Body composition, gastrointestinal, and reproductive differences between broiler breeders fed using everyday or skip-a-day rearing programs

Daily feeding frequency affects feed intake and body weight management of growing layers

The objective of this study was to investigate the effect of feeding behavior on feed intake and body weight in growing layers and the underlying mechanisms, thereby providing a scientific foundation for optimal feeding practices in growing layers' management. A total of 144 Hy-line brown growing layers of 10 wk old and similar body weight, were divided into 3 treatment groups with different feeding frequency and equal cumulative daily feeding amount: the once-a-day feeding group (F1) was fed at 9:00 am every day, with feeding amount of 150 g/layer; the twice-a-day feeding group (F2) were fed at 9:00 am and 13:00 pm every day, with each feeding amount of 75 g/layer; the 4 times-a-day feeding group (F4) were fed at 9:00 am, 11:00 am, 13:00 pm, and 15:00 pm every day, with each feeding amount of 37.5 g/layer. Pre-experiment lasted for 1 wk and formal experiment lasted for 8 wk. The results indicated that the daily feed intake and body weight were decreased (P < 0.05) while feed conversion ratio was not affected (P > 0.05) as daily feeding times increased. The glandular stomach proportion was significantly increased in twice-a-day feeding group, while liver proportion and ileum length were significantly increased in 4 times-feeding group (P < 0.05). Additionally, 4 times-feeding daily resulted in a significant elevation of blood glucose levels, which may have suppressed feed intake (P < 0.05). In 4 times-feeding group, the plasma triglyceride levels increased as feeding times, accompanied by a notable up-regulation in the mRNA level of appetite-suppressing gene, hypothalamic pro-opiomelanocortin (POMC) and glandular stomach ghrelin. This modulation effectively suppressed the subsequent feed intake and body weight. Therefore, 4 times feeding daily is recommended in growing layers' management, because it reduced the feed cost without affecting the feed conversion efficiency.

Dual-energy X-ray absorptiometry: an effective approach for predicting broiler chicken body composition

Two trials were carried out to develop and validate linear regression equations for body composition prediction using Dual-energy X-ray absorptiometry (DEXA). In Trial 1, 300 Cobb500 male chickens raised from 1 to 42 d of age were scanned in DEXA to estimate total weight, fat mass, soft lean tissue (SLT) mass, bone mineral content (BMC), and fat percentage. DEXA estimates were compared to body ash, crude fat, SLT (sum of protein and water) and scale body weight. The dataset was split, with 70% used for prediction equations development and 30% for testing, and the 5k-fold cross-validation analysis was used to optimize the equations. The R2, mean absolute error (MAE), and root-mean-squared error (RMSE) were used as precision and accuracy indicators. A negative correlation (ρ = -0.27) was observed for ash content, while no correlation was observed for protein content (P > 0.05). Predictive linear equations were developed to assess broiler weight (R2 = 0.999, MAE = 25.12, RMSE = 38.99), fat mass (R2 = 0.981, MAE = 13.87, RMSE = 21.28), ash mass (R2 = 0.956, MAE = 3.98, RMSE = 5.61), SLT mass (R2 = 0.997, MAE = 35.73, RMSE = 52.45), water mass (R2 = 0.997, MAE = 29.56, RMSE = 43.94), protein mass (R2 = 0.989, MAE = 12.94, RMSE = 19.05), fat content (R2 = 0.855, MAE = 0.81, RMSE = 1.05), SLT content (R2 = 0.658, MAE = 1.01, RMSE = 1.28), and water content (R2 = 0.678, MAE = 0.99, RMSE = 1.27). All equations passed the test. In Trial 2, 395 Cobb500 male chickens were raised from 1 to 42 d of age and used for validation of prediction equations. The equations developed for weight, fat mass, ash mass, SLT mass, water mass, and protein mass were validated. In conclusion, DEXA was found to be an effective approach for measuring the body composition of broilers when using predictive equations validated in this study for estimate calibration.

Effects of energy restriction during growing phase on the productive performance of Hyline Brown laying hens aged 6 to 72 wk

The aim of this study was to assess the effects of energy-restricted feeding during growing phase on the productive performance of Hyline Brown laying hens aged 6 to 72 wk. A total of 720 six-week-old layer chicks were allocated equally to 3 groups with 6 replicates of 40 pullets each, and were fed 1 of 3 diets that were nutritionally similar except for the apparent metabolizable energy corrected for nitrogen (AMEn) content. At the age of 6 to 17 wk, the pullets in the control group were given diet with 2,850 kcal/kg AMEn, and were fed ad libitum. The levels of AMEn in diet of pullets in the experimental groups were 90% (2,565 [2,850 × 90%] kcal/kg) and 80% (2,280 [2,850 × 80%] kcal/kg) of that in control group, and the daily amount of feed was restricted to the absolute quantity of the diet consumed by pullets in control group. At the age of 18 to 72 wk, all the hens were fed with the same diets ad libitum. As energy restriction increased in the growing phase, body weight (BW) dropped at the ages of 12 and 15 to 23 wk (at 23 wk: P = 0.001; at other ages: P < 0.001), but it showed no significant difference at 24 wk (P = 0.071). At 20 wk, restricting energy induced a delay in the development of sexual organs, including the ovary stroma, oviduct, and small yellow follicle (P < 0.05), as well as a delay in sexual maturity (P < 0.05). Consequently, the laying rate in the first and second periods dropped linearly (P = 0.046, 0.030, and 0.038, P < 0.001, respectively). The coefficient of variation (CV) in the BW at 19, 20, and 21 wk (P = 0.040, 0.023, and 0.042, respectively), the CV of age at first egg (P < 0.001), and CV of individual egg number at age 18 to 72 wk (P < 0.001) decreased linearly. There was a linear increase in the laying rate of hens in the later periods (at age 32-72 wk, P < 0.05), as well as in the average total egg number per hen and average laying rate at the age of 18 to 72 wk (P = 0.006). The average egg mass also showed a linear increase with increasing levels of energy restriction (P < 0.001). In summary, although appropriate energy restriction during growing phase delayed sexual maturity and sexual organ development in early-laying Hyline Brown pullets, it improved uniformity of BW, age at first egg laying, and individual egg number, and increased egg number per hen, laying rate, average egg mass, and number of settable eggs from 18 to 72 wk of age.