Fecal excretion of Campylobacter jejuni by young dairy calves and the relationship with neonatal immunity and personality traits.

AIMS: Zoonotic pathogens in bovine herds are major concerns for human and animal health, but their monitoring in animals can be challenging in the absence of clinical signs. Our objective was to determine the association between fecal excretion of Campylobacter jejuni, neonatal immunity, and personality traits of calves. METHODS AND RESULTS: Forty-eight dairy calves were reared in three indoor pens from birth to 4 weeks of life. Microbial analyses of the fecal samples collected weekly revealed that the proportion of calves naturally contaminated with C. jejuni in each pen reached 70% after 3 weeks of life. High (>16 g l-1) levels of IgG levels in the serum of neonatal calves were negatively (P = .04) associated with fecal detection of C. jejuni over the trial period. Calves that spent more time interacting with a novel object tended to be positive (P = .058) for C. jejuni. CONCLUSIONS: Overall, the findings indicate that the immunity of neonatal dairy animals and possibly the animal's behavior may contribute to the fecal shedding of C. jejuni.

Behavior of dairy cows managed outdoors in winter: Effects of weather and paddock soil conditions.

Dairy cows are motivated to access dry lying surfaces and will seek protection from wind and rain, but winter conditions may limit these opportunities when cows are managed outdoors. The primary aim of this observational study was to determine the effects of weather and paddock soil conditions on lying behavior of dairy cows managed outdoors during winter and fed crop in situ, a practice occurring in New Zealand with year-round grazing of dairy cows. A secondary aim was to characterize eating and ruminating behaviors during winter weather and paddock soil conditions. Four groups (99 nonlactating, pregnant cows each) were managed on 4 outdoor paddock areas on the same farm; the groups were fed pasture silage and grazed either kale (2 groups) or fodder beet (2 groups). Behaviors were recorded using validated leg-based (lying behavior) and ear-based (eating and ruminating time) accelerometers on 30 focal cows in each group over 32 d. Soil depth and wetness were scored daily at 25 points along 4 transects within each paddock area using recognized technical measures (penetrometer, soil volumetric water content), which were compared with practical tools for farmer use (ruler, moisture meter, percentage of sites in paddock scored as dry, wet, sodden, or with surface water pooling). Rainfall occurred most days during the study (mean 1.6 mm/d; maximum 12.2 mm/d), resulting in wet and muddy paddocks (mud depth with ruler: mean 6 cm, maximum 18 cm; paddock sites scored as wet or sodden: mean 34%, maximum 100%; paddock sites with surface water pooling: mean 27%, maximum 100%). Group lying time was 9.6 ± 2.3 h/d (mean ± standard deviation); however, 21% of cows consistently lay less than 8 h/d (to a minimum of 4.9 h/d). A mixed regression model tested the effects of daily weather and paddock soil conditions on daily lying time, with group as the observational unit, day as repeated measure, crop type as a fixed effect, crop type interactions with explanatory variables, and random intercepts of group and paddock within group. Lying time was less on the day of and day after rainfall (24 and 29 min/d less for 1 mm increase in rainfall, respectively). Two days after rainfall, lying time rebounded to about 1 h longer than before the rainfall. On the day after the heaviest rainfall event, group average lying time was only 2.5 ± 1.9 h/d (mean ± standard deviation); in 2 groups, 30% and 38% of cows, respectively, did not lie down at all for 24 h. Lying time decreased with deteriorating paddock soil conditions, especially with increasing surface water pooling, suggesting that this may be a useful measure to estimate the quality of the lying surface. Descriptively, ruminating time appeared to decrease with increased surface water pooling, possibly due to decreased lying time. Our results demonstrated that dairy cows could experience periods of short or no lying time during inclement weather and muddy paddock soil conditions. Prior rainfall and surface water pooling may be useful measures to determine if lying time, and thus animal welfare, are compromised.

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.

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: 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.

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.

Stepping behavior and muscle activity of dairy cattle standing on concrete or rubber flooring for 1 or 3 hours.

The type of flooring in dairy cattle systems influences cows' health and welfare. Although concrete is common, the use of more compressible flooring, such as rubber, is increasing. Cows prefer to stand and walk on rubber surfaces than on concrete; however, it is largely unknown how walking and standing for longer periods of time influence muscle activity and fatigue. Therefore, we used measures of behavior and muscle activity to investigate the potential benefits of providing a rubber flooring surface to dairy cattle. Sixteen lactating Holstein cows were forced to stand on either concrete or rubber flooring for 1 or 3 h in a 2 × 2 crossover design. Surface electromyograms (SEMG) and skin surface temperature were used to evaluate muscle activity, fatigue, and movement of muscle activity between the hind legs. Activity of 2 muscles, the bicep femoris and middle gluteal, was assessed during both static contractions, when cows transferred weight to each hind leg, before and after 1 and 3 h of standing, and dynamic contractions, associated with steps and with shifts in weight without steps. In addition, we evaluated stepping rate, time between each step, feeding behavior, skin surface temperature, and latency to lie down after standing. Standing duration influenced both the behavior and muscle activity of cows. Stepping rate increased with standing time for cows on both flooring types. Static muscle activity parameters of the bicep femoris muscle were higher after 3 h of standing for cows standing on both flooring types (2.3 and 3.6% increases in median amplitude and median power frequency, respectively) compared with the change after 1 h and compared with baseline values before the standing treatment. Flooring type influenced the behavior and muscle activity of the cows, particularly during the first hour of exposure; cows standing on rubber had a higher stepping rate, shorter interval between steps, and higher number of SEMG shifts (muscle activity shifts with or without visible steps) than cows on concrete. There was no difference in skin surface temperature, feeding behavior, or latency to lie down between the treatments. The results show that standing on a rubber flooring caused a different initial behavioral response compared with standing on concrete; however, possible reasons for these changes are unclear. Standing for 3 h resulted in an increase in stepping rate and in some muscle activity parameters; however, the results regarding muscle fatigue in relation to flooring type are inconclusive.

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.

Technical note: Comparison of instantaneous sampling and continuous observation of dairy cattle behavior in freestall housing.

Recording behavior at fixed intervals (instantaneous sampling) can reduce labor relative to observing continuously. However, instantaneous sampling may inaccurately estimate potentially important responses, such as how frequently cows perform a behavior (i.e., the number of bouts). Our objective was to validate the use of instantaneous sampling for capturing how long and how frequently cows in freestall housing lie down or visit the feed bunk and water trough. We predicted that more frequent sampling would be needed to accurately reflect the behaviors that cows spent less time performing. In addition, we predicted that instantaneous sampling would underestimate how often cows engaged in behaviors that they frequently performed in short bouts or with short intervals between bouts, as some of these events may occur between sample intervals. Continuous video observations of 18 lactating Holstein-Friesian dairy cows were conducted for 48-h periods. Instantaneous samples (1 and 30 s, and 1, 3, 5, 10, 15, and 30 min) were generated from continuous data, with the samples recorded at 1-s intervals representing true values. Estimates from each sample interval ≥30 s were compared pairwise to true values with regression analysis. Sample intervals were considered accurate if they met 3 criteria: coefficient of determination ≥0.9 (i.e., strongly related to true values), slope=1, and intercept=0 (i.e., did not over- or underestimate true values). The amount of time cows spent lying (12.1±1.8h/24h, mean ± standard deviation) or visiting the water trough (1.1±0.8h/24h) and feed bunk (5.6±0.8h/24h) were accurately captured using sample intervals ≤30, 10, and 5 min, respectively. In addition, sample intervals ≤3 min accurately estimated the number of lying bouts (10.3±2.4 per 24h), likely because cows were recumbent for long periods (74.0±17.4 min, on average, with <6% of bouts lasting <5 min) and rarely resumed lying soon after standing up (0.4% of intervals between lying bouts were <30 s). However, shorter sample intervals may be needed in situations where cows more frequently transition between lying and standing. In contrast to lying in this study, cows visited the water trough and feed bunk for shorter periods (3.5±1.7 and 25.6±5.8 min, respectively) and frequently returned to these resources soon after leaving (17 and 7% of intervals between visits were <30 s long). As some of these events likely occurred between sample intervals, all sample intervals ≥30 s underestimated the number of times cows visited the water trough and feed bunk (18.5±6.2 and 14.1±4.4 per 24h, respectively). Therefore, continuous observation is needed to determine how often cows visit these resources.

Cooling cows efficiently with water spray: Behavioral, physiological, and production responses to sprinklers at the feed bunk.

Dairies commonly mount nozzles above the feed bunk that intermittently spray cows to dissipate heat. These sprinklers use potable water-an increasingly scarce resource-but there is little experimental evidence for how much is needed to cool cows in loose housing. Sprinkler flow rate may affect the efficacy of heat abatement, cattle avoidance of spray (particularly on the head), and water waste. Our objectives were to determine how sprinkler flow rate affects cattle behavioral, physiological, and production responses when cows are given 24-h access to spray in freestall housing, and to evaluate heat abatement in relation to water use. We compared 3 treatments: sprinklers that delivered 1.3 or 4.9L/min (both 3min on and 9min off, 24h/d) and an unsprayed control. Nine pairs of high-producing lactating Holstein cows received each treatment at a shaded feed bunk for 2d in a replicated 3×3 Latin square design [air temperature (T): 24-h maximum=33±3°C, mean ± SD]. Cows spent 5.8±0.9h/24h (mean ± SD) at the feed bunk overall, regardless of treatment. With few exceptions, cows responded similarly to the 1.3 and 4.9L/min flow rates. Sprinklers resulted in visits to the feed bunk that were on average 23 to 27% longer and 13 to 16% less frequent compared with the control, perhaps because cows avoided walking through spray. Indeed, when the sprinklers were on, cows left the feed bunk half as often as expected by chance, and when cows chose to walk through spray, they lowered their heads on average 1.7- to 3-fold more often than in the control. Despite possible reluctance to expose their heads to spray, cows did not avoid sprinklers overall. In warmer weather, cows spent more time at the feed bunk when it had sprinklers (on average 19 to 21min/24h for each 1°C increase in T), likely for heat abatement benefits. Compared with the control, sprinklers resulted in 0.3 to 0.7°C lower body temperature from 1300 to 1500h and 1700 to 2000h overall and attenuated the rise in this measure on warmer days (for each 10°C increase in T, body temperature increased by on average 0.5 to 0.7°C with sprinklers vs. 1.6°C without). Sprinkler access also resulted in milk yield that was, on average, 3.3 to 3.7kg/24h higher than in the control treatment. In this hot and dry climate, 1.3L/min cooled cows more efficiently than 4.9L/min, as the lower flow rate achieved equivalent reduction in body temperature and increase in milk yield relative to no spray, despite using 73% less water.

Cooling cows efficiently with sprinklers: Physiological responses to water spray.

Dairies in the United States commonly cool cattle with sprinklers mounted over the feed bunk that intermittently spray the cows' backs. These systems use potable water-an increasingly scarce resource--but there is little experimental evidence about how much is needed to cool cows or about droplet size, which is thought to affect hair coat penetration. Our objectives were to determine how sprinkler flow rate and droplet size affect physiological measures of heat load in a hot, dry climate, and to evaluate cooling effectiveness against water use. The treatments were an unsprayed control and 6 soaker nozzles that delivered four 3-min spray applications of 0.4, 1.3, or ≥ 4.5 L/min (with 2 droplet sizes within each flow rate) and resulting in 30 to 47% of spray directly wetting each cow. Data were collected from high-producing lactating Holsteins (n = 19) tested individually in ambient conditions (air temperature = 31.2 ± 3.8°C, mean ± standard deviation). Cows were restrained in headlocks for 1h and received 1 treatment/d for 3d each, with order of exposure balanced in a crossover design. When cows were not sprayed, physiological measures of heat load increased during the 1-h treatment. All measures responded rapidly to spray: skin temperature decreased during the first water application, and respiration rate and body temperature did so before the second. Droplet size had no effect on cooling, but flow rate affected several measures. At the end of 1h, 0.4 L/min resulted in lower respiration rate and skin temperature on directly sprayed body parts relative to the control but not baseline values, and body temperature increased to 0.2°C above baseline. When 1.3 or ≥ 4.5 L/min was applied, respiration rate was lower than the control and decreased relative to baseline, and body temperature stayed below baseline for at least 30 min after treatment ended. The treatment that best balanced cooling effectiveness against water usage was 1.3 L/min: although ≥ 4.5 L/min reduced respiration rate relative to baseline by 4 more breaths/min than 1.3 L/min did (-13 vs. -9 breaths/min, respectively), each additional liter of water decreased this measure by only ≤ 0.1 breaths/min (≤ 1% of the total reduction achieved using 1.3 L/min). We found similar water efficiency patterns for skin temperature and the amount of time that body temperature remained below baseline after treatment ended. Thus, when using this intermittent spray schedule in a hot, dry climate, applying at least 1.3 L/min improved cooling, but above this, additional physiological benefits were relatively minor.

Effects of space allowance on the behavior and physiology of cattle temporarily managed on rubber mats.

Dairy cattle managed in some pasture-based systems, such as in New Zealand, are predominantly kept outdoors all year around but are taken off pasture for periods, especially in wet weather to avoid soil damage. The use of rubber matting for such stand-off practices is becoming more common to improve animal welfare, and our objective was to investigate the effects of different space allowances on cow behavior and physiology when managed temporarily on rubber mats during a weather-induced stand-off period. Thirty pregnant, nonlactating Holstein-Friesian dairy cows were divided into 6 groups of 5 and exposed to 6 treatments following a Williams designed 6×6 Latin square. The treatments consisted of 6 space allowances on a 24-mm rubber surface during a simulated weather-induced stand-off period: 3.0, 4.5, 6.0, 7.5, 9.0, and 10.5 m(2)/cow. The stand-off period consisted of 18 h in the treatment pens followed by 6 h at pasture to allow for their daily feed intake (no feed was available during stand-off, following normal farm practice), for 3 consecutive days, with 6 d of recovery on pasture between treatments. When cows had more space available during the stand-off period, they spent more time lying on the rubber mats and less time lying on pasture during their daily 6-h feed break. Mean lying times (24 h, pasture and rubber mats combined) for the different space allowances were for 3.0 m(2)=7.5 h, 4.5 m(2)=10.2 h, 6.0 m(2)=11.9 h, 7.5 m(2)=12.4 h, and 10.5 m(2)=13.8 h. At 6.0 m(2) of space allowance per cow, the animals spent similar times lying per 24 h as when the cows were on recovery on pasture in between treatments (11.9 and 11.2 h, respectively). Aggressive interactions and nonaggressive lying disturbances were more frequent at lower space allowances (aggressive interactions decreased by 35% from 3.0 to 4.5 m(2)/cow, with a slower decline thereafter). Cows were dirtier after the stand-off period, particularly at lower space allowances. All cows had higher gait scores after the stand-off period; however, this change was unaffected by space allowance and very minor. Stride length, plasma cortisol, and body weight were all unaffected by the stand-off period and space allowance. The results suggest that to reduce aggressive behavior and maintain adequate lying times, dairy cattle managed temporarily on rubber matting for up to 18 h per day, without feed, should have a space allowance of at least 4.5 to 6.0 m(2) per cow.

Dairy cows use and prefer feed bunks fitted with sprinklers.

Sprinklers reduce heat load in cattle, but elicit variable behavioral responses: cows readily use water in some studies, but in others either avoid it or show no preference. Nevertheless, on US dairies, a common way to cool cows is with nozzles mounted over the feed bunk that intermittently spray (i.e., 5 min on, 10 min off, as in this study) animals' backs while they feed. The objectives of this study were to determine how this type of sprinkler system affects behavior (single-treatment phase), and to assess preferences when cows were allowed to choose between feed bunks with or without sprinklers (choice phase). Data were collected 24h/d for lactating Holsteins tested in groups of 3 cows (n=8 groups) in warm ambient conditions [air temperature (mean ± standard deviation): 24-h average=24.5±2.5°C, maximum=36.0±3.5°C]. In the single-treatment phase, cows were fed from shaded bunks with or without sprinklers for 2 d/treatment, with order of exposure balanced in a crossover design. When sprinklers were present, cows spent more time at the bunk, both feeding [sprinkler vs. no sprinkler: 3.5 vs. 2.5h/24h, standard error (SE)=0.12h] and standing without feeding (4.3 vs. 2.3h/24h, SE=0.32 h) than when no sprinklers were present. Sprinklers lowered the average 24-h core temperature (38.8 vs. 39.2°C, SE=0.08°C), particularly on warmer days. Water cooling also mitigated the effects of weather on feeding time, which decreased with increasing heat load (air temperature and temperature-humidity index) when cows did not have sprinklers, but was unchanged when sprinklers were provided. In the choice phase, feed was provided ad libitum in both treatments for 5 d and preference was assessed. All groups preferred the feed bunk with sprinklers (78 vs. 22% of time spent near both feed bunks, SE=3.9%), and the magnitude of this preference increased linearly with heat load. In both phases of the study, cows protected their heads from direct spray when head position was elective (i.e., standing without feeding): cows were more likely to put their heads through the head gates when the sprinklers were on than off (single-treatment phase: 78 vs. 59%, respectively, of time spent standing without feeding, SE=2.8%; choice phase: 71 vs. 52%, SE=2.0%). In conclusion, although cows avoided wetting their heads, this is the first study to demonstrate that cattle readily use and clearly prefer sprinklers mounted above the feed bunk, possibly due to the cooling provided by this resource.

Chicken genomics: feather-pecking and victim pigmentation.

Feather-pecking in domestic birds is associated with cannibalism and severe welfare problems. It is a dramatic example of a spiteful behaviour in which the victim's fitness is reduced for no immediate direct benefit to the perpetrator and its evolution is unexplained. Here we show that the plumage pigmentation of a chicken may predispose it to become a victim: birds suffer more drastic feather-pecking when the colour of their plumage is due to the expression of a wild recessive allele at PMEL17, a gene that controls plumage melanization, and when these birds are relatively common in a flock. These findings, obtained using an intercross between a domestic fowl and its wild ancestor, have implications for the welfare of domestic species and offer insight into the genetic changes associated with the evolution of feather-pecking during the early stages of domestication.

The genetic architecture of a female sexual ornament.

Understanding the evolution of sexual ornaments, and particularly that of female sexual ornaments, is an enduring challenge in evolutionary biology. Key to this challenge are establishing the relationship between ornament expression and female reproductive investment, and determining the genetic basis underpinning such relationship. Advances in genomics provide unprecedented opportunities to study the genetic architecture of sexual ornaments in model species. Here, we present a quantitative trait locus (QTL) analysis of a female sexual ornament, the comb of the fowl, Gallus gallus, using a large-scale intercross between red junglefowl and a domestic line, selected for egg production. First, we demonstrate that female somatic investment in comb reflects female reproductive investment. Despite a trade-off between reproductive and skeletal investment mediated by the mobilization of skeletal minerals for egg production, females with proportionally large combs also had relatively high skeletal investment. Second, we identify a major QTL for bisexual expression of comb mass and several QTL specific to female comb mass. Importantly, QTL for comb mass were nonrandomly clustered with QTL for female reproductive and skeletal investment on chromosomes one and three. Together, these results shed light onto the physiological and genetic architecture of a female ornament.

Quantitative trait loci for BMD and bone strength in an intercross between domestic and wildtype chickens.

UNLABELLED: With chicken used as a model species, we used QTL analysis to examine the genetic contribution to bone traits. We report the identification of four QTLs for femoral traits: one for bone strength, one for endosteal circumference, and two affecting mineral density of noncortical bone. INTRODUCTION: BMD is a highly heritable phenotype, governed by elements at numerous loci. In studies examining the genetic contribution to bone traits, many loci have been identified in humans and in other species. The goal of this study was to identify quantitative trait loci (QTLs) controlling BMD and bone strength in an intercross between wildtype and domestic chickens. MATERIALS AND METHODS: A set of 164 markers, covering 30 chromosomes (chr.), were used to genotype 337 F2-individuals from an intercross of domesticated white Leghorn and wildtype red junglefowl chicken. DXA and pQCT were used to measure BMD and bone structure. Three-point bending tests and torsional strength tests were performed to determine the biomechanical strength of the bone. QTLs were mapped using forward selection for loci with significant marginal effects. RESULTS: Four QTLs for femoral bone traits were identified in QTL analysis with body weight included as a covariate. A QTL on chr. 1 affected female noncortical BMD (LOD 4.6) and is syntenic to human 12q21-12q23. Also located on chr. 1, a locus with synteny to human 12q13-14 affected endosteal circumference (LOD 4.6). On chr. 2, a QTL corresponding to human 5p13-p15, 7p12, 18q12, 18q21, and 9q22-9q31 affected BMD in females; noncortical (LOD 4.0) and metaphyseal (LOD 7.0) BMD by pQCT and BMD by DXA (LOD 5.9). A QTL located on chr. 20 (LOD 5.2) affected bone biomechanical strength and had sex-dependent effects. In addition to the significant QTLs, 10 further loci with suggestive linkage to bone traits were identified. CONCLUSIONS: Four QTLs were identified: two for noncortical BMD, one for endosteal circumference, and one affecting bone biomechanical strength. The future identification of genes responsible for these QTLs will increase the understanding of vertebrate skeletal biology.

The Dominant white, Dun and Smoky color variants in chicken are associated with insertion/deletion polymorphisms in the PMEL17 gene.

Dominant white, Dun, and Smoky are alleles at the Dominant white locus, which is one of the major loci affecting plumage color in the domestic chicken. Both Dominant white and Dun inhibit the expression of black eumelanin. Smoky arose in a White Leghorn homozygous for Dominant white and partially restores pigmentation. PMEL17 encodes a melanocyte-specific protein and was identified as a positional candidate gene due to its role in the development of eumelanosomes. Linkage analysis of PMEL17 and Dominant white using a red jungle fowl/White Leghorn intercross revealed no recombination between these loci. Sequence analysis showed that the Dominant white allele was exclusively associated with a 9-bp insertion in exon 10, leading to an insertion of three amino acids in the PMEL17 transmembrane region. Similarly, a deletion of five amino acids in the transmembrane region occurs in the protein encoded by Dun. The Smoky allele shared the 9-bp insertion in exon 10 with Dominant white, as expected from its origin, but also had a deletion of 12 nucleotides in exon 6, eliminating four amino acids from the mature protein. These mutations are, together with the recessive silver mutation in the mouse, the only PMEL17 mutations with phenotypic effects that have been described so far in any species.

QTL analysis of a red junglefowl x White Leghorn intercross reveals trade-off in resource allocation between behavior and production traits.

Behaviors with high energetic costs may decrease in frequency in domestic animals as a response to selection for increased production. The aim of this study was to quantify production traits, foraging behavior, and social motivation in F2 progeny from a White Leghorn x red junglefowl intercross (n = 751-1046) and to perform QTL analyses on the behavioral traits. A foraging-social maze was used for behavioral testing, which consisted of four identical arms and a central box. In two arms there was ad libitum access to the birds' usual food, and in the other two there was novel food (sunflower seeds) mixed with cat litter. In one arm with each of the two food sources, social stimuli were simulated by the presence of a mirror. Each bird could therefore feed on novel or well known food either alone or in the perceived company of a conspecific. Egg production, sexual maturity (females), food intake, and growth were measured individually, and residual food intake and metabolic body weight were estimated using standard methods. A genome scan using 104 microsatellite markers was carried out to identify QTLs affecting behavioral traits. Phenotypic growth rates at different ages showed weak associations in both sexes. Sexual maturity and egg weight were not strongly correlated to growth, indicating that these traits are not genetically linked. Time spent in each arm and in the central part of the maze was analyzed using principal component analyses. Four principal components (PC) were extracted, each reflecting a pattern of behavior in the maze. Females with early onset of sexual maturity scored higher on the PC1 reflecting preference for free food without social stimuli, and females with higher egg production scored higher on the PC2 reflecting exploration. Males with an overall higher growth rate and higher residual food intake scored higher on the PC3, which possibly reflected fear of the test situation, and tended to score higher on the PC4 reflecting low contrafreeloading. Significant QTLs were found for PC1 and PC4 scores on chromosomes 27 and 7, respectively. The location of the QTLs coincided with known QTLs for growth rate and body weight. The results suggest a trade-off between energy-demanding behavior and high production and that some of this may be caused by genetic linkage or pleiotropic gene effects.

A global search reveals epistatic interaction between QTL for early growth in the chicken.

We have identified quantitative trait loci (QTL) explaining a large proportion of the variation in body weights at different ages and growth between chronological ages in an F(2) intercross between red junglefowl and White Leghorn chickens. QTL were mapped using forward selection for loci with significant marginal genetic effects and with a simultaneous search for epistatic QTL pairs. We found 22 significant loci contributing to these traits, nine of these were only found by the simultaneous two-dimensional search, which demonstrates the power of this approach for detecting loci affecting complex traits. We have also estimated the relative contribution of additive, dominance, and epistasis effects to growth and the contribution of epistasis was more pronounced prior to 46 days of age, whereas additive genetic effects explained the major portion of the genetic variance later in life. Several of the detected loci affected either early or late growth but not both. Very few loci affected the entire growth process, which points out that early and late growth, at least to some extent, have different genetic regulation.

Major growth QTLs in fowl are related to fearful behavior: possible genetic links between fear responses and production traits in a red junglefowl x white leghorn intercross.

The aim of this work was to study fear responses and their relation to production traits in red junglefowl ( Gallus gallus spp.), White Leghorn ( Gallus domesticus ), and their F2-progeny. Quantitative trait locus (QTL) analyses were performed for behavioral traits to gain information about possible genetic links between fear-related behaviors and production. Four behavioral tests were performed that induce different levels of acute fear (open field [OF], exposure to a novel object, tonic immobility, and restraint). Production traits, that is, egg production, sexual maturity (in females), food intake, and growth, were measured individually. A genome scan using 105 microsatellite markers was carried out to identify QTLs controlling the traits studied. In the OF and novel object tests (NO), Leghorns showed less fear behavior than junglefowl, whereas junglefowl behaved less fearfully in the tonic immobility test (TI) and were more active in the restraint test. In the F2 progeny, only weak phenotypic associations were found between production traits and fear behavior. A significant QTL for TI duration was found on chromosome 1 that coincided with a QTL for egg weight and growth in the same animals. Another QTL for NO in males coincided with another major growth QTL. These two known growth QTLs affected a wide range of reactions in different tests. Several other significant and suggestive QTLs for behavioral traits related to fear were found. These QTLs did not coincide with QTLs for production traits, indicating that these fear variables may not be genetically linked to the production traits we measured here. The results show that loci affecting important production traits are located in the same chromosomal region as loci affecting different fear-related behaviors.