| In China, forages are in short supply, and the quality is low. High grain diets are widely used. Cattle are fed high concentrate dies to meet the energy and nutrients demands, which is associated with a rapid decline in ruminal pH and causes subacute rumen acidosis (SARA). At the same time, high concentrate diets can disturb the balance of microbial in rumen, result in the large amounts release of bacterial endotoxin (LPS) from gram-negative bacteria in the rumen, then increase the concentrations of LPS in the rumen fluid and feces. High concentrations of LPS can translocate into the bloodstream through the digestive tract barriers, which increases LPS concentrations in the blood, causes the body systemic inflammation, increases the body’s immune activation, and redistributes nutrients, thereby reducing the milk production performance of dairy cows.According to the current situation, large-scale dairy farms are in a lack of high quality roughage in our country, and diets generally contain high concentrate, our study imitates the domestic typical models of diets, and is mainly aimed to evaluate the effects of feeding different types of diet with different ingredient compositions and concentrate proportions on the release of ruminal LPS and immune activation in the mammary gland of dairy cows.Trial1:this trial was intended to study the effect of three different types of diet with different ingredient compositions and concentrate proportions on concentration of LPS in mammary gland, and explore the inner link between high concentration of plasma LPS and the degradation of milk roduction performance by monitoring the state of immune activation. Nine mid-lactation Chinese Holstein cows blocked by milk yield (20.86±3.00kg/d), lactation period(193+21d) were used as the experimental animals. Experimental animals were randomly divided into three groups and designed as3x3Latin square. The duration of the trial was21days, and samples were gathered in the last7 days. Three groups were fed different diets respectively. Diet1:single straw diet1(CSl), roughage was maize straw, concentrate was mainly composed of corn, wheat bran and soybean meal, concentrate to forage ratio was63:37; Diet2:single straw diet2(CS2), roughage was maize straw, the species of concentrate were much more abundant than CS1, which were made of corn, wheat bran, soybean meal, cottonseed meal, corn gluten, corn protein powder and DDGS, concentrate to forage ratio was63:37; Diet3:mixed forage diet (MF), roughage were chinese wildrye, alfalfa hay and whole plant corn silage, concentrate was mainly composed of corn, soybean meal and cottonseed, concentrate to forage ratio was41:59. Results showed that:(1) the concentrations of LPS in rumenal fluid and mammary gland arterial plasma in CS1and CS2group were significantly higher than that in MF group (P<0.05), the concentrations of LPS in mammary gland venous plasma had no significant difference (P>0.05).(2) The flow of LPS in mammary gland in CS2group was significantly higher than MF group (P<0.05), mammary gland in the three groups had no effect on the removal and clearance of LPS (P>0.05).(3) In CS1and CS2groups, the proportions of CD3, CD4, CD8and CD14in venous blood, and the concentrations of of IL-1(3, IL-6, IL-8, IFN-y and IgM in venous blood were higher than MF group, but the difference was not significant (P>0.05).(4) In MF group, the milk efficiency,4%fat corrected milk production efficiency, milk fat and milk protein synthesis efficiency were significantly higher than that in CS1and CS2group (P<0.01).(5) There were significant positive correlation between the dietary concentrate to forage ratio and the concentration of LPS in arteries (P<0.05).(6) Three groups had no significant effect on rumen pH, the concentration of lactic acidã€VFA in rumen and the content of histamine in mammary gland arteriovenous plasma (P>0.05). Results indicated that the difference between raw materials in diets have no effects on the content of LPS in mammary gland and immune activation status in cows, the concentrate to forage ratio of dietary had a certain influence on the content of LPS in mammary gland and immune activation. High grain diets can increase the concentrations of LPS in rumen, mammary gland, and activate the body’s immune level in a certain degree, this can reduce the precursors which are synthesised milk compositions, thereby decrease the milk production performance of dairy cows. Further research is needed to carry out to explain the specific mechanism of the nutrients redistribution.Trial2:this study was intended to investigate the effects of different modes of diet on the release of LPS in rumen, the concentration of LPS in mammary gland arteriovenous and the status of immune activation. Thirty mid-lactation Chinese Holstein cows blocked by milk yield (24.32±3.86kg/d), body weight (542.7±56.5kg), and body condition score (2.86±0.29) were used as the experimental animals. Experimental animals were randomly divided into three groups. Each group was10heads, and were fed different diets until the milk composition was reached significant difference (6weeks). Experimental diets were divided into3groups:high concentrate straw diet (HCS), low concentrate straw diet (LCS) and low concentrate mixed forage diet (LMF). HCS and LCS groups only had corn straw, the roughage of LMF group was chinese wildrye, alfalfa hay and whole plant corn silage. Three groups had the same concentrate, the main raw materias of the concentrate were corn, soybean meal and cotton seed. The concentrate to forage ratio of HCS, LCS and LMF group were65:35,46:54and46:54, respectively. The results showed that:(1) the concentration of LPS in rumen fluid in HCS group was significantly higher than that in LCS and LMF group (P<0.01), the average concentration of LPS in feces in HCS group was24,095EU/g (wet weight), which was significantly higher than that in LCS and LMF group (P<0.01).(2) The content of LPS in mammary gland arteriovenous plasma in HCS group were significantly higher than in LCS group (P<0.05), and has no significant difference between HCS and LMF group (P>0.05). The flow of LPS in mammary gland between HCS and LCS/LMF group were extremely significant difference (P<0.01), at the same time, the LCS and LMF flow of LPS was extremely significant difference (P<0.01).(3) The dietary concentrate to forage ratio was significantly positive correlated with the concentrations of LPS in mammary gland arteriovenous plasma (P<0.05). The concentration of LPS in mammary gland artery and the flow of LPS in mammary gland were significantly negative correlated to the milk production efficiency of cows (P<0.05).(4) The immune activation state of body of HCS group was enhanced, showing the concentration of CD3, CD14, IgG and the appreciation rate of lymphocytes to PHA were significantly increased(P<0.05). At the same time, the immune response of mammary gland can also strengthen, the proportion of neutrophils, cytokines (IL-1β, IL-6, IL-8), acute phase proteins (CRP, Hp) content in mammary veins plasm of HCS group were significantly higher than LCS group and LMF group.(5) The milk production performance of LMF was superior to the same nutrient level of HCS group, both of them were better than the lower nutrient levels of LCS group.(6) Rumen pH, the concentrations of VFA, lactic acid and histamine in rumen were in basic consistent in HCS and LMF, all of them had significantly difference between HCS/LMF and LCS. There had no difference in the concentrations of lactic acid and histamine in mammary gland arteriovenous plasma among three groups. Results indicate that high grain diets can promote the release of LPS in the rumen, and can cause higher LPS content in rumen fluid and feces. Furthermore, the translocation of LPS causes an increasing entry of LPS into the body and the mammary gland, and thus results in systemic immune activation and local immune activation in the mammary gland, which reduces the precursors used to synthesize milk components and decreases the milk production performance of dairy cows. |
