Effects of supplemental source of magnesium and inclusion of buffer on ruminal microbial fermentation in continuous culture
Fecha
2021-07
Tipo
artículo original
Autores
Arce Cordero, José Alberto
Ravelo, Anay D.
Vinyard, James R.
Monteiro, Hugo Fernando
Agustinho, Bruno Calvo
Sarmikasoglou, Efstathios
Bennett, Sarah L.
Faciola, Antonio Pinheiro
Título de la revista
ISSN de la revista
Título del volumen
Editor
Resumen
Magnesium oxide (MgO) is the most common supple mental source of Mg for dairy cows and a proven ruminal alkalizer when supplemented above NRC (2001)
recommendations. However, overfeeding MgO may
increase feeding costs, whereas the effects of alternative
sources of Mg on ruminal fermentation are not well
known. Moreover, it is still unclear if Mg supplementation influences the effects of bicarbonate-based buffers
on ruminal fermentation. We aimed to evaluate the effect of Mg source on ruminal fermentation with diets
formulated to a final concentration of 0.25% Mg, and to
determine if the effect of sodium sesquicarbonate as a
buffer varies with the source of Mg. We used 8 fermentors in a duplicated 4 × 4 Latin square design with a
2 × 2 factorial arrangement of treatments, by combining 2 factors: (1) Mg source: using either MgO or an
alternative source consisting of a blend of CaMg(OH)4
and CaMg(CO3)2 (BLN) and (2) sodium sesquicarbonate buffer inclusion, at 0 or 0.6% of dry matter intake.
Based on preliminary tests of reactivity, we hypoth esized that BLN plus buffer would allow for greater
ruminal pH, acetate molar proportion, and NDF digestibility than diets with MgO or without buffer. Four
10-d periods were completed, where the last 3 d were
used for pH measurements and collection of samples for
volatile fatty acids (VFA), ammonia (NH3-N), Mg solubility, N metabolism, and nutrient digestibility. Effects
of Mg source (source), sodium sesquicarbonate inclusion (buffer), and their interaction (source × buffer)
were tested with the MIXED procedure of SAS (SAS
Institute Inc.). We did not find an effect of Mg source
on ruminal fermentation variables; however, concentration of soluble Mg in ruminal fluid was greater for MgO
compared with BLN. On the other hand, buffer supplementation increased average ruminal pH, acetate molar
proportion, and branched-chain VFA molar proportion;
tended to increase NDF digestibility; and decreased
both area under the curve and time below pH 6.0. An
interaction of source × buffer was found for propionate,
butyrate, and NH3-N, the first one decreasing and the 2
others increasing only when buffer was supplemented to
the BLN diet. Our results indicate that supplementing
Mg with either MgO or BLN promotes similar ruminal
fermentation in diets with total concentration of 0.25%
Mg. Further evaluations are needed to assess Mg availability and animal performance in dairy cows fed BLN.
Descripción
José Alberto Arce Cordero realizó esta publicación durante un programa de doctorado patrocinado por la Universidad de Costa Rica
Palabras clave
Alkalizer, In vitro, pH