Effects of Dietary Forage Proportion on Feed Intake, Growth Performance, Nutrient Digestibility, and Enteric Methane Emissions of Holstein Heifers at Various Growth Stages
Lifeng Dong | Binchang Li | Qiyu Diao
Enteric methane (CH<sub>4</sub>) emissions from young ruminants contribute to a substantial proportion of atmospheric CH<sub>4</sub> accumulation. Development of emission inventory and mitigation approaches needs accurate estimation of individual emission from animals under various physiological conditions and production systems. This research investigated the effect of different dietary concentrate contents on feed intake, growth performance, nutrient digestibility and CH<sub>4</sub> emissions of heifers at various stages, and also developed linear or non-linear prediction equations using data measured by sulphur hexafluoride tracer technique. Increasing dietary concentrate contents increased feed intake and growth rate, enhanced nutrient digestibility, and reduced enteric CH<sub>4</sub> emissions. Heifers at the age of 9, 12, and 15 months with an average weight of 267.7, 342.1, and 418.6 kg produced 105.2, 137.4, and 209.4 g/day of CH<sub>4</sub>, and have an average value of CH<sub>4</sub> energy per gross energy intake (Y<sub>m</sub>) 0.054, 0.064, 0.0667, respectively. Equations relating CH<sub>4</sub> emission values with animal and feed characteristics were developed with high determination coefficients for heifers at different growth stages. Dietary concentrate contents had significant influence on overall performance of heifers. These data can be used to develop regional or national emission inventories and mitigation approaches for heifers under various production regimes in China.
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