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Inclusion of calcium-magnesium tetrahydroxide as a dietary source of inorganic Mg alters ruminal pH and fermentation in a dual-flow continuous culture system.

J. A. Arce-Cordero

Abstract:

91
Inclusion of calcium-magnesium tetrahydroxide as a dietary source of inorganic Mg alters ruminal pH and fermentation in a dual-flow continuous culture system.
J. A. Arce-Cordero*, H. F. Monteiro, V. L. N. Brandao, X. Dai, S. Bennett, J. Vinyard, A. P. Faciola. Department of Animal Sciences, University of Florida Gainesville, FL.

Ruminal acidosis is a major issue affecting modern cattle industry. Buffers such as sodium sesquicarbonate are normally fed to reduce negative effects of acidosis; however, some mineral sources may play a role as controllers of ruminal pH. We aimed to evaluate the effects of inclusion of CaMgCO3 and CaMg(OH)4 on microbial fermentation, hypothesizing that their inclusion as supplemental sources of inorganic Mg (iMg) would allow for similar ruminal fermentation conditions to those observed in a positive control diet formulated with MgO as the sole source of iMg plus a buffer. Four treatments were defined by the main source of iMg in the diet: (1) CO3 [100% iMg from CaMg(CO3)2]; (2) CO3/OH [50% iMg from CaMg(CO3)2, 50% iMg from CaMg(OH)4]; (3) OH [100% iMg from CaMg(OH)4]; (4) MgO/Na (100% iMg from MgO, plus 0.6% sodium sesquicarbonate). Nutrient concentration was the same across treatments (16% CP, 30% NDF, 1.69 MCal NEl/kg, 0.68% Ca, and 0.22% Mg from which 0.05% corresponds to iMg). Four fermenters were used in a 4 � 4 Latin square design with 4 periods of 10 d each. In the last 3 d of each period samples were collected for analyses of nutrient digestibility, soluble Mg, VFA, and NH3-N, while pH was measured at 0, 1, 2, 4, 6, 8, and 10 h post morning feeding to estimate hours below pH of 6 (pH < 6) and area under the pH curve (pH AUC). Bacteria pellets were harvested for 15N analysis and estimates of N metabolism. Treatment effects were analyzed with PROC MIXED of SAS, while effects of CaMgCO3 and CaMg(OH)4 were evaluated by orthogonal contrasts. Inclusion of CaMg(OH)4 increased pH AUC (P = 0.02); molar proportion of butyrate (P = 0.02), and decreased pH < 6 (P < 0.01), showing a similar effect to that one observed in the positive control treatment formulated with MgO and buffer. No effects of CaMgCO3 and CaMg(OH)4 were found on soluble Mg, nutrient digestibility and N metabolism. Results indicate that feeding CaMg(OH)4 as a mineral source may aid in the control of ruminal pH.

Keywords: in vitro, acidosis, buffers.

Biography: Jose obtained his MS degree in ruminal nutrition at Colorado State University in 2016, then he started his PhD program at University of Florida where he is currently a PhD candidate and his main research focus has been the effects of micronutrients supplementation on ruminal fermentation