| Abstrakt: |
The objective of this study was to evaluate the effects of daily weather parameters on feed intake in developing beef bulls. Weaned Angus bulls (n= 12; initial BW = 255.6 ± 5.6 kg) were acclimated to consuming a grain-based diet in a GrowSafe Model 6000 feed intake monitoring system in Prairie, MS. Then weather data were recorded each minute on-site by an automated system during a 70-d feeding period starting on May 16, 2016. Daily minimum and maximum temperature, relative humidity, and barometric pressure data were classified into LOW ( < −0.5 SD), MODERATE (−0.5 to 0.5 SD), and HIGH ( > 0.5 SD) levels. Precipitation data were classed as no rain or rain based on the presence or absence of daily precipitation. Data were evaluated using the PROC MIXED procedure of SAS specific for repeated measures with LSMEANS separation evaluated at a = 0.05. Daily feed intake was affected by the interaction of daily maximum temperature and maximum relative humidity (P< 0.01) such that, unexpectedly, bulls consumed 1.7 kg more feed at the HIGH levels of both maximum temperature ( > 34.2°C) and relative humidity ( > 98.1%) versus the LOW levels ( < 31.2°C and < 93.1%, respectively) of these variables. The interaction of daily minimum temperature and minimum humidity (P< 0.01) followed a similar feed intake pattern in which bulls consumed 1.3 kg more feed at the HIGH levels of both minimum temperature ( > 21.8°C) and relative humidity ( > 48.2%) as compared to the LOW levels ( < 18.8°C and < 38.8%, respectively) of these variables. Feed intake increased (P= 0.01) (9.4, 10.0, and 10.7 kg) as maximum barometric pressure level decreased, respectively, from > 765.7, 763.7 to 765.7, and < 763.7 mm Hg. Feed intake was comparable between the HIGH and MODERATE daily minimum barometric pressure levels but was 1.2 kg less (P< 0.01) at the LOW level ( < 760.5 mm Hg) relative to the HIGH ( > 762.5 mm Hg) and MODERATE (760.5 to 762.5 mm Hg) levels. On days when it rained, feed intake was depressed (P< 0.01) by 0.9 kg. These data suggest that environmental conditions contribute to daily feed intake fluctuations in growing cattle and that a combination of several weather parameters are involved in shifts in feeding behavior responses. |
