Efficiency of energy utilization by lactating Alpine goats
I. Tovar-Luna, A. L. Goetsch, R. Puchala, T. Sahlu, and H. C. FreetlyJournal of Animal Science 87(E-Supplement 2):486. 2009
Thirty-six lactating Alpine does (50.5 ± 1.2 kg BW) were used to determine the effect of stage of lactation on energy utilization. Twelve does were assigned for measurement periods in early, mid-, and late lactation (28-35, 91-98, and 189 to 196 d of lactation). For six does of each group, after measures with ad libitum consumption of a 60% concentrate diet, feed intake was restricted to the ME requirement for maintenance (MEm) for 8 d followed by a 4-d fasting period. For the other six does, fasting immediately followed ad libitum consumption. Heat production or energy expenditure (EE) was measured using a head-box calorimetry system the last 2 d with ad libitum intake, near maintenance intake, and fasting. Ad libitum intake of ME was affected (P < 0.05) by stage of lactation (22.2, 24.0, and 18.4 MJ/d), and was similar when fed near MEm (9.8, 10.4, and 10.8 MJ/d) in early, mid-, and late lactation, respectively. Recovered energy in milk did not differ in early and mid-lactation and was lower (P < 0.05) in late lactation (8.77, 7.84, and 5.40 MJ/d respectively; SE = 0.418). Efficiency of ME utilization for maintenance (km) based on ME intake and EE by does fed near maintenance and when fasting was similar (P > 0.05) among stages of lactation (0.780, 0.813, and 0.803 in early, mid-, and late, respectively; SE = 0.0459). However, MEm (based on fasting after ad libitum intake divided by km) was similar (P > 0.05) in early and mid-lactation and lowest (P > 0.05) in late lactation (494, 472, and 412 kJ/kg BW0.75; SE = 23.7, respectively). Efficiency of use of dietary ME for lactation (kl-d) was not influenced (P > 0.05) by stage of lactation (0.615, 0.574, and 0.569 in early, mid-, and late lactation, respectively; SE = 0.0191). Although km and kl-d by lactating goats were similar among stages of lactation, the MEm requirement appears lower in late lactation than at early times.
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