Effects Of Yucca Extract On Milk Performance, Immune Function And Ammonia Emission In Dairy Cattle

The present experiments were conducted to study the effects of yucca extract (YE) on ammonia generation and microorganism number in cow manure, and rumen fermentation, milking performance, apparent digestibility of nutrients, immune and antioxidative function in dairy cows, in order to provide a theoretical basis for determining the appropriate dosage of YE in diets of dairy cows. The paper included five experiments:Experiment1, the fresh cow manure was collected and mixed, then they were divided into24flasks. Each flask contained200g manure, and0,0.5%,1%,2%YE was supplemented into the flask respectively. The flasks were put in the37℃constant temperature water bath and100mL fresh air was injected into the flask every three or two hours, so the released ammonia was collected into the bottle containing H2SO4solution and the content of ammonia was analysed after four days. In addition, the contents of ammonia nitrogen and total nitrogen of manure in flasks were detected at the same day. Total aerobic bacteria, E. coli, and Lactobacillus in the manure were tested, too.Experiment2, the rumen fluid was collected from the Holstein cows, and the fermentation function was tested in vitro. The experiment was designed using single factor completely randomized design in order to study the effect of different concentrations of YE (0,0.3%,0.6%,1.2%and2.4%) added into the rumen culture fluid on the gas production in the different culture periods (2、6、12、18and24h), the pH value of the culture fluid at h24, NH3-N concentration, quantity of the bacterial protein (BCP), degradation rate of dry matter and the amount of greenhouse gas production.Experiments3-5, single factor completely randomized experimental design was adoped. Eighteen Holstein cows were selected and randomly divided into three dietary groups according to their age, body weight, lactation stage and milk production. Each group contained six cows. The three groups were different by adding three different concentrations of YE into their diets. The control group didn’t contain YE; high dosage group contained200mg/kg YE; low dosage group contained100mg/kg YE. The experiment pieod was sixty days. The measured indexes included milk production, digestible rate of nutrients, immune and antioxidative ability, microbial composition and ammonia production in manure.The results were concluded as follows:1. YE supplement reduced the ammonia production (P<0.05) and2%YE group had the lowest value in ammonia production. The total nitrogen contents in the YE treated groups were greatly higher than the control group (P<0.05). Supplementing YE into the manure could reduce the amount of total aerobic bacteria, and the YE treated groups were greatly lower than the control group (P<0.05). Lactobacillus contents in the YE treated groups were greatly higher than control group (P<0.05), and the value in1%treated group was the highest.2.2.4%YE treated group significantly downregulated composition of NH3-N (p=0.046), gas production of2.4%YE at18h was markedly lower than the control and the0.3%YE treated group (p=0.024); gas production was significantly decreased by0.6%、1.2%and2.4%YE treated groups at1～12h compared to the control (p=0.042),CO2content of1.2%and2.4%YE treated groups were significantly lower than the control, when2.4%YE was supplemented into the medium N2O content was degreased notably (p=0.049), CH4content of all treated groups were significantly lower than the control p=0.018), CO2content of2.4%YE treated group was decreased compared to the control and the0.3%YE treated group (P=0.039), whereas, N2O content of1.2%and2.4%YE were notably upregulated compared to the0.3%and0.6%YE treated groups (P=0.004); there were degreasing tendency of rumen dry matter degradation and Ph, but BCP content increased, there was no difference between treated groups and the control (P>0.05)3. YE could improve nutrient digestibility. The NDF digestibility of lower dosage group, EE and ADF digestibility of the high treat group were higher than the control group (P<0.05). The ratio of total solids in the high dosage group was greatly increased at the late stage of the experiment, while the milk fat content and the milk protein content were greatly increased at the whole period of the experiment (P<0.05). Additionally, supplementing YE into diets could down-regulate the SCC and MUN in the milk compared to the control group (p<0.05).4. The amount of IgG, IgM, IgA and sCD4in the YE treated groups was higher than the control group. IgG and IgM in the two YE treated groups were significantly higher than the control group (P<0.05). The amount of IgA in the serum of the low dosage group was greatly higher than the control group (P<0.05). Additionally, YE could reduce the amount of sCD8in the serum (p=0.01). The activity of the CAT, SOD and GSH-Px in the YE treated groups was higher than the control group, and the activity of CAT in the high dosage group was greatly higher than the control group (P<0.05), however, the contents of MDA in the two YE treated groups were both lower than the control group.5. Supplementing YE into diets down-regulated ammonia production in manure, and the efficiency was improved with expanding the experiment time (p<0.01) Additionally, YE decreased the amount of the total aerobic bacteria and E. coli in the manure, and promoted the growth of the Lactobacillus.