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Title: Effects of stage of lactation and level of feed intake on energy utilization by Alpine dairy goats

Author
item TOVAR-LUNA, I - University Of Chapingo
item PUCHALA, R - Langston University
item SAHLU, T - Langston University
item Freetly, Harvey
item GOETSCH, A - Langston University

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2010
Publication Date: 10/1/2010
Citation: Tovar-Luna, I., Puchala, R., Sahlu, T., Freetly, H.C., Goetsch, A.L. 2010. Effects of stage of lactation and level of feed intake on energy utilization by Alpine dairy goats. Journal of Dairy Science. 93(10):4829-4837.

Interpretive Summary: A complete understanding of energy requirements is necessary for optimal performance of lactating dairy goats. The energy requirement for maintenance relative to metabolic size in late lactation was less than in early and mid-lactation, but with a similar requirement in megajoules per day, this difference may have been partially attributable to tissue energy gain throughout lactation. Method of determination can influence the maintenance energy requirement and efficiencies of energy use for maintenance and lactation. Level of feed intake, such as restricted intake after ad libitum consumption, can have substantial effect on estimates of energy utilization by lactating dairy goats.

Technical Abstract: Thirty-six lactating Alpine does were used to determine effects of stage of lactation and level of feed intake on energy utilization. Twelve does were assigned to measurement periods in early, mid-, and late lactation (wk 5, 13, and 27, respectively). For six does of each group, after ad libitum consumption of a 60% concentrate diet feed intake was restricted to near the ME requirement for maintenance (MEm) for 8 d followed by fasting for 4 d. Fasting was immediately after ad libitum consumption for other does. Intake of ME was similar among stages of lactation with ad libitum intake (22.1, 22.1, and 19.8 kJ/d, respectively). The efficiency of ME utilization for maintenance determined with does fed near MEm averaged 81%. Fasting heat energy was greater with ad libitum vs. near MEm consumption (368 vs. 326 kJ/kg BW0.75) and was numerically lowest among stages in late lactation with near MEm intake (334, 350, and 295 kJ/kg BW0.75) and ad libitum consumption (386, 384, and 333 kJ/kg BW0.75 in early, mid-, and late lactation, respectively). The efficiency of use of dietary ME for lactation was greater for consumption near MEm than for ad libitum intake (67.9 vs. 58.6%) and with ad libitum consumption tended to decrease with advancing stage of lactation (63.9, 57.3, and 54.5% for early, mid-, and late lactation, respectively). Estimated MEm was greater with ad libitum than near MEm intake and was lowest during late lactation (429, 432, and 358 kJ/kg BW0.75 with near MEm intake, and 494, 471, and 399 kJ/kg BW0.75 with ad libitum consumption in early, mid-, and late lactation, respectively). Although, because of increasing BW as the experiment progressed, MEm in MJ/d was similar among stages of lactation with both levels of intake. The efficiency of ME use for maintenance and lactation was similar among stages of lactation and greater with intake near MEm than ad libitum (77.1 vs. 67.7%). In conclusion, the MEm requirement in kJ/kg BW0.75 of does in late lactation was less than in early and mid-lactation. Method of determination can influence estimates of efficiency of energy use for maintenance and lactation, with marked effect of restricted feed intake subsequent to ad libitum consumption compared with use of nonlactating animals. Level of feed intake can have substantial effect on estimates of energy utilization by lactating dairy goats.