Knowledge of carcass merit will help the meat duck breeder identify superior stock and accelerate genetic improvement. Selection for leanness will enhance product acceptance by the consumer. Heritability values for carcass traits are in the medium-high range. Feed intake level during rearing is critical for reproduction. The objectives were to evaluate (1) the response of breast muscle thickness of the F1 progeny from parent breeders selected for maximum muscle thickness at market age and (2) the effect of 2 levels of feed restriction during development for subsequent egg production. In a commercial flock, 4842 Pekin ducks (Brome Lake Ducks Ltd.) were individually weighed and measured by ultrasound for breast muscle thickness (MT, mm) at 47 days of age. Three groups of 120 females and 25 males each were selected and allocated to the following groups: (1) control (CT), randomly selected; (2) maximum body weight (BW), and (3) maximum MT. From 7 to 23 wk old, one half of breeders followed a conventional restriction (CR) at 67 g feed/kg body weight daily, the other half were slightly more restricted following a Macdonald restriction (MR) at the same intake as CR but with a weekly skip-a-day feeding. (Abstract shortened by UMI.)

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Four experiments were conducted to determine the reproductive, metabolic, growth and IGF-I response to ultrasound selection for increased breast muscle thickness (MT) in Pekin ducks. Selection for body weight had a negative ( P < 0.05) effect on the reproductive performance while the selection for greater breast muscle thickness resulted in egg production, fertility and hatchability similar to those of the control line (C). Males from the MT line reached market weight at 6 wk but the breast muscle thickness improved from 6 to 7 wk. Compared to females from the C line, MT females had higher (P < 0.05) carcass yield, plasma glucose, and body protein; lower fat and plasma uric acid; and no difference (P > 0.05) in plasma triglycerides and total cholesterol. Males responded more efficiently to increasing dietary protein than females, and males selected for greater MT can be slaughtered at an earlier age when a high protein feeding program (HP) was followed. Males receiving HP had greater (P < 0.05) pectoralis muscles yield, longer keel bone, and lower breast skin and total skin fat yields. Female dissection data show similar (P > 0.05) effects of high and medium protein programs. Increasing dietary protein reduced (P < 0.05) carcass fat and increased (P < 0.05) crude protein (CP). In vivo breast muscle measurement correlated positively (P < 0.05) with body weight, pectoralis yield, and keel bone length. Birds with higher pectoralis yield tended to have more CP and less fat in their carcasses. A low correlation (r = 0.19) was found for the caliper measurement of breast skin plus fat thickness and carcass fat. We determined the metabolic differences between lean and fat male and female ducks, associated metabolic parameters and body composition, and assessed the difference between two feeding solutions for the determination of metabolic endogenous losses. There was a positive correlation between breast muscle:total breast muscle thickness ratio (MT/TO