Sampling strategy and measurement device affect vaginal temperature outcomes in lactating dairy cattle.

Body temperature (BT) is widely used to evaluate health and heat load status in cattle. Despite its importance, studies vary in how BT is measured and in the biological interpretation of the results. Costs, practicality, labor, and welfare concerns can affect how BT is measured, including frequency of measurement and the type of device used. Inaccurate BT outcomes may have implications for cattle welfare; for example, animals may only receive treatment when fever is identified. Our objectives were (1) to compare measurement of vaginal temperature (VT) using relatively small, inexpensive, and low-accuracy loggers (±0.5 to ±1°C, iButton range; Embedded Data Systems, Lawrenceburg, KY) to a high-accuracy logger (±0.1°C; StarOddi, Gardabaer, Iceland), and (2) to evaluate how different BT sampling strategies correspond to 24-h VT in lactating dairy cows. To address the first objective, VT data from 54 cows were recorded every 45 min for 12 d/cow, on average, using 2 different types of temperature loggers (StarOddi DST centi-T and iButton DS1921H or DS1922L) attached to a shortened, hormone-free controlled internal drug release insert. Average VT obtained from both loggers were compared using mixed models and regression analyses. In addition, we tested the consistency of the low-accuracy loggers in detecting cows with elevated BT using the kappa coefficient of concordance. To address the second objective, VT data from 20 cows were recorded every min for 9 to 11 d/cow using StarOddi loggers. Using these data, we estimated average VT using 11 sampling strategies (every 5, 10, 15, 30, 45, 60, and 120 min, 1×/d recorded in the morning or afternoon, 2×/d, or 3×/d). Estimates and observed means were compared using linear regression. Compared with StarOddi loggers, the iButtons either underestimated (H model: 38.7 vs. 38.0 ± 0.06°C) or overestimated VT (L model: 38.7 vs. 39.2 ± 0.04°C). When considering elevated or fever VT thresholds, iButtons did not correctly classify animals; kappa coefficients of concordance were ≤0.35. Measuring VT as often as every 120 min resulted in more accurate estimates compared with strategies that recorded it once to thrice per day. These results indicate that the type of device (i.e., data logger) and sampling strategies affect BT outcomes and that these decisions affect the interpretation of BT data.

Innovative cooling strategies: Dairy cow responses and water and energy use.

Producers in the western United States commonly use spray water at the feed bunk and fans in the lying area to mitigate heat stress in dairy cows. Often, spray water cycles on and off with fans turning on when a preset air temperature is reached. Although this method can be effective, innovative strategies are needed to reduce water and energy use. We evaluated the effectiveness and resource efficiency of 4 cooling treatments on behavioral and physiological responses in dairy cows housed in a freestall barn: (1) conductive cooling in which mats with recirculating evaporatively cooled water were buried under sand bedding (Mat; activated at 18.9°C); (2) targeted convective cooling in which evaporatively cooled air was directed toward the cows through fabric ducts with nozzles at both the feed bunk and lying areas (Targeted Air; activated at 22°C); (3) evaporative cooling, with spray water in the feed area and fan over the freestalls (Baseline; activated at 22°C); and (4) evaporative cooling with half the amount of spray water used in the Baseline and the fan moved to the feed bunk (Optimized Baseline; activated at 22°C). In a crossover design, 8 groups of cows (4/group) producing an average (± standard deviation) of 37.5 ± 4.5 kg/d of milk were tested for 3 d per treatment. For ethical reasons, beginning at 30°C, the Mat treatment was supplemented with Baseline cooling and the Targeted Air treatment had spray water at the Optimized Baseline rate. We recorded body temperature, posture, and location within the pen every 3 min for 24 h/d, and respiration rates every 30 min daily from 1000 to 1900 h. Daily air temperature averaged (±SD) 26.3 ± 7.1°C during 24 h and 33.3 ± 4°C from 1000 to 1900 h. We used pairwise comparisons of each treatment to Baseline to evaluate response variables. Milk production did not differ across treatments, nor did time spent lying (51 ± 2%/d on average). Respiration rates did not differ across treatments overall (61 ± 3 breaths/min), but on an hourly basis, cows in the Mat treatment had a significantly higher rate than those in Baseline, at h 10 and 11 (70 vs. 58-59 breaths/min). Body temperature averaged 38.7 ± 0.05°C across treatments and was 0.2 to 0.3°C higher in the Mat treatment than in Baseline at h 10, 11, 20, 21, and 22. These results collectively indicate that the Mat treatment did not effectively reduce indicators of heat load compared with Baseline. In contrast, Targeted Air and Optimized Baseline were both effective but differed in aspects of efficiency. Targeted Air used the least amount of water but the most energy of all options tested. In conclusion, more efficient heat abatement options were identified, particularly an Optimized Baseline strategy, which cut water use in half, required the same amount of energy as the Baseline, and maintained similar physiological and behavioral responses in cows.

Cooling cows with sprinklers: Effects of soaker flow rate and timing on behavioral and physiological responses to heat load and production.

Spray strategies (e.g., flow rate and spray timing) may affect the surrounding microclimate and how cows use soakers, affecting cooling efficiency. Our objective was to evaluate the combined effects of spray timing (i.e., frequency, low: 3 min on, 6 min off; or high: 1.5 min on, 3 min off) and flow rates (3.3 or 4.9 L/min) on behavioral and physiological responses to heat load and production in Holstein cows managed in a freestall barn. In a 2 × 2 Latin square design, 3 cohorts of 4 pairs of cows averaging (±standard deviation) 36.7 ± 5.4 kg/d of milk were tested for 3 d/treatment. Water was sprayed at the feedline from 0815 to 2330 h when air temperature and relative humidity averaged 27 ± 3°C and 37 ± 7%, respectively. The overall quantity of water sprayed was not affected by spray timing; it varied only as a function of flow rate. Cows' posture and location within the pen were measured continuously, whereas feeding and body temperature were recorded every 3 min over 24 h/d. Respiration rates were recorded daily every 45 min from 0900 to 2000 h. Neither spray timing nor flow rates affected posture, location in the pen, feeding activity, or respiration rates. Overall, on average, cows spent 12.6 ± 0.4 h/d lying down and 5.8 ± 0.3 h/d in the feed bunk area. While in the feed bunk area, cows spent 78 ± 3% of their time feeding. Average respiration rate ranged from 57 to 59 ± 3 breaths/min across treatments. Although body temperature tended to be reduced when using higher flow rate, this difference was 0.1°C when comparing 24-h averages (4.9 vs. 3.3 L/min: 38.6 vs. 38.7 ± 0.1°C). Body temperature differences, however, were more marked and statistically different when soakers were cycling, especially between 1100 and 2200 h. Despite this, the magnitude of the hourly differences were <0.2°C. Milk production also tended to increase by 1.5 kg/d when using higher flow rates. When using the same water volume, spray timing did not affect cow behavior, physiology, or production. Flow rate had a small effect on milk production and body temperature but the biological relevance of these differences is unclear, especially in this situation where all cows were relatively cool.

Cooling cows with sprinklers: Timing strategy affects physiological responses to heat load.

After shade, sprayed water is the most common heat abatement resource provided in dairy farms in the western United States, but little is known about how to manage this resource to improve cow cooling and water-use efficiency. Our objective was to evaluate the cooling effectiveness of 4 spray strategies, using 2 water volumes (approximately 74 or 44 L/nozzle) over 45 min. Strategies varied based on spray frequency (using the same water volume) and the time that water was on and off (using different water volumes). In a crossover design, 20 Holstein cows (milk yield: 38.9 ± 4.2 kg/d) were restrained in shaded head gates and tested twice for each control (shade only) and 4 spray treatments (minutes water on | off, frequency: number of cycles/45 min): 1.5 on | 3 off, 10 cycles; 1.5 on | 6 off, 6 cycles; 3 on | 6 off, 5 cycles; and 3 on | 12 off, 3 cycles (water temperature average ± standard deviation: 26 ± 2°C). Air temperature and humidity averaged 29 ± 5°C and 26 ± 13%, respectively, during testing periods. Body temperature (BT), respiration rate (RR), skin temperature of the leg and shoulder, and air temperature surrounding the cow were measured. Compared with shade alone, all water treatments reduced heat load in cattle. Body temperature, for example, was at least 0.3°C lower (maximum reduction: 0.5°C) for sprayed cows after 45 min (39.0 vs. ≤38.7°C). The only change associated with spraying cows more often using the same water volume (thus manipulating both times on and off) was that applying water more frequently tended to reduce RR by 7 breaths/min. On the other hand, manipulating either time on or off (thus, water volume) affected most responses. Increasing the time on from 1.5 to 3 min (time off: 6 min) or shortening the time off from 12 to 6 min (time on: 3 min) or from 6 to 3 min (time on: 1.5 min) reduced BT by at least 0.1°C (maximum reduction: 0.2°C) and leg temperature by ≥0.2°C after 45 min. Shortening the time off also tended to reduce RR (7 breaths/min). Similarly, shoulder and surrounding air temperatures were, respectively, 0.5 and 0.4°C lower when reducing the time off from 6 to 3 min. In conclusion, applying the same water volume more often had minimal effects on responses to heat load on restrained cattle over a 45-min period. In contrast, spraying cows for longer or reducing the time off (thus, using more water) improved cow cooling compared with strategies that used less water.

Cooling cows with sprinklers: Spray duration affects physiological responses to heat load.

Sprayed water reduces heat load in cattle. Determining appropriate spraying strategies (i.e., time on and off) may improve cooling efficiency and reduce water use. Our objective was to evaluate the effects of a single spray on the surrounding air temperature (AT), time it takes the coat to dry, and physiological responses to heat load in dairy cows. In a crossover design, spray duration (0, 0.5, 1.5, 3, and 13 min; flow rate: 4.9 L/min) was tested in 15 Holstein cows (milk yield: 37.7 ± 2.6 kg/d) restrained in shaded head gates at the feed bunk for up to 1.75 h. Each treatment was replicated on 3 d (15 d total/cow) when AT, humidity, and temperature-humidity index averaged 31 ± 3°C, 27 ± 10%, and 76 ± 2, respectively (mean ± SD). Water temperature at the nozzle outlet and dripping from the cow was measured every 1 s and averaged (mean ± SD) 29.7 ± 1.4 and 30.3 ± 0.8°C, respectively. Respiration rate, skin temperature of the shoulder and upper leg, and the surrounding AT were measured before and after the spray application and every 3 min for 30 min. At the same intervals, using water-sensitive paper we measured the time the coat took to dry. In contrast to the control, immediately after the spray was turned off, all water treatments reduced skin temperature on the shoulder (range of mean ± SE: -1.1 to -4.4 ± 0.2°C). Within the same period, treatments ≥1.5 min reduced respiration rate (range: -7 to -24 ± 2 breaths/min) and the surrounding AT (range: -0.3 to -1.7 ± 0.0°C). Only spraying cows for ≥3 min reduced leg surface temperature during spray duration (range of reduction: -0.1 to -0.6 ± 0.0°C). Spray duration had little effect on the time it took the coat to dry. Cows sprayed for 13 min took 2 min longer to dry compared with the other treatments (15.9 vs. 13.8, 14.9, and 14.2 ± 0.6 min, respectively, for 0.5, 1.5, and 3 min). No additional cooling was observed in this phase except on windier days, when leg temperature and respiration rate reductions tended to be more marked (slope estimates: -0.06 and -3.6, respectively). Cooling benefits, as well as changes in AT surrounding the leg, were more pronounced when water was sprayed for longer. In this study, cooling was observed primarily when water was turned on, not during the time it took the coat to dry.

Assessing heat load in drylot dairy cattle: Refining on-farm sampling methodology.

Identifying dairy cattle experiencing heat stress and adopting appropriate mitigation strategies can improve welfare and profitability. However, little is known about how cattle use heat abatement resources (shade, sprayed water) on drylot dairies. It is also unclear how often we need to observe animals to measure high heat load, or the relevance of specific aspects of this response, particularly in terms of panting. Our objectives were to describe and determine sampling intervals to measure cattle use of heat abatement resources, respiration rate (RR) and panting characteristics (drooling, open mouth, protruding tongue), and to evaluate the relationship between the latter 2. High-producing cows were chosen from 4 drylots (8 cows/dairy, n=32) and observed for at least 5.9h (1000 to 1800h, excluding milking) when air temperature, humidity, and the combined index averaged 33°C, 30%, and 79, respectively. Use of heat abatement resources was recorded continuously; RR and the presence and absence of each panting characteristic were recorded every 5min. From the observed values, estimates using the specified sub-sampling intervals were calculated for heat abatement resource use (1, 5, 10, 15, 20, 30, 60, 90, and 120min), and for RR and panting (10, 15, 20, 30, 60, 90, and 120min). Estimates and observed values were compared using linear regression. Sampling intervals were considered accurate if they met 3 criteria: R2≥0.9, intercept=0, and slope=1. The relationship between RR and each panting characteristic was analyzed using mixed models. Cows used shade (at corral or over feed bunk) and feed bunk area (where water was sprayed) for about 90 and 50% of the observed time, respectively, and used areas with no cooling for 2min at a time, on average. Cows exhibited drooling (34±4% of observations) more often than open mouth and protruding tongue (11±3 and 8±3% of observations, respectively). Respiration rate varied depending on the presence of panting (with vs. without drool present: 97±3 vs. 74±3 breaths/min; open vs. closed mouth: 104±4 vs. 85±4 breaths/min; protruding vs. non-protruding tongue: 105±5 vs. 91±5 breaths/min). Accurate estimates were obtained when using sampling intervals ≤90min for RR, ≤60min for corral shade and sprayed water use, and ≤30min for drooling. In a hot and dry climate, cows kept in drylots had higher RR when showing panting characteristics than when these were absent, and used shade extensively, avoiding areas with no cooling. In general, 30min intervals were most efficient for measuring heat load responses.

Social Licking in Pregnant Dairy Heifers.

Housing affects social behaviors, such as competition, but little work has addressed affiliative behaviors. This study compared social licking (SL) in pregnant heifers housed indoors (in a free-stall barn) versus outdoors (on pasture), and relationships with competition, feeding and physical proximity to others. Six heifer groups were observed during two six-hour-periods in both treatments. The total number of social events (SL and agonistic interactions) was four times higher when heifers were housed indoors compared to pasture (546 ± 43 vs. 128 ± 7 events/group; P < 0.05). SL as a ratio of the total number of social events was similar in the two treatments (12% vs . 8% of interactions, free-stall and pasture, respectively; P > 0.05). Housing did not affect how the SL bout was initiated and terminated, the duration, the body part licked and behavior preceding licking ( P > 0.05). Animals in close proximity showed higher rates of SL ( P < 0.0001) but not agonistic interactions ( P > 0.05). A previous agonistic event did not predict occurrence or the role of heifers in the following licking event. The higher stocking density indoors likely resulted in increased social interactions.