Progress 01/01/04 to 12/31/05
Outputs
Three experiments were conducted, with results of the first addressed in the report for the preceding year. Two manuscripts have been submitted to a scientific journal and are currently being peer-reviewed. Twenty-four yearling Boer x Spanish goats were used in crossovers of experiments 2 and 3 to determine effects of tethering on forage selection, intake and digestibility, grazing behavior and energy expenditure (EE) with forage moderate to high in mass and high or low in nutritive value. In experiment 2, four 0.72-ha pastures of wheat (Triticum aestivum) and berseem clover (Trifolium alexandrium) were grazed in mid-spring. Each pasture hosted six animals, three with free movement and three 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 pasture was used to determine forage selection, fecal output or grazing behavior and EE. Mass of forage DM before grazing in Tethered areas averaged 2,649 and 2,981
kg/ha in periods 1 and 2, respectively. The CP concentration in ingesta was greater (231 and 203 g/kg; SE = 8.2) for Free vs Tethered animals; the level of NDF (540 and 559 g/kg; SE = 16.6) and in vitro true DM digestion (IVTDMD)(757 and 765 g/kg; SE = 12.0) were similar between treatments. Intake of ME was greater for Free vs Tethered animals (12.7 and 10.4 MJ/day; SE = 0.89), and there were small treatment differences in in vivo apparent digestibility of OM (0.717 and 0.723; SE = 0.0024) and NDF (0.633 and 0.652 for Free and Tethered, respectively; SE = 0.0092). There were no treatment effects on time spent ruminating or grazing (405 and 366 min/d; SE = 42.5), although EE was greater for Free vs Tethered animals (633 and 512 kJ/kg BW0.75 for Free and Tethered, respectively; SE = 27.4). The same goats when younger were used in experiment 3 with similar methods. Pastures consisted of wheat, rye (Secale cereale), vetch (Vicia sativa), ryegrass (Lolium multiflorum) and white clover
(Trifolium repens) and were grazed in late spring. Tethers were 4.11-m long for access to 53.1 m2, with tethered areas moved each day. Mass of forage DM throughout pastures averaged 1,550 and 1,734 kg/ha in periods 1 and 2, respectively. Treatment did not influence ingesta concentration of CP (157 and 141 g/kg; SE = 7.0) or NDF (521 and 543 g/kg; SE = 17.5) or IVTDMD (0.747 and 0.730 for Free and Tethered, respectively; SE = 0.0129). There was no treatment effect on time spent ruminating, but grazing time (444 vs 363 min/day; SE = 34.1) and EE were greater for Free vs Tethered animals (600 and 465 kJ/kg BW0.75; SE = 21.0). In conclusion, based on results of these experiments and the previous one, tethered animals to model ones with free movement may be acceptable for some measures such as ingesta composition but appears inappropriate for others, such as EE. Free grazing compared with tethering may impact EE in a manner not solely attributable to ME intake, distance traveled and(or)
grazing time, with impact throughout the day rather than only when grazing.
Impacts
These results will aid in future study of the behavior and physiology of grazing ruminants. For example, tethering may be used to model grazing ruminants with free movement for some measures such as ingesta composition but not for others such as energy metabolism. The finding that free grazing compared with tethering affects energy expenditure in a manner not solely attributable to energy intake, distance traveled and(or) grazing time, with influence throughout the day rather than only when grazing, suggests that detailed physiological measures of grazing ruminants can occur during periods of short-term restraint. This project and ensuing, facilitated research will lead to improved grazing management strategies for efficient utilization of forage resources.
Publications
- No publications reported this period
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Progress 01/01/05 to 12/31/05
Outputs
Twenty-four yearling Boer x Spanish goats were used to determine effects of tethering on forage selection, intake, and digestibility, grazing behavior, and energy expenditure with forage of high nutritive value and low to moderate mass. Four 0.72-ha pastures of wheat (Triticum aestivum) and berseem clover (Trifolium alexandrium) were grazed in December and January. Each pasture hosted six animals, three with free movement and three attached to a 4.11 m tether for access to a circular area of 53.1 m2. One animal of each treatment and pasture was used to determine forage selection, fecal output, or grazing behavior and energy expenditure (EE). Measures were in the second week of 2-week periods. Mass of forage DM before grazing in Tethered areas averaged 1280 and 1130 kg/ka in periods 1 and 2, respectively. The CP concentration in ingesta was greater ((P < 0.05) 23.9 and 20.9%; SE = 0.80) and the NDF level was lower (P < 0.05) for Free vs. Tethered animals (50.3 and
53.8%; SE = 1.20); in vitro true DM digestion was similar between treatments (80.8 and 80.7% for Free and Tethered, respectively; SE = 0.96). Intakes of DM (1013 and 968 g/day; SE = 78.6), NDF (511 and 521 g/day; SE = 39.9), and ME (10.9 and 10.7 MJ/day; SE = 0.90) were similar between treatments, but CP intake was greater (P < 0.05) for Free vs. Tethered animals (241 and 203 g/day; SE = 17.2). There were small treatment differences in in vivo apparent digestiiblity of OM ((P < 0.05); 78.0 and 81.4%; SE = 0.49), CP ((P < 0.05); 80.0 and 81.7%; SE = 0.67), and NDF ((P < 0.08) 77.7 and 76.0% for Free and Tethered, respectively; SE = 0.78). There were no treatment effects on time spent ruminating, idle, or eating (346 and 347 min/day for Free and Tethered, respectively; SE = 42.5). EE was considerably greater (P < 0.05) for Free vs. Tethered animals (571 and 489 kJ/kg BW0.75 for Free and Tethered, respectively; SE = 8.9). Based on estimates of ME intake and recovered energy and an
assumed efficiency of use of ME for energy accretion, this difference equated to an energy cost for free movement of 111 kJ/kg BW0.75. A greater distance traveled for Free than for Tethered goats presumably accounted for some but doubtfully all of this difference, suggesting that free movement influenced other physiological conditions impacting EE. In conclusion, tethering would seem to offer a production advantage over free grazing of less energy used for activity. Tethered ruminants may not be a perfect model for ones with free movement in all areas of study, but might be appropriate for some purposes given that potential differences are taken into account.
Impacts
If tethering adequately simulates grazing by free-moving, unrestrained ruminants, then more basic or fundamental experimental methodologies can be employed with grazing ruminants than possible with unrestrained animals. This project and ensuing, facilitated research will lead to improved grazing management strategies for efficient utilization of forage resources.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
Long-term goals of the research program that this project will initiate are to gain a thorough understanding of interactions between ruminant animal and herbage characteristics in nutrient utilization so as to optimize future grazing management strategies. The general supporting objective of the proposed project is to validate use of tethering to study responses of meat goats to grazing conditions. Specific objectives are to investigate effects of grazing unrestrained versus tethered on grazing behavior, energy expenditure, forage intake, and composition of forage selected by meat goats on pastures with different forage quality and available mass (wheat forage at 2,500-3,000 kg/ha and orchardgrass/fescue at 1,000-1,500 kg/ha). The hypothesis is that tethering goats will adequately simulate unrestrained grazing with both low and high forage quality and available mass. That is, it is theorized that forage intake, chemical composition of selected forage, grazing
behaviors (e.g., time spent grazing, ruminating, and resting, bite size, number of bites, and rate of biting), and heat production or energy expenditure will not statistically differ between tethered and unrestrained goats. The experiments are crossovers with eight growing meat goat wethers used to estimate grazing behaviors and energy expenditure, fecal output, forage intake, and composition of selected forage. Two of three planned experiments with different forage conditions have been conducted, the first in the early summer and the second in the late-fall/early winter period of 2004. A third experiment will occur with high forage availability and nutritive value in mid-spring of 2005. Laboratory analyses for samples on the first two experiments are underway.
Impacts
If tethering adequately simulates grazing by free-moving, unrestrained ruminants, then more basic or fundamental experimental methodologies can be employed with grazing ruminants than possible with unrestrained animals. This project and ensuing, facilitated research will lead to improved grazing management strategies for efficient utilization of forage resources.
Publications
- No publications reported this period
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