Effects of the amount of barley and time of access to grass silage on the voluntary intake, eating behaviour and production of dairy cows

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AbstractThree separate changeover experiments were conducted to investigate the effect of the amount of rolled barley and time of access to silage on the voluntary intake, eating behaviour and production of dairy cows. In Experiment 1, twenty‐four milking cows were used to compare the effect of 4 1 and 6 1 kg d−1 rolled barley on voluntary intake and milk production. In Experiment 2, fourteen cows were used in a comparison of the effect on voluntary intake and milk production of 5‐ and 22‐h access to silage. Experiment 3 measured the effects on intake of silage of 2 and 4 kg d−1 rolled barley and of 5‐ and 22‐h access to silage. In Experiment I, increasing the amount of barley eaten reduced intake of silage by 0–50 kg dry matter (DM) per kg barley DM but in Experiment 3 with 5‐h access to silage there was no significant difference between the amounts of silage eaten with 2 and 4 kg d−1 barley. However, in Experiment 3 when allowed 22‐h access to silage, the replacement rate was 0–53 kg DM silage per kg DM barley. Increasing access from 5 to 22 h increased silage intake by 37% in Experiment 1 and by 27% in Experiment 3. Milk yield was significantly increased by 4% when extra barley was given in Experiment 1 but there was no significant effect in Experiment 3. Increasing the time of access to silage led to an 11% increase in milk yield in Experiment 2 but there was no significant effect in Experiment 3. There was much variation between cows in the depression of silage intake per kg change in barley DM eaten with coefficients of variation of 131% and 109% in Experiments 1 and 3, respectively. When allowed access to silage for 22 h daily, on average, each cow spent 180 min eating silage in ten meals, although there was appreciable variation between cows in eating behaviour. The amount of barley did not affect the cows' rate of eating silage nor the duration of eating.