Comparative performance, blood chemistry, and carcass composition of two lines of Pekin ducks reared mixed or separated by sex

Male and female Pekin ducks selected (Fz generation) for greater breast mus cle thickness (MT) and an unselected control (C) were used in this study un der mixed- or separated-sex rearing. Ducks in the separated-sex program had significantly higher body weights than the birds in the mixed-sex program. The ducks selected for greater breast muscle thickness exhibited superior (P < 0.05) body weight up to 42 d of age. Males from the MT line reached ma rket weight at 6 wk, but the breast muscle thickness, measured by ultrasoun d scanning, improved significantly from 6 to 7 wk of age. Males had greater (P < 0.05) breast muscle thickness than females. At both ages and for both sexes, the MT line had greater (P < 0.05) breast muscle thickness than the C line. The MT ducks consumed more (P < 0.05) feed up to 6 wk, but no sign ificant difference was found in cumulative feed consumption at 7 wk, and th e lines did not differ (P > 0.05) in feed:gain ratio. Males had significant ly higher cumulative feed consumption at 6 wk but had a more desirable (P < 0.05) feed:gain ratio than females at 7 wk. Compared with females from the C line, MT females had significantly higher carcass yield, higher body pro tein, and lower fat. The MT females had higher plasma glucose and lower uri c acid than the C females, but no significant difference was found between the MT and C lines for plasma triglycerides and total cholesterol. The resu lts of this study support the utility of ultrasound scanning in duck select ion, the separated rearing of ducklings, and the possibility of reducing th e slaughter age of lean males.