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Efficiency of energy utilization by lactating Alpine goats

I. Tovar-Luna, A. L. Goetsch, R. Puchala, T. Sahlu, and H. C. Freetly

Journal 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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