| In order to find a convenient collection method of methane,suitable forage-concentrate ratio for weaned calves growth and to reduce the methane production and to study the effect of new plant extracts on the methane production of dairy cows,so as to further explore the mechanism of intestinal methane emission in ruminants,this research includes following aspects :Experiment 1: Effects of different collection methods on the determination of intestinal methane emissions from weaned calves using SF6 tracer method.Eightteen 6-month-old calves were selected and divided into A,B and C groups with same diet.We did 3 gas extraction methods to collect the gas around the bovine nose,including traditional sampling,12 times sampling within 24 hours?one hour interval?and 12 times sampling per hour.The results showed that the results of the three methods had no significant difference?P>0.05?,and the gas collection method could be selected rely on the test convenience.Experiment 2: In order to study the effects of different forage-concentrate ratio on the production performance,nutrient digestion and metabolism and intestinal methane emission of weaning calves,32 animals with similar body weight of 3 months were selected and randomly divided into A,B,C,and D groups were fed with a whole mixed diet of 80: 20,70: 30,60: 40 and 50: 50,respectively.The results showed that the average daily gain?ADG?in group A was significantly higher than that in group C and D?P<0.01?,and group B was significantly higher than group D?P<0.01?;DMI and NDF apparent digestibility?P <0.05?.The apparent digestibility of ADF in group A was significantly higher than that in group B and D?P<0.05?,and that in group C was significantly higher than that in group D?P<0.01?.The results showed that methane emission,methane emission per unit weight,unit methane and methane energy were consistent,and group D was significantly higher than that in group A,B and C?P<0.05?.The apparent digestibility,total digestibility,digestive energy metabolism and apparent metabolic rate of group A were significantly higher than those of group D?P<0.05?.Feeding weaning calves,with the increase in the level of concentrate in the diet,weaning calves feed intake,apparent digestive energy,the total digestibility rate is increased,daily gain significantly increased,and appropriate The level of concentrate can reduce methane emissions.Experiment 3: In order to study the effects of different coarse and coarse ratios on rumen fermentation characteristics and microflora structure of weaning calves,this study was based on the experiment II,and the samples of cattle rumen fluid were collected and returned to laboratory by cryopreservation.The results showed that NH3-N and acetic acid in group A were significantly higher than those in group D?P<0.05?,and the level of propionic acid in group C was significantly higher than that in group D?P<0.05?.The ratio of acetic acid to propionic acid?A / P?was significantly lower than that of group A?P<0.05?.The proportion of group A was significantly higher than that of the other three groups?P<0.05?.Compared with group A?P<0.05?,the proportion of Vibrio butyric acid was higher than that of group A?P<0.05?.The results showed that the increase of the ratio of roughage in the diet of weaning calves could positively affect the growth and reproduction of Vibrio butyric acid,Protozoa and methanogens in rumen and reduce the content of NH3-N and acetic acid.Experiment 4: In order to investigate the differences in intestinal methane emissions from Holstein milk and dry milk cow at the same dietary level,the Holstein milk bull?group A?and the dry cow?group B?The contents of p H,NH3-N,VFA and rumen microflora were measured by using sulfur hexafluoride?SF6?tracer technique to measure the methane emission in the intestine of the dairy cattle.The The results showed that methane production per unit weight,methane production per day and unit methane intake were significantly higher than those in group B?P<0.05?.The content of acetic acid and acetic acid / propionic acid in group A was significantly higher than that in group B?P<0.05?.The ratio of propionic acid and butyric acid was not significant?P>0.05?.The ratio of rumen protozoan,methanogens,yellow rumen cocci and white rumen cocci to rumen total bacteria in group A was significantly higher than that in group B?P<0.05?,and the content of fungi was significantly lower than that of group B?P<0.05?.The results showed that the ability of rumen microbes to decompose carbohydrates to produce acetic acid was greater than that of dried cow,and its ability to produce methane was greater than that of dry cows.Experiment 5: In the fourth test period of 13d?42d,add an additional 8g(head·d-1)aloe vera powder,and determine the intestinal methane emissions and rumen-related indicators to study whether the aloe vera powder can reduce the Holstein dairy cattle intestinal methane Emissions have a positive impact.The results showed that the methane emissions of A and B groups were 381.23 L·d-1 and 279.33 L·d-1,respectively,which were significantly lower than those of 538.15 L·d-1 and 361.99 L·d-1?P<0.05?,decreased by 29.16% and 22.84% respectively.?P<0.05?.The concentration of methyl acetate in group A was significantly lower than that in group A?P<0.05?.The amount of acetic acid in group A was significantly lower than that in group A?P<0.01?,NH3-N content was significantly decreased?P<0.05?,butcate/propionic acid did not change significantly?P<0.01?,and the content of acetic acid,propionic acid and butyric acid in group B was significantly decreased,but the difference was not significant?P>0.05?.The proportion of methanogens and protozoa in rumen rumen was significantly lower in group A?P<0.05?.The results showed that the addition of aloe vera powder in the diets could reduce the methane emission in the intestine of the dairy cows.The significant decrease of methanogens in rumen fluid of dairy cows may be related to the anthraquinones contained in aloe vera powder. |
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