Influence Of Dietary Nicotinic Acid Supplementation On Lipid Metabolism And Meat Quality And The Mechanisms In Chickens

Three experiments were conducted to study the effects of dietary supplemental nicotinic acid (NA) on lipid metabolism and meat quality in 3 genotypes of chicken. Fast-growing AA broilers were compared with 2 genotypes of a slow-growing local breed, Beijing-you, that had undergone selection for and against intramuscular fat content, respectively (BJY+IMF & BJY-IMF). Birds were fed diets (basal contained approximately 25 mg NA/kg) supplemented with 0,30,60, and 120 mg NA/kg, and the apparent characteristics, plasma lipid metabolism, enzyme activity, and expression of related genes were investigated.Expl. The influence of supplemental dietary NA on growth performance, carcass characteristics, and meat quality were evaluated. The treatments were arranged 3×4 factorial completely randomized design.624 female birds that were 1 d old were allotted to 4 treatments with 6 replicates per treatment. Birds were fed diets (containing～25 mg NA/kg) supplemented with 0,30,60,120 mg/kg NA, respectively. A sample of 72 birds from each line was slaughtered at 8 wk (market age for AA) and additional BJY were slaughtered at their market age of 16 wk. The results indicated that:①Broilers fed corn-soybean meal based-diets require approximately 60 mg NA/kg to maximize the growth performance;②The impacts of supplemental NA on average daily gain, average daily feed intake, and the tolerance of NA deficiency were much greater for AA broilers than for BJY+IMF and BJY-IMF;③Supplemental NA increased the percentage of abdominal fat, thickness of subcutaneous fat plus the skin, and width of intermuscular fat band and then decreased;④Drip loss of breast and thigh muscle was decreased with 60 mg NA/kg,while the pH value and tenderness of thigh muscle was improved;⑤Supplementing 120 mg NA/kg decreased the IMF content of AA and BJY+IMF. Interesting, for BJY+IMF,120 mg NA/kg supplementation increased IMF both in breast and thigh muscle while decreased the undesirable abdominal fat.Exp2. The effects of supplemental dietary NA on plasma lipid metabolism, concentrations of adipocytokines, and enzyme activity, were examined.The treatments design was the same with Expl. The results showed that:①BJY+IMF and BJY-IMF had higher concentrations of plasma free fatty acid (FFA) and adiponectin,and hepatic malic dehydrogenase (MDH) activity compared to AA broilers; The enzyme activity of plasma liprotein lipase (LPL) was highest in BJY+IMF, followed by BJY-IMF, and lowest in AA;②Dietary NA supplementation impacted the concentrations of plasma FFA, total cholesterol (TCH),low- and high-density lipoprotein cholesterol (LDLC & HDLC) interaction effects between breed/age and NA on these items were significant; The concentration of plasma TCH of AA broilers tended to decrease with additional NA; Supplementation from 0-60 mg NA/kg tend to increase plasma TG and FFA levels, but values decreased slightly with 120 mg NA/kg; Supplementing 120 mg NA/kg significantly improved plasma TCH, LDLC and FFA levels of BJY+IMF;③On day 56, with the increasing of NA, plasma leptin in BJY-IMF tend to increase and then decrease, while it decreased linear in BJY+IMF. At market time, the plasma leptin level was down-regulated with 120 mg NA/kg.④Increasing supplemental NA increased and then decreased the plasma Adiponectin concentration in AA broilers, with the ADG and fat deposition in the opposite trend, which suggested that the affects of NA on BW and fat deposition maybe related with plasma adiponectin concentration.Exp3. The impacts of supplemental dietary NA on hepatic transcription and gene expression in abdominal fat tissue and breast muscle related to lipid metabolism and meat quality were evaluated. The treatments were arranged 2×4 factorial completely randomized design. Portions of liver, abdominal fat and breast muscle of AA and BJY+IMF mentioned in Expl were sampled for analysis of mRNA abundances. The results indicated that:①Compared with BJY+IMF at day 56, the AA broilers had higher hepatic apolipoprotein A-Ⅰ(ApoA-Ⅰ) and adiponectin mRNA levels, and lower A-FABP, H-FABP, adiponectin and PPARy mRNA levels in abdominal fat tissue and lower A-FABP, H-FABP, PPARa and LPL mRNA levels in breast muscle.②Compared with BJY+IMF at market time, the AA broilers had higher hepatic ApoA-Ⅰ, ApoB and adiponectin mRNA levels, higher A-FABP, H-FABP, PPARa mRNA in breast, and lower A-FABP,H-FABP,Adiponectin mRNA in abdominal fat tissue.③ApoA-Ⅰand ApoB mRNA levels appeared cubic response to supplemental NA.④On day 56, A-FABP mRNA in abdominal fat tissue had quadratic response to additional NA, with the increasing supplemental NA, A-FABP mRNA in breast decreased linear, while H-FABP decreased and then increased. At market time, supplemental NA could up-regulated A-FABP and down-regulated H-FABP in abdominal fat tissue.⑤Increasing supplemental NA increased and then decreased the expression of Adiponectin expression of liver and abdominal fat in AA broilers, with the ADG and fat deposition in the opposite trend. The results indicated that the affected of NA on BW and fat deposition maybe related to the changes in transcription of adiponectin.⑥Increasing supplemental NA increased and then decreased the expression of PPARa in abdominal fat. The PPARy mRNA levels in abdominal fat tissue of BJY+IMF at 56d of age were improved with 120 mg NA/kg. PPARy mRNA levels in breast had quadratic response to additional NA.⑦The expression of ATGL in abdominal fat was up-regulated with 30 mg NA/kg and then decreased with higher NA level.In conclusion, growth performance and meat quality could be improved with 60 mg NA/kg. The regulation of NA on adiponectin expression in liver and abdominal fat maybe change the plasma concentration of adiponectin and then influence the BW and fat deposition.