Pasture-grazed Dairy Research Articles

Individualised feeding of concentrate supplement according to milk yield did not increase milk production in pasture-grazed cows near peak lactation

ABSTRACT In grazing systems, feeds other than pasture are often used to increase dry matter intake and milk production. The study aimed to evaluate the effect of individually feeding pasture-grazed dairy cows near peak lactation based on their individualised milk production compared with a flat-rate feeding regime. All cows in the flat-rate treatment were offered 4 kg wet weight (3.6 kg DM) of concentrate/d. In the individualised feeding treatment, cows were offered 6, 4, and 2 kg wet weight/d (5.4, 3.6 and 1.8 kg DM/d) in the high, moderate, and low production groups, respectively. Individualised feeding of concentrates based on cow milk production did not alter milk or milk component yield at a herd level, but increased milk yield and tended to increase yield of fat, protein, and lactose in cows in the medium milk yield tertile. Individualised feeding reduced milk protein yield in cows in the low milk yield tertile, compared with flat rate feeding. The results do not support individualised feeding in grazing dairy systems where the maximum level of concentrate offered/ is ≤ 6 kg DM/d and milk production/cow ≤30 kg milk/d or ≤2.5 kg fat and protein/d.

Predicting future adoption of early-stage innovations for smart farming: A case study investigating critical factors influencing use of smart feeder technology for potential delivery of methane inhibitors in pasture-grazed dairy systems

Globally, livestock farmers are challenged with reducing greenhouse gas emissions to mitigate climate change. A potential option for pasture-based dairy farmers involves including methane-inhibiting compounds in the diet. A novel approach to deliver these compounds with the required frequency and precision is via smart-feeders, an existing smart farming technology used to feed supplements automatically to animals in-paddock. For this innovation to be successful, however, it must integrate with farm systems and provide farmers with a positive value proposition. The aim of this study was to examine the farm system and technology factors influencing potential uptake of in-paddock smart technologies for delivering methane inhibitors in pasture-grazed systems. We utilized an adoption prediction tool (ADOPT) to model the adoption outcomes of smart-feeders as methane inhibitor delivery mechanisms on dairy farms, with input from industry experts and farmers via focus groups. The results indicated low adoption of smart-feeders in a pasture-based system context. This was further explored with a sensitivity analysis of seven critical ADOPT factors which were identified as influential through the farmer focus groups. We modelled the impact of the seven critical ADOPT factors for two smart-feeder concepts to evaluate their relative adoption potential. The adoption modelling showed that while factors such as technology cost and function were important, adoption would also be highly influenced by future regulation settings, innovation uncertainty, and the alignment with farmer values and worldviews about their farm system. This research highlighted that in-paddock delivery technology, and processes for its use on-farm, represents an early-stage innovation and therefore is vital that farmers and other stakeholders are involved in further development to ensure adoption factors are addressed.

Perspective: Can early embryonic losses be reduced in lactating dairy cows?

Perspective: Can early embryonic losses be reduced in lactating dairy cows?

The first week following insemination is the period of major pregnancy failure in pasture-grazed dairy cows.

A 60% pregnancy success for inseminations is targeted to optimize production efficiency for dairy cows within a seasonal, pasture-grazed system. Routine measures of pregnancy success are widely available but are limited, in practice, to a gestation stage beyond the first 28 d. Although some historical data exist on embryonic mortality before this stage, productivity of dairy systems and genetics of the cows have advanced significantly in recent decades. Accordingly, the aim was to construct an updated estimate of pregnancy success at key developmental stages during the first 70 d after insemination. Blood samples were collected for progesterone concentrations on d 0 and 7. A temporal series of 4 groups spanning fertilization through d 70 were conducted on 4 seasonal, pasture-grazed dairy farms (n = 1,467 cows) during the first 21 d of the seasonal breeding period. Morphological examination was undertaken on embryos collected on d 7 (group E7) and 15 (group E15), and pregnancy was diagnosed via ultrasonography on approximately d 28 and 35 (group E35) as well as d 70 (group E70). Fertilization, embryo, and fetal evaluation for viability established a pregnancy success pattern. Additionally, cow and on-farm risk factor variables associated with pregnancy success were evaluated. We estimated pregnancy success rates of 70.9%, 59.1%, 63.8%, 62.3%, and 56.7% at d 7, 15, 28, 35, and 70, respectively. Fertilization failure (15.8%) and embryonic arrest before the morula stage (10.3%) were the major developmental events contributing to first-week pregnancy failures. Embryo elongation failure of 7% contributed to pregnancy failure during the second week. The risk factors for pregnancy success that were related to the cows included interval between calving and insemination, and d-7 plasma progesterone concentrations, whereas insemination sire was associated with pregnancy outcome. Most pregnancy failure occurs during the first week among seasonal-calving pasture-grazed dairy cows.

Responsible robotics design-A systems approach to developing design guides for robotics in pasture-grazed dairy farming.

Application of robotics and automation in pasture-grazed agriculture is in an emergent phase. Technology developers face significant challenges due to aspects such as the complex and dynamic nature of biological systems, relative cost of technology versus farm labor costs, and specific market characteristics in agriculture. Overlaying this are socio-ethical issues around technology development, and aspects of responsible research and innovation. There are numerous examples of technology being developed but not adopted in pasture-grazed farming, despite the potential benefits to farmers and/or society, highlighting a disconnect in the innovation system. In this perspective paper, we propose a “responsibility by design” approach to robotics and automation innovation, using development of batch robotic milking in pasture-grazed dairy farming as a case study. The framework we develop is used to highlight the wider considerations that technology developers and policy makers need to consider when envisaging future innovation trajectories for robotics in smart farming. These considerations include the impact on work design, worker well-being and safety, changes to farming systems, and the influences of market and regulatory constraints.

Complete Genome Sequences of Three Clostridiales R-7 Group Strains Isolated from the Bovine Rumen in New Zealand.

ABSTRACTMembers of the Clostridiales R-7 group are abundant bacterial residents of the rumen microbiome; however, they are poorly characterized. We report the complete genome sequences of three members of the R-7 group, FE2010, FE2011, and XBB3002, isolated from the ruminal contents of pasture-grazed dairy cows in New Zealand.

The analysis of serum mineral profile of cows before and after calving: A case study

The analysis of serum mineral profile of cows before and after calving: A case study

Short communication: Evaluation of an eating time sensor for use in pasture-based dairy systems

The assessment of grazing behavior is important for research and practice in pasture-grazed dairy farm systems. However, few devices are available that enable assessment of cow grazing behavior at an individual animal level. This study investigated whether commercially available Smarttag "eating time" sensors (Nedap Livestock Management, Groenlo, the Netherlands) were suitable for recording the grazing time of cows. Smarttag sensors were mounted on the neck collars of multiparous Holstein-Friesian cows in a herd in Taranaki, New Zealand. Cows were randomly selected each observation day from the milking herd for 8 separate days across a 1-mo period. Trained observers conducted 90-min observation periods to evaluate the relationship between the sensor eating time measure and grazing time. A set of 5 defined cow behaviors (2 "head up" and 3 "head down" behaviors) were assessed. In total, observations of 37 cows were recorded in 14 sessions over 8 d in the study period, providing 55.5 total hours of observations. Observation data were aligned with sensor data according to the sensor time stamps and grouped into matching 15-min intervals. Interobserver reliability was assessed both before and after the main trial period, and the mean percentage eating time per observer had a coefficient of variation of 0.46% [mean 93.2, standard deviation (SD) 0.425] before and 0.07% (mean 96.3, SD 0.074) after. In the main trial, the relationship between observed (mean 70.8%) and sensor-derived (mean 69.3%) percentage eating time over the observation period gave a Pearson correlation coefficient of 0.971, concordance correlation coefficient 0.968, mean difference 1.50% points, and SD 5.8% points. Therefore, sensor-identified percentage "eating time" and observed percentage active grazing time were shown to be both very well correlated and concordant (in agreement, with high correlation and little bias). Therefore, the relationship between observed and sensor-derived data had a high degree of agreement for identifying cow grazing activity. In conclusion, Smarttag sensors are a valid and useful tool for estimating grazing activity at time periods of 1 h or more.

Cow-level risk factors for reproductive tract disease diagnosed by 2 methods in pasture-grazed dairy cattle in Ireland

The cow-side diagnosis of reproductive tract disease (RTD) involves identifying the presence of purulent vaginal discharge (PVD) and ultrasonographic endometritis (UE). The objectives of our study were to obtain prevalence estimates for RTD diagnosed by 2 methods (PVD and UE scoring) and to investigate the risk factors for increased probability of RTD if these methods are used in isolation or in combination. Our retrospective observational cohort study tested the hypothesis that RTD assessed by 2 methods would have similar risk factors, and that those would be mainly cow- and calving-related factors. We analyzed data from 5,049 pre-breeding examinations (PBE) from 2,460 spring-calved cows on 8 farms between 2014 and 2018. Cow-related details assessed were days in milk at PBE, breed, lactation number, dry period length, body condition score at calving and PBE, 305-d milk yield, predicted transmitting ability for production and fertility, the presence of a corpus luteum at PBE, and positive diagnosis the previous year. Calving details assessed were type of sire, calf sex, twinning, stillbirth, calving difficulty score, and retained fetal membranes. We conducted statistical analyses using 4 multivariable logistic regression models to identify the risk of RTD diagnosed by (1) PVD in isolation, (2) UE in isolation, (3) the presence of either PVD or UE; and (4) the presence of both PVD and UE. We accounted for herd, cow, and year as random effects in all 4 models. The overall prevalence of RTD in models 1, 2, 3, and 4 were 7.5, 6.7, 11.6, and 2.6%, respectively. Days in milk at PBE, the interaction between days in milk and retained fetal membranes, twinning, and the predicted transmitting ability for calving interval were consistently significant risk factors for positive scores in all 4 models. Considerable calving difficulty [adjusted odds ratio (AOR) = 13.64], Holstein Friesian dam breed (AOR = 2.58), first lactation (AOR = 2.39), and body condition score at PBE (AOR = 1.64) were risk factors for a positive PVD score but not for a positive UE score. Fifth lactation (AOR = 1.69), a beef-sired calf (AOR = 1.46), and the absence of a corpus luteum at PBE (AOR = 1.57) were risk factors for a positive UE score but not for a positive PVD score. These results support the hypothesis that most of the risk factors for PVD and UE are the same but some are distinctly different, implying that in some instances the 2 methods diagnose separate components of the RTD complex.

Prediction of blood β-hydroxybutyrate content and occurrence of hyperketonemia in early-lactation, pasture-grazed dairy cows using milk infrared spectra

The objective of this study was to evaluate the ability of milk infrared spectra to predict blood β-hydroxybutyrate (BHB) concentration for use as a management tool for cow metabolic health on pasture-grazed dairy farms and for large-scale phenotyping for genetic evaluation purposes. The study involved 542 cows (Holstein-Friesian and Holstein-Friesian × Jersey crossbreds), from 2 farms located in the Waikato and Taranaki regions of New Zealand that operated under a seasonal-calving, pasture-based dairy system. Milk infrared spectra were collected once a week during the first 5 wk of lactation. A blood "prick" sample was taken from the ventral labial vein of each cow 3 times a week for the first 5 wk of lactation. The content of BHB in blood was measured immediately using a handheld device. After outlier elimination, 1,910 spectra records and corresponding BHB measures were used for prediction model development. Partial least square regression and partial least squares discriminant analysis were used to develop prediction models for quantitative determination of blood BHB content and for identifying cows with hyperketonemia (HYK). Both quantitative and discriminant predictions were developed using the phenotypes and infrared spectra from two-thirds of the cows (randomly assigned to the calibration set) and tested using the remaining one-third (validation set). A moderate accuracy was obtained for prediction of blood BHB. The coefficient of determination (R2) of the prediction model in calibration was 0.56, with a root mean squared error of prediction of 0.28 mmol/L and a ratio of performance to deviation, calculated as the ratio of the standard deviation of the partial least squares model calibration set to the standard error of prediction, of 1.50. In the validation set, the R2 was 0.50, with root mean squared error of prediction values of 0.32 mmol/L, which resulted in a ratio of performance to deviation of 1.39. When the reference test for HYK was defined as blood concentration of BHB ≥1.2 mmol/L, discriminant models indicated that milk infrared spectra correctly classified 76% of the HYK-positive cows and 82% of the HYK-negative cows. The quantitative models were not able to provide accurate estimates, but they could differentiate between high and low BHB concentrations. Furthermore, the discriminant models allowed the classification of cows with reasonable accuracy. This study indicates that the prediction of blood BHB content or occurrence of HYK from milk spectra is possible with moderate accuracy in pasture-grazed cows and could be used during routine milk testing. Applicability of infrared spectroscopy is not likely suited for obtaining accurate BHB measurements at an individual cow level, but discriminant models might be used in the future as herd-level management tools for classification of cows that are at risk of HYK, whereas quantitative models might provide large-scale phenotypes to be used as an indicator trait for breeding cows with improved metabolic health.

Effect of DGAT1 variant (K232A) on milk traits and milk fat composition in outdoor pasture-grazed dairy cattle

ABSTRACT An amino acid substitution (K232A) in the enzyme diacylglycerol acyl-CoA acyltransferase 1 (DGAT1) has been reported to explain variation in milk traits and milk fatty acid (FA) profile. In this study, associations between K232A, and milk traits including milk FA composition, were studied in wholly pasture-fed New Zealand Holstein-Friesian × Jersey cross-bred (KiwicrossTM) dairy cows. With a high frequency of K variant (61.9%), the KK cows produced more milk fat on average (5.41 ± 0.04%), than the AA cows (4.43 ± 0.06%). The milk volume, fat concentration and protein concentration for the AK cows were between the values for the genotypes AA and KK. More C16 : 0 (saturated fatty acid), conjugated linoleic acid (CLA) and polyunsaturated fatty acid (C18:3 cis-9, 12, 15) were found in the milk of the KiwicrossTM cows, and the influence of DGAT1 K232A on these FAs during the mid- and late- stage of lactation were significant. The AA cows produced more (P < 0.001) CLA (1.137 ± 0.047 g/100 g) and C18:3 cis-9, 12, 15 (0.855 ± 0.015 g/100 g), but less C16:0 (35.170 ± 0.355 g/100 g) than the KK cows (0.934 ± 0.025 g/100 g, 0.778 ± 0.009 g/100 g and 38.010 ± 0.250 g/100 g respectively).

Effect of altering the type of dietary carbohydrate early postpartum on reproductive performance and milk production in pasture-grazed dairy cows

The objective of this study was to assess the effect of increasing dietary starch for approximately 30 d postpartum on reproduction outcomes in pasture-grazed, seasonal-calving dairy cows. Cows (n = 948) from 3 commercial herds were blocked by age (2, 3, and >3 yr), breed, and expected calving date and randomly assigned to 1 of 2 postpartum treatment groups: high starch (34.7 ± 1.9% nonstructural carbohydrate; mean ± SD) or low starch (22.5 ± 0.4% nonstructural carbohydrate). The high-starch group in all 3 farms received 4.0 to 4.5 kg/d of a 75:25 cracked corn:barley grain mixture in the dairy parlor, split evenly between the morning and afternoon milkings. The low-starch cows received 5.0 to 5.5 kg/d of a 50:50 mixture of palm kernel meal:soy hulls (herds 1 and 3) fed in the parlor; low-starch cows in the remaining herd (herd 2) did not receive a concentrate feed. Cows were cograzed on ryegrass-white clover dominant pastures and were offered corn silage (herds 1 and 3) and canola, corn distillers grain, and palm kernel meal (herd 1) throughout the study. At 1 mo before the start of the seasonal breeding period, the high-starch supplement was removed, and within each herd treatment groups were managed similarly through breeding. Presence of purulent vaginal discharge was assessed at 28 DIM, and tail paint was assessed weekly from 2 to 6 wk postpartum for signs of estrus. The interval to first observed estrus was unaffected by treatment (32.7 vs. 33.5 ± 2 d for high and low starch, respectively), but there were tendencies for a herd × treatment interaction for proportion of cows pregnant to first service and for pregnancy within 6 wk. This interaction was significant for the proportion of cows finally pregnant; a lower proportion of high-starch cows were pregnant to first service, pregnant by 6 wk, and pregnant by the end of the seasonal breeding period in herd 1, but diet did not affect these outcomes in the other herds. Our results do not support a positive effect on reproduction from increasing dietary starch in seasonally bred grazing dairy cows. However, the interactions indicate variability in the herd response to dietary starch early postpartum and imply that pregnancy rate could potentially be compromised through the provision of starch to grazing dairy cows in early lactation (i.e., prebreeding). The experiment was not designed to define the reasons for these interactions, but differences should be considered in future research on the subject.

The β-lactoglobulin content of bovine milk: Development and application of a biosensor immunoassay

An optical biosensor immunoassay exploiting surface plasmon resonance is described for the quantification of β-lactoglobulin in milk. Samples were diluted with buffer, and the protein estimated from binding with a polyclonal antibody immobilised on the sensor surface. Analytical method performance characteristics including range, detection limit, precision and accuracy were determined and reported. The temporal variability in the β-lactoglobulin content of milk from pasture-fed cows during early lactation and across a production season was investigated. The content of β-lactoglobulin decreased from >10 mg mL−1 in early colostrum to <5 mg mL−1 in mature milk, and the β-lactoglobulin content of skim milk powder trended from 25 to 60 mg g−1 across a season. In view of its allergenicity, these data will improve understanding of the expression of innate β-lactoglobulin in the milk of pasture-grazed dairy herds, thereby providing information that is applicable to the formulation of bovine milk-based products.

Parasite control in pasture-grazed dairy cattle: are we at the edge of a precipice?

Gastrointestinal nematode (GIN) parasites are one of the most production-limiting infections of pasture-based dairy cattle in Australasia. Intensification of dairy production systems in both countries has meant that farmers have come to rely heavily on anthelmintic drenches to control GIN parasitism. However, anthelmintic resistance is now widespread in New Zealand, particularly to the market-leading macrocyclic-lactones. Less work has been conducted on anthelmintic resistance in Australia but preliminary results of a study currently underway suggests that there are high levels of resistance on Victorian dairy farms. The identification and mitigation of risk factors for the development of resistance is crucial for long-term sustainability of control. These include the use of drenches with variable efficacy – particularly pour-on and injectable formulations. New Zealand studies suggest that this may be as a result of active not reaching parasites within the gut lumen as effectively as oral formulations. Also, the raising of young stock as monocultures is a risk factor for the development of resistance as it significantly reduces the numbers of unselected (and presumably susceptible) parasites on pasture. These risks can be mitigated: using effective drenches removes more resistant parasites. This often means the use of combination products containing more than one anthelmintic class. Combination products are more effective in the face of existing resistance, and can slow the development of resistance. Also, ensuring an adequate level of unselected parasites on pasture for ingestion by young stock will delay the development of resistance. While there are differences between dairying systems, both countries are likely to benefit from more active and collaborative research efforts to improving parasite control practices on dairy farms in their respective countries.

Premilking teat disinfection: Is it worthwhile in pasture-grazed dairy herds?

A controlled trial was conducted in 5 pasture-grazed commercial dairy herds in Australia in 2012 to determine whether premilking teat disinfection and drying of teats reduces clinical mastitis incidence during early lactation by at least 50%. A 50% reduction was estimated to be the minimum required to justify additional costs of labor, disinfectants, and other resources if premilking teat disinfection was implemented in a 500-cow herd averaging 8 clinical cases per 100 cow-months. A secondary aim was to determine whether this premilking teat disinfection routine reduces incidence of new udder infections. Treatment was applied in each herd for approximately 60 d (range of 59.5 to 61 d), commencing in each herd soon after the start of the herd's main or only calving period. Within each herd, cows were allocated to either the treatment (premilking disinfection) or the control (no premilking disinfection) group based on their herd identity number. During the trial period, any cow having a new case of clinical mastitis or an individual cow cell count greater than 250,000 cells/mL of milk (when preceded by individual cow cell counts of 250,000 cells/mL of milk or below) was deemed to have had a new infection. Overall, neither clinical mastitis incidence nor new infection rate differed significantly between treatment and control groups. Over the whole study period, 98 of the 1,029 cows in the premilking disinfection group and 97 of the 1,025 cows in the control group had clinical mastitis. Total cow-days at risk of clinical mastitis were similar in each group. However, clinical incidence rates were markedly lower in treatment cows in one herd (herd 3; incidence rate ratio=0.34) and there was some evidence that new infection incidence rates were lower in treated cows in this herd (incidence rate ratio=0.42). Rainfall during the study period was below long-term district average in all 5 study herds. Cows’ teats were less dirty than in previous, wetter years for the 4 herds where no significant clinical mastitis response was detected but some teat soiling was observed in herd 3 during the study period. Routine application of premilking teat disinfection in pasture-grazed herds is unlikely to produce a worthwhile (economic) reduction in the number of clinical mastitis cases when teats are relatively clean and dry and the clinical mastitis incidence is low. However, premilking disinfection might be worthwhile during periods when teats are heavily soiled and the incidence of clinical mastitis due to environmental pathogens is high.

Temporary alterations to postpartum milking frequency affect whole-lactation milk production and the energy status of pasture-grazed dairy cows

This study investigated the immediate and long-term effects of temporary alterations to postpartum milking frequency (MF) on milk production, body condition score (BCS), and indicators of energy status in pasture-grazed cows supplemented with concentrates. Multiparous Holstein-Friesian cows (n=150) were randomly assigned to 1 of 5 groups at calving: milked twice daily (2×) throughout lactation (control), or milked either once daily (1×) or 3 times daily (3×) for 3 or 6wk immediately postpartum, and then 2× for the remainder of lactation. During wk 1 to 3 postpartum, cows milked 1× produced 15% less milk and 17% less energy-corrected milk (ECM) than cows milked 2×. This immediate production loss increased to 20% less milk and 22% less ECM during wk 4 to 6 postpartum for cows that remained on 1× milking; these animals also produced less than 1× cows switched to 2× milking after 3wk. During wk 8 to 32, when all cows were milked 2×, those previously milked 1× had sustained reductions in milk (−6%) and ECM (−8%) yields, which were not affected by the duration of reduced postpartum MF. In contrast, cows milked 3× postpartum had 7% greater milk yields during wk 1 to 6 compared with 2× controls, irrespective of the duration of increased MF. Milk yields also remained numerically greater (+5%) during wk 8 to 32 in cows previously milked 3×. Nevertheless, yields of ECM were not increased by 3× milking, because of lower milk fat and protein contents that persisted for the rest of lactation. In addition, indicators of cow energy status reflected an increasing state of negative energy balance with increasing MF. Cows milked 1× postpartum had greater plasma glucose and lower plasma nonesterified fatty acid concentrations during the reduced MF, and plasma glucose remained lower for 2wk after cows had switched to 2× milking. Moreover, BCS was improved relative to 2× controls from wk 5 to 6. In contrast, cows milked 3× had lower plasma glucose concentrations, greater plasma nonesterified fatty acid concentrations, and greater BCS loss during wk 1 to 3; however, greater body fat mobilization was not sustained, indicating that additional energy supplements may be required to achieve better milk production responses. In conclusion, temporary 1× milking had lactation-long negative effects on milk and milk component yields but improved cow energy status and BCS, whereas temporary 3× milking immediately increased milk yield but did not improve milk fat and protein yields in pasture-grazed cows.

Treatment with a nonsteroidal antiinflammatory drug after calving did not improve milk production, health, or reproduction parameters in pasture-grazed dairy cows

Previous research results have indicated an increase in pregnancy rate in pasture-grazed cows treated with a nonsteroidal antiinflammatory drug (NSAID) 3 to 4wk postcalving, when a high proportion of nucleated cells from within the uterus were polymorphonucleated; however, no effect on milk production was detected. It was hypothesized that this lack of effect on milk production was because the administration of the NSAID was too late after calving. The aims of the current study were to evaluate the timing of administering a propionic acid-derived NSAID (i.e., carprofen) on milk production, metabolic status, uterine health, and reproductive performance. Six-hundred and thirty-nine cows (134 primiparous and 505 multiparous) calving between July 4 and September 5, 2012, in 2 herds (herd 1: n=228; herd 2: n=411) were enrolled. Using a randomized block design, cows were allocated to 1 of 3 treatment groups as they calved: (1) no treatment (control; n=221), (2) NSAID administered on d 1, 3, and 5 postcalving (early; n=214), and (3) NSAID administered on d 19, 21, and 23 postcalving (late; n=204). Milk production and composition, and body condition were determined weekly. Blood was sampled at 4 time points (1 precalving and 3 postcalving) to determine the effects of treatment on indicators of metabolic health and energy status. Uterine health was determined by measuring the proportion of nucleated cells that were polymorphonucleated following cytobrush sampling of the uterus between d 13 to 24 and d 30 to 49 postcalving. Irrespective of timing of application, NSAID did not affect milk production, body weight, or body condition during early lactation. Treatment with an NSAID 19 to 23d postcalving increased the proportion of cows submitted for breeding during the first 3wk of the seasonal breeding program (control: 85%, early: 83%, and late: 92%), but did not affect conception or pregnancy rates. No detectable effect of treatment on uterine health or circulating metabolites and minerals existed, although cows in the early NSAID treatment group had marginally lower serum β-hydroxybutyrate concentrations (0.1mmol/L) than the other groups between 2 and 26d in milk. In conclusion, administration of this particular NSAID at either 1 or 3wk after calving did not improve milk production, indicators of health, or reproductive performance.

Using activity-based monitoring systems to detect dairy cows in oestrus: a field evaluation

AIM: To assess the use and performance of activity-based oestrus detection systems (ODS) on two commercial dairy farms using a gold standard based on profiles of concentrations of progesterone in milk, artificial insemination (AI) records and pregnancy diagnosis results.METHODS: Two activity-based ODS were evaluated in mature cows on two large pasture-grazed dairy farms (>500 cows) over the first 3 weeks of AI. Farm 1 (n=286 cows) used a leg-mounted device and cows were drafted automatically based on activity alerts. Decisions regarding AI were then made based on tail-paint and cow history for these cows. Farm 2 (n=345 cows) used a collar-mounted device and activity alerts were used in conjunction with other information, before the farmer manually selected cows for AI. The gold standard to define the timing of oestrus was based on profiles of concentrations of progesterone in milk measured twice-weekly, used in conjunction with AI records and pregnancy diagnosis results. Sensitivity and positive predictive value (PPV) were calculated for the activity-based ODS data only, and then for AI decisions, against the gold standard.RESULTS: Farm 1 had 195 confirmed oestrus events and 209 activity alerts were generated. The sensitivity of the activity-based ODS was 89.2% with a PPV of 83.3%. Using tail-paint and cow history to confirm activity-based alerts 175 cows were inseminated, resulting in a sensitivity of 89.2% and an improved PPV of 99.4%. Farm 2 had 343 confirmed oestrus events, and 726 alerts were generated by the activity-based ODS, giving a sensitivity of 69.7% with a PPV of 32.9%. A total of 386 cows had AI records, giving a sensitivity of 81.3% and PPV of 72.3%.CONCLUSIONS: The two activity-based ODS were used differently on-farm; one automatically selecting cows and the other supporting the manual selection of cows in oestrus. Only one achieved a performance level suggested to be acceptable as a stand-alone ODS. Use of additional tools, such as observation of tail paint to confirm activity-based oestrus alerts before AI, substantially improved the PPV.CLINICAL RELEVANCE: A well performing activity-based ODS can be a valuable tool in identifying cows in oestrus prior to visual confirmation of oestrus status. However the performance of these ODS technologies varies considerably.

Prevalence of subclinical ketosis in mainly pasture-grazed dairy cows in New Zealand in early lactation

AIMS: The main aim of this study was to describe the prevalence of primary subclinical ketosis (SCK) in mainly pasture-grazed dairy cows in three dairy-farming regions of New Zealand 7–12, and 35–40 days post-calving. A second aim was to investigate herd- and cow-level factors associated with the prevalence of SCK.METHODS: A cross-sectional longitudinal prevalence survey was undertaken in 1,620 dairy cows from 57 herds. A random sample of cows without disease in the prior 30 days were enrolled at one farm visit within 5 days of calving, and blood samples were collected 7 and 28 days later (7–12 and 35–40 days post-calving) for measurement of beta-hydroxy butyrate (BHBA) concentrations using an electronic cow-side meter. SCK was defined as blood BHBA concentration ≥1.4 mmol/L.RESULTS: Mean cow-level prevalence of SCK varied with interval post-calving (16.8 and 3.2% at 7–12 days and 35–40 days post-calving, respectively) and age (13.0 and 13.1% of 2-year olds and ≥8-year olds, respectively, compared to 7.2% of 3–4-year-old cows). Mean herd-level prevalence of SCK was 14.3 (min 0, max 60.0)% and 2.6 (min 0, max 24.4)% at 7–12 days and 35–40 days post-calving, respectively, and was greater in Southland (13.3%) than Waikato and Canterbury herds (6.9 and 4.7%, respectively).CONCLUSIONS: This is the first population-based report of the prevalence of SCK in New Zealand dairy herds and demonstrates that age and interval post-calving are important risk factors determining prevalence; and that there is wide variation in prevalence between herds.CLINICAL RELEVANCE: Subclinical ketosis may be unrecognised but common in many New Zealand dairy cows in the first 2 weeks of lactation.

The responsiveness of subclinical endometritis to a nonsteroidal antiinflammatory drug in pasture-grazed dairy cows

The objective of this study was to determine if the inflammation associated with subclinical endometritis (SCE) is a part of the mechanism by which reproductive performance is reduced in cows with this disease. If it is, reducing inflammation associated with SCE with a nonsteroidal antiinflammatory drug (NSAID) should reduce the severity [as measured by average polymorphonuclear cell (PMN) percentage] of uterine pathology and improve reproductive performance. It was also investigated whether the NSAID treatment reduced metabolic indicators of systemic inflammation previously reported to be altered in cows with SCE. Holstein-Friesian and Friesian-Jersey cross dairy cows (n=213) were paired by calving date and d-14 uterine PMN percentage and randomly assigned to 3 injections at intervals of 3 d of an NSAID (1.4 mg of carprofen/kg; n=104) between 21 and 31 d postpartum or left as untreated controls (n=109). Cows with ≥14% PMN (upper quartile of PMN percentage) in the cytological sample collected at d 14 postpartum were defined as having SCE. The average d-14 PMN percentage was low (9.9%) and a high self-cure rate of SCE (>90%) at d 42 was observed. Treatment with an NSAID reduced plasma concentrations of aspartate aminotransferase and increased pregnancy rate in SCE cows. However, no effect of the NSAID treatment was observed on PMN percentage at d 42, postpartum anovulatory interval, or milk production. Compared with cows without SCE, cows with SCE had lower plasma albumin concentration, albumin:globulin ratio, and body condition score, but higher nonesterified fatty acids on the day of calving. These results indicate that cows with SCE are experiencing a physiological dysfunction, including lower body condition, liver dysfunction, and greater metabolic challenge during the periparturient period. Further research is required to determine the effect of NSAID on SCE and to evaluate the influence of timing of drug application on treatment effectiveness.