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Effect of time of day, ambient temperature, and relative humidity on feeding behavior of growing meat goats

T. A. Gipson, L. J. Dawson, S. P. Hart, and T. Sahlu

Proceedings of the 9th International Conference on Goats. Page 186-187. International Goat Association. 2008

Heat stress decreases feed intake in livestock. However, little information on feeding behavior and heat stress is known in goats. The objective of this research was to examine the effects of time of day and heat stress on feeding behavior in growing meat bucks. In a 12-wk buck performance test, feed intake of 55 bucks (27 in 2005 and 28 in 2006) was recorded using a completely automated electronic feeding system, which records feed intake of each individual animalís visit. Dry matter intake (DMI), feeding duration (DUR), and consumption rate (RATE) were calculated for daytime (06:00 to 18:00 h) and nighttime (18:00 to 06:00 h) feeding behavior. Relative humidity and ambient temperature were recorded every 10 min and an average temperature-humidity index (THI) calculated for the corresponding period. Heat stress was classified according to THI; NO stress (THI < 72), MILD stress (72 < THI < 78), and SEVERE stress (79 < THI < 89). A repeated measures design using mixed model methodology was employed to analyze feeding behavior. DMI, DUR, and RATE were dependent variables. Independent variables included year (2005 or 2006), time of day (day or night), and heat stress level (NO, MILD, or SEVERE) as classification variables and the linear and quadratic effects of age in days. Night DMI was less (P<0.05) than day DMI (528g vs. 700g) and NO was greater (P<.05) than MILD or SEVERE (650g vs. 591 and 602 g, respectively). DMI during night was 558, 507, and 520 g and during day was 742, 676, and 684 for NO, MILD, and SEVERE, respectively. DUR was less (P<0.05) during night than day (29 min vs. 41 min) and greater (P<0.05) for NO than for MILD or SEVERE (37 min vs. 35 and 35, respectively). DUR at night was 32, 28, and 29 min and during day was 42, 41, and 41 min for NO, MILD, and SEVERE, respectively. RATE (20 g/min) was not affected (P>0.05) by time of day or stress level. Generally, time of day and heat stress level significantly affected the feeding behavior of growing meat bucks.


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