Estimation of methane production by lactating and dry crossbred Holstein cows in Thailand.

The methane (CH4) produced by lactating and dry crossbred Holstein cows, together with factors affecting CH4 production, were investigated using data obtained from balance trials of cows in Thailand (48 observations). The CH4 production per dry matter intake (DMI) of lactating cows tended to be lower than that for dry cows (25.7 L/kg vs. 28.7 L/kg DMI; P ‹ 0.10), which was due to the higher energy intake of lactating cows. A positive correlation was observed between CH4 production and DMI (r = 0.70; P ‹ 0.001). The CH4 production was also founded to be related to crude fiber (CF) and nitrogen free extract (NFE) intake from a multiple regression equation (r = 0.77, P ‹ 0.001), and the coefficient of CF was higher than that of NFE, indicating higher methanogenesis of CF than of NFE. The decreasing CH4 production per milk production with the increase in milk production (r = -0.62; P = 0.003) shows that improvements in the individual milk yield suppress the CH4 production per milk production. From the findings of the present study and available statistical information in Thailand, it was estimated that CH4 production by cows increased as the cow population increased over a 5-year period from 1999. Because the CH4 production per milk yield showed little change from 1999 to 2004, in terms of milk productivity and suppression of CH4 production, improving individual milk yield will be important in Thailand.