The objective of this experiment was to study the effects of infusion lipopolysacchride (LPS) on the amino acid composition and gene expressions related to protein metabolism in milk of dairy cows by semi in vivo and in vitro tests. Six multipara Holstein lactating cows were selected in the in vivo test, and randomly divided into experimental and control groups with three cows in each group. A cross test design was applied. The test consisted of two experimental periods (7 d each) and an interval period (14 d). Cows in the experimental group were infused LPS (Escherichia coli O111: B4, 0.01μg/kg) into external pudendal artery, as those in the control group were infused physiological salt solution. Mammary epithelial cells were applied in the in vitro test, and the supplemental level of LPS in a basal culture medium was 0, 0.1 and 10.0 ng/mL, respectively. After 24 h, the relative expression level of target genes was determined using qRT-PCR. The results showed that contents of essential amino acids (EAA) and branch-chain amino acids (BCAA) in milk were firstly ascended and then descended (P>0.05) as the infusion time prolonged, and maximum contents appeared at 6 h; the non-essential amino acids (NEAA) content in milk was increased at the beginning and then decreased (P>0.05), and the minimum content appeared at 6 h. LPS increased mRNA expression levels of S6K1 and 4EBP1 in mammary epithelial cells (P>0.05), and the effects showed dosage dependent. LPS did not significantly affect mRNA expression levels of mTOR and JAK2 (P>0.05), but they tended to increased. Compared with the control group, LPS enhanced the mRNA expression of STAT5 significantly (P<0.05). Therefore, LPS affects the amino acid composition in milk by interrupt pathways of mTOR and JAK2/STAT5.
ZANG Changjiang
,
ZHANG Yangdong
,
WANG Jiaqi
,
HU Tao
,
BU Dengpan
,
JIN Di
,
ZHOU Lingyun
,
LI Fadi
. Effects of Lipolysacchride on Amino Acid Composition and Gene Expressions Related to Protein Metabolism in Milk of Dairy Cows[J]. Chinese Journal of Animal Nutrition, 2012
, 24(9)
: 1770
-1777
.
DOI: 10.3969/j.issn.1006-267x.2012.09.021
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