Liquid molasses interacts with buffers to affect ruminal fermentation, milk fatty acid profile, and milk fat synthesis in dairy cows fed high-concentrate diets

Abstract

We aimed to evaluate the effects of feeding sugarcane liquid molasses (LM) with or without a commercial buffer mix (BFM) on ruminal fermentation parameters, milk fatty acid (FA) profile, and milk yield and composition in dairy cows fed high-concentrate diets (35:65 forage-to-concentrate ratio). Eight multiparous Holstein cows (4 ruminally cannulated) averaging 165 ± 12 d in milk at the beginning of the study were randomly assigned to a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Each period lasted 21 d with 14 d for diet adaptation and 7 d for data and sample collection. Cows were fed the following diets: (1) no LM or BFM supplementation (CTRL), (2) LM without BFM supplementation (MOL), (3) BFM without LM supplementation (BUF), and (4) LM plus BFM supplementation (COMBO). These 4 isonitrogenous and isoenergetic diets were formulated by replacing (dry matter basis) 5% ground corn with LM, whereas BFM replaced wheat bran at 0.8% of the diet. Significant LM × BFM interactions were observed for the duration of ruminal pH below 5.8, molar proportion of propionate, acetate-to-propionate ratio, milk proportions of trans-10 18:1 and total trans FA, and concentration and yield of milk fat. Feeding MOL and BUF alone were effective on reducing the time that ruminal pH remained below 5.8 compared with the CTRL treatment, and the COMBO diet decreased it further. A similar pattern was observed for the ruminal molar proportion of propionate. The milk proportions of trans-10 18:1 and total trans FA dropped significantly with BFM or LM supplementation versus cows fed CTRL, and the COMBO diet decreased these variables further. Note, however, that these changes elicited by the COMBO diet were not in the same magnitude as those caused by MOL or BUF fed alone. The ruminal molar proportion of acetate increased with the BUF diet and that of butyrate increased in cows fed MOL, but mean ruminal pH was not affected by treatments. Diets with LM resulted in increased concentrations of short-and medium-chain FA in milk fat. The yield of 3.5% fat-corrected milk increased significantly in cows fed MOL or BUF due to the improved concentration of milk fat. A trend and a significant increase for energycorrected milk were observed with feeding MOL or BUF, respectively. Overall, inclusion of LM and BFM appears to reduce milk trans-10 18:1 FA and total trans FA by modulating ruminal pH and volatile FA profile in cows fed high-concentrate diets.

Effects of substitution of beet pulp for barley or corn in the diet of high-producing dairy cows on feeding behavior, performance, and ruminal fermentation

“…The average ruminal pH of cows in the present study was 6.30. This value is high and inconsistent with previous studies where high-concentrate diets were tested (Voelker and Allen, 2003b;Kahyani et al, 2019;Nasrollahi et al, 2019;Razzaghi et al, 2020). Two main differences between the present study and these referenced reports were different sorting activities of cows and supplementation of sodium bicarbonate.…”

“…The effect of ingestion of long particles on increased ruminal pH may be related to increased chewing activity and improved ruminal health and function (Mertens, 1997). Using sodium bicarbonate in the present study also could have contributed to the higher ruminal pH that was observed, compared with previous studies that did not use sodium bicarbonate (Voelker and Allen, 2003b;Nasrollahi et al, 2019;Razzaghi et al, 2020).…”

Effect of dietary supplementation or cessation of magnesium-based alkalizers on milk fat output in dairy cows under milk fat depression conditions

“…In fact, the addition of 0.4% magnesium oxide and 0.8% calciummagnesium dolomite to the diet did not affect feed in-take in our study. Other studies in lactating dairy cows showed that buffering or alkalizing agents had no effect on lactation performance, either in typical (Cabrita et al, 2009;Rauch et al, 2012) or high-concentrate diets (Kalscheur et al, 1997;Khorasani and Kennelly, 2001); however, other studies (Neville et al, 2019;Razzaghi et al, 2020) reported increased feed intake. Rauch et al (2012) reported that there was no difference in feed intake and milk yield between control and calciummagnesium dolomite diets on commercial dairy farms, but differences in dietary starch and NDF contents compared with our study were evident (starch = 15.7 vs. 35.2% and NDF = 33.9 vs. 28.7%, on DM basis).…”

“…In addition, there are divergent results regarding the effects of feeding buffers on milk yield. Some studies have documented no effects (Bach et al, 2018;Razzaghi et al, 2020), whereas others have reported increased milk yield (Razzaghi et al, 2021) with the addition of buffering or alkalizing agents.…”

“…In vivo studies have shown that regulation of rumen pH by the addition of buffer reduces the production of BH intermediates associated with MFD (Kalscheur et al, 1997;Cabrita et al, 2009). Similarly, different types of magnesium-based alkalizers have been proposed to stabilize rumen pH and thus reduce the occurrence of MFD (Neville et al, 2019;Razzaghi et al, 2020). Bach et al (2018) reported that a magnesium-based product can neutralize rumen pH and maintain milk fat content more efficiently than sodium bicarbonate when cows are challenged with 3 kg/d of additional barley in the ration.…”