Table 2.
Feed intake and feeding behavior parameters of 8 growing heifers fed ad libitum alfalfa silage and Pearson correlation (r) of feeding behavior parameters with daily methane production (CH4p) and yield (CH4y), all measured in respiration chambers
| Item | Mean | SD | Maximum | Minimum | CV | Correlation (r) with: |
|
|---|---|---|---|---|---|---|---|
| CH4p1 | CH4y | ||||||
| DMI (kg/d) | 10.8 | 1.56 | 14.2 | 7.5 | 14.5 | 0.71* | −0.77* |
| Feed bin visit frequency (/d) | 97 | 34 | 169 | 47 | 35.1 | 0.06 | −0.45* |
| Number of meals2 (/d) | 13 | 2.9 | 22 | 9 | 21.7 | 0.78* | −0.11 |
| Eating time (min/meal) | 14.7 | 3.74 | 22.3 | 7.8 | 25.4 | −0.50* | 0.13 |
| Meal duration (min/meal) | 34.7 | 13.4 | 71.4 | 19.4 | 38.8 | −0.35 | −0.16 |
| Total eating time (min/d) | 186 | 25.3 | 241 | 132 | 13.6 | 0.04 | 0.14 |
| Total mealtime (min/d) | 436 | 112.5 | 642 | 232 | 25.8 | 0.08 | −0.29 |
| Meal size (kg of DM/meal) | 0.8 | 0.15 | 1.21 | 0.59 | 19.2 | −0.25 | −0.57* |
| Eating time eating rate (g of DM/min) | 57.4 | 12.7 | 91.4 | 39.6 | 22.1 | 0.47* | −0.48* |
| Mealtime eating rate (g of DM/min) | 30.4 | 8.87 | 46.7 | 17.2 | 29.2 | 0.30 | −0.10 |
| Interval between meals (min/interval) | 75.6 | 16.02 | 110.8 | 40.3 | 21.2 | −0.26 | −0.24 |
1
The 24-h measured CH4 production was calculated by averaging all ~3-min CH4 values recorded in a 24-h period by the chamber system.
2
Meal criteria was defined as described previously (Tolkamp et al., 2000; von Keyserlingk and Weary, 2010) based on the frequency distribution of intervals of the feed bin exit time to next entry time expressed on a log scale (Figure 1).
*
P < 0.05.