Study Shows Cows Can Adjust to Limit-feeding TMR
Round-the-clock TMR availability may not be necessary to keep lactating cows on an even plane of digestion, according to a study recently published in the Journal of Dairy Science.
Researchers at the University of Bologna in Italy conducted the trial, which sought evaluate feeding, rumination, and rumen pH responses to ad-lib versus restricted TMR feeding, with or without supplemental, free-choice hay.
They divided eight, second-lactation, 2X-milked Holstein cows into four study groups. Two groups were provided 24-hour access to TMR, while the other two had the TMR removed for five hours before evening milking and feeding. Ad libitum, long-stem grass hay was offered additionally to one of the 24-hour and 19-hour TMR groups, respectively.
The TMR formulation was identical for all groups, and the grass hay offered to two of the groups was the same as that used in the TMR, but not part of the formulated diet. The three-week study provided a two-week adjustment period, with dry-matter intake (DMI), rumination activity, and rumen pH monitored electronically for seven days thereafter.
Among the study’s findings, authored by a team led by Pennsylvania State University Professor of Dairy Science Jud Heinrichs, were:
- Restricted cows – with or without supplemental hay -- altered their feeding behavior by eating a large meal when feed was reintroduced. Overall, they had a lower, total DMI.
- Access to free-choice hay made a significant difference in DMI patterns. Ad-lib (24-hour) animals had a greater total DMI when hay was offered, while DMI for the restricted (19-hour) group was very similar, with or without hay.
- Regardless of TMR or hay availability, all groups exhibited an inverse relationship between eating times and rumination, as to be expected.
- Restricted cows ruminated more than those with constant access to TMR during the five hours per day when they did not have access to TMR. But total daily rumination time was consistent among all four groups, and all animals in the study achieved rumination times about the values considered to be the minimum threshold for normal rumination.
- Rumen pH varied less throughout the day for restricted-fed cows, but ranges in pH values were similar among all four groups.
The authors concluded that when fed very finely chopped diets, cows were able to adjust to changes in feed availability and access to long hay. Restricting TMR access, with or without access to free-choice hay, was not found to be detrimental to overall digestive patterns, and could be beneficial in terms of feed efficiency.
They noted this information could have value in attempting to improve energy-corrected milk feed efficiency, and/or adapt feeding behaviors in various climate conditions, such as night feeding in hot weather.