Response surface models to predict broiler performance and applications for economic analysis

Assessing Temperature Distribution inside Commercial Stacked Cage Broiler Houses in Winter

The temperature inside broiler houses is crucial to broiler health, welfare, and productivity. High stocking density in broiler houses can easily lead to nonuniform temperature conditions, which would cause broilers to suffer cold and heat stress. It is essential to assess the temperature distribution inside broiler houses and investigate the factors that affect temperature uniformity. Therefore, in this study, temperature, wind velocity, and differential pressure were monitored in the aisle, at the sidewall inlet, and outside the sidewalls of a commercial stacked-deck cage broiler house in Northeast China aiming to continuously monitor the temperature throughout the entire fattening period. Results show that the maximum temperature difference increased from 1.85 °C to 6.43 °C, while the daily fluctuation increased from 2.27 °C to 5.80 °C. The highest temperature was consistently recorded at the side of the exhaust fans (p < 0.001) in the longitudinal direction. In the lateral direction, the temperature difference varies periodically with solar radiation. The average temperature at the southern location (23.58 ± 1.97 °C), which faces the sun, was higher than that at the northern location (23.35 ± 1.38 °C), which is in the shade, during periods of solar radiation (p < 0.001) at the last testing period. However, without solar radiation, the northern location recorded a warmer temperature (23.19 ± 1.41 °C) compared to the southern location (22.30 ± 1.67 °C) (p < 0.001). The lateral temperature differences are strongly positively correlated with solar radiation and wind speed (p < 0.001). In conclusion, the inside temperature nonuniformity and fluctuation increased as the broiler age increased, which affected the production performance of broilers. Nonuniform solar radiation and wind speed can lead to differences in the inlet temperature and air volume between both sidewalls, thereby affecting the uniformity of the lateral temperature inside the house.

Feed-additive probiotics accelerate yet antibiotics delay intestinal microbiota maturation in broiler chicken

BACKGROUND

Reducing antibiotics overuse in animal agriculture is one key in combat against the spread of antibiotic resistance. Probiotics are a potential replacement of antibiotics in animal feed; however, it is not clear whether and how probiotics and antibiotics differ in impact on physiology and microbial ecology of host animals.

RESULTS

Host phenotype and fecal microbiota of broilers with either antibiotics or probiotics as feed additive were simultaneously sampled at four time points from birth to slaughter and then compared. Probiotic feeding resulted in a lower feed conversion ratio (FCR) and induced the highest level of immunity response, suggesting greater economic benefits in broiler farming. Probiotic use but not antibiotic use recapitulated the characteristics of age-dependent development of gut microbiota in the control group. The maturation of intestinal microbiota was greatly accelerated by probiotic feeding, yet significantly retarded and eventually delayed by antibiotic feeding. LP-8 stimulated the growth of many intestinal Lactobacillus spp. and led to an altered bacterial correlation network where Lactobacillus spp. are negatively correlated with 14 genera and positively linked with none, yet from the start antibiotic feeding featured a less-organized network where such inter-genera interactions were fewer and weaker. Consistently, microbiota-encoded functions as revealed by metagenome sequencing were highly distinct between the two groups. Thus, "intestinal microbiota maturation index" was proposed to quantitatively compare impact of feed additives on animal microecology.

CONCLUSIONS

Our results reveal a tremendous potential of probiotics as antibiotics' substitute in poultry farming.

Update of model to predict sensible heat loss in broilers

The present study was conducted to adjust and adapt some parameters of the model of production and heat loss by convection and conduction, so as to predict the actual feed intake (aFI) of broilers reared in sheds. The re-parameterised models were the sensible heat loss by convection from surface (HS) and by conduction (HC) in birds. The HS model was re-parameterised to calculate the heat loss of poultry reared in sheds and the parameters of thermal resistance of feathers (RF) and skin (RS) of poultry were inserted. The HC model was re-parameterised for birds in sheds and the RF, RS and the thermal resistance of the litter (R) were inserted. The re-parameterised HS model was HS = [A × QV × (TB – TA)]/[(TB – 17) × (RF + RS)], where TA is the air temperature, QV is the volume factor, TB is the surface temperature of the bird (°C) and A was estimated to be 11.94 watts (W). The values found in the model ranged from 0.75 W for birds with 100 g BW subjected to 33°C TA, 50% HU, 0.1 m/s wind speed (V) and 12.53 W for birds with 4100 g subjected to 33°C TA, 80% HU and 0.1 m/s V. The values found in the re-parameterised HC model (HC = [(TB – TC) × k × AR × QA]/[L × (RF + RS + R)], where K is the thermal conductivity of the litter, AR is the contact area of bird with the litter and QA is the area factor, and L is the litter height) ranging from 0.017 W to chickens with 100 g BW in comfortable conditions and 0.17 W for birds with 4100 g in thermal discomfort condition. The present study showed that the re-parameterisation of heat-loss equations is more accurate to predict the heat flux in broilers under different environmental conditions.