The aim was to determine whether administration of melatonin would alter the yield and composition of milk from grazing dairy cows in summer. Twelve sets of spring-calving identical twin Friesian cows were used in the experiment. In late-November (late spring), one twin from each set was given slow-release melatonin implants behind the ears (108 mg melatonin/cow). Two further implantations occurred at 4-weekly intervals to maintain increased circulating concentrations of melatonin for 12 weeks. The other twin served as a control. Milk yield and composition were measured twice prior to treatment and then four times over the following 12 weeks. Concentrations of melatonin, prolactin and insulin-like growth factor 1 (IGF-1) were measured in blood plasma twice before treatment and then either seven (melatonin and prolactin) or three (IGF-1) further times during the experiment. Management procedures for all cows were similar and cows grazed a daily pasture allowance of approximately 30 kg DM/cow as their sole feed source. In melatonin-treated cows there was a decrease in mean concentrations of prolactin in plasma, but concentrations of IGF-1 did not change. Melatonin reduced milk yield by 6 weeks after treatment and by the end of the 12-week experimental period milk yield in melatonin-treated cows had fallen by 23%. Melatonin also reduced concentrations of lactose in milk, but increased concentrations of fat, protein and casein, changes that were broadly similar to those that occur in late lactation in seasonally calving dairy cows. Thus, the results suggest that some of the variation in the volume and quality of milk throughout the season in New Zealand dairy systems may be due to changes in photoperiod mediated by increased concentrations of plasma melatonin in association with decreased concentrations of plasma prolactin.

The transition from pregnancy to lactation (i.e. the transition period) is a time of significant metabolic challenge, with a several-fold increase in a cow’s requirement for energy, protein and minerals within days of calving. A successful transition involves the initiation and coordination of changes in multiple tissues that facilitate the provision of these nutrients to the cow and, more specifically, to the mammary gland, often at the considerable expense of other tissues. Failure to coordinate the necessary changes effectively results in transition period maladaptation, which can broadly be grouped into three categories: (1) negative energy balance and metabolic diseases associated with energy metabolism; (2) immune dysfunction and inflammation; and (3) metabolic diseases associated with mineral deficiency. Because reinitiation of ovarian activity, follicle recruitment, ovulation, fertilisation and, potentially, even maternal recognition of pregnancy and implantation occur against the backdrop of this metabolic and immunological disturbance in early lactation, the role of nutrition in ensuring a smooth transition between the pregnant and lactating state is important. In this paper we integrate recent research findings with previous knowledge of the interaction between transition cow metabolism and nutrition and reproductive outcomes, and offer new insights into key elements of successful cow management to avoid transition ‘maladaptation’ and improve pregnancy rates.

A study was undertaken in cattle to evaluate changes in milk L-lactate in relation to mastitis. A healthy, rear quarter of the udder of each of ten cows in mid-lactation was infused with 1000 colony-forming units (cfu) of Streptococcus uberis following an afternoon milking. Foremilk samples were taken at each milking from control and treated quarters and antibiotic treatment was applied following the onset of clinical mastitis or after 72 h. One cow did not become infected. Six quarters showed clinical symptoms of mastitis within 24–40 h and this was associated with a more than 30-fold increase in milk L-lactate (to 3·3 mM) and an increase in somatic cell count (SCC) from 4·5×10³ to 1×10⁷ cells/ml. Three cows were subclinical, with cell counts ranging from 1·5×10⁶ to 1×10⁷ cells/ml. In these animals, milk lactate ranged from 0·7 to 1·5 mM in the infected quarters up to 40 h post-infection, compared with less than 0·1 mM in control quarters. Milk was examined from 137 cows in mid-lactation which were known to have mastitis. Foremilk samples were taken aseptically from control and infected quarters of cows on commercial farms. Mean milk L-lactate concentrations and SCC were 0·14±0·02 mM and 1·85±0·3×10⁵ cells/ml, respectively, in control (bacteriologically negative) samples. However, L-lactate concentrations exceeded 2·5 mM in the presence of some types of infection, the level of the lactate response being closely related to the impact of the infection on SCC. L-Lactate concentrations were relatively elevated in milk samples taken post partum, declining from 0·8 to 0·14 mM over the first few days of lactation. In conclusion, milk L-lactate has potential as an indicator of clinical and subclinical mastitis in 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.

Lying behaviour and activity were measured in healthy grazing dairy cows during the transition from late gestation to early lactation (i.e. the transition period). Behaviour data derived from IceTag® or IceQube® (IceRobotics, Edinburgh, Scotland, UK) tri-axial accelerometers were collated from 311 cow parities of mixed age and breed (Holstein–Friesian, Jersey and crossbred Holstein–Friesian × Jersey) cows from four experiments. The IceTag and IceQube devices captured lying and step data at 1- and 15-min intervals respectively. Behaviour was recorded during the transition period (Day –21 prepartum to Day 34 postpartum) to determine daily lying time, number of lying bouts (LB), mean LB duration and number of steps. The effect of rainfall and air temperature on lying behaviour and activity during two periods, namely, prepartum (Day –21 to Day –3) and postpartum (Days 3–34) was evaluated. Multiple-regression analysis determined that decreased air temperature and increased rainfall is associated with a decline in daily lying time, number of LB and LB duration during both prepartum and postpartum periods. Exposure to both wet and cold conditions exacerbated the behavioural response. The results highlighted the importance of considering the effects of air temperature and rainfall and the interaction of these two climate variables when analysing lying behaviour and activity. Further work is required to quantify the trigger points for this activity modulation, to help understand the balance of welfare experiences in the life of a grazing cow.

The effect of an intramammary infection (IMI) at calving on the milk yield of heifers during their first 200 d in milk (DIM) was estimated by comparing monozygotic twins, where one member had a naturally occurring IMI detected at the first milking after calving and the other twin did not. Data collected weekly over a full lactation for 29 twin pairs were used to estimate the effects of a peri-calving Streptococcus uberis IMI on milk yield and composition. Data for 19 twin pairs were used to estimate the effects of pericalving coagulase-negative staphylococci (CNS) IMI. A heifer with a Strep. uberis IMI produced 200 kg (7%) less milk during the first 200 d of lactation compared with her uninfected twin, with significant differences evident throughout the 200-d period. Similar milk losses were recorded for heifers that developed CM or remained subclinical. An elevated milk SCC for infected heifers was only apparent for the first month (d 2-30), although SCC tended to remain high during the second (d 31-60) and third (d 61-90) months. Milk protein concentrations were greater in the Strep. uberis-infected twin over the 200-d period, whereas fat and lactose concentrations showed little change. An IMI caused by Strep. uberis was associated with a lower milk yield, whereas an IMI by CNS was not, despite CNS-infected twins having a higher SCC than their uninfected twin for the first 30 d of lactation.