Diphasic allometric growth of some skeletal bones and the digestive tract in White Leghorn pullets consuming ad libitum and restricted diets

Timing of growth affected broiler breeder feeding motivation and reproductive traits

The amount and timing of growth are important factors that affect age at first egg, body conformation, reproductive performance, and hunger in broiler breeders. To investigate the effect of growth pattern on feeding motivation and reproductive performance, 10 unique growth trajectories were designed with 2 levels of the amount of early growth and 5 levels of timing of growth around puberty. A 3-phase Gompertz model that described growth in phase 1 (prepubertal), phase 2 (pubertal), and phase 3 (postpubertal) was used to design the growth trajectories. Second growth phase inflection point (I₂) was advanced by 0, 5, 10, 15, or 20% of the coefficient estimated from the breeder-recommended target BW. The growth trajectories were designed with 2 discrete levels of total gain in the prepubertal phase (g₁); g₁ was either the prepubertal phase gain coefficient, estimated from the breeder-recommended BW (Standard g₁) target, or 10% higher (High g₁). Forty females were randomly assigned to the growth trajectories using a precision feeding (PF) system. Analysis of covariance was conducted on dependent variables in ten 4-wk periods with g₁ and periods as discrete fixed effects, I₂ as a continuous fixed effect, and age as a random effect. Differences were reported at P ≤ 0.05. For every week of earlier I₂, body weight at photostimulation (BWPS) increased by 126 g; BW at first egg (BWFE) increased by 94 g; 24 wk shank length increased by 0.038 and 1.495 mm in the Standard g₁ and High g₁ treatments; 24 wk body fat increased by 0.38%; pullets came to lay earlier by 0.49 d; egg weight (EW) increased by 0.27 g; egg production and egg mass (EM) increased by 0.33 egg/hen/d and 0.916 g/d in the High g₁ treatment but decreased by 0.27 egg/hen/d and 0.29 g/d in the Standard g₁ treatment, respectively. Increasing g₁ reduced feeding motivation index by 1.6 and 0.8 visits/meal during rearing and laying phase, respectively. Earlier pubertal growth showed prominent effects on the reproductive performance.

Multiphasic poultry growth models: method and application

Growth and development are complex phenomena. To date, most growth modeling research has focused on a single growth phase, which is sufficient and useful for describing ad libitum fed animals processed at a prepubertal age, such as broilers or turkeys produced for meat. However, multiphase growth models are necessary to describe and predict growth and further to hypothesize about optimizing growth of reproducing animals such as broiler breeder hens. Therefore, the objective of the present study was to develop and evaluate multiphasic models to describe the growth of various types of poultry raised to reproductive age. Coefficients for monophasic, diphasic, and triphasic Gompertz model forms were estimated using a variety of BW trajectories published by primary breeders. The fit of these models was evaluated for a representative laying line hen, broiler breeder hen and rooster, and turkey hen. The coefficient of determination (R²), root mean square error, and the Bayesian information criterion were used to evaluate the fit of each model. The diphasic model was found to be the best fit for the turkey hen, while the triphasic model was the most suitable model for all the chicken lines studied. Hypotheses can be formulated based on any of the continuous model parameters, and the resulting BW trajectories can be implemented and evaluated in a systematic way. The biological relevance of the continuous parameters in multiphasic Gompertz models provides an opportunity to implement a robust hypothesis-based approach for future optimization of growth curves.

Determination of body width in brown and white layer pullets by image analyses

1. Specific legal requirements for keeping pullets are not available in the European Union. However, two of the most important rearing factors for pullets are sufficient perching and feeder space. Both factors represent horizontal space dimensions which derive from the body width of the birds. 2. The body width of two strains of layer pullets (brown (BL) and white (WL) layer pullets) based on the measurement of distances in digital images was conducted on front-view digital photographs of BL and WL pullets taken at 8, 12 and 19 weeks of life. 3. Depending on live weight, age and body position, BL pullets measured an average body width between 10.70 ± 1.10 and 13.96 ± 1.11 cm. The width of WL pullets ranged from 10.30 ± 0.86 to 13.00 ± 1.14 cm. 4. Compared with WL, BL pullets occupied more horizontal space during rearing. Age influenced the body width of BL and WL pullets at the end of rearing. The tested body positions of the pullets did not affect the measured body width. 5. The biometric data obtained in this study are a useful basis for developing legal requirements for pullets, especially for defining minimum perch width and feeder space allowances.

Effects of caponization on growth performance, carcass composition, and meat quality of medium growth broilers

A 2-trial experiment was conducted to evaluate the effects of caponization on growth performance, carcass composition, and meat quality of medium growing broilers. Male chicks were caponized at 3 wk of age and reared until either 18 (trial 1) or 24 (trial 2) wk of age. In trial 1, the experimental groups included intact males, sham-operated chickens, and capons, whereas trial 2 comprised only intact males and capons. The concentration of testosterone was drastically reduced by caponization but remained detectable (trial 1). In both trials, BW was lower for capons during 4 to 9 or 10 wk of age when contrasted to intact males (P < 0.05). In trial 1, capons had heavier livers than intact males and sham-operated chickens. In addition, they had lighter hearts than sham-operated chicks (P < 0.05). In trial 2, capons displayed smaller drumstick and heart weights (P < 0.05). There was a tendency for increased fat pad weight in capons (P < 0.10). Caponization resulted in increased skin-fat weights of the thigh and the breast of 24 wk of age. This was also valid for carcass fat, when expressed as a percentage of the cold carcass weight, and intramuscular fat. Caponization had no effect on pH 24 h postmortem and cooking loss. Capons' breasts had lower shear values and displayed lighter, more yellow, and less red meat than that of intact males. Conclusively, caponization, without affecting growth performance, altered meat quality characteristics, resulting in special quality chicken meat.

Effect of early feed restriction on myofibre types and expression of growth-related genes in the gastrocnemius muscle of crossbred broiler chickens

The purpose of this study was to investigate the immediate and long-term effects of early feed restriction (ER) on morphology and gene expression of lateral gastrocnemius muscle. Newly hatched crossbred broiler chickens were allocated into control and ER groups, the latter being free-fed on alternate days from hatch to 14 days of age (14 d), followed by ad libitum feeding as the control group until 63 d. The lateral gastrocnemius muscle was taken at 14 and 63 d, respectively for myofibre typing by both myosin ATPase staining and relative quantification of myosin heavy chain (MyHC) mRNA for slow-twitch (SM), red fast-twitch (FRM) and white fast-twitch (FWM) myofibres. The body weight and lateral gastrocnemius weight were significantly lower in the ER group, accompanied by significantly reduced serum triiodothyronine. The ER group exhibited significantly higher SM and FRM MyHC expression at 14 d, but lower SM expression at 63 d. Myosin ATPase staining revealed a similar pattern. The percentage of SM was higher at 14 d while lower at 63 d in the ER group. These morphological changes were accompanied by changes of mRNA expression for growth-related genes. The ER group expressed lower insulin-like growth factoar I (IGF-I) and higher IGF-I receptor (IGF-IR) at 14 d, yet significantly increased growth hormone receptor and IGF-IR mRNA at 63 d. These results indicate that ER may delay the slow to fast myofibre conversion as an immediate effect, but would result in a lower percentage of slow fibres owing to compensatory growth in the long term, which involves changes of mRNA expression for the growth-related genes in the muscle.

Effect of varying metabolizable energy and crude protein concentrations in diets of Pearl Gray guinea fowl pullets. 2. Egg production performance

The effect of ME and CP concentrations during the growth phase of Pearl Gray guinea fowl pullets on their egg production performance was evaluated. In a 3 x 3 factorial arrangement, five hundred forty 1-d-old Pearl Gray guinea keets were randomly assigned to experimental diets with 2,900, 3,000, and 3,100 kcal of ME/kg of diet; each contained 20, 22, and 24% CP, respectively, from 0 to 8 wk of age (WOA). From 9 to 16 WOA, experimental diets had 3,000, 3,100, and 3,200 kcal of ME/kg of diet, and each contained 17, 19, and 21% CP, respectively. At 17 to 22, 23 to 27, and 28 to 56 WOA, experimental diets were composed of 3,000, 2,900, and 2,800 kcal of ME/kg, and each had 18, 17, and 16% CP, respectively. Dietary treatments were replicated 4 times, and feed and water were provided ad libitum. Body weights were measured weekly from 0 to 22 WOA, and at 28 to 56 WOA the birds were observed for feed consumption, age at first egg, hen-day egg production (HDEP), egg weight, egg mass (EM), feed conversion ratio (FCR), internal egg quality (IEQ), shell thickness (ST), and BW at the end of each 28-d lay period for 7 consecutive periods. Mortality was recorded as it occurred. Overall, BW gains were higher (P < 0.05) in birds fed 3,000 and 3,100 Kcal of ME/kg and 24% CP from 0 to 8 WOA than other dietary treatments. Percentages HDEP, EM, and IEQ were higher (P < 0.05) and FCR was lower (P < 0.05) in pullets fed 3,000 and 3,100 kcal of ME/kg diet at 0 to 8 WOA than those fed 2,900 kcal of ME/kg. Birds on 22 and 24% CP diets at 0 to 8 WOA also exhibited higher HDEP, EM, and lower FCR than those on 20% CP diets. Thus, feeding 3,000 to 3,100 kcal of ME/kg of diet and 22 to 24% CP at 0 to 8 WOA and 3,100 to 3,200 kcal of ME/kg of diet and 19 to 21% CP at 9 to 16 WOA improved HDEP, EM, IEQ, and FCR of Pearl Gray guinea fowl laying pullets at 28 to 56 WOA.

Developmental changes of parathyroid hormone/parathyroid hormone-related peptide and calcitonin receptor binding properties in the chicken calvaria and kidney

The equilibrium dissociation constant (Kd) and the maximum binding capacity (Bmax) of receptors for parathyroid hormone (PTH)/parathyroid hormone-related peptide (PTHrP) and calcitonin (CT) in the membrane fraction of the calvaria and the kidney of chickens were examined from 1 d after the hatch up to 24 wk of age by the use of radioligand binding assays. The Kd values of the PTH/PTHrP receptor in both tissues were decreased at 10 and 24 wk in female birds, whereas the values were increased at 24 wk in male birds. The Bmax values of the PTH/PTHrP receptor in both tissues were decreased at 10 wk and returned to baseline at 24 wk in female birds. The values were increased at 24 wk in male birds. The Kd and Bmax values of CT receptors in the both tissues were constant during the experimental period in female and male birds. The results suggest that the binding properties of PTH/PTHrP receptor and of CT receptor may be influenced by gonadal hormones relating to sexual maturation.