| Increasing attention has been paid to the harm of heat stress on livestock and poultry. Researchers are trying from different aspects, genetic or nutritional, to alleviate heat stress response. At present, with the double values of nutrition and medicinal, chinese herbal medicines are gradually applied in animal production. A large number of clinical trials showed that extracts from radix bupleuri have increased the body blood circulation and decreased the body’s core temperature, which has been widely used in poultry production and which, however, has not been reported in ruminant production. Therefore, this experiment aimed to study effects of radix bupleuri extract on relieving heat stress.1. Effects of Saikosaponin (SSA) on rumen fermentation in vitro. Four treatments consisted of supplemental SSA at0,0.25,0.5and1.0mg/g of DM, which were assigned randomly to5of20incubation bottles together with0.5g TMR,50mL basal media and25mL rumen fluid obtained from rumen-cannulated lactating Holstein dairy cows. Cumulative gas production (GP) was continuously measured in an automated trace gas recording system (AGRS-Ⅲ, Beijing) at39℃during48h of incubation. Relative content of the bacterial community in culture fluid in vitro was analyzed by real-time quantitative PCR (RT-PCR). Results revealed that SSA at0.25g/kg improved dry matter degradability (DMD, P=0.08), total gas production (GP, P<0.05) and total volatile acid (TVFA) concentration (P<0.05). SSA at0.5and1.0g/kg did not affect GP kinetics and DMD, while increased acetate and TVFA concentration (P<0.05). SSA increased the relative quantity of Ruminococcus albus and Streptococcus bovis (P<0.05), while decreased the content of Prevotella brevis and Ruminobacter amylophilus (P<0.05). Therefore,0.25～1.0g/kg SSA supplementation improved gas production, VFA concentrations and major microbial species in the culture fluid in vitro, which meant that SSA may be beneficial to manipulate rumen microbial fermentation in vitro.2. Effects of radix bupleuri extract (RBE) on relieving heat-stressed lactating cows. Forty Holstein cows were assigned to one of four groups according to milk yield, days in milk and parity in a completely random block design. One of four treatment diets, assigned randomly to one of four groups, consisted of RBH supplementation at0,0.25,0.5or1.0g/kg based on dry matter (DM). The experiment lasted for10wk in hot summer. During the experiment, weekly average temperature-humidity index (THI) was overall more than72, which indicated that the cows were subjected to HS model during10wk experiment. The results revealed that there was no treatment effect on body condition and that average respiration rates were decreased for cows fed RBH supplementation, especially significantly for cows fed at0.5g/kg. Moreover, average rectal temperatures were decreased regardless of levels at any time, especially at the hot time of a day (P<0.01). Additionally, Cows supplemented with RBH increased dry matter intake and milk production compared with control (P<0.05), of which cows fed RBH at0.25and0.5g/kg highly significantly improved milk yield,4%Fat-corrected milk, Energy-corrected milk and feed efficiency. There was no treatment effect on milk composition, while milk protein yield (P<0.01) and milk fat yield (P<0.05) were increased at0.25and0.5g/kg. Rumen pH, ammonia-N concentration and TVFA concentration were not different among groups, while cellulase activity was decreased. RT-PCR revealed no difference in cellulolytic bacteria among groups, while RBE decreased relative quantity of Butyrivibrio fibrisolven and Prevotella brevis (P=0.05), and tended to decrese relative concentration of Prevotella ruminicola (P=0.05). DGGE profiles showed that the quantity of bands was similar, and that they were assigned to different clusters by different supplemental doses with DGGE fingerprint similarity less than0.54overall. Shannon-Weiner index decreased (P<0.05) especially with1.0g/kg RBH, while the dominance index increased (P<0.05) especially at0.25and0.5g/kg levels compared with the control. Overall, supplemental RBH at0.25or0.5g/kg could ameliorate the negative effects of high ambient temperature and improve lactation performance in heat-stressed lactating Holstein cows without influence on diversity of the bacterial community.Overall, SSA may be beneficial to manipulate rumen microbial fermentation in vitro. RBE supplementation may alleviate side effects of high tempture on lactating cows, and improve milk production in heat-stressed cows without negative effects on rumen fermentation and body condition. |
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