Effect of rumen neutralizers on lactation performance, digestibility, chewing, and rumen pH of dairy cows in late lactation

Abstract

A calcinated Mg source was developed to have persistent and high neutralizing action on rumen pH (pHix-Up. Timab, France). Our objective was to compare the lactation performance, intake, diet digestibility, rumen pH, and chewing behavior of cows fed either pHix-Up (PHP) or sodium bicarbonate (BIC). Fifteen Holstein cows (29.5 kg/d, 620 kg, 193 DIM) were individually fed a sequence of PHP (0.5% of DM), BIC (1% of DM), or control (CTL) in 5, 3 × 3 Latin squares, with 21-d periods. A mean value per cow during d 14 to 17 of each period was obtained and treatment means were compared by pairwise t-tests. The model had the effects of cow, period, and treatment. Diets had 22.6% starch, 36.2% NDF, and 4.2% ether extract (EE) in DM. PHP tended to increase milk fat concentration (3.81%) relative to CTL (3.63%, P = 0.06) and BIC (3.65%, P = 0.10). No differences were detected in milk yield (27.5 kg/d, P ≥ 0.12) and DMI (22.6 kg/d, P ≥ 0.21). PHP increased (P ≤ 0.05) the secretions (g/d) of unsaturated and oleic fatty acids in milk relative to BIC. The total-tract digestibility of EE tended (P = 0.10) to be higher on PHP than CTL (92.8 vs 91.5% of intake). The daily minimum reticular pH tended (P = 0.07) to be higher on PHP (5.90) than CTL (5.82). pH mean (6.29), maximum, range, and daily time spent ≤ 6.2 (524 min) and ≤ 5.8 (43 min) did not differ (P ≥ 0.17). Urine excretion was higher (P < 0.01) on BIC (20.9 L/d) than CTL (15.5 L/d) and PHP (16.9 L/d), and tended (P = 0.06) to be higher on PHP than CTL. Relative to CTL, cows on PHP tended (P = 0.06) to spend less time ruminating per day (460 vs 489 min) and per unit of rumen pH (73 vs 78 min) and had lower (P = 0.01) total chewing time per day (818 vs 864 min). The excretion of allantoin in urine was highest on BIC (P < 0.01). BIC increased rumen microbial yield, but had no effect on diet digestibility, rumen pH, and lactation performance of late lactation dairy cows. Overall, PHP tended to increase milk fat concentration, total-tract EE digestibility, the secretion of preformed unsaturated fatty acids in milk fat, and minimum rumen pH.