| At present, the theory and technology of making functional milk by dietary has made much progress at home and abroad. But there is much work to do to fully regulate content of trace nutrients in milk by dietary. A large number of studies have shown that dietary addition of conjugated linoleic acid diets (CLA), selenium, vitamin E and zinc can increase content of CLA, selenium, vitamin E and zinc in milk. But the study of effecting of dietary addition of calcium salts of CLA (Ca-CLA)on content of c9,t11-CLA in milk fat has not been reported. In addition, if adding both dietary selenium and vitamin E is better than adding a separate in diet, that is still not very clear. Also, the study of effecting of dietary addition of zinc gluconate on milk production and the content of zinc in milk in dairy cattle has not been reported. To solve the above problems, this study was aimed to summarize the follow rules:(1) Effect of dietary addition of calcium salts of CLA on milk production and content of c9,t11-CLA in milk fat in dairy cattle; (2) if adding both dietary selenium and vitamin E is better than adding a separate in diet to increase content of selenium and vitamin E in milk and plasma in dairy cattle; (3) Effect of dietary addition of zinc sulfate, zinc peptide and zinc gluconate on content of zinc in milk and plasma in dairy cattle. The study included the follow 3 trials:Trial 1 was intended to investigate the effect of dietary addition of Ca-CLA on milk production and content of c9,t11-CLA in milk fat. Forty Chinese Holstein cows in mid lactation with same parity and similar milk yield were randomly assigned to 5 groups and they were fed different diets with the addition of Ca-CLA at 0 g/d,20g/ d,80 g/d,140 g/d and 200 gCLA/d, respectively. The duration of the trial was 60 d (10 d of preliminary trial and 50 d of trial). The milk yield, concentrations of milk components, and content of c9,t11-CLA in milk fat were measured on Day 1, Day 10, Day 20, Day 30, Day 40 and Day 50, respectively. The results showed:(1) dietary addition of CLA had no significant effects on milk yield and concentrations of protein and lactose in milk (P>0.05); (2) The content of milk fat decreased exponentially as the addition of CLA increased (P<0.05). Compared with the addition of 0 g/d of CLA, addition of 20g/d,80 g/d,140 g/d and 200 g/d of CLA decreased percentage of milk fat over the entire trial period by 13.1%,19.7%,20.7% and 30.2%, respectively; (3) The concentration of c9,t11-CLA in milk fat increased linearly as the addition of CLA increased (P<0.05). And the content of c9,t11-CLA in milk fat over the entire trial period increased by 87.9%,143.5%,140.4% and 276.7%, respectively. The content of c9,t11-CLA in milk over the entire trial period increased by 61.7%,135.8%,116.0 % and 158.1%, respectively. In conclusion, dietary addition of Ca-CLA is an effective means to produce high CLA and low fat milk.Trial 2 was intended to investigate the effect of dietary addition of organic Se and vitamin E on milk production and the contents of Se and vitamin E in milk and plasma in dairy cattles in order to improve milk quality. Thirty-tow Chinese Holstein cows in mid lactation with same parity and similar milk yield were randomly assigned to 4 groups:control group (fed basal diet), basal diet+organic Se group, basal diet+ vitamin E group, basal diet+organic Se+vitamin E group. The duration of the trial was 60 d (10 d of preliminary trial and 50 d of trial). The milk yield, concentrations of milk(?) mpouents including Se and vitamin E in milk and plasma were measured on Day 1, Day 10, Day 20, Day 30, Day 40 and Day 50, respectively. The result showed:(1) Dietary addition of organic Se and vitamin E had no significant effects on milk yield and concentrations of protein, fat, lactose and total solid in milk (P> 0.05); (2) The contents of Se in milk and plasma increased due to dietary addition of organic Se (P <0.001); (3) The contents of vitamin E in milk and plasma increased as a result of dietary addition of vitamin E (P<0.001); (4) The interaction of organic Se and vitamin E in increasing their respective content in both plasma and milk was not found in the study. In conclusion, dietary addition of organic Se and vitamin E is an effective means to produce high Se and vitamin E milk.Trial 3 was intended to investigate the effect of dietary addition of zinc sulfate, zinc peptide and zinc gluconate on milk production and the contents of zinc in milk and plasma in dairy cattles. Thirty-tow Chinese Holstein cows in mid lactation with same parity and similar milk yield were randomly assigned to 4 groups:control group (fed basal diet), basal diet+zinc sulfate group, basal diet+zinc peptide group, basal diet+ zinc gluconate group. The duration of the trial was 60 d (10 d of preliminary trial and 50 d of trial). The milk yield, concentrations of milk components and content of zinc in milk and plasma were measured on Day 1, Day 10, Day 20, Day 30, Day 40 and Day 50, respectively. The result showed:(1) Dietary addition of zinc sulfate, zinc peptide and zinc gluconate had no significant effects on concentrations of protein, fat, lactose and total solid in milk (P> 0.05); (2) Dietary addition of zinc gluconate increased milk yield (P<0.05); (3) The content of zinc in milk and plasma increased as a result of dietary addition of zinc gluconate (P<0.05), but dietary addition of zinc sulfate and zinc peptide had no significant effects on content of zinc in milk and plasma. In conclusion, dietary addition of zinc gluconate is an effective means to produce high zinc milk.The study indicate (1) as the addition of CLA increased, the content of milk fat decreased exponentially and the concentration of c9,t11-CLA in milk fat increased linearly. (2) Dietary addition of organic Se and vitamin E had no significant effects on milk yield and concentrations of protein, fat, lactose and total solid in milk, but that could increase the contents of vitamin E in milk and plasma. The interaction of organic Se and vitamin E in increasing their respective content in both plasma and milk was not found in the study. (3) Dietary addition of zinc gluconate increased content of zinc in milk and plasma, but dietary addition of zinc sulfate and zinc peptide had no significant effects on content of zinc in milk and plasma. |
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