Molecular mechanisms of growth depression in broiler chickens(Gallus Gallus domesticus)mediated by immune stress:a hepatic proteome study

Background:Immunological stress decreases feed intake,suppresses growth and induces economic losses.However,the underlying molecular mechanism remains unclear.Label-free liquid chromatography and mass spectrometry(LC-MS)proteomics techniques were employed to investigate effects of immune stress on the hepatic proteome changes of Arbor Acres broilers(Gallus Gallus domesticus)challenged with Escherichia coli lipopolysaccharide(LPS).Results:Proteomic analysis indicated that 111 proteins were differentially expressed in the liver of broiler chickens from the immune stress group.Of these,28 proteins were down-regulated,and 83 proteins were up-regulated in the immune stress group.Enrichment analysis showed that immune stress upregulated the expression of hepatic proteins involved in defense function,amino acid catabolism,ion transport,wound healing,and hormone secretion.Furthermore,immune stress increased valine,leucine and isoleucine degradation pathways.Conclusion:The data suggests that growth depression of broiler chickens induced by immune stress is triggered by hepatic proteome alterations,and provides a new insight into the mechanism by which immune challenge impairs poultry production.

Effects of dietary leucine supplementation on the gene expression of mammalian target of rapamycin signaling pathway and intestinal development of broilers

This experiment was to investigate the effects of dietary leucine supplementation on the gene expression of mammalian target of rapamycin(mTOR) signaling pathway and intestinal development of broilers. A total of 384 one-day-old broilers were randomly assigned into 4 treatments with 6 replicates(16 broilers per replicate). Broilers in these treatment groups were offered the following diets with 1.37,1.77,2.17 and2.57% of leucine. These diet treatments were named 1.37 TM, 1.77 TM, 2.17 TM, and 2.57 TM. The experiment lasted 21 days and all birds had free access to feed and water. Results indicated that there was no significant difference in body weight, average daily gain and average feed intake among all treatments(P > 0.05). The broiler duodenal villus height in 2.57 TM was the lowest, but the highest occurred in1.37 TM on d 7 and 14(P < 0.05). The villus height in the jejunum and ileum increased along with leucine level from 1.37 to 2.17%. The villus height of jejunum was significantly higher in 2.17 TM than in 1.37 TM on d 7 and 14, and the ratio of villus height to crypt depth(V:C) in the duodenum, jejunum and ileum increased significantly(P < 0.05) on d 21. The gene expression level of mTOR in the duodenum decreased with increasing leucine level and was higher in 1.37 TM than in 2.57 TM on d 7 and 14(P < 0.05). On d 14 and 21 of the trial, the expression of S6 K1 in the duodenum was higher in 1.37 TM than in 2.57 TM(P < 0.05), and the expression of mTOR, S6 K1 in the jejunum and ileum increased with increasing leucine level form 1.37 to 2.17%, whereas a significant difference occurred between 1.37 TM and 2.17 TM(P< 0.05).In conclusion, the addition of leucine fails to enhance the growth performance of broilers. However,leucine can improve intestinal development by enhancing villus height and V:C ratio in the jejunum and ileum. Moreover, the expression of mTOR, S6 K1 increased as the level of dietary leucine was elevated from 1.37 to 2.17%.

Effects of aflatoxins on growth performance and skeletal muscle of Cherry Valley meat male ducks

This study aims to evaluate the effects of aflatoxins on growth performance and skeletal muscle of Cherry Valley meat male ducks as they grow and develop. One-day-old healthy meat male ducks(n = 180) were randomly divided into 2 groups; there were 6 replicates in each group and 15 ducks in each replicate. The control group was fed a basic diet, and the experimental group was fed a mold-exposed cottonseed meal diet containing aflatoxins instead of normal cottonseed meal. The experimental period was 35 days, and divided into two stages of 1 to 14 days(early stage) and 15 to 35 days(late stage). During the experimental period, live weight, breast muscle weight and thigh muscle weight of meat male ducks were measured weekly. Results showed as follows: 1) aflatoxins contained in the mold-exposed diet significantly reduced daily weight gain and feed intake, and increased feed-to-gain ratio of meat male ducks at different ages(P < 0.05); 2) the Gompertz equation(W_t = W_m exp {-exp [-B(t-t~*)]}) could successfully fit the growth curve and growth and developmental patterns of skeletal muscles of Cherry Valley meat male ducks(R^2≥0.97); 3) the relationship between chest muscle and live weight was the best described by a power regression and polynomial regression(R^2 = 0.99); the relationship between live weight and thigh muscle weight was the best described by linear regression, polynomial regression, and power regression(R^2 = 0.99); 4) aflatoxins in the mold-exposed diet significantly reduced live weight, breast muscle weight and thigh muscle weight of Cherry Valley meat male ducks at various ages; and 5) aflatoxins delayed the age at peak in growth of meat male ducks, and reduced weights at the peak for breast muscle, thigh muscle and whole body as well as the maximal daily weight gain. In summary,aflatoxins delayed growth of Cherry Valley meat male ducks and development of skeletal muscle.