| An experiment was conducted to investigate the effect of dietary zinc(Zn) source on laying performance, egg quality, hatching performance of eggs, plasma and tissue antioxidant capacity and relevant molecular indices of broiler breeder hens under different temperatures, and discussed the anti-heat stress effect and possible mechanism of dietary Zn on broiler breeder hens.One hundred and forty-four twenty-three-week-old female broiler breeders were randomly allotted to 6 treatments with 6 replicates of 4 birds per replicate based upon body weight(BW). A completely randomized factorial design involved in 2 environmental temperatures: 21?1℃ normal temperature and 32?1℃ high temperature and 3 dietary Zn treatments(a no Zn addition corn-corn starch-soy isolate protein meal basal diet(9.98 mg of Zn/kg), and the basal diet supplemented with 110 mg of Zn/kg of diet as either Zn SO4?7H2O or Zn proteinate with the moderate chelation strength(Qf =30.73). The adaptation period was 7 weeks, the Zn depletion period was 3 weeks, and the experimental period was 9 weeks. The eggs of the last 3 consecutive days of the 3rd, 7th, 9th week in the experimental period, the plasma samples of d 224, 249, 291, and the liver and pancreas in the end of the experiment were collected for further analyses.Compared with normal temperature, heat stress significantly decreased the laying rate and average egg weight(P<0.0002), the eggshell quality of hatching eggs in the 3rd, 7th, 9th week, the yolk color score of the 3rd week and the yolk Zn content of the 9th week, the plasma ALP and Cu Zn SOD activities of d 249(P<0.002). Heat stress significantly increased the RT of broiler breeder hens in d 249 and 291, the broken egg rate and feed/egg ratio(P<0.0001), the plasma TRI and MDA contents, CK activity of d 249, the Cu Zn SOD activities, MT contents and the HSP70 m RNA levels of liver and pancreas and HSP90 m RNA level of liver and pancreas(P<0.06). Compared with no Zn addition, added organic Zn had higher(P<0.08) yolk color score of the 3rd week, plasma Cu Zn SOD activity of d 249, plasma MDA content of d 291 and liver Zn content, and no significant difference(P>0.35) was observed between no Zn addition and added inorganic Zn. Compared with no Zn addition, added organic Zn and inorganic Zn had higher(P<0.04) birth rate, and healthy young chicken rate of hatching eggs in the 3rd week, the yolk Zn content of the 9th week and the MT content of liver, and no significant difference(P>0.34) was observed between added inorganic and organic Zn. Compared with added inorganic Zn, added organic Zn had lower(P<0.10) HSP70 and HSF2 m RNA levels of liver, and no significant difference(P>0.26) was observed between no Zn addition and added inorganic Zn. Under normal temperature, compared with no Zn addition and added organic Zn, added inorganic Zn had higher(P<0.003) plasma ALP activity of d 291, and no significant difference(P>0.99) was observed between no Zn addition and added organic Zn, however, under high temperature, no significant difference(P>0.36) was observed among 3 dietary Zn treatments. Under normal temperature, no significant difference(P>0.13) was observed in the pancreas Zn content and HSF3 m RNA levels of liver and pancreas among 3 dietary Zn treatments, however, under high temperature, compared with added inorganic Zn, added organic Zn had higher(P<0.05) pancreas Zn and lower(P<0.002) HSF3 m RNA levels of liver and pancreas, meanwhile, added inorganic Zn had higher(P<0.03) pancreas Zn than no Zn addition, and no significant difference(P>0.69) was observed in HSF3 m RNA levels of liver and pancreas between no Zn addition and added organic Zn.Above all,(1) High temperature impaired laying performance, eggshell quality, and plasma antioxidant capacity of broiler breeder hens, and under high temperature, high temperature could significantly increase the Cu Zn SOD activities, Zn contents and HSP70 m RNA levels of liver and pancreas, and HSP90 m RNA level of liver, in order to protect the body from the effects of heat stress.(2) Dietary Zn regardless of source significantly increased the yolk Zn content, birth rate, and healthy young chicken rate of hatching eggs, Zn and MT contents of liver and pancreas, and especially the effects of the organic Zn on increasing decreasing the HSP70, HSF2 m RNA levels of liver and plasma Cu Zn SOD activity and the yolk color score were much better than that of the inorganic Zn.(3) The effect of this kind of Zn proteinate with the moderate chelation strength on increasing the pancreas Zn content was better than that of the inorganic Zn sulfate under high temperature, and added organic Zn could protect the HSF3 m RNA levels of liver and pancreas from the effects of heat stress. |
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