ARS | Publication request: HEAT PRODUCTION BY GRAZING EWES WITH LOW FORAGE MASS AND SUPPLEMENTAL GRAIN

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: April 9, 1997
Publication Date: N/A

Technical Abstract: Three mature Dorset ewes were used in a 3 x 3 Latin square (two 28-d periods and one 35-d) to determine effects of level of supplemental corn (0, .5, and 1.0% BW; DM) on intake, digestion, grazing behavior, and heat production by the whole body and splanchnic and extra-splanchnic tissues with grazing of paddocks low in forage mass. Live and dead forage mass ranged from 1 to 4 kg and 27 to 40 kg DM per 0.036-ha paddock, respectively; initial ewe conditions were 71 +/- 2.5 kg shrunk BW, 47 +/- .4% fat, and 11 +/- .1% protein; and in periods 1, 2, and 3 hand-plucked forage samples were 17, 20, and 29% CP and 62, 56, and 58% NDF, respectively. Intake of ME (1.39, 2.32, and 3.16 Mcal/d; SE .11) and energy accretion (-1.09, .02, and .39 Mcal/d; SE .224) increased linearly with increasing corn level (P<.01 and =.04, respectively), and grazing time decreased ((P=.06) 76, 63, and 48% of daylight for 9, .5, and 1.0% BW of corn, respectively; SE 4.9). However, corn level did not affect (P>.10) whole body heat (2.48, 2.30, and 2.77 Mcal/d; SE .171), heat increment (.91, .80, and 1.24 Mcal/d; SE .172), splanchnic bed heat (1.09, 1.12, and 1.05 Mcal/d; SE .091), or extra-splanchnic tissue heat (1.39, 1.18, and 1.72 Mcal/d for 0, .5, and 1.0% BW of corn, respectively; SE .241). In conclusion, with increasing intakes of corn, total DM, and ME, increased heat produced in dietary energy metabolism for tissue maintenance or maintenance plus energy accretion may only have compensate for decreased grazing-related or -specific heat production by both splanchnic and extra-splanchnic tissues of ewes, resulting in decreased tissue mobilization or increased energy accretion.