Effects Of Niacin And Chromium Nicotinate On Heat-stressed Dairy Cows And Weanling-stressed Calves

The purpose of this study is to discuss the effects of niacin and chromium nicotinate on the heat-stressed dairy cows and weanling-stressed calves ,the mechanisms were also concerned.In experiment I, 36 Holstein dairy cows were randomly divided into control group, niacin group and chromium nicotinate group according to their parturition numbers, milk yield and lactation period. The test lasted 60 days, the concentrate of niacin group was added with 800mg/kg Niacin, the chromium nicotinate group was 10mg/kg chromium nicotinate while there was no addition in the control group.The results showed feeding niacin and chromium nicotinate could lessen the decline tendency of milk yield which were raised respectively by 12.02% (p < 0.05) and 4.86%, compared with the control group and increase the roughage intake of heat-stressed dairy cows to some extent; The milkfat percentage, lactoprotein, SNF were raised respectively by 5%, 2.8%, 1.8% by feeding chromium nicotinate. PRL, T3, T4 levels of the serum were all significantly increased (p < 0.05 ) and COR level of the serum was significantly dropped by 8.80% (p < 0.05) by feeding chromium nicotinare; PRI^ TS> T4> GLUlevels of the serum were raised by 14.27% (p < 0.05) , 22.22% (p < 0.05), 11.46%, 3.12% respectively and the COR level of serum was not significantly dropped by niacin addition, compared with the control.In experiment II, 15 Holstein dairy cows which parturition numbers was from 2 to 4 were randomly divided into control, niacin, chromium nicotinate groups according to their parturition numbers, milk yield and lactation period. There were 5 dairy cows in every group. The niacin group was added with 800mg/kg Niacin, the chromium nicotinate group was added with lOmg/kg chromium nicotinate while there was nothing addition in the control. This experiment which was divided into test A and test B lasted 75 days.In test A, feeding niacin could raised acidity and CitraAcid and TS content of milk by 9.1%> 28.6%> 4.7% in the testing anaphase, compared with the testing prophase. Feeding chromium nicotinate could raised acidity and CitraAcid and TS content of milk by 7.3%^ 30.8%> 4.2% in the testing anaphase, compared with the testing prophase. However, there were no effects on the other by niacin and chromium nicotinate .In test B, (1) Feeding niacin and chromium nicotinate could raise the roughage intake by 0.4%, 1.2%, compared with the control group. (2) Increasing tendency of rectal temperature were alleviated by niacin and chromium nicotinate, however, there were no effects on temperature of body surface; Feeding chromium nicotinate kept respiratory rate comparatively stable on heat-stress dairy cows. (3) Feeding niacin and chromium nicotinate lessened the decline tendency of milk yield and lactoprotein; Acidity of milk was raised by 1.2%, 5.2% respectively; CitrAcid content of milk was raised by 6.3%, 23% respectively in the testing anaphase, compared with the testing prophase; Acidity and CitraAcid content ofmilk of the control had no changes in the testing period; FFA of milk was evidently raised (p<0.05), compared with the control group. Mlikfat percent was markedly dropped(p<0.05) by feeding chromium nicotinate. (4) The levels of T3, PEL in serum were markedly raised (p<0.05) and the level of COR in serum was markedly dropped (p<0.05) in the niacin and chromium nicotinate groups, compared with the control. (5) There was no effect on serum glucose (p>0.05), but serum urea nitrogen, cholesterol decreased (p<0.05) significantly and serum triglyceride decreased by 11%> 3.1% in the niacin and chromium niotinate groups respectively as compared to the control. (6) Feeding chromium nicotinate evidently raised leucocyte numbers and lymphocyte percent of blood (p<0.05); Leucocyte numbers of blood were evidently raised hi the niacin group as compared to the control group (p<0.05);In experiment III, 30 Holstein weanling calves in similar body weight were divided into the control group, niacin, chromium nicotinate groups. Effects of niacin and chromium nicoti...