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1.
J Dairy Sci ; 106(12): 9552-9567, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37678773

RESUMO

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.


Assuntos
Doenças dos Bovinos , Transtornos de Estresse por Calor , Animais , Bovinos , Feminino , Transtornos de Estresse por Calor/prevenção & controle , Transtornos de Estresse por Calor/veterinária , Resposta ao Choque Térmico , Temperatura Alta , Umidade , Lactação/fisiologia , Leite , Temperatura , Wisconsin , Estudos Cross-Over
2.
Vet Clin North Am Food Anim Pract ; 35(1): 139-156, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30686460

RESUMO

Ventilation systems for adult dairy cattle can be divided into natural and mechanical systems. Mechanical systems include tunnel and cross ventilation. Hybrid systems incorporate both mechanical and natural ventilation design elements. All systems need to provide appropriate airspeeds at the stalls, adequate ventilation rates, and a methodology to operate year-round. Typically, mechanical ventilation systems cost double to operate compared with natural systems, and the differences between mechanical systems are modest. Selection of high-efficiency fans and regular maintenance are higher priorities for proper fan operation than the choice between ventilation systems, which can be herd size, location, and owner preference dependent.


Assuntos
Bovinos/fisiologia , Abrigo para Animais , Ventilação , Animais , Indústria de Laticínios/métodos , Feminino
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