Effect Of Ammonia In Houses On Lipid Metabolism Of Broilers

This study was to evaluate the effect of ammonia on growth performance and lipid metabolism of broilers, which was to provide data to environment control and premium chicken meat production.This study was included three parts.Experiment 1: The aim of this experiment was to study the effect of ammonia on growth performance and body fat distribution of broiler chickens. The trial was adopted one-factor completely random design. A total of 400 21-day-old Arbor Acres(AA) male broilers were randomly divided into 4 respiratory chambers, and each chamber was a treatment. There were 4 replicates in each treatment, and 25 broilers in each replicate. The following ammonia concentrations were set in different groups: <3 mg.kg-1(control group), 25±3, 50±3, 75±3 mg.kg-1 respectively. The entire experimental period was 21 days: the starter phase was 21-31 d, and the later phase was 32-42 d. Broilers were provided ad libitum access to feed and water in nets. Broilers were slaughtered to sampling at 32 d and 42 d of age. The environment of the respiratory chambers were controlled automatically. The results showed as follows: 1) Growth performance: ADFI and ADG showed a linear decrease(P<0.05), while F/G did not change significantly at 21–31 d or 32–42 d of age(P>0.05) with increasing ammonia concentration. At 21–31 d of age, compared to control group, ADFI showed a decrease by 2.25%, 7.09%, and 12.34% at 25, 50, and 75 mg.kg-1 ammonia treatments, respectively, while ADG showed a decrease by 1.62%, 16.90%, and 23.38%. At 32–42 d of age, ADFI showed a decrease by 12.85%, 25.82%, and 30.14% respectively, while ADG showed a decrease by 6.47%, 26.45%, and 45.04% respectively. 2) Body fat distribution: At 32 d of age, Subcutaneous fat thickness showed a linear increasing trend(0.05<P<0.10) with increasing ammonia concentration. The percentage of breast muscle fat showed a linear decrease(P<0.05), while the percentage of abdominal fat, inter-muscular fat width, hepatic fat, and thigh muscle fat did not change significantly(P>0.05) with increasing ammonia concentration. According to the correlation coefficients and probabilities, ADFI showed low, significant positive correlation with the percentage of breast muscle fat(0<|r|<0.40, P<0.05). Inter-muscular fat width showed a moderate positive correlation with the percentage of hepatic fat(0.40<|r|<0.70, P<0.05), and low positive correlation with subcutaneous fat thickness(0<|r|<0.40, P<0.05). Subcutaneous fat thickness showed a low positive correlation with the percentage of hepatic fat(0<|r|<0.40, P<0.05). All other variable combinations did not show any significant correlation(P>0.05). At 42 d of age, the percentage of abdominal fat showed a linear increase(P<0.05), but subcutaneous fat thickness showed a quadratic decrease(P<0.05) with increasing ammonia concentration. The percentages of hepatic fat and breast muscle fat showed a linear decrease(P<0.05), while the percentage of inter-muscular fat width and thigh muscle fat did not change significantly(P>0.05) with increasing ammonia concentration. ADFI did not show any significant correlation with any body fat distribution variables(P>0.05). 3)the composition of fatty acid: At 42 d of age, there were no significant difference in the composition of fatty acid of breast(P>0.05). But the stearic and the total saturated fatty acids showed a quadratic increase in the thigh(P<0.05), and were highest when exposed to 50 mg.kg-1. On the contrary, unsaturated fatty acids showed a quadratic decrease(P<0.05), and were lowest when exposed to 50 mg.kg-1. Palmitoleic, oleic and monounsaturated fatty acid showed a tread of decrease(0.05<P<0.10).Experiment 2: The aim of this experiment was to study the effect of ammonia on serum lipids and the content of lipid metabolism-related hormones of broiler chickens. the experimental design was the same as experiment 1. The results showed that: 1) Serum lipids: At 32 d of age, TC, TG, HDL-C, LDL-C, and HDL-C/LDL-C did not show any significant differences between ammonia treatments(25, 50, and 75 mg.kg-1) and the control(<3 mg.kg-1). At 42 d of age, HDL-C and HDL-C/LDL-C showed a linear increase(P<0.05), while TC, TG, and LDL-C did not change significantly(P>0.05) with increasing ammonia concentration. 2) The content of apolipoprotein: At 32 and 42 d of age, serum apo AⅠ concentration decreased linearly(P<0.05), while apo B concentration did not change significantly(P>0.05) with increasing ammonia concentration. 3) The activity of HL and LPL: At 32 d and 42 d of age, the activity of HL showed a linear decrease(P<0.05) with increasing ammonia concentration. The activity of LPL did not change significantly(P>0.05). The activity of HL and LPL in the liver did not change significantly at the age of 32 d(P>0.05), while they showed a linear decrease at 42 d of age(P>0.05) with increasing ammonia concentration. 4) The content of lipid metabolism-related hormones: At 32 d of age, T3, T4, T3/T4, and INS did not change significantly(P>0.05) with increasing ammonia concentration. At 42 d of age, the content of T4 showed a linear increase(P<0.05) with increasing ammonia concentration. The content of T4 and T3/T4 increased significantly in the 25 mg·kg-1 ammonia treatment(P>0.05) compared to the control(<3 mg.kg-1).Experiment 3: The aim of this experiment was to study the effect of ammonia on the relative expression of lipid metabolism-related genes in the livers of broiler chickens. The experimental design was same as experiment 1. The results showed that: At 32 d of age, the relative expression of ME and FAS in the liver increased at the 50 mg·kg-1 ammonia concentration(P<0.05) compared to the control. The relative expression of ACC and CPTⅠ in the liver did not change significantly(P>0.05) with increasing ammonia concentration. At 42 d of age, the relative expression of ACC in the liver increased significantly at the 75 mg·kg-1 ammonia concentration(P<0.05) compared to the control, however, the relative expression of ME, FAS, and CPTⅠ did not change significantly(P>0.05) with increasing ammonia concentration.In summary, ammonia decreased the growth performance of broiler chickens, changed the body fat distribution caused by the increased thyroid hormone levels in the serum and the relative expression of lipid synthesis genes in the liver.