The daily patterns of the change in chewing behavior, feed intake, rumen pH and milk composition in high producing Holstein dairy cows

It has been demonstrated that feeding behavior with influencing rumen pH can change milk fat percentage, but the pattern of the change in feeding behavior and relative change in rumen pH and milk fat percentage is not considered. The objective of this study was to investigate the change in the daily pattern of chewing activity, feed intake, rumen pH and milk composition in high- producing Holstein dairy cows fed a high concentrate diet.
eighty seven high-producing (50.1 ± 11.1kg/d) dairy cow in mid-lactation (103 ± 26.5 DIM) with the average body weight of 630 ± 76.8 kg and parity number of 2.35 ± 1.39 were used. The cow enrolled in the experiment during three 24-d periods consists of 14 days of adaptation and 10 days sampling. Diet consisted of 35 % forage and 65% concentrate and fed as TMR twice daily. All cows were subjected to measuring chewing activities, feed consumption at 2, 4, 6 h after morning feeding, and milk production and composition. Rumen pH was measured for all cows using rumencenthesis and 14 cows were subjected to continuous measurement of rumen pH using indwelling sensors with capability of continuous calibration and wireless transmission of data.
the result of this study showed the eating activity of cows was observed mostly during the day between 0700 and 2000, whereas rumination activity was during night. Cows had eating rate of 3 kg/h during first 2 h after morning feeding while in other times eating rate diminished as little as 1 kg/h. Rumen pH declined fallowing the start point of eating time and in 2 h after evening feeding at lowest pH. The duration of pH under 5.8 was about 840 min/d that indicated cows at acidosis condition. In consistent with rumen pH, milk fat depressed in night milking and then it continued up to morning milking. Regression analysis indicated that dry matter intake at 2h after morning feeding has a major effect of modulating rumen pH depression.
Cows eating patterns could have a major impact on rumen pH and the duration of rumen pH depression which further affect milk fat. The increased feed intake during first 2h after feeding could improve rumen pH.