Effects of night-locking and stage of production on forage intake, digestion, behavior, and energy utilization by meat goat does grazing grass/legume pasture

Abstract

Twenty-three Boer (75%)×Spanish (25%) multiparous does, eight with ruminal cannula, grazed grass/legume pastures in different stages of production. Four cannulated and eight non-cannulated does were confined in a building at night and had pasture access from approximately 07:00 to 19:00h (Night); other animals had continual pasture access (Past). Data collection periods 15days in length were in late gestation (L-G; 137±5.2days), early lactation (E-L; 43±2.1days), late lactation (L-L; 97±1.1days), the dry period (Dry), and early gestation (L-G; 65±5.9days). Most does had a litter size of 2, and kids were weaned at 118±1.0days. Ingesta collected from cannulated does after rumen-evacuation averaged 19.9, 12.5, 14.7, 13.4, and 19.9% CP (SE=0.59) and 50.8, 59.2, 63.1, 61.4, and 38.1% NDF in L-G, E-L, L-L, Dry, and E-G, respectively; (SE=1.55). Kid ADG tended (P<0.08) to be greater for Past than for Night (138 vs. 118g; SE=7.4). Intake of ME (823 vs. 735kJ/kg BW0.75; SE=27.5) was greater for Night than for Past (P<0.05). There were treatment differences in time spent grazing (4.5 and 5.8h; SE=0.28) and resting (18.5 and 16.7h for Night and Past, respectively; SE=0.25). Energy expenditure (EE) was greater (P<0.05) for Past than for Night (754 vs. 687kJ/kg BW0.75; SE=14.5). Recovered energy (RE) in and EE for tissue gain were similar between treatments. RE in tissue gain was greatest among periods (P<0.05) in Dry (6, 0, 11, 113, and 22kJ/kg BW0.75 in L-G, E-L, L-L, Dry, and E-G, respectively; SE=8.5). RE of lactation from dietary ME was greater for Past vs. Night regardless of period (244 vs. 194kJ/kg BW0.75; SE=16.1). However, RE of lactation derived from mobilized tissue differed between treatments (P<0.05) in E-L but not L-L (54, 15, 175, and 11kJ/kg BW0.75 in Night/E-L, Night/L-L, Past/E-L, and Past/L-L, respectively; SE=16.0). EE associated with activity tended to be greater (P<0.07) for Past than for Night (243 vs. 202kJ/kg BW0.75; SE=14.4) and was greatest among periods in E-G (184, 219, 193, 176, and 343kJ/kg BW0.75 in L-G, E-L, L-L, Dry, and E-G, respectively; SE=22.7). In conclusion, ‘night-locking’ decreased activity EE to an extent less than the depression in MEI. The greatest impact of Night was in E-L, with reduced RE of lactation and a tendency for lower kid ADG.