Dynamics of chewing and eating behavior, lying behavior, and salivary characteristics associated with duration of high grain feeding in cows with or with no phytogenic supplement

This study evaluated the adaptive changes in chewing and eating behavior, lying behavior, and salivary properties due to the switch from forage to high grain and the duration of high grain feeding in cows, with or without a phytogenic feed additive. Nine non-lactating cannulated Holstein cows were used in a cross-over design with two experimental periods. Each period included one week of forage feeding, one week of diet transition, and four weeks of high grain feeding (35:65 forage to concentrate ratio; DM basis). Cows were either not supplemented (CON) or supplemented with a phytogenic additive (PHY) characterised by menthol, thymol and eugenol. Switching to high grain decreased (P < 0.01) rumination time compared to forage feeding; however, compared to week 2, rumination time increased (P < 0.01) by 73.8 and 53.21 min/d in weeks 3 and 4 on high grain, respectively. In week 4 on high grain, the PHY-supplemented cows tended (P = 0.08) to ruminate (263 vs. 204 min/d) and chew (406 vs. 347 min/d) longer compared to CON counterparts. The change to high grain increased (P < 0.05) sorting for long and medium size feed particles compared to forage diet, and there was a further increase (P < 0.05) in sorting for long and medium size feed particles in week 3 and 4 on high grain compared to the initial stage of the high grain challenge. Interestingly, PHY supplementation contributed to a more uniform intake of the diet by reducing (P < 0.05) the sorting of both medium and fine particles. Compared to week 1, lying time increased (P < 0.05) by 50 min/d in week 3 on high grain. High grain diet decreased (P < 0.05) salivary pH in week 1, while PHY supplementation helped maintaining this variable at physiological level during this initial grain challenge. Salivary bicarbonate was lower (P < 0.05) in weeks 3 and 4 compared to week 2 on high grain. Overall, the switch to high grain and the duration of feeding influenced chewing and eating behavior, lying behavior and salivary characteristics. Effects were still found 3 or 4 weeks after the diet switch; whereas PHY supplementation contributed to a more uniform nutrient intake by decreasing sorting behavior, which was reflected in stabilized salivary pH at the beginning of the grain challenge, and a tendency for increased chewing activity. However, more research is warranted to evaluate the positive role of PHY supplementation in decreasing feed sorting on metabolic health status and welfare of high-producing dairy cows, which are commonly affected due to high grain feeding.