Effect of Different Roughages on Milk Protein and Milk Fat Synthesis in Dairy Cows

The main purpose of this study was to determine the effect of a corn straw or mixed diet on milk production, milk composition and the expression of genes associated with lactation in mid-lactation Chinese Holstein cows. In this study, 10 healthy Chinese Holstein cows were randomly assigned to two groups and fed with different diets respectively, corn straw （CS） or mixed forage （MF） diet. CS group was fed roughage consisting of 53.8% corn straw only and the forge to concentrate （F ： C） ratio [dry matter （DM）] was about 40： 60. MF group was fed roughage consisting of 3.7% Chinese wildrye and 23.4% alfalfa hay, the forge to concentrate （F ： C） ratio （DM） was 70： 30. All the cows were fed 8 weeks and body weight, dry matter intake, body condition score, fat, protein, lactose, milk yield, total solid and somatic cell count （SCC） were recorded. Quantitative real-time PCR （qRT-PCR） was used to analyze cow mammary gland samples representing two different diets. The results suggested that different diet types had significant effects on milk yield, lactose, milk fat, milk protein, dry matter intake and somatic cell count in dairy cows, and cows fed MF diet improved milk production and lactation performance clearly （P〈0.05）. In addition, mRNA expression of genes ACC, roTOR, STATS, CSN2, PPAR）,, FABP3 and PTEN in MF group was extremely significantly higher than that in CS group （P〈0.05）. mRNA expression ofAKT1, FAS, SCD and SREBPlc in MF group was significantly higher than that in CS group （P〈0.01）. In summary, the milk yield and composition in mixed forage group were significantly improved than those in corn straw group.

Rumen Degradation Regularity of Dry Matter and Crude Protein of Common Roughage in Beef Cattle

Three individuals of Horqin yellow cattle equipped with permanent fistula, weighed （548 ±21） kg, were sdected as the experimental animals. The ru- men degradation characteristics of dry matter （DM） and crude protein （CP） of roughage at 6, 12, 24, 48 and 72 h were measured by nylon bag method. The re- suits showed that the effective degradation rates of DM and CP of alfalfa hay were the highest, while higher contents of rapid degradation part and potential degrada- tion part of DM and CP also resulted in higher degradation rates of DM and CP. The effective degradation rates of CP and DM of roughage presented strong positive correlation with CP, but showed strong negative correlation with neutral detergent fiber （NDF）. The effective degradation rates of CP of five roughages successively were alfalfa hay 〉 alfalfa block 〉 ryegrass 〉 silage corn 〉 straw.

Effect of Corn Stalks Treated with Carbonylamines in Different Concentrate and Forage Rations and Nitrogen Conditions on Rumen Fermentation in Vitro

[ Objective] To investigate the effects of concentrate/roughage ratios and nitrogen levels on in-vitro rumen fermentation of urea-treating corn stalk. [ Method] The concentrate/roughage ratios were 7： 3, 5：5 and 3： 7. The crude protein levels were 11% and 14%. The in-vitro culture time was 2, 4, 6 and 48 h. [ Result] The pH value of broth decreased significantly with the decline in the proportion of roughage （ P 〈 0.01 ） and with the increase in the crude protein levels （P 〈 0.05）. The ammonium nitrogen concentration and acetic acid/propionic acid ratio of the fermen- ted products decreased with the increase in the crude protein levels and proportion of concentrate in diet. The diet with concentrate/roughage ratio of 5：5 and crude protein level of 14% had significantly higher digestibility of dry matter and organic matter than other diets （ P 〈 0.05）. The digesti- bility of organic matter increased gradually with the increasing proportion of concentrate and crude protein level. With the increase in the proportion of concentrate, the microbial protein levels increased remarkably, while the acetic acid/propionic acid ratio declined. [ Conclusion] The concentrate/ roughage ratios and nitrogen levels affect rumen fermentation and microbial growth during in-vitro culture. However, the best supplementary feeding results of urea-treatinq corn stalks can be obtained when the concentrate/rouahaae ratio is below 5：5 and the crude protein level is 14%.