K. L. Kerrisk

Quarter-milking-, quarter-, udder- and lactation-level risk factors and indicators for clinical mastitis during lactation in pasture-fed dairy cows managed in an automatic milking system

OBJECTIVES   To identify risk factors and indicators at quarter-milking and other levels for clinical mastitis during lactation in pasture-fed cows managed in an automatic milking system. DESIGN   A retrospective nested case-control study using data collected over a 31-month period. A total of 803,948 quarter-milkings from 249 cows were available for analysis, of which 245 were selected as clinical mastitis quarter-milking cases and 2450 unaffected quarter-milkings were selected as controls. Most of the diagnoses of clinical mastitis had been made after clinical assessments of quarters following automated alerts by the milking system. Potential risk factors and indicators were assessed using univariable and multivariable multilevel logistic models. RESULTS   Quarters that are milked infrequently and have low yield, fast peak milk flow rates, blood in the milk and/or elevated milk conductivity are at increased risk of clinical mastitis. Quarters were also at increased risk between days 10 and 29 of lactation, and during higher parity lactations. Milk fat and protein concentrations and the fat:protein ratio were not significantly associated with the development of clinical mastitis. Neither quarter position (fore or rear) nor side (left or right) was associated with clinical mastitis occurrence. Quarters that had been clinically affected more than 30 days previous in the current lactation were not at increased risk of redeveloping clinical mastitis. CONCLUSIONS   Under the study conditions, the risk of clinical mastitis increased for quarter-milkings in quarters that were milked less frequently in the previous 7 days, were low-yielding, had fast peak milk flow rates and had more milkings in which blood was detected in milk and/or the milk conductivity was elevated. Risk was also increased in days 10-29 of lactation and in higher parity lactations.

Comparison of 2 systems of pasture allocation on milking intervals and total daily milk yield of dairy cows in a pasture-based automatic milking system

Cows milked in pasture-based automatic milking systems (AMS) have greater milking intervals than cows milked in indoor AMS. Long milking intervals greater than 16h have a negative effect on milk yield and udder health. The impact of 2 systems of pasture allocation in AMS on milking interval and yield was investigated at the FutureDairy AMS research farm (Elizabeth Macarthur Agricultural Institute, New South Wales Department of Primary Industries, Camden, New South Wales, Australia) in late November to early December 2010. Two- (2WG) versus 3-way grazing (3WG) allocations per 24-h period were compared in a field study to test the hypothesis that an increase in the frequency of pasture allocation would reduce the milking interval and, therefore, increase milking frequency. The study involved the entire milking herd of 145 cows, with (mean ± SD) DIM=121±90d, 7-d average milking frequency=1.52±0.41 milkings/cow per day, and 7-d average milk yield=21.3±7.6kg/cow per day. Cows were milked using 2 DeLaval VMS milking units (DeLaval International AB, Tumba, Sweden). Cows in the 3WG treatment had 31% reduced milking interval, 40% greater milking frequency, and 20% greater daily milk production compared with 2WG. Increased milking frequency and milk production for 3WG was associated with greater utililization levels of the AMS milking units throughout the day. These results support the recommendation that, wherever possible, farmers installing AMS should incorporate sufficient infrastructure to accommodate 3WG, which provides additional flexibility with managing extremely long (and short) milking intervals.

Rumination and activity levels as predictors of calving for dairy cows.

The Australian dairy herd size has doubled over the last 20 years substantially increasing the time that farmers require for individual animal attention to monitor and intervene with events such as calving. Technology will help focus this limited labour resource on individual cows that require assistance. The objective of this experiment was to first determine the profiles of rumination duration and level of activity as determined by sensors between, and within, days around calving and second to use these data to predict the day of calving for pasture-based dairy cows. After 2 weeks from the expected calving date, 27 cows were fitted with SCR HR LD Tags, located in 40×90 m2 paddock and offered ad libitum oaten hay and 2 kg grain-based concentrate/cow per day until calving. Hourly activity and rumination data for each cow, as determined by the SCR tags, were fitted with linear mixed models and all parameters were estimated using restricted maximum likelihood. Rumination duration decreased by 33% over the day prior and the day of calving, with the decline in rumination duration starting the day prepartum. Activity levels were maintained prepartum but increased in the days postpartum. The day of calving was recorded and used to determine the gold standard positive (the day before calving) and negative (all other) dates. A threshold rumination level of 0.9 (decline in rumination duration of 10%) gave the optimal combination of 70% sensitivity and 70% specificity. This experiment shows the potential to use rumination duration to predict the day of calving and the opportunity to use sensor data to monitor animal health.

precision dairy farming in Australasia: adoption, risks and opportunities

Dairy farm management has historically been based on the experiential learning and intuitive decision-making skills of the owner-operator. Larger herds and increasingly complex farming systems, combined with the availability of new information technologies, are prompting an evolution to an increasingly data-driven ‘precision dairy’ (PD) management approach. Automation and the collection of fine-scale data on animals and farm resources via precision technologies can facilitate enhanced efficiency and decision making on dairy farms. The proportion of dairy farmers using this approach is relatively small (between 10 and 20% of farmers); however, industry trends suggest a continual increase in the use of precision technologies. Australasian PD farms have reported both positive and negative stories regarding the approach but to date there has been little industry attention or co-ordination in Australia or New Zealand. A series of workshops was held in late 2011 between industry-good representatives, researchers and farmers, from Australia and New Zealand, to discuss the opportunities and risks associated with PD. To take advantage of the emerging PD opportunity the trans-Tasman workshop group suggested five focus areas including: industry-good co-ordination and leadership in precision dairy; working to define the on- and off-farm value of PD; improving the technology available to farmers; integration of PD within farming systems for improved management; and developing learning and training initiatives for farmers and service providers. Action in these focus areas will enable future dairy farmers to implement the PD approach with enhanced confidence and effectiveness.

Review: Milking robot utilization, a successful precision livestock farming evolution

Automatic milking systems (AMS), one of the earliest precision livestock farming developments, have revolutionized dairy farming around the world. While robots control the milking process, there have also been numerous changes to how the whole farm system is managed. Milking is no longer performed in defined sessions; rather, the cow can now choose when to be milked in AMS, allowing milking to be distributed throughout a 24 h period. Despite this ability, there has been little attention given to milking robot utilization across 24 h. In order to formulate relevant research questions and improve farm AMS management there is a need to determine the current knowledge gaps regarding the distribution of robot utilization. Feed, animal and management factors and their interplay on levels of milking robot utilization across 24 h for both indoor and pasture-based systems are here reviewed. The impact of the timing, type and quantity of feed offered and their interaction with the distance of feed from the parlour; herd social dynamics, climate and various other management factors on robot utilization through 24 h are provided. This novel review draws together both the opportunities and challenges that exist for farm management to use these factors to improved system efficiency and those that exist for further research.

Effect of pre- versus postmilking supplementation on traffic and performance of cows milked in a pasture-based automatic milking system.

Cows milked in a pasture-based automatic milking system tend to have a lower daily milking frequency in comparison with cows milked in indoor systems. Milking events with intervals beyond 16h have been reported to have a negative effect on milk yield and udder health, and therefore it is important to minimize their occurrence. As feed is the main incentive to encourage cow traffic around the system, a study was conducted to compare pre- (PRE) versus postmilking (POST) supplementary feed placement strategies in a pasture-based automatic milking system. We hypothesized that PRE cows would have a stronger incentive to walk voluntarily from the paddock to the dairy facility to get milked (due to the reward being more immediate), thereby reducing their milking interval and increasing daily milking frequency and milk yield. The PRE cows returned to the dairy facility sooner (PRE=11.9 vs. POST=13.27h) but had longer milking intervals (PRE=15.3 vs. POST=14.28h). This was due to the additional time spent in the prefeeding area (PRE=56 versus POST=23min) combined with a longer average time spent in the premilking waiting yard (PRE=97 versus POST=77min). Treatment did not affect daily milk yield per cow. The result of this study demonstrates the potential of manipulating feeding management strategies to influence cow behavior and traffic in voluntary milking systems.

Plasma oxidative stress biomarkers and progesterone profiles in a dairy cow diagnosed with an ovarian follicular cyst

This study was conducted to examine the oxidative stress biomarkers in a cow diagnosed with a follicular cyst in her left ovary. Progesterone (P4) and plasma oxidative stress status was measured in 13 Holstein cows after synchronization of oestrus with controlled internal drug release (CIDR) and prostaglandinF2α (PGF2α) protocol. The presence and size of ovarian structures were monitored by transrectal ultrasound at 4 hourly intervals. Of the 13 cows, 12 were monitored until ovulation was detected and recorded, whereas one cow failed to ovulate and developed a follicular cyst. Oxidative stress biomarkers; reactive oxygen metabolites (ROMs), biological antioxidant potential (BAP), oxidative stress index (OSI), glutathione (GSH), ceruloplasmin and advanced oxidation protein products (AOPP) were measured in the cystic cow and compared to those of the 12 ovulated cows and are referred to as higher or lower if they are outside the mean ± standard error of mean of those of ovulated cows. The cystic cow had lower ROMs and OSI between 36 and 84 h after PGF2α injection and at 9 h, from 36 to 60 h after PGF2α injection respectively. On the other hand, antioxidant (BAP and GSH) was higher in the cystic cow compared to her ovulated herd mates. The observed imbalance between oxidant and antioxidant might have disrupted the physiological events for ovulation to occur, leading to cystic ovarian disease.

Changes in plasma oxidative stress biomarkers in dairy cows after oestrus synchronisation with controlled internal drug release (CIDR) and prostaglandinF2α (PGF2α)

This study was designed to evaluate the plasma profiles of oxidative stress biomarkers, progesterone and ovarian follicle diameter in ovulatory versus an-ovulatory cows. Twenty cows were synchronised using controlled internal drug release (CIDR) and prostaglandinF2a (PGF2a) protocol. Plasma samples were analysed for progesterone (P4), oxidative stress (OS) biomarkers; reactive oxygen metabolites (ROMs), biological antioxidant potential (BAP), oxidative stress index (OSI = ROMs/BAP · 100), advanced oxidation protein products, ceruloplasmin and glutathione (GSH). Plasma P4 concentration was greater in ovulated cows 24 hours (h) after PGF2a treatment but lower 48 h after PGF2a treatment compared with that of an-ovulated cows at those sampling sessions (P < 0.05). Ovulated cows were diagnosed with greater ovarian follicle diameter compared with that of their herd mates not diagnosed for ovulation. Significant interaction of time of PGF2a treatment and ovulation status (ovulatory versus an-ovulatory) with the plasma concentrations of OSI, BAP and GSH were observed. Ovulated cows had significantly lower BAP compared with that of an-ovulated cows (P < 0.05) 9 h, 48 h, 60 h and 128 h after PGF2a treatment. Plasma concentrations of GSH were lower (P < 0.05) in ovulated cows than that of an-ovulated cows 60 h and 96 h after PGF2a treatment. However, OSI was greater (P < 0.05) in ovulated cows than that of an-ovulated cows 9 h, 48 h, 60 h and 128 h after PGF2a treatment. Significant associations were observed between OS status and sampling time. Oxidative stress status may have important physiological role in facilitating the ovulation process in oestrus synchronised dairy cows.

Effects of bail activation sequence and feed availability on cow traffic and milk harvesting capacity in a robotic rotary dairy

This study was conducted to investigate the effects of different bail activation sequences in combination with feed availability on cow traffic and harvesting capacity in a novel prototype robotic rotary (RR; DeLaval AMR, Tumba, Sweden). The RR can milk up to 50 cows/h. However, in voluntary cow traffic systems, the number of cows presenting may be low at certain times of the day (or during certain months or seasons in seasonal calving systems). In these circumstances, the ratio of active bails to the number of cows available may be undesirably high, with consequential negative effects on system efficiency and milk quality (the RR does not flush individual units automatically after each milking). Activating only 50% of the bails may be a management strategy chosen to cope with periods of underutilization. Four treatments with a total activation of 50% of bails [8 bails with activation sequences of 8, 4, 2, or 1 consecutive bail(s)], with or without the presence of feed on the RR, were observed during sixteen 4-h observation periods after a system wash. The absence of feed resulted in a significant increase in the proportion of available bails remaining idle, but no significant differences were observed across the 4 bail activation sequences. Overall, the effect of bail activation sequence on cow traffic was negligible, but the sequences that had more consecutive bail activations resulted in more robot operations being conducted simultaneously and more milk being harvested per minute of robot operation time. A feeding function upon entry to the RR platform, in combination with bails activated sequentially, would lead to a more efficient use of the RR.

Changes in milk oxidative stress biomarkers in lactating dairy cows with ovulatory and an-ovulatory oestrous cycles

This study was conducted to evaluate changes in milk profiles of oxidative stress (OS) biomarkers in dairy cows with ovulatory and an-ovulatory oestrous cycles. Thirty healthy, cycling Holstein cows averaging 60±17 days in milk, and producing 33±6kg of milk per day (the week before commencing the study) were enrolled in this study. Composite milk samples were collected thrice weekly and assayed for the following OS biomarkers: lipoperoxides (LPO), biological advanced potential, superoxide dismutase (SOD), advanced oxidation protein products (AOPP), ceruloplasmin, glutathione (GSH), β-carotene and glutathione peroxidase (GSH-Px). Milk samples were also tested for fat and protein composition and the fat:protein ratio (FPR) was categorized as low (≤1.31), medium (1.32-1.56) and high (>1.57) to evaluate their main effect and the interaction effect of FPR and the week of study on OS using linear mixed models with cow identification being a random factor. Cows with ovulatory oestrous cycles (n=20) presented significantly greater SOD levels than cows that did not ovulate ((n=10; P<0.05). On the other hand, LPO, GSH-Px and GSH concentrations were lower in ovulated cows compared to the an-ovulated cows (P<0.05). The highest level of LPO and AOPP were noted at prooestrus phase while β-carotene presented the lowest value at that phase of oestrous cycle. It could be postulated that the elevated level of milk SOD and the observed lower level of LPO, GSH-Px and GSH in ovulating cows may be an essential event preceding the ovulatory response.