| This study was conducted to alleviate heat stress in lactating cows. Based on the investigation of meterological data and dairy production in Zhejiang Province, heat-alleviating decoction was chosen to improve the heat tolerance of dairy cattle. One modified Baihu-decoction powder (BDP) was constructed and selected as the dietary additive. The suitable applying time was investigated through eating behavior and rumen fermentation trial in vitro. Further study was conducted to detect effects of BDP on lactating performance, thermal and metabolism status, and immune traits in heat-stressed cows. A method to integrate subjective and objective weighting was used to evaluate the main effect of BDP under heat stress. The targets through which BDP alleviates heat stress was made clear in lactating cows.1. Survey on meterological data and dairy production in main milk-producing areas in Zhejiang ProvinceIn Zhejiang Province, dairy cows are mainly distributed in Jinhua and Hangzhou Prefectures. Daily temperature and humidity index (THI) ranged from75to80from June to September in these regions. The minimum temperature is above25℃in July and August, suggesting that the dairy cows would endure heat stress in the whole days during these two months. Milk yield declines sharply in the early-lactation cows when exposed to summer heat, followed by mid-lactation cows. To alleviate heat stress, dairy farmers have adopted seasonal production strategy. In summer, milk production is the first management focus, and the health of the cows is considered. Natural ventilation barns are built and installed with fans, sometimes water air conditioners. Total mixed ration (TMR) is reformulated to account for the reduced dry matter intake (DMI) and increased nutrient requirements. Some vitamins and minerals are also supplemented. Although various measures are applied, milk production level is still unsatisfactory. DMI by dairy cows in June is similar to that in May, but milk yield would decline by10percent. In July, DMI is reduced to the lowest, while the cows mobilize body reserve to maintain milk production. In August and September, DMI recovers gradually, but feed efficiency keeps low.2. Effects of different Chinese medicine additives on alleviation heat stress in cowsThis study was conducted to select optimal Chinese medicine additives to alleviate the heat stress in dairy cows. Two BDP additives were built and compared with Indigowoad Leaf extract. Eighty-two mid-lactating cows were randomly allocated into eight blocks to receive four treatments, one south and one north block for each treatment. Dietary treatments included control and three treatment diets containing150g BDP-A,120g BDP-B, or15g Indigowoad Leaf extracts, respectively. Addition of BDP A and B could increase milk yield by7.2and7.7%, respectively. The BDPs tended to depress the rectal temperature and increase the respiration rate. Ratio of plasma IL-2R to IL-2was87.3and101.6%higher in the BDP-A and B added treatments, respectively. Overall, BDP-B was superior to other additives to alleviate heat stress for dairy cows.3. Feeding behavior and rumen fermentation in vitro in dairy cows influenced by different Chinese medicine additivesIn the above feeding trial, some cows did not prefer to BDP. In this trial, three heat-clearing decoctions were used to detect their effects on feeding behavior of lactating cows. Forty late-lactating Holstein cows were randomly allocated to four groups to receive four treatments:control, heat-clearing and stomachic decoction, summer-heat clearing decoction and BDP. All cows were fed the same basal TMR and added without or with one of the three decoctions at a dose of150g per day per head. The DMI was negatively correlated to barn temperature and THI (P<0.01). No significant response was observed of feed behavior to heat-clearing herb decoctions addition when the cows were in weak heat stress. Because of constantly decreased DMI with the trial period, feed efficiency was higher in the latter period, and all the cows lost their body weight of20to30kg during the trial, suggesting that cows mobilized body reserve to maintain milk production.An in vitro trial was conducted to evaluate the effects of the above3heat-clearing decoction on rumen fermentation and microflora. Heat-clearing decoctions decreased gas and volatile fatty acid production and increased pH in early fermentation stage, while fermentation parameters did not change from12to24h. Addition of BDP significantly decreased acetate proportion in rumen fluid at3h, with the increased propionate and butyric acid proportion, while Butyrivibrio fibrisolvens and R. flavefaciens proportion at6h was increased in BDP group. It seems that BDP may change fermentation pattern via regulating rumen microflora.4. Lactation performance and physiological function of Chinese Holstein cows influenced by BDPUsing the selected BDP, a study was conducted to evaluate its effects on lactation performance, thermal status and immune traits in lactating cows during hot season. Twenty mid-lactating cows were used in a randomized block design. The cows in each group were fed the same basal diet and added without or with120g BDP. Addition of BDP had no effect on DMI and milk yield, but significantly increased milk fat percent, with1.1kg more fat corrected milk (FCM) higher in the BDP-group. Rectal temperature did not change in cows fed BDP, while respiration rate and heart rate were significantly increased by BDP. There were no significant differences in the peripheral blood rheology and whole hemacyte indexes between two treatments, but all the indices were numerically lower in the cows fed BDP. Addition of BDP significantly increased plasma concentration of non-esterisfied fatty acids (NEFA), while there were no changes in plasma concentration of urea nitrogen (PUN), glucose and some related hormones. No significant differences were detected for total anti-oxidant capacity and MDA assay between two treatments, while concentration of hydroxyl in plasma and peroxide in erythrocyte significantly decreased by addition of BDP. BDP tended to decrease WBC and RBC in peripheral blood, while PCV and HGB not changed. Concentration of cGMP was significantly improved by addition of BDP, while cAMP to cGMP ratio did not change. Addition of BDP tended to decrease IL-1β concentration. No significant differences were observed for IL-6and prostaglandin E2assay between two treatments. From the results in this study, it is indicated that BDP could alleviate the negative effects of environment-induced hyperthermia on lactating cows.5. Comprehensive evaluation of BDP as anti-heat stress additive for dairy cowsA method to integrate subjective and objective weighting was used to evaluate the main effect of BDP under heat stress. Based on the data in dairy feeding trial,16indices were chosen to evaluate BDP effects on cows’heat stress. These indices included milk yield,3.5%FCM, DMI, rectal temperature, respiration rate, PUN, NEFA, superoxide dismutase, MDA, hydroxyl, white blood cell, red blood cell, IL-1, IL-6and cGMP. For reverse indices such as rectal temperature, PUN, NEFA, H2O2, MDA, IL-1and IL-6, their reciprocal was taken before standardized processing. All the forward indices data were divided by the individual average to obtain non-dismentionized data. The Analytic Hierarchy Process (AHP) was employed to give objective weight based on4guidelines (lactation performance, thermal status, metabolic state and immune traits). Subjective weight was calculated by mean square method. Factors weights were calculated by combination of the subjective with objective weight. Nine indices were rejected for too low weight. Finally, a lineal model was built with seven indices.The score for BDP and control group was calculated by applying the linear model. It is observed that the first target through which BDP alleviated heat stress was white blood cell in peripheral blood, and followed by hydroxyl in plasma.Above all, weather conditions from June to September probably induce heat stress in dairy cows in Zhejiang Province, while cows may endure constant heat load during July and August. Addition of BDP could increase respiration rate and heart rate, and reduce blood cell content along with increased cGMP. The selected BDP may improve lactation performance and alleviate blood oxidative stress. The BDP is suitable for addition in diet for dairy cows in weak heat stress. |
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