Modulation of rumen pH by sodium bicarbonate and a blend of different sources of magnesium oxide in lactating dairy cows submitted to a concentrate challenge

Abstract

With the objective of evaluating the potential effects of sodium bicarbonate or a magnesium-based product on rumen pH and milk performance of dairy cattle exposed to a dietary challenge, 30 lactating Holstein cows (648 ± 67 kg of body weight; 44.4 ± 9.9 kg/d of milk yield; 155 ± 75 d in milk) were blocked by parity (9 primiparous and 21 multiparous) and randomly distributed to 3 treatment groups. One group received a total mixed ration (TMR) that acted as a control (CTR), a second group (SB) received the same TMR but with an additional supplementation of 0.8% of sodium bicarbonate, and a third group (MG) received the same TMR as CTR but an additional supplementation of 0.4% of a magnesium-based product (pHix-Up, Timab, Dinard, France). After 1 wk of exposure to this TMR, all 3 rations were supplemented with 1 kg/d of barley, which was then increased 1 kg/wk until reaching 3 kg/d of barley during wk 4 of the study. Every kilogram of barley replaced 1 kg of forage in the diet. Individual feed intake and behavior were monitored using electronic feed bins. Seven cows per treatment were equipped with an intraruminal bolus that recorded pH every 15 min. As the severity of the barley challenge increased, dry matter intake decreased, but this decrease was more pronounced in SB cows than in MG cows, with an intermediate response for CTR cows. The MG cows produced more milk when challenged with 2 or 3 kg/d of additional barley than when challenged with 1 kg/d, whereas CTR cows produced less milk with the 3 kg/d challenge compared with 1 or 2 kg/d, and the SB cows maintained milk production. Milk fat content decreased with barley challenges, with CTR cows experiencing a more severe decrease than SB cows, which maintained stable butterfat values throughout the study, and MG cows showed a decline in milk fat content only with the 3 kg/d of additional barley. Meal size was also reduced as the severity of barley challenge increased, and this reduction was more modest in MG cows than in SB cows. The number of daily meals consumed by SB and MG cows was more constant than that recorded in CTR cows. Cows on the CTR and SB treatments showed a marked decrease in rumen pH with the 3 kg/d of additional barley, whereas MG cows maintained stable rumen pH during the barley challenges and had greater average rumen pH (5.93 ± 0.04) than CTR cows (5.83 ± 0.04) with the 3 kg/d of additional barley; SB cows showed intermediate values (5.85 ± 0.04). Last, MG cows spent less time (32.3 ± 6.1%) with rumen pH ≤5.8 when exposed to the 3 kg/d of barley challenge than CTR and SB cows (50.7 ± 5.02%). In conclusion, supplementation with MG prevents the decline in dry matter intake and milk production induced by a rumen challenge, whereas supplementation with SB prevents the decay in milk production but does not prevent the decrease in feed intake. These changes were probably due to the ability of the MG treatment to prevent a reduction in rumen pH when challenging cows with 3 kg/d of additional barley in the ration.

Production performance and nutrient digestibility of lactating dairy cows fed low-forage diets with and without the addition of a live-yeast supplement

“…If the challenging rumen environmental conditions were attenuated by the inclusion of these buffers, then the action of the supplemental yeast may have been hindered. In agreement with this possibility, after challenging high-producing cows by replacing forages with barley grain, Bach et al (2018b) reported that rumen pH was greater for cows fed 200 g/d of sodium bicarbonate or 100 g/d of a magnesium oxide-based product compared with cows not fed any buffer.…”

Effects of calcium carbonate, magnesium oxide and encapsulated sodium bicarbonate on measures of post‐ruminal fermentation

“…When compared to control diets, greater levels of supplemental calcium carbonate or limestone (12 to 24 g/kg) reduced intake, milk yield or milk protein (Clark, Plegge, Davis, & McCoy, ; Rogers et al, , ). Supplementation with up to 8 g/kg magnesium oxide increased intake, milk yield or milk fat in some studies that used corn silage as the primary forage source (Erdman et al, ; Teh et al, ), but not in other studies that used different primary sources of forage (Bach, Guasch, Elcoso, Duclos, & Khelil‐Arfa, ; Holtenius, Kronqvist, Briland, & Spörndly, ; Stokes, Vandemark, & Bull, ; Thivierge et al, ). Inclusion of 40 g/kg magnesium oxide to corn silage based diets increased milk fat percentage without affecting yields of milk or milk fat (Xin, Tucker, & Hemken, ).…”

“…Supplementation with limestone or calcium carbonate increased rumen pH and decreased butyrate in one study (Keyser, Noller, Wheeler, & Schaefer, ), but no effects were found by others (Clark et al, ; Rogers et al, ). Effects of supplementing magnesium oxide on rumen pH are also variable, with some observing no effect (Stokes et al, ), others observing an increase (Erdman et al, ) and others observing an increase dependent on the source of magnesium oxide or ration composition (Bach et al, ; Xin et al, ). Similar to the current study, Erdman et al () and Xin et al () found no effect of supplementing magnesium oxide on total rumen VFA concentration, although changes in the molar proportions of acetate, propionate, butyrate or isobutyrate have been observed (Erdman et al, ; Stokes et al, ; Xin et al, ).…”

Ruminal Microbiome Manipulation to Improve Fermentation Efficiency in Ruminants

“…Therefore, maintaining ruminal pH at the average level (5.8-7.2) is an essential factor to balance the rumen microorganisms between acid producers and consumers. In this context, buffering reagents and alkalizer (e.g., sodium bicarbonate, magnesium oxide, and calcium magnesium carbonate), direct-fed microbials, and malate supplementation may increase pH in the rumen and production when ruminants are fed with high-grain based diets [66,68] [69]. Marden et al [70] reported that the inclusion of 150 g of sodium bicarbonate increased total ruminal VFA concentration by 11.7% compared to the control diet fed to lactating cows.…”