Description

Enteric methane (CH4) emissions were measured in forty spring calving cows offered one of two (n=20) contrasting diets (High Grass; HG, Low Grass; LG) over 10 weeks in early lactation (8th February – 18th April 2021). All cows were blocked for breed and parity and balanced on milk production, economic breeding index (EBI), bodyweight and body condition score and randomly allocated to treatments. The HG grazing treatment cows were offered their full daily nutrient requirement from grazed grass and concentrate with no silage supplementation. The LG grazing treatment cows were offered a restricted (~60%) amount of their daily nutrient requirement from grazed grass with the deficit being supplied by 3 kg DM/cow of grass silage fed daily. Concentrate supplementation was the same for both treatments at 2.7 kg DM/cow/day. All forage samples were analysed using near – infrared spectrometry to evaluate quality parameters. Milk yield was recorded daily with milk composition determined weekly. Daily CH4 emissions were monitored using Greenfeed technology. Individual animal dry matter intake (DMI) was determined at five time points using the n-alkane technique. Over the 10 week experiment collected data was averaged fortnightly in 5 periods (period 1-5) prior to analysis. Milk yield and milk solids (fat plus protein) production were similar for both treatments. The HG treatment tended to have greater total DMI (TDMI) with a significant diet by period interaction evident. Daily CH4 emissions (g/d) were not effected by treatment, however there was a treatment by period interaction. This resulted in a significant treatment effect for CH4 yield (g/kg TDMI). This was complemented with a significant treatment by period interaction with the greatest difference in CH4 yield evident in period 4. Increasing the proportion of highly digestible grazed grass in the diet in early lactation can aid in reducing enteric CH4 emissions in pasture based dairy systems.

DOI

https://doi.org/10.13023/95rh-tm25

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Spring Grass Availability and Silage Supplementation Impact on Dry Matter Intake and Enteric Methane Emissions in Grazing Dairy Cattle

Enteric methane (CH4) emissions were measured in forty spring calving cows offered one of two (n=20) contrasting diets (High Grass; HG, Low Grass; LG) over 10 weeks in early lactation (8th February – 18th April 2021). All cows were blocked for breed and parity and balanced on milk production, economic breeding index (EBI), bodyweight and body condition score and randomly allocated to treatments. The HG grazing treatment cows were offered their full daily nutrient requirement from grazed grass and concentrate with no silage supplementation. The LG grazing treatment cows were offered a restricted (~60%) amount of their daily nutrient requirement from grazed grass with the deficit being supplied by 3 kg DM/cow of grass silage fed daily. Concentrate supplementation was the same for both treatments at 2.7 kg DM/cow/day. All forage samples were analysed using near – infrared spectrometry to evaluate quality parameters. Milk yield was recorded daily with milk composition determined weekly. Daily CH4 emissions were monitored using Greenfeed technology. Individual animal dry matter intake (DMI) was determined at five time points using the n-alkane technique. Over the 10 week experiment collected data was averaged fortnightly in 5 periods (period 1-5) prior to analysis. Milk yield and milk solids (fat plus protein) production were similar for both treatments. The HG treatment tended to have greater total DMI (TDMI) with a significant diet by period interaction evident. Daily CH4 emissions (g/d) were not effected by treatment, however there was a treatment by period interaction. This resulted in a significant treatment effect for CH4 yield (g/kg TDMI). This was complemented with a significant treatment by period interaction with the greatest difference in CH4 yield evident in period 4. Increasing the proportion of highly digestible grazed grass in the diet in early lactation can aid in reducing enteric CH4 emissions in pasture based dairy systems.