TY - JOUR
T1 - Effects of different levels of methionine and ruminally undegradable protein on the amino acid profile of effluent from continuous culture fermenters
AU - Bach, Alex
AU - Stern, Marshall D.
PY - 1999/12
Y1 - 1999/12
N2 - Eight dual-flow continuous culture fermenters were used to study the effects of feeding different levels of methionine and ruminally undegradable protein (RUP) on the amino acid (AA) profile of protein residue after microbial fermentation. Four isocaloric (1.76 Mcal/kg of NE1) and isonitrogenous (17.7% CP) diets were formulated based on NRC recommendations for a 630-kg cow producing 42 kg/d of milk. Two dietary treatments, diets HmLr (high methionine, low RUP) and HmHr (high methionine, high RUP), were formulated to meet, but not exceed, more than 140% of each estimated individual AA requirement for milk production. Diets LmLr (low methionine, low RUP) and LmHr (low methionine, high RUP) were formulated to meet the estimated individual AA requirement except for methionine. Diets HmLr and LmLr contained 35% RUP, and diets HmHr and LmHr contained 43% RUP. Digestion of DM, OM, and NDF was not affected (P > .05) by treatments. Tyrosine, cystine, and threonine ranked as the most resistant AA to microbial fermentation, whereas methionine and lysine ranked among the most degradable. In general, microbial degradation of individual AA followed the same pattern as CP degradation, being higher in diets HmLr and LmLr and lower in diets HmHr and LmHr. Because true microbial digestion of methionine, cystine, tyrosine, and isoleucine was reduced in the presence of high levels of methionine, we concluded that supplementation of dietary methionine could increase flows of these amino acids to the duodenum.
AB - Eight dual-flow continuous culture fermenters were used to study the effects of feeding different levels of methionine and ruminally undegradable protein (RUP) on the amino acid (AA) profile of protein residue after microbial fermentation. Four isocaloric (1.76 Mcal/kg of NE1) and isonitrogenous (17.7% CP) diets were formulated based on NRC recommendations for a 630-kg cow producing 42 kg/d of milk. Two dietary treatments, diets HmLr (high methionine, low RUP) and HmHr (high methionine, high RUP), were formulated to meet, but not exceed, more than 140% of each estimated individual AA requirement for milk production. Diets LmLr (low methionine, low RUP) and LmHr (low methionine, high RUP) were formulated to meet the estimated individual AA requirement except for methionine. Diets HmLr and LmLr contained 35% RUP, and diets HmHr and LmHr contained 43% RUP. Digestion of DM, OM, and NDF was not affected (P > .05) by treatments. Tyrosine, cystine, and threonine ranked as the most resistant AA to microbial fermentation, whereas methionine and lysine ranked among the most degradable. In general, microbial degradation of individual AA followed the same pattern as CP degradation, being higher in diets HmLr and LmLr and lower in diets HmHr and LmHr. Because true microbial digestion of methionine, cystine, tyrosine, and isoleucine was reduced in the presence of high levels of methionine, we concluded that supplementation of dietary methionine could increase flows of these amino acids to the duodenum.
KW - Amino Acids
KW - Degradation
KW - Fermentation
KW - In Vitro
KW - Rumen
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U2 - 10.2527/1999.77123377x
DO - 10.2527/1999.77123377x
M3 - Article
C2 - 10641887
AN - SCOPUS:0033256011
SN - 0021-8812
VL - 77
SP - 3377
EP - 3384
JO - Journal of animal science
JF - Journal of animal science
IS - 12
ER -