RESUMO
Two trials (E1 and E2) were performed to assess the behavior of eight Holstein dairy cows with 367 ± 58 kg of body weight and 10.52 ± 0.08 kg of milk yield. A 4 × 4 Latin square design (four periods of lactation and four levels of solar blockage) with four paddocks was used. Each paddock contained a wood shading structure covered with a cloth that blocked 30% (T1), 50% (T2), 70% (T3), or 100% (T4) of direct solar radiation. In the first trial (E1) each shade structure was located approximately 40 m from the feeder and water troughs; in the second trial (E2), the distance was reduced to 5 m. Air temperature (TA, °C), relative humidity (RH, %), wind speed (U, ms-1), black globe temperature (TG, K), mean radiant temperature (TMR, K), radiant heat load (RHL, W m-2), and local shortwave radiation (RS, W m-2) were recorded at 15-min intervals from 08:00 to 17:00 h. Four behavioral activities were recorded: grazing, eating at the feed trough, ruminating, and idling. For each of these activities, animal posture (lying or upright) and location (under shade or exposed to sunlight) were recorded. The meteorological conditions showed similar variations from 8:00 to 17:00 h between the two trials. However, the air temperatures in E1 were lower (± 2 °C) than those in E2. In a PCA analysis, the first and the second principal components explained 56.87% and 21.85%, respectively, of the total variation in the behavioral variables. Under the E1 conditions, the animals did not seek shade, whereas in E2, the dairy cows spent 35 ± 5% of their time lying and idling in the shade. At a solar radiation blockage of 100%, cows were in the shade more than 60% of the time due to the intensity of solar radiation, which was 722.19 ± 14.59 W m-2 at 11:45. In a PCA analysis, the first and the second principal components explained 65.18 and 22.3%, respectively, and 87.48% together, of the total variation in the original variables. Consequently, it was possible to develop a shade index (IST) based on the first two components. In E1, animals spent very little time in the shade, spending only 0.15% of total time under the shade, irrespective of blockage. However, E2 cows used shade, reaching almost 80% of time under the shade, at midday, when the blockage was 100%.
Assuntos
Temperatura Corporal , Energia Solar , Animais , Comportamento Animal , Bovinos , Feminino , Temperatura Alta , Lactação , Luz SolarRESUMO
Freestall housing for dairy cows was created to reduce the amount of bedding and labor needed to keep stalls clean. However, some aspects of stall design may restrict stall usage by cows. The aim of this study was to assess dairy cow preference and usage of a conventional stall (with a neck rail and metal stall dividers) and an alternative stall design with no neck rail or stall dividers other than a wooden board protruding slightly (8cm) above the lying surface. In the no-choice phase of the study, 48 cows were randomly assigned to 8 groups (of 6 cows each); groups were alternately allocated to the 2 treatments. Each group was observed for 7 d on one treatment and then switched to the alternate treatment for 7 d. For the choice phase (also 7 d), groups in adjacent pens were merged (to form 4 groups, each with 12 cows) and cows had free access to both treatments within the merged pen. In the no-choice phase, cows spent more time standing with 4 hooves in the alternative versus conventional freestall (0.60±0.06 vs. 0.05±0.06h/d), but stall designs had no effect on time spent lying down (13.2±0.4 vs. 12.9±0.4h/d). In the choice phase, cows spent more time lying down in the conventional freestall (9.4±0.8 vs. 4.1±0.8h/d) and more time standing with all 4 hooves in the alternative stall (0.24±0.03 vs. 0.02±0.03h/d). These results illustrate how different stall design features can affect different types of stall use; the more open design facilitated standing fully in the stall, but the protruding partitions likely made the stall less suitable for lying.