Evaluation of alternative nonlinear mixed effects models of duck growth

Improving a nonlinear Gompertz growth model using bird-specific random coefficients in two heritage chicken lines

Growth models describe body weight (BW) changes over time, allowing information from longitudinal measurements to be combined into a few parameters with biological interpretation. Nonlinear mixed models (NLMM) allow for the inclusion of random factors. Random factors can account for a relatively large subset of the total variance explained by bird-specific measurement correlation. The aim of this study was to evaluate different NLMM using birds from 2 heritage chicken lines; New Hampshire (NH) and Brown Leghorn (BL). A total of 32 birds (16 mixed sex birds from each strain) were raised to 17 wk of age. After 12 wk, half were continued on ad libitum (AL) feed intake, and half were pair-fed, using a precision feeding system; they were given 95% of the AL intake of a paired bird closest in BW. Residual feed intake (RFI) of birds, as an indicator of production efficiency, was increased in pair-fed BL birds as a result of minor feed restriction. Growth data of the birds were fit to a mixed Gompertz model with a variety of different bird-specific random coefficients. The model had the form: BW=Wm×exp−exp−b(t−tinf); where Wm was the mature BW, b was the rate of maturing, t was age (d), t_inf was the inflection point (d). This fixed-effects model was compared with NLMM using model evaluation criteria to evaluate relative model suitability. Random coefficients, Wm_u ∼ N(0,V_Wm) and b_u ∼ N(0,V_b)_, were tested separately and together and their differences, for strains, sex, and feeding treatments, were reported as different where P ≤ 0.05. The model with both random coefficients was determined to be the most parsimonious model, based on an assessment of serial correlation of the residuals. NLMM coefficients allow stochastic prediction of the mean age and its variation that birds need to achieve a certain BW, allowing for unique new decision support modeling applications; these could be used in stochastic modeling to evaluate the economic impact of management decisions.

Selected growth parameters of farm-raised mallard (Anas platyrhynchos L.) ducklings

The aim of this study was to determine changes in selected growth parameters of farm-raised mallard ducklings from hatch to 42 d of age. The largest increases in body and carcass weights of ducklings and weights of the analyzed tissue components were noted during the first 28 d of the rearing period, except for breast and wing muscles. In comparison with other muscle groups, the growth rate of breast and wing muscles was lower from hatch to 14 d of age, greatest between 14 and 28 d, and remained high up to 42 d of age. The average body weight of mallard ducklings increased more than 16-fold (from 39.7 to 644.8 g, P ≤ 0.01), and the average carcass weight increased more than 26-fold (from 14.4 to 384.5 g, P ≤ 0.01). The growth rates of carcass and tissue components varied considerably. Wing weight increased 84.5-fold (from 0.80 to 67.6 g, P ≤ 0.01), followed by breast weight, which increased 48-fold (from 1.7 to 82.9 g, P ≤ 0.01). Slower growth rates were noted in the remaining carcass parts: back, 23-fold; neck, 19.2-fold; and legs, 17.1-fold (from 5.4 to 92.2 g, P ≤ 0.01).

Characterization of whole body compositional growth of male ducks during the twenty-nine day post-hatch period

Schinckel, A. P., Einstein, M. E., Ajuwon, K. M. and Adeola, O. 2013. Characterization of whole body compositional growth of male ducks during the twenty-nine day post-hatch period. Can. J. Anim. Sci. 93: 113–122. Changes in whole body dry matter, lipid, ash, energy, crude protein, and amino acids were evaluated during a 29 d post-hatch period in White Pekin ducks. Drakes were assigned to slaughter 1, 8, 15, 22, or 29 d post-hatch with four replicates of four ducks per slaughter period. The body weight (BW) data were fitted to the Weibull function with the form:[Formula: see text]where BWit is the BW of the ith duck at t days of age and A, B, C, and IP are parameters. The value of IP, the inflection point, which minimized the residual SD, was 40 d. Values of A (8591 g, SE=190), B (42.87, SE=11.5), and C (1.7399, SE=0.050) resulted in an R 2 of 0.9836 and residual SD of 83.7 g. Allometric (Y=A BWB), linear-quadratic and exponential (Y=exp (b0+b1BW+b2 (BW)2) functions of BW were fitted to the chemical component and amino acid mass data. Dry matter percentage of the ducks increased (P<0.01) with age. The protein content of the dry matter decreased (P<0.01) from day 1 to day 8 (69 to 58.2%) and then increased to 60% by d 29. Concentrations of several amino acids were affected (P<0.05) by age. The predicted accretion rates of Lys, Trp, and Met relative to protein accretion increased as age increased. The predicted daily accretion rates for major indispensable amino acids increased rapidly the first 5 d post-hatch and subsequently increased but at a decreasing rate to day 29 post-hatch. The relative growth rates of chemical components and indispensable amino acids were affected by age indicating that the nutrient requirements of ducks differ from day 1 to day 29 post-hatch. Compositional growth and amino acid accretion data can be used to model the nutrient requirements of ducks.

Dietary cholecalciferol lowers the maximal activity of intestinal mucosa phytase in ducklings fed low-phosphorus diets

Onyango, E. M. and Adeola, O. 2011. Dietary cholecalciferol lowers the maximal activity of intestinal mucosa phytase in ducklings fed low-phosphorus diets. Can. J. Anim. Sci. 91: 399–404. The role of cholecalciferol and phosphorus in the regulation of intestinal mucosa phytase was investigated in White Pekin ducklings. Ninety-six 7-d-old male ducklings were grouped by weight into six blocks of four cages with four ducklings per cage. The average weights of the individual birds in the six subgroups were: 282, 270, 263, 255, 247 and 236 g, respectively. Four corn-soybean meal-based mash diets were randomly assigned to cages within each block. The four diets consisted of cholecalciferol at 0 or 75 µg kg–1 and total phosphorus at 3.6 or 7.0 (or 0.12 or 0.46 available phosphorus, respectively) g kg−1 in a 2×2 factorial arrangement. Birds were fed the experimental diets for 9 d under conditions that excluded ultraviolet light. Ducklings fed diets with cholecalciferol concentration at 75 µg kg−1 of diet showed a lower maximal activity and Km value of intestinal mucosa phytase (P<0.05), and higher apparent ileal digestibility of calcium (P<0.0001). Ducklings fed diets with total phosphorus concentration at 7.0 g kg−1 of diet showed no change in intestinal mucosa phytase activity, but had higher weight gain, feed intake, tibia ash, ileal digestibility of phosphorus (P<0.0001), and feed efficiency (P<0.001). In conclusion, dietary cholecalciferol decreased the maximal activity and Km value of intestinal mucosa phytase in ducklings fed low-phosphorus diets.

Production benefits of the crossbreeding of indigenous and non-indigenous ducks--growing and laying period body weight and production performance

To evaluate different crosses and purebreds ducks in respect to various economic traits and to estimate different crossbreeding genetic parameters, a 3 x 3 complete diallel cross involving indigenous duck (DD), Khaki Campbell (KK) and White Pekin (WW) were used to produce three purebreds (DD, KK, WW) three crossbreds (DK, DW, KW) and three reciprocals (KD, WD, WK). A total of 609 ducklings produced were reared on deep litter and the females (316 in number) were evaluated for growing and laying period body weight along with the production performance traits. Different crossbreeding genetic parameters were estimated for different traits. All the traits in respect to body weight gain during growing and laying period and different production traits including laying house mortality rate showed significant (p <or= 0.05) difference between different genetic groups. In general, crossbreds perform better than the purebreds for most of the traits studied. General combining ability (GCA), specific combining ability (SCA) and reciprocal effect (RE) were significant (p <or= 0.01) for body weight and production traits. Egg weight showed significant (p <or= 0.01) difference in respect to GCA, SCA and RE for all the ages of measurement except RE for 30th week egg weight. Laying period mortality rate was only significant (p <or= 0.05) for SCA. Most of the crossbreds recorded heterosis rate in desirable direction for majority of the traits. Overall results revealed that the crossbreds perform well in respect to different traits than the purebreds and may be used to take advantage of heterosis. DW performs well in respect to majority of the traits measured and is of importance for commercial exploitation. Further, pure line selection with development of specialised sire and dam line followed by crossing may be of importance to enhance the performances in the crosses.