| This study aimed to evaluate the effects of heat and humidity stress on dairy goats and the regulate function of Pyridine carboxylic acid chromium, then sift related early warning indice. Therefore, we can provide reference for the future study on heat stress mechanism. This study was mainly conducted from the following work:1) dynamic monitoring the THI in Wuhan in summer;2) effects of heat stress on welfare indice of dairy goats and regulation function of Pyridine carboxylic acid chromium;3) effects of heat stress on rumen fermentation indice of dairy goats and regulation function of Pyridine carboxylic acid chromium;4) effects of heat stress on blood antioxidant indice and HSP70mRNA expression of dairy goats and regulation function of Pyridine carboxylic acid chromium;5) sifting related early warning indice.The first part we dynamic monitored THI in Wuhan in July and August. The THI was recorded at8:00,10:00,12:00,14:00,16:00,18:00and20:00every day. Furthermore, we draw the charts which reflect the tendency of THI. The results showed that:1) every day the THI showed a trend of decreasing after the first rise, reached the highest at14:00and the lowest at8:00, the value of the average THI could be more than79.5;2) THI in Wuhan in July and August ranged between75to85with little volatile.The second part we studied the effect of heat stress on the goats’ welfare and the regulate function of Pyridine carboxylic acid chromium. This experiment was arranged as a3×3Latin square design and three Saanen dairy goats weighting20.75±1.88kg were selected. The experiment divided three periods and every period included three groups: control group, heat stress group and supplement Cr group.THI in control group was below70with the air-condition so the goats was not in heat stress; the other two groups had similar THI above80. The result showed that heat stress had no significant effect on average daily gain, feed intake and feed conversion efficiency(P>0.05); heat stress had no significant effect on time of standing, lying, intaking, carding and times of drinking and carding(P>0.05), but significantly reduced times of ruminating(P<0.05); heat stress had no significant effect on rectal temperature(P>0.05) while significantly increased breathing rate at12:00,14:00,16:00,18:00and average daily value(P<0.05). Adding Carboxylic Acid Pyridine Chromium significantly increased rectal temperature and breathing rate(P<0.05).The third part we studied the effect of heat stress on the goats’rumen fermentation indice and the regulate function of Pyridine carboxylic acid chromium. The result showed that heat stress significantly reduced dry matter degradation rate after6h intaking, pH (P <0.05), significantly increased the concentrations of NH3-N, TVFA, Acetate acid, Propionate acid (P<0.05), significantly decreased acetate/propionate (A/P)(P<0.05). Supplementation of carboxylic acid pyridine chromium significantly increased dry matter degration after3h,6h,12h intaking (P<0.05), the concentration of Acetate acid, Butyrate acid, A/P of goats in heat stress (P<0.05), significantly decreased the concentration of Propionate acid (P<0.05), while there were no significant effects on pH and NH3-N concentration (P>0.05).The fourth part we studied the effect of heat stress on the goats’blood antioxidant indice, HSP70mRNAexpression and the regulate function of Pyridine carboxylic acid chromium. The result showed that heat stress significantly decreased T-AOC at17:00,20:00and daily average value (P<0.05) and supplement Cr group’s daily average T-AOC was higher than HS group (P<0.05). The activities of GSH-Px in HS group were lower than control group at11:00,14:00,17:00and daily average value (P<0.05). Heat stress significantly decreased daily average SOD activity (P<0.05). The concentrations of MDA in supplement Cr group were higher than other two groups at11:00,14:00and daily average value (P<0.05). Heat stress significantly decreased the levels of HSP70mRNA expression at8:00,11:00and daily average value (P<0.05) and supplement of Cr decreased the expression level to some extent(P>0.05) but significantly increased the expression at20:00(P<0.05).The fifth part we studied the correlation between THI and other indice. The result showed that the breathing rate and concentrations of NH3-N could be established linear equation and quadratic equation. The linear equation of THI and breathing rate was Y=3.768X-279.1, R2=0.822, P=0.0048; the quadratic equation of THI and breathing rate was Y=0.6896X2-108.02X+4249.4, R2=0.8404, P=0.0255. The linear equation of THI and concentrations of NH3-N was Y=-1.225X+110.7, R2=0.845, P=0.0034; the quadratic equation of THI and concentrations of NH3-N was Y=-0.539X2+86.26X-3433, R2=0.951, P=0.0024.In summary, the conclusions of this study were:1) THI showed a trend of decreasing after the first rise, reached the maximum value at14:00and the minimum value at8:00, the average THI could be more than72;2) heat stress significantly reduced times of ruminating, increased breathing rate; significantly increased the concentration of TVFA, decreased pH value so that change the fermentation mode; reduced blood antioxidant capacity in different level and increased the HSP70mRNA expression. Pyridine carboxylic acid chromium could regulate breathing rate, rectal temperature and HSP70mRNA expression;3)goats’ breathing rate and concentrations of NH3-N could establish correlationship with THI and acted as early warning indice. |
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