Effects Of The Ratios Of Concentrates To Roughages On Methane Emission,Growth Performance And Nutrient Digestion Of Replacement Heifers At Different Ages

In this study,we investigated the effects of different concentrate-roughage ratio diets on methane emissions?growth performance and apparent digestibility of nutrients from Holstein cows at 9,12,and 15 months of age.Methane emissions were determined by sulphur hexafluoride?SF₆?tracer technology.The details is divided into the following three aspects:Experiment 1:The objectives of the present study was to investigate the effects of different ratio of concentrate-to-forage on methane emissions,growth performance and apparent digestibility of nutrients of 9-month-old Holstein cows.The trail was designed by single factor experiment.According to the principle of similar body weigh,fifteen?body weight=274±24.4 kg,age=9.4±0.56?cows were divided into three groups??,?and III?,which was fed three total mixed rations?TMR?with the concentrate level of30%and 40%and 50%.The whole experiment period was 18 days,with a 10d adaption period and 8d trial period.The results showed that:1)Diets with feed concentrate levels of 30%,40%,and 50%correspond to methane production of 117 g/d,107 g/d,and 97g/d,and methane energy accounts for 6.1%,5.0%,and 4.2%.2)With the increase of concentrate-to-forage ratio,CH₄ daily emissions,and mathane energy?CH₄E?as a proportion of total energy intake was significantly decreased?P<0.05?;3)The apparent digestibility of dry matter,organic matter and crude fat did not change significantly with the increase of concentrate-to-forage ratio?P>0.05?;the appearance digestibility of crude protein in group III was significantly higher than that of?and??P<0.05?.However,the apparent digestibility of NDF and ADF was significantly lower in group III than??P<0.05?.In summary,the daily emission of methane from9-month-old dairy cows is 97-117g,and the ratio of methane energy to total energy intake is 4.2%-6.1%.Appropriately increasing the ratio of concentrate-to-forage can effectively reduce methane emissions and the ratio of methane energy to total energy intake of 9-month-old dairy cows.Experiment 2:The objectives of the present study was to investigate the effects of different ratio of concentrate-to-forage on methane emissions,growth performance and apparent digestibility of nutrients of 12-month-old Holstein cows.The trail was designed by single factor experiment.According to the principle of similar body weigh,fifteen?body weight=334.7.4±35.2 kg,age=11.9±0.34?cows were divided into three groups??,?and III?,which was fed three total mixed rations?TMR?with the concentrate level of 30%and 40%and 50%.The whole experiment period was 18 days,with a 10d adaption period and 8d trial period.The results showed that:1)Diets with feed concentrate levels of 30%,40%,and 50%correspond to methane production of159 g/d,133 g/d,and 119 g/d,and methane energy accounts for 6.7%,5.0%,and 4.4%.2)The concentrante's level of diets significantly affect rumen methane emissions.With the increase of concentrate-to-forage ratio,CH₄ daily emissions,and mathane energy?CH₄E?as a proportion of total energy intake was significantly decreased?P<0.05?.3)Dietary crude ratio significantly affects feed digestibility.The apparent digestibility of DM,OM,CP and NFC was significantly lower in group?than III?P>0.05?.However,the apparent digestibility of NDF ADF and EE was did not change significantly when concentrate-to-forage ratio increased?P>0.05?.Daily gain was significantly higher in group?than?and III.In summary,the daily emission of methane from 12-month-old dairy cows is 119-159g,and the ratio of methane energy to total energy intake is 4.4%-6.7%.Appropriately increasing the ratio of concentrate-to-forage can effectively reduce methane emissions and the ratio of methane energy to total energy intake of 12-month-old dairy cows.Experiment 3:The objectives of the present study was to investigate the effects of different ratio of concentrate-to-forage on methane emissions,growth performance and apparent digestibility of nutrients of 15-month-old Holstein cows.The trail was designed by single factor experiment.According to the principle of similar body weigh,fifteen?body weight=425.33±35.2 kg kg,age=14.52±0.34?cows were divided into three groups??,?and III?,which was fed three total mixed rations?TMR?with the concentrate level of 30%and 40%and 50%.The whole experiment period was 18 days,with a 10d adaption period and 8d trial period.The results showed that:1)Diets with feed concentrate levels of 30%,40%,and 50%correspond to methane production of230 g/d,215 g/d,and 194 g/d,and methane energy accounts for 7.7%,6.7%,and 5.7%.2)The concentrante's level of diets significantly affect methane emissions of 15-month-old.With the increase of concentrate-to-forage ratio,CH₄ daily emissions,and methane energy?CH₄E?as a proportion of total energy intake was significantly decreased?P<0.05?.3)Dietary crude ratio had significant effect on DMI and daily gain,which was significantly higher in group III than I?P<0.05?.Increasing dietary lean ratio was beneficial to promote apparent digestibility of DM,OM,CP and NFC,which was significantly higher in group III than group I?P<0.05?.The apparent digestibility of NDF and ADF between treatment groups was not significant?P>0.05?.In summary,the daily emission of methane from 15-month-old dairy cows is 194-230g,and the ratio of methane energy to total energy intake is 5.7%⁷.7%.Appropriately increasing the ratio of concentrate-to-forage can effectively reduce methane emissions and the ratio of methane energy to total energy intake of 15-month-old dairy cows.Overall conclusion:Methane emissions increased significantly with the increase of age and body weight in the 9 to 15-month-old reserve cows.When the dietary concentrate level was increased in the range of 30%to 50%,methane emissions were significantly reduced and the feed digestion was significant improved.