Effects of calcium–magnesium carbonate and calcium–magnesium hydroxide as supplemental sources of magnesium on microbial fermentation in a dual-flow continuous culture
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Fecha
2020-12-22
Tipo
artículo original
Autores
Arce Cordero, José Alberto
Monteiro, Hugo Fernando
Brandao, Virginia. L. N.
Dai, Xin
Bennett, Sarah L.
Faciola, Antonio Pinheiro
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Resumen
Supplemental sources of Mg can
also aid in ruminal pH regulation due to their al kaline properties. Magnesium oxide (MgO) is the
most common source of Mg for ruminants and
can help controlling ruminal pH; however, the al kaline potential of other sources of Mg has not
been evaluated. We aimed to evaluate the inclusion
of calcium–magnesium carbonate (CaMg(CO3
)2
)
and calcium–magnesium hydroxide (CaMg(OH)4
)
alone or in combination as supplemental sources
of Mg in corn silage-based diets and its impact
on ruminal microbial fermentation. We hypothe sized that inclusion of CaMg(OH)4
would allow
for ruminal fermentation conditions resulting
in a greater pH compared to the inclusion of
CaMg(CO3
)2
. Four treatments were defined by the
supplemental source of Mg in the diet: 1) Control
(100% MgO, plus sodium sesquicarbonate as
a buffer); 2) CO3
[100% CaMg(CO3
)2
]; 3) OH
[100% CaMg(OH)4
]; and 4) CO3
/OH [50% Mg
from CaMg(CO3
)2
, 50% Mg from CaMg(OH)4
].
Nutrient concentration was held constant across
treatments (16% CP, 30% NDF, 1.66 Mcal NEl/
kg, 0.67% Ca, and 0.21% Mg). Four fermenters
were used in a 4 × 4 Latin square design with
four periods of 10 d each. Samples were collected
for analyses of nutrient digestibility, soluble Mg,
VFA, and NH3
, while pH was measured at 0, 1, 2,
4, 6, 8, and 10 h post morning feeding to estimate
% time when pH was below 6 (pH-B6) and area
under the pH curve for pH below 6.0 (pH-AUC).
Bacteria pellets were harvested for 15N analysis
and estimates of N metabolism. Treatment ef fects were analyzed with the mixed procedure of
SAS, while effects of using either CaMg(CO3
)2
or CaMg(OH)4
as Mg source in comparison to
Control treatment were evaluated by orthog onal contrasts. Similar pH-related variables were
observed for Control, OH, and CO3
/OH treat ments, which had smaller pH-AUC and pH-B6
than CO3
(P ≤ 0.01). Butyrate molar proportion
was greater in Control and CO3
/OH than in CO3
and OH (P = 0.04). Orthogonal contrasts showed
lower flow of bacterial N (P = 0.04), lower bu tyrate molar proportion (P = 0.08) and greater
pH-AUC (P = 0.05) for diets with CaMg(CO3
)2
in
comparison with the Control. Concentration of
soluble Mg in ruminal fluid (P = 0.73) and nu trient digestibility (P ≥ 0.52) were similar across
treatments. Under the conditions of this experi ment, using CaMg(OH)4
alone or combined
with CaMg(CO3
)2
allowed for a less acidic rumi nal fermentation pattern than a diet with only
CaMg(CO3
)2
.
Descripción
La Universidad de Costa Rica apoyó el programa de doctorado de José Alberto Arce Cordero
Palabras clave
Alkalinizer, Buffer, MINERAL, Ruminal acidosis