Energy expenditure of Angora bucks in peak breeding season estimated with the doubly-labeled water technique

We used the doubly-labeled water (DLW; (H2O)-H-2-O-18) method to compare to tal 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 an d allocated pairwise to one of four breeding groups (n = 30 does/group). Su bjects were infused i.v. with (H2O)-H-2-O-18 that provided 200 mg (H2O)-H-2 and 250 mg (H2O)-O-18/kg BW. Blood samples were collected over a 15-d peri od, with 3- to 4-d intervals for isotope enrichment measurements. Total DLW -derived energy expenditure (TEE) was similar (P = .55) between bucks and w ethers (2,578 vs 2,365; SE 239 kcal/d). Large variation was observed among wethers in TEE, courtship, and attempted mountings. Total energy expended c orrected for that in mohair production (CTEE) tended (P = .09) to be greate r in sexually active wethers (133 +/- 8 kcal ME/[kg BW.75.d(-1)]; n = 3) th an in bucks (110 +/- 7 kcal ME/[kg BW.75.d(-1)]; n = 4). Energy expended on activity (EEa) by these wethers was highly correlated (r = .98) with the n umber of does marked, which may explain high variability among wethers in E Ea. 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 Ango ra bucks, CTEE during the breeding season was 9% greater than the maintenan ce energy requirement. In conclusion, breeding activities in single-buck br eeding groups did not markedly increase energy requirements of Angora bucks .