RESUMEN
Cold and heat stress present welfare challenges for dairy calves. The consequences of thermal stress on biological functioning have been well documented, and many housing and management strategies have been evaluated to mitigate those detrimental impacts. In cold weather, mitigation strategies have largely focused on nutritional interventions or limiting heat loss with resources such as bedding or jackets. In hot weather, heat abatement strategies such as supplemental shade, increased environmental air exchange through passive ventilation, and forced air movement through mechanical ventilation have been evaluated. Recently in Wisconsin's continental climate, our group evaluated how 2 aspects of calf welfare-the needs for thermal comfort and social contact (i.e., pair or group housing vs. individual housing)-may align or conflict in winter and summer, respectively. In both seasons, calves pair-housed in outdoor hutches preferred social proximity. When 2 calves shared a hutch, the heat load was greater than for a single calf, which may be beneficial for thermal comfort in winter. In summer, the potential detriments from the additional heat load of 2 calves was mitigated with passive hutch ventilation, which calves preferred. Nonetheless, knowledge gaps remain regarding the impacts of thermal stress on calves' affective states, and much remains unknown about their preferences and motivations for specific thermal stress mitigation resources. Future research to address these gaps could improve our understanding of calf welfare and inform best practices for calf management.
RESUMEN
Cold stress negatively affects the welfare of calves in outdoor hutches. No studies have examined the potential benefits of pair housing calves to buffer against cold stress. Our study evaluated the effects of pair versus individual housing on thermoregulatory, behavioral, and growth performance responses of calves in outdoor hutches during a Wisconsin continental winter. Forty-eight Holstein-Friesian heifer calves were enrolled into 1 of 2 housing treatments: individually (n = 16 calves) or pair housed (n = 16 pairs; 32 calves). Calves were fed milk twice daily, with ad libitum access to starter and water. Step-down weaning began on d 42 of life, and all milk was removed on d 54. Data collection continued through d 59. Calves were restricted inside a hutch (pair-housed calves in the same hutch) for 1 h during wk 4, 6, and 9 of life; internal hutch air temperature (T) was recorded with data loggers, and rectal temperature (RT) was recorded outside the hutch before and after restriction. On the subsequent 3 d in those weeks, calves' locations (outside or inside a hutch) were recorded at 15-min intervals using time-lapse cameras. Linear mixed models (change in T and RT after 1 h) and generalized linear mixed models with a ß distribution (proportion of time spent inside hutches) were used to evaluate the fixed effects of housing treatment, week of life, and their interaction. For pair-housed calves, preference to be together was evaluated using one-sample t-tests comparing the proportion of time they were observed in the same location against 50% (chance, no preference), separately for each week of life. Predicted dry matter intake (DMI) of starter and body weight (BW) were standardized by day of life using regression models and used to calculate average daily gain (ADG) and feed conversion ratio (FCR; DMI of starter/ADG). Linear mixed models were constructed for each measure, separately for the preweaning, weaning, and postweaning periods, with a fixed effect of housing treatment; the models for BW included birth weight as a covariate. All mixed models included a random term for housing unit (individual or pair of calves) nested within treatment. Hutch T increased more after 1 h with pair-housed calves inside than with those housed individually (+2.3 vs. 1.4°C, respectively; standard error of the mean = 0.26°C). However, no treatment differences were detected in RT. Individually housed calves spent more time inside the hutches than pair-housed ones (93.9 vs. 90.7% of total time, respectively; standard error of the mean = 0.8%), and the latter chose to be together most of the time, regardless of location (90.0 ± 1.3%, 88.6 ± 1.2%, and 79.4 ± 4.2% in wk 4, 6, and 9 of life, respectively). After weaning, there was some evidence suggesting that pair-housed calves had greater starter DMI than those housed individually. No effects of housing type were found on FCR, BW, or ADG. Our study is the first to explicitly examine the potential benefits of pair housing for alleviating cold stress in outdoor-housed dairy calves, and we found limited evidence in support of our hypotheses.
Asunto(s)
Conducta Animal , Vivienda para Animales , Animales , Bovinos , Femenino , Destete , Conducta Animal/fisiología , Regulación de la Temperatura Corporal , Leche , Alimentación Animal , Dieta , Peso CorporalRESUMEN
Dairy calves are social creatures who are highly motivated for access to a companion. Additionally, heat stress negatively affects the welfare and productivity of calves housed in outdoor hutches. However, no studies have examined the potential tradeoffs pair-housed calves face between competing motivations for social contact and thermal comfort. We evaluated the effects of hutch ventilation on thermoregulatory and behavioral responses of pair-housed calves in outdoor hutches during a Wisconsin summer. Fifty Holstein-Friesian heifer calves were pair-housed (n = 25 pairs) in adjacent hutches with a shared outdoor area. In each pair of hutches, 1 was ventilated (V) with 2 windows at the rear base and the rear bedding door propped open; the other had no rear windows and a closed bedding door (nonventilated, NV). Calves were exposed to 4 conditions for 1 h each (1100-1200 h and 1230-1330 h on 2 consecutive days during wk 4, 6, and 9 of life) in a 2 × 2 factorial design in a balanced order: individually or in pairs in the NV or V hutch. Immediately before and after the 1 h hutch restriction period, respiration rate (RR) and rectal temperature (RT) were recorded while calves were outside. On the subsequent 3 d in those weeks, the locations of each calf (outdoors or inside a hutch) were recorded at 15-min intervals using time-lapse cameras. Linear mixed models were used to evaluate the fixed effects of ventilation, number of calves inside the hutch, week of life, and their interactions, on change in temperature-humidity index (THI), RR, and RT after 1 h; pair of calves was the subject of the repeated statement. Within weeks, the proportion of time calves spent in each hutch and together were averaged across the 3 d of observation. One-sample t-tests were used to evaluate preferences compared with 50% (chance, no preference): (1) for the V (vs. NV) hutch and (2) to be together (or separate) in either the V or NV hutch as well as overall. The THI gain inside the V hutch after 1 h with calves present was lower relative to the NV hutch (0.90 vs. 1.79 units, respectively, standard error of the mean [SEM] = 0.16). Calves in wk 9 of life increased the hutch THI more than in wk 6 of life (1.81 vs. 0.72 units respectively, SEM = 0.16). After 1 h, RR decreased versus was unchanged, respectively, when calves were in the V versus NV hutch (-14.4 vs. -0.9 breaths/min, respectively, SEM = 1.4 breaths/min). No differences were detected in RT. Calves chose to be together most of the time regardless of location (wk 4, 6, and 9, respectively: 83.1% ± 2.4%, 80.3% ± 2.1%, and 78.0% ± 3.1%). Calves had no hutch preference during wk 4 but developed a preference for the V hutch as they aged (wk 4, 6, and 9, respectively: 47.3% ± 4.5%, 61.2% ± 5.1%, and 72.8% ± 4.3%). This is the first study to demonstrate passive ventilation improves animal welfare by reducing heat stress in pair-housed dairy calves in outdoor hutches.
Asunto(s)
Vivienda para Animales , Respiración , Animales , Bovinos , Femenino , Ambiente , Ventilación , TemperaturaRESUMEN
Heat abatement (e.g., soakers, fans) effectively reduces the negative physiological and production effects of heat stress, but no previous studies have documented effective interventions for the reduced lying times observed in response to hot weather. Although likely adaptive for heat dissipation, the reduction in motivated lying behavior may be an animal welfare concern. We evaluated the effect of air speed from fans with variable frequency drives on the heat stress responses of cows in a naturally ventilated freestall barn. Eight groups of lactating Holsteins (16 cows/group) were exposed to 3 treatments in a replicated crossover design: control (fans off, 0.4 ± 0.2 m/s, measured 0.5 m above the stall surface to represent cow resting height) versus 60% (1.7 ± 0.5 m/s; ≥1 m/s in all stalls) and 100% (2.4 ± 0.8 m/s) fan power. Each treatment was applied for 3 d of acclimation and 4 d of data collection. The effects of treatment on daily maximum vaginal temperature (VT) and lying time (LT; both measured with data loggers), respiration rate (RR; recorded from video), unshaved scapular skin temperature (ST), milk yield (MY), and dry matter intake (DMI) were analyzed using linear mixed models. All models included the fixed effect of treatment and a repeated term for treatment day within group of cows, with group as the subject. The models for LT, VT, and RR also included a fixed effect for same-day temperature-humidity index (THI; recorded in the pens with data loggers) and the THI × treatment interaction. The models for DMI and MY, using data from the latter 3 d of each treatment period, also included a fixed effect for the previous day's THI and the -1 d THI × treatment interaction. Lying time differed among treatments (100% vs. 60% fan power vs. control: 14.2 vs. 13.9 vs. 13.2 h/d, respectively, SEM = 0.15 h/d), but both fan treatments prevented the reduction in LT observed in the control treatment as THI increased. Relative to the control, both fan treatments effectively reduced ST, RR, and VT and increased DMI and MY. In the control, average values were elevated for both RR (68.7 ± 1.5 breaths/min, mean ± SEM, greater than a common benchmark of 60 breaths/min) and VT (39.3 ± 0.05°C) but remained in the normal range in both fan treatments (54.2 vs. 50.7 breaths/min in the 60% vs. 100% fan power treatments; 39.0°C in both fan treatments). Both fan treatments resulted in greater overall MY (42.6 vs. 43.0 ± 0.4 kg/d in the 60% vs. 100% fan power treatments) relative to the control (41.0 kg/d) and similarly avoided the reduction in MY when -1 d THI increased. Compared with natural ventilation alone, fans delivering air speeds of at least 1 m/s at cow resting height were effective not only for reducing thermoregulatory responses, but also for maintaining lying time, DMI, and MY in heat stress conditions. This is the first study to demonstrate an intervention to improve animal welfare by maintaining lying times during periods of heat stress.
Asunto(s)
Enfermedades de los Bovinos , Trastornos de Estrés por Calor , Animales , Bovinos , Femenino , Trastornos de Estrés por Calor/prevención & control , Trastornos de Estrés por Calor/veterinaria , Respuesta al Choque Térmico , Calor , Humedad , Lactancia/fisiología , Leche , Temperatura , Wisconsin , Estudios CruzadosRESUMEN
Social housing of preweaned calves can benefit their welfare, but housing and cross sucking are potential barriers to adoption for farmers. For farms using outdoor hutches, an option is to pair adjacent hutches with a shared fence. Our objective was to investigate milk- or starter-feeding strategies to mitigate cross sucking in this system. Holstein heifers were housed in pairs (n = 32 pairs) and divided into 4 treatments (n = 8 pairs each) in a 2 × 2 factorial design: milk in an open bucket with starter in only a bucket (OB-SB), milk in an open bucket and starter in both a bucket and a specialized teat bottle (Braden bottle; OB-BB), milk in a slow-flow teat bucket with starter in only a bucket (TB-SB), or milk in a slow-flow teat bucket and starter in both a bucket and a specialized teat bottle (TB-BB). When starter was first offered (d 6 ± 1 of life, mean ± SD), calf latency to approach was recorded, averaged within pairs, and compared between starter treatments using a linear mixed model with fixed effect of treatment and random effect of pair within treatment. Calves were initially bottle fed; milk treatments began on d 14 ± 1 of life and ended when calves were completely weaned (d 53 ± 1). Calves were observed for behaviors such as drinking milk and cross sucking twice weekly for 30 min during the afternoon milk meal using continuous video, with values averaged within pairs. Linear mixed models were run separately before (wk 3-6) and after (wk 7-8) weaning, with fixed effects of milk- and starter-feeding treatments, week, and the 2- and 3-way interactions, with week as repeated measure and pair as subject. Pairs with Braden bottles and buckets approached starter sooner than those with only buckets (Braden bottles vs. no Braden bottles: 13.1 ± 6.1 vs. 33.2 ± 6.1 min, LSM ± SEM). Before weaning, pairs with open buckets for both milk and starter cross sucked for at least twice as long (OB-SB: 2.9 ± 0.3 min) as all other treatments (OB-BB: 1.5 ± 0.3 min; TB-SB: 0.4 ± 0.3 min; TB-BB: 0.5 ± 0.3 min). This pattern held during weaning, when cross sucking increased overall (OB-SB: 3.9 ± 0.4 min; OB-BB: 1.8 ± 0.4 min; TB-SB: 0.9 ± 0.4 min; TB-BB: 1.6 ± 0.4 min). Regardless of starter treatment, calves spent less time cross sucking when fed milk in teat buckets, which extended the milk meal relative to open buckets (teat bucket vs. open bucket: preweaning = 7.0 ± 0.2 vs. 1.6 ± 0.2 min; weaning = 3.0 ± 0.1 vs. 0.6 ± 0.1 min). When calves are fed milk in open buckets, a novel option for reducing cross sucking is to provide starter through a specialized bottle. Nonetheless, providing milk in slow-flow teat buckets had the greatest effect on reducing cross sucking by directing suckling to the teat instead of another calf or pen objects.