Effects Of Different Dietary Patterns On Production Performance, Biochemical Indicators And Lactation-related Hormones Of Blood In Mid Lactating Dairy Cows

Chinese dairy industry development is rapid, and made remarkable achievements. However, the low-quality of milk has been a severe challenge for its healthy development. The main reasons are lack of high-quality roughage and inadequate and unreasonable utilization of existing roughage resource. By preparing two typical corn stalks roughage diets and typical high-quality mixed roughage diet with corn stalks-specific roughage recourse of northern China, this paper was aimed to study the effect of different dietary patterns on milk quality, and provide scientific basis for dairy cow breeding under existing roughage recourse condition in China-Experiment1Effects of different dietary patterns on production performance in mid lactating dairy cowsThirty Holstein dairy cows in mid lactation (120±24d,2-3parities) were randomly assigned to three groups, ten cows each group with similar body weight (554±21kg) and milk yield (24.30±1.47kg/d). Single-factor block design was applied in this experiment. The experimental diets were:1) IMF, with hay, corn silage and alfalfa mixed roughage;2) CS1, with only corn stalks roughage and with equal level of proximate nutrients to IMF;3) CS2, with only corn stalks roughage and with same proportion of roughage to IMF. The experiment lasted for90days with30days per period; the consecutive TMR, milk and blood samples were collected during last three days of each period. The results showed that no significant differences (p>0.05) were observed in body weight, dry matter intake and somatic cells in mid lactatking dairy cows; however, the effects of different diets on production performances including milk yield and milk composition were significant:milk yield of MF group was significantly higher than CS1group, and that of CS1group was significantly higher than CS2group (p<0.05); MF group showed a significant high level of milk protein content compared with CS2group (p<0.05), milk protein content of CS1 group was between MF group and CS2group and had no significant difference with both MF group and CS2group(p>0.05); MF group showed significant higher milk fat content than CS1group (p<0.05), milk fat content of CS2group was between MF group and CS2group and had no significant difference with both MF group and CS1group(p>0.05).Experiment2Effects of different dietary patterns on biochemical indicators of serum in mid lactating dairy cowsBased on experimentl, research the concentrations of biochemical indicators in venous serum by cows under different dietary patterns. The result showed that there were no changes(p>0.05) observed in biochemical indicators CHO、TG、TP、ALT、FFA、Na+、 K+、Cl-、TCO2、GLU、ALB and3-MH. Nonetheless, cows fed with CS1was markedly higher in venous serum AST than cows fed with MF and CS2(p<0.05), CS2had higher AST than MF, but they showed no difference (p>0.05); BUN in cows fed with CS2or MF was markedly lower (p<0.01) than that of cows fed CS1, CS2had higher AST than MF, but there showed no significant difference between them (p>0.05).Experiment3Effects of different dietary patterns on lactation-related hormones in mid lactating dairy cowsBased on experiment1, researched the concentrations of lactation related hormones in venous serum by cows under different dietary patterns. The result showed no differences between3treatments in lactation-related hormones LGF-I, LE, PRL, INS, COR (p>0.05), but serum GH of cows fed with CS2or MF was significantly lower than that of cows fed with CS1(p<0.05), CS2showed higher but not significant difference than MF (p>0.05).The study suggested that changes in production performances were significant among three treatments, and all treatments showed stable fluctuations. Mid lactating dairy Cows fed with low-quality roughage diet that is nutritional balanced (CS1) could obtain better production performances.