Abstract
<p>Heat stress in beef cattle is still one of the issues affecting animal performance in the beef cattle industry. Our objective was to evaluate the effect of two summer annual forages such as alyceclover (<em>Alysicarpus vaginalis</em> L.), and pearl millet (<em>Pennisetum glaucum</em>) with natural (trees) or artificial shade (80% shade) on grazing behavior and on reducing the heat load of crossbred yearling heifers. On three consecutive years from mid-July to mid-September, 36 (<em>Bos taurus</em> × <em>B. indicus</em>) heifers (body weight [BW] = 321±11.3 kg) were randomly allotted (n = 3) and continuously stocked in 12-1.33 ha paddocks in a 2 × 2 factorial arrangement of treatments (2 forage types and 2 shade types) with three replicates. Heifers grazing on alyceclover gained more (p = 0.03) than those grazing pearl millet (0.94 and 0.80 kg, respectively). Grazing behavior variables were not affected (p &gt; 0.05) by forage type and forage type x shade type interaction; however, shade type affected grazing and lying time (p &lt; 0.05). Time of day (TOD) affected (p &lt; 0.05) grazing and standing time, number of steps taken, respiration rate, and panting scores. These negative effects are related with the greatest temperature humidity index between 1100 and 1459 h. When data were analyzed by TOD, the negative effect on grazing behavior variables was not different for heifers with access to natural or artificial shades. Under the conditions of the present experiment, artificial shade provided protection for cattle. Grazing behavior parameters can be used to monitor heat load in grazing cattle.</p>
Highlights
Heat stress is a result of a negative balance between the net amount of energy flowing from the animal and the amount of heat energy produced and received by the animal, causing a greater accumulation of heat than cannot be dissipated
Ambient temperature determined under the artificial shades and trees with common outdoor digital thermometers indicated that, on average, there was a difference of approximately 1.7 oC more under the artificial shades at all times
Artificial shades that provided 80% interference promoted an acceptable environment for grazing cattle
Summary
Heat stress is a result of a negative balance between the net amount of energy flowing from the animal and the amount of heat energy produced and received by the animal, causing a greater accumulation of heat than cannot be dissipated Prolonged exposure to heat stress conditions in cattle reduces feed intake, growth, milk production, and reproductive efficiency (Hahn, 1985). Across the United States, heat stress results in estimated total annual economic losses of $370 million in the beef industry. Beef cattle farms around the country are affected by heat waves (CDFA, 2006; Drovers Cattle Network, 2011) or normal weather conditions (high temperature and humidity like in the Gulf Coast region) that can severely affect animal performance and the profitability of the farm. Cattle with access to shade have consistently shown a reduction in core body temperature and respiration rate, these positive effects are not always linked to improving performance (Mitloehner et al, 2001)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
