| A portion of roughage must be added to the dairy cow diet to reduce the risk of rumen acidosis.Previously,we generally believed that roughage in the diet was used to maintain stable rumen p H by promoting chewing and ruminant activity and increasing salivary secretion in cows.However,a growing number of studies suggest that salivary secretion may have little effect in neutralizing rumen p H and that the fermentability of the diet is the critical factor in determining rumen p H.This provides a theoretical basis for the use of low-quality roughage.On this basis,the hypothesis was made: compared with high-quality hay,low-quality wheat straw has a slower rate of fermentation and degradation in the rumen,which can alleviate the decrease of rumen p H caused by the intake of concentrate in dairy cows.The inhibition of feed intake can be helped by reducing the particle size.In this experiment,60 healthy lactating Holstein cows with an average parity of 2～3,body weight of 667 ± 36 kg,average milk yield of 33.38 ± 2.06 kg / d,and lactation days of 160 ±33 d were randomly divided into 3 groups,20 in each group.Three groups of cattle were randomly assigned to three different diets.The feeding amount of concentrate in the three groups was the same.The control group was the basic diet of the cattle farm,containing 2.5 kg alfalfa;on the basis of the same total number of NDF in the experimental group,50 % and 100 %alfalfa hay were replaced with wheat straw powder particles,respectively.The 50 % substitution group contained 0.75 kg wheat straw powder particles and 1.25 kg alfalfa,and the 100 %substitution group contained 1.5 kg wheat straw powder particles.Each cow in the experimental group was fed an additional 0.5 kg molasses per day to improve the palatability of the wheat straw powder pellet diet.This experiment was carried out in Tai ’an Jinlan Dairy Cattle Breeding Co.,Ltd.,and the test period was 10 weeks.The test results are as follows:(1)Compared with the control group,there was no significant difference in feed intake in the 50% replacement group(P > 0.05);the dry matter intake of 100% replacement group decreased significantly(P < 0.05),and the intake of crude protein and acid detergent fiber decreased significantly.(2)Compared with the control group,the milk fat,milk protein yield,milk urea nitrogen,somatic cell count and 4 % standard milk of cows in the 50% replacement group and the 100%replacement group did not change significantly(P > 0.05),but the milk yield in the 100%replacement group decreased significantly(P < 0.05).(3)50% replacement group and 100% replacement group significantly reduced the blood urea concentration of dairy cows(P < 0.05).50% replacement group and 100% replacement group significantly increased the concentration of insulin,growth hormone and insulin-like growth factor-I in the blood of dairy cows(P < 0.05).(4)50% replacement group and 100% replacement group significantly reduced the urinary nitrogen excretion of dairy cows(P < 0.05),and the utilization rate of nitrogen had a significant increase trend.(5)The test treatment had no significant effect on rumen fluid p H,but significantly increased the concentrations of valeric acid and propionic acid in the 100% replacement group(P < 0.05).The experimental treatment did not change the dominant flora of the rumen fluid of cows.Still,it significantil reduced the relative abundance of fibro-degrading bacteria such as UGG-2 of the rumen cocci family(P < 0.05).This experiment proved that after improving the palatability of wheat straw powder granules,replacing 50% alfalfa hay with wheat straw powder granules on the basis of the same total number of NDF had no significant effect on dairy cows and reduced the cost of diet.The milk yield of dairy cows decreased significantly at 100% substitution.It is concluded that the suitable proportion of wheat straw powder particles to replace alfalfa hay is 50%,and whether a larger proportion of substitution can be carried out needs to be tested. |
PDF Full Text Request