Effects of tethering on forage selection, intake, and digestibility, grazing behavior, and energy expenditure by Boer x Spanish goats grazing high quality forage
Patra, A. K., R. Puchala, G. Detweiler, L. J. Dawson, T. Sahlu, and A. L. GoetschJournal of Animal Science 86:1245-1253. 2008
Twenty-four yearling Boer x Spanish goats were used in a crossover experiment to determine effects of tethering on herbage selection, intake, and digestibility, grazing behavior, and energy expenditure (EE) with high quality herbage. Four 0.72-ha paddocks of wheat (Triticum aestivum) and berseem clover (Trifolium alexandrium) were grazed in the spring. Each paddock hosted 6 animals, 3 with free movement and 3 attached to a 3-m tether for access to an area of 28.3 m2 that was moved daily. One animal of each treatment and paddock was used to determine herbage selection, fecal output, or grazing behavior and EE. Herbage DM mass in tethered areas before grazing averaged 2,649 and 2,981 kg/ha in Periods 1 and 2, respectively. The CP concentration in ingesta was greater (P < 0.05; 23.1 and 20.3 ± 0.82%) for free vs tethered animals, although in vitro true DM digestion (75.7 and 76.5 ± 1.20%) did not differ (P > 0.05) between treatments. Intake of ME based on in vitro true DM digestion and fecal output was greater (P < 0.05) for free vs tethered animals (12.7 and 10.4 ± 0.89 MJ/d). No treatment effects were observed (P > 0.05) on time spent ruminating or grazing (405 and 366 ± 42.5 min/d, respectively), although mean EE was greater (P < 0.05) for free vs tethered animals (633 and 512 ± 27.4 kJ/kg BW0.75 for free and tethered, respectively), with differences (P < 0.05) between treatments at each hour of the day. Tethering animals may be acceptable to model ones with free movement for some measures such as ingesta composition but appears inappropriate for others, such as energy metabolism.
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