Energy expenditure of Angora bucks in peak breeding season estimated with the doubly-labeled water technique.
We used the doubly-labeled water (DLW; 2H2(18)O) method to compare total energy expenditure (TEE) of Angora bucks and wethers over a 15-d period during peak breeding season. Four bucks (57+/-3 kg) and four wethers (45+/-2 kg) were fitted with marking harnesses to measure sexual activity and allocated pairwise to one of four breeding groups (n = 30 does/group). Subjects were infused i.v. with 2H2(18O) that provided 200 mg 2H2O and 250 mg H2(18)O/kg BW. Blood samples were collected over a 15-d period, with 3- to 4-d intervals for isotope enrichment measurements. Total DLW-derived energy expenditure (TEE) was similar (P = .55) between bucks and wethers (2,578 vs 2,365; SE 239 kcal/d). Large variation was observed among wethers in TEE, courtship, and attempted mountings. Total energy expended corrected for that in mohair production (CTEE) tended (P = .09) to be greater in sexually active wethers (133+/-8 kcal ME/[kg BW.75 x d(-1)]; n = 3) than in bucks (110+/-7 kcal ME/[kg BW.75 x d(-1)]; n = 4). Energy expended on activity (EEa) by these wethers was highly correlated (r = .98) with the number of does marked, which may explain high variability among wethers in EEa. Bucks marked more does (18+/-1; P < .05) than wethers (8+/-3), but a weak relationship (r = .36) existed between number of does marked and EEa, suggesting individuality in style and persistence while courting. In Angora bucks, CTEE during the breeding season was 9% greater than the maintenance energy requirement. In conclusion, breeding activities in single-buck breeding groups did not markedly increase energy requirements of Angora bucks.
Toerien
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E (Kika) de la Garza Institute for Goat Research, Langston, OK 73044, USA.
Sahlu
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Wong
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D000821:Animal Feed; D000818:Animals; D001947:Breeding; D003903:Deuterium; D004734:Energy Metabolism; D007553:Isotope Labeling; D008297:Male; D012621:Seasons; D012726:Sexual Behavior, Animal; D012756:Sheep / Q000378:metabolism*
D003903:Deuterium