Submitted to: British Poultry Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/25/2001
Publication Date: N/A
Citation: Interpretive Summary: In commercial poultry breeding, the selection for faster growth is often made by weighing all birds at a particular age. This approach has several drawbacks. One problem is a poor yield of breast meat, the most valuable component part at the time of marketing. The problem is largely due to slower maturation of breast-muscle growth. In addition, this selection procedure is not capable of describing patterns of body and muscle growth. Animal growth generally follow a sigmoidal pattern. Some birds mature early, but remain small. Others mature later, but grow large. Two important parameters of growth are the genetic potential for growth and the time to reach maturity. When animal growth is described by a growth curve, these parameters can be presented as biologically interpretable constants in a mathematical equation. In this study, serial measurements of body weight, breast-muscle weight, and weights of other component parts were analyzed by ygrowth curves. When growth data of four lines of ducks at a commercial breeder in 1991 and 1998 were analyzed, growth curves were able to discriminate among the four lines for body and breat-muscle growth. Based on the relative growth rate, a new growth curve equation (LLRGR) was formulated to better describe bird growth. Growth curve analysis proved to be an exceptionally useful tool to select ducks for faster growth and particularly for faster breast muscle growth. This approach proved especially powerful in predicting the line peformance precisely, and the predicted performance was verified in the field. Use of growth curve analysis in selection of ducks results in faster and efficient genetic improvement and better market birds for the comsumers.
Technical Abstract: Growth patterns of male ducks from four lines (Lines A, B, C, and D) selected for market weight were analyzed and compared to growth patterns of ducks in the respective line seven generations earlier. Growth curves were analyzed using procedures derived from the Weibull sigmoidal function and the linear-linear relative growth rate model, and simple allometry. The ducks were fed ad libitum under 24-hour lighting throughout the experiment. At weekly intervals from the time of hatch through 70 days of age, 16 ducks were killed to determine body, carcass, breast-muscle, leg and thigh-muscle, and abdominal fat weights. Line A was the heaviest line, followed by Line B, Line C, and Line D. However, body weight, carcass weight, and breast-muscle weight at 49 days of age were not significantly different between Line A and Line B. After seven generations of selection, the breast-muscle yield was increased to >19% and the abdominal fat percent twas reduced to <1.4% in all lines. With the Weibull growth curve analysis of body weight, genetic selection increased the asymptotes, while leaving the age of the inflection point constant in all lines (21.3-26.0 days). For breast-muscle growth, ducks reached the inflection point 12.8-14.3 days later than for body weight. Between Line A and Line B, asymptotes for body weight, asymptotes for breast muscle weight, and allometric growth coefficients of breast-muscle and leg and thigh muscles from 14 days through 49 days were not significantly different. The relative growth rate model discriminated body and breast-muscle growth patterns of Line A and B. The initial decline in the relative body growth rate was less and the time to reach the transition was longer in Line A than B. The initial decline in the relative breast-muscle growth rate was greater in Line A than Line B.