplementation treatments: low N [0 g/d urea; 21% total dietary CP of dry matter (DM)], medium N (350 g/d urea; 26% total dietary CP of DM), or high N (690 g/d urea; 31% total dietary CP of DM), in a completely randomized design. The amount of urea provided daily increased gradually for all cows over a 21-d period, with target urea supplementation reached by d 21. Milk yield decreased linearly at a rate of 2.35 kg/100 g of urea intake when urea supplementation exceeded 350 g/d for 4 d (~2% of DM intake). Cows from the low- and medium-N treatments subsequently entered metabolism stalls from d 25 to 31 to collect urine, feces, and milk for total N collection. Estimated urinary N output (g/d) increased linearly with N intake (g/d), and the slope of the relationship (slope = 0.86; R2 = 0.82) was consistent with international published results. Because of the consistency of our results with previously documented relationships, our findings indicate that supplementation of urea to a basal pasture diet is a suitable technique for modeling different N intakes from pasture diets to evaluate urinary N mitigation strategies. Urea supplementation, however, should not exceed ~2% of DM intake.

Graduate Student Literature Review: Evaluating the appropriate use of wearable accelerometers in research to monitor lying behaviors of dairy cows.

Until recently, animal behavior has been studied through close and extensive observation of individual animals and has relied on subjective assessments. Wearable technologies that allow the automation of dairy cow behavior recording currently dominate the precision dairy technology market. Wearable accelerometers provide new opportunities in animal ethology using quantitative measures of dairy cow behavior. Recent research developments indicate that quantitative measures of behavior may provide new objective on-farm measures to assist producers in predicting, diagnosing, and managing disease or injury on farms and allowing producers to monitor cow comfort and estrus behavior. These recent research developments and a large increase in the availability of wearable accelerometers have led to growing interest of both researchers and producers in this technology. This review aimed to summarize the studies that have validated lying behavior derived from accelerometers and to describe the factors that should be considered when using leg-attached accelerometers and neck-worn collars to describe lying behavior (e.g., lying time and lying bouts) in dairy cows for research purposes. Specifically, we describe accelerometer technology, including the instrument properties and methods for recording motion; the raw data output from accelerometers; and methods developed for the transformation of raw data into meaningful and interpretable information. We highlight differences in validation study outcomes for researchers to consider when developing their own experimental methodology for the use of accelerometers to record lying behaviors in dairy cows. Finally, we discuss several factors that may influence the data recorded by accelerometers and highlight gaps in the literature. We conclude that researchers using accelerometers to record lying behaviors in dairy cattle should (1) select an accelerometer device that, based on device attachment and sampling rate, is appropriate to record the behavior of interest; (2) account for cow-, farm-, and management-related factors that could affect the lying behaviors recorded; (3) determine the appropriate editing criteria for the accurate interpretation of their data; (4) support their chosen method of recording, editing, and interpreting the data by referencing an appropriately designed and accurate validation study published in the literature; and (5) report, in detail, their methodology to ensure others can decipher how the data were captured and understand potential limitations of their methodology. We recommend that standardized protocols be developed for collecting, analyzing, and reporting lying behavior data recorded using wearable accelerometers for dairy cattle.

Associations between lying behavior and activity and hypocalcemia in grazing dairy cows during the transition period.

Hypocalcemia is a common metabolic disorder of transition dairy cows that is considered a gateway disease, increasing the risk of other health disorders and reducing cow performance. Clinical milk fever is associated with long periods of recumbency, and it is plausible that cows experiencing non-paretic hypocalcemia may spend more time lying; hence, lying behavior and activity measures may be useful in identifying at-risk cows. The objective of this study was to describe associations among blood calcium (Ca) status at calving and lying behavior and activity measures during the transition period in grazing dairy cows. Blood was sampled on the day of calving (d 0), and d 1, 2, 3, and 4 postcalving, and analyzed for total plasma Ca concentration. Twenty-four multiparous Holstein-Friesian and Holstein-Friesian × Jersey grazing dairy cows were classified, retrospectively, as clinically hypocalcemic (CLIN; blood Ca ≤ 1.4 mmol/L at 1 or more consecutive samplings within 48 h postcalving, but without parturient paresis). These cows were pair-matched (using milk production potential from their estimated breeding value for milk protein, mean body weight at wk -5 and -6 precalving, and, where possible, parity) with 24 cows classified as subclinically hypocalcemic (SUB; blood Ca > 1.4 and < 2.0 mmol/L at 2 consecutive samplings within 48 h postcalving), and 24 cows classified as normocalcemic (NORM; blood Ca ≥ 2.0 mmol/L at 3 consecutive samplings within 72 h postcalving). Lying behavior and activity were monitored using triaxial accelerometers from -21 to +35 d relative to calving. Data were summarized to calculate daily lying time (h/d), daily number of lying bouts (LB; no./d), mean LB duration (min/bout), and the number of steps taken (steps/d). On d 0, the CLIN group were less active and spent approximately 2.6 h longer lying than the SUB and NORM groups, particularly between 0200 and 1400 h. On d 0, the NORM group had fewer LB (16.3/d) than the SUB and CLIN groups (18.2 and 19.2/d, respectively). These differences in behavior were no longer detected 2 d postcalving, and no further differences were observed. The day before calving, the CLIN group spent 1.4 h longer lying down than did the SUB and NORM groups. Further, the relative change in steps from a precalving baseline period (d -14 to -7) until d 0 was positively, linearly associated with blood Ca concentration within 24 h postcalving. Future work should consider daily and temporal changes in behavior in individual cows to determine the potential for these measures to allow early detection of hypocalcemia.

Selenium requirements in grazing dairy cows: a review.

In New Zealand, the recommended intake of Se for dairy cattle (0.03 mg/kg dry matter (DM)) is lower than in the United Kingdom and Australia (0.1 and 0.04 mg/kg DM, respectively), and much lower than in the United States of America (0.3 mg/kg DM). Advisors in New Zealand often suggest that New Zealand intake recommendations are far too low and that recommendations from the United States of America should be used. This has created confusion as farmers are given very different advice depending on which recommendations their advisor uses. In this review, we assess whether the published evidence supports the existing dietary requirements and associated Se status thresholds, or if change is required. We focus particularly on the evidence-base in cattle fed a primarily pasture-based diet, as it is critical that dietary recommendations are derived from data created using cows fed similar diets. Accordingly, we also consider whether the increased use of fodder crops, especially during the dry period, is likely to have altered the Se requirements of dairy cows in New Zealand. We report that the science behind the dietary requirements for Se is robust, being supported by factorial models validated using New Zealand data, and on-farm experimental studies. Published nutritional data suggest that the increased use of fodder crops is unlikely to have altered the dietary balance of pro- and antioxidant factors in New Zealand dairy cows in a way that would meaningfully affect Se requirements. However, the lack of specific data on the vitamin E and fatty acid content of the crops being fed in New Zealand means that more information is needed to confirm this conclusion. In general, the existing New Zealand recommendations for Se-status thresholds are supported, although studies are still lacking to properly characterise the upper threshold of the marginal range. Nevertheless many studies in New Zealand, of herds with marginal or low adequate Se status (using New Zealand recommendations), have failed to show an effect of Se supplementation on milk production, intramammary infection or reproductive performance, so it is highly unlikely that the upper threshold of the range is much higher than the current recommendation. Proponents of the hypothesis that Se intakes in New Zealand dairy cattle should be increased by at least 10 times the current recommendations are therefore not using the evidence base correctly.

Lying behavior and activity during the transition period of clinically healthy grazing dairy cows.

Lying behavior and activity may provide useful information for the prediction of an imminent calving and the health of transition dairy cows; however, it is important first to understand what constitutes typical lying behavior and activity because this has not been defined for grazing dairy cows during the transition period. Our objective was to describe changes in lying behavior and activity in grazing dairy cows during the transition period using varying phenotypes typical of commercial dairy herds under grazing systems. Behavior data from IceTag or IceQube (IceRobotics, Edinburgh, Scotland) triaxial accelerometers were collected for 310 cow parities from multiparous, mixed-age (mean ± standard deviation; 4.5 ± 1.65 yr), and mixed-breed [Holstein-Friesian (HF), n = 216; and HF × Jersey, n = 94] grazing dairy cows from 4 parent experiments. The IceTags or IceQubes captured lying and activity data during the transition period (-21 to 34 d relative to calving) to allow the calculation of daily lying time (h/d), daily lying bouts (LB; no./d), mean LB duration (min/bout), and the number of steps taken (steps/d). Lying behavior and activity were analyzed using a repeated measures ANOVA during 3 periods: PRE (-21 to -3 d), POST (3 to 21 d), and the day of calving (d 0). Lying time was lower on d 0 (7.25 h/d) compared with PRE and POST lying times (10.3 and 8.58 h/d, respectively), with more frequent LB on d 0 (12.9 no./d) compared with the PRE and POST daily LB (8.15 vs. 7.74 no./d). Cows took more steps POST (4,424 steps/d) compared with d 0 and PRE (4,105 and 2,289 steps/d, respectively). Regression analysis determined that daily lying time decreased substantially from -3 to 0 d (slope = -1.03 ± 0.07 h/d) and from -2 and -1 d for daily LB (slope = 5.09 ± 0.54 no./d), which may be due to the calving event itself but also reflect restlessness. Daily lying time, daily LB, LB duration, and number of steps taken were substantially altered at the time of the calving event in grazing dairy cows. Cows were more active, spent less time lying, and took more steps postcalving compared with precalving, and it appears that this behavior may largely be due to activity associated with twice daily milking. Mean lying behavior and activity measures were more highly variable across individuals than across groups. Information available via activity monitors may contribute to the improvement of individual management of transition dairy cows, and this research provides a benchmark for typical changes in behavior during the transition period in grazing systems.