While the relationship between diet composition and enteric methane emission from ruminants is well understood there is a lack of data that compares methane emission with eating behaviour. The aim of this study was to evaluate the effect of 2 silages and 2 concentrates on eating behaviour recorded using the Rumiwatch system, and to quantify the between-cow variation in eating behaviour and methane emission and possible correlations. Twenty-four lactating Holstein cows were used in a crossover study with two 21 days periods. The cows were divided in 6 blocks of 4 cows each, with either 1st or 2nd lactation cows. Each cow received 2 of 4 diets, in a design balanced for carryover effects. Diets were 2×2 factorial arranged, with maize silage (MS) or grass-clover silage (GS), as 100% of forage inclusion and 55% of diet dry matter (DM), and barley (BA) or dried beet pulp (DB), as 21.5% of diet DM. Eight Rumiwatch
units were used on 2 blocks simultaneously for 4 consecutive days (d 12-15 for even blocks and d 15-18 for odd blocks). In a staggered progression, each block spent d 19-21 in respiration chambers to record gas exchange. Eating,
ruminating and total chewing time, as well as methane emission and DM intake (DMI) were averaged within cow and period. Dependent variables were analysed in a linear mixed model including interaction between dietary factors, and
effect of period and block as fixed effects, and cow as random effect. Cows fed MS had lower eating time (358 vs 384 min/d; P=0.04), eating rate (17.2 vs 19.2 min/kg DM; P<0.01) and total chewing time (796 vs 862 min/d; P=0.02)
compared to cows fed GS diets. Cows fed BA had lower eating rate than cows fed DB (17.3 vs 19.2 min/kg DM; P<0.01). Average and between-cow variation (model mean ± sd for random cow) were 440±30, 508±10 and 947±40
min/d for eating, rumination and total chewing. Average and between-cow variation for eating rate was 21.5±1.5 min/kg DMI. A negative correlation was found between random cow solutions for eating rate and daily methane
production (r=−0.61; P<0.01) but no correlation was found when methane was related to DMI. In this study dietary factors affected eating behaviour, but no relationship between eating behaviour and methane per kg DMI was found.