Effects Of Feeding Two Typical Diets To Lactating Cows On Rumen Fermentation And Immunity

The objectives of this study were to evaluate the association of feeding a corn straw or mixed forage diet to lactating cows on rumen fermentation and immunity.Trial1:This part was designed to evaluate effect of different forage patterns on ruminal pH, temperature and oxidation reduction potential (ORP) and their rhythms. Eight primiparous, lactating and ruminally fistulated Holstein cows with similar body weight, milk yield and days in milk were used in this study. Cows were randomly assigned to1of2dietary treatments after being blocked by milk yield and body weight and fed with either com straw (CS) or mixed forage (MF) as basal diet, respectively. This experiment lasted for16weeks, with2-week of preliminary period and14-week of trial period. Ruminal pH, temperature and ORP were real-time monitoring by a wireless data logger at the9th and16th week, respectively. The result showed that ruminal pH value, temperature and ORP were all within normal physiological limits in both groups, and the CS group had significantly higher (P<0.01) pH value compared to the MF group, whereas temperature and ORP were markedly lower (P<0.01) in the CS treatment. In the CS group, pH value at the time ante ingestion, the time at rumination and post ingestion were significantly higher (P <0.05) than those in MF group. Compared to MF group, minutes for ruminal pH below5.6tended to be less (P=0.07) in CS group. However, minutes for pH below5.2were not affected by experimental treatments (P>0.05). The results of this study indicated that rumen fermentation parameters were affected by forage patterns.Trial2:This experiment was designed to evaluate effect of feeding a corn straw or mixed forage diet on mixed-rumen bacterial fatty acid profiles in lactating cows. Twelve primiparous, lactating and ruminally fistulated Holstein cows with similar body weight, milk yield and days in milk were used in this study. Cows were randomly assigned to1of2dietary treatments after being blocked by milk yield and body weight and fed with two different diets as mentioned in Trial1, respectively. This experiment lasted for32d, with14d of preliminary period and18d of trial period, and rumen samples were obtained via rumen fistulas during the last3days of trial period. The result showed that compositions of Cl6:0, C18:3,<C16:0, medium chain fatty acid and long chain fatty acid in mixed-rumen bacterial samples were significantly higher in cows fed MF diet (P<0.01), while compositions of C18:0、 cis9C18:l and>C16:0were significantly higher in cows fed CS diet (P<0.05). Contents of C12:0、C14:0and C22:0were tended to be higher in MF group compared with those fed CS diet (P<0.10), while other profiles of rumen bacterial fatty acid were not affected by dietary treatments. The results of this study indicated that different dietary patterns caused the alteration of rumen microbial fatty acid profiles rather than saturation in lactating cows.Trial3:This part was conducted to evaluate effect of feeding a corn straw or mixed forage diet on immunity of lactating cows by analysing compositions of serum immunoglobulins (Igs), cytokines, inflammation factors, biochemistry indexes and plasma lymphocyte subsets. Twenty primiparous, lactating Holstein cows with similar body weight, milk yield and days in milk were used in this study. Cows were randomly assigned to1of2dietary treatments after being blocked by milk yield and body weight and fed with two different diets as mentioned in Trial1, respectively. This experiment lasted for2months, blood samples were obtained via jugular vein before morning feeding at the last day of the trial period. The result showed that levels of serum IgA, secretory IgA (slgA), interleukin-2(IL-2), IL-4, IL-6, IL-10, IL-12, interferon-alpha (IFN-a), IFN-y, tumor necrosis factor-alpha (TNF-a), prostaglandin E2(PGE2), glucose, calcium, beta-hydroxybutyric acid (BHBA),25-hydroxyvitamine D3and plasma CD4+lymphocyte subset, CD8+lymphocyte subset and CD4+/CD4+ratio were not affected by experimental treatment (P>0.05), and cows fed CS diet tended to have higher serum IgE, IgM and insulin-like growth factors-1(IGF-1) compositions than those in MF group (P<0.10), while serum IgG and albumin (ALB) level were tended to be higher in MF group (P<0.10). The results of this study illustrated that different dietary systems had no effect on immunity and serum biochemistry indexes in lactating cows.