Study On Feed Intake And Digestibility Of Forage In Different Phenological Periods For Grazing Holstein Diary Cow

In order to provide a scientific theoretical basis to the establishment of feeding standard and amounts of supplementary feeding and to the calculation of reasonable amounts of grazing capacity for livestock in Hulunbeier meadow steppe,4N-HCl insoluble ash(AIA) method,fecal crude protein index(FCPI) method,insoluble detergent acid lignin(ADL)method and two stage technique for the digestion in vitro were used to determine the feed intake and digestibility of forage in Hulunbeier meadow steppe for grazing adult Holstein dairy cow in the mid-lactation period.Meanwhile, the intake of nutrients, minerals and composition of forage intake for grazing cow in different phenological periods were also determined.The results were as follows:1. The feed intake of grazing cow in the phenological phase of green,green–grass,maturity and grass–withering were respectively 2.83～4.58 ,6.39～10.26 ,11.76～12.46 ,11.88～12.96 kg/d,the feed intake on metabolic body weight in the same period for them were respectively 27.67～44.73, 63.72～102.66, 117.98～124.90, 121.34～131.95 g/d·kgBW0.75,the difference of feed intake in different phenological phase was significant (p<0.05);In the phenological phase of green two stage technique for the digestion in vitro is better than the other three methods,but in the phenological phase of green–grass the result of AIA method is closer to the actual result,while four methods all can be used for determination of feed intake of grazing dairy cows in the phenological phase of maturity and grass–withering;2. The daily intake of DE in the phenological phase of green,green–grass,maturity and grass–withering were respectively 5.06～8.18, 17.47～23.23, 29.46～31.21, 24.26～26.13 Mcal/d,and the daily intake of CP were respectively 0.46～0.73, 0.88～1.41, 1.25～1.41, 0.90～0.97 kg/d,the difference of nutrients intake in different phenological phase was significant (p<0.05);3. The daily intake of Ca in the phenological phase of green, green–grass,maturity and grass–withering were respectively 11.60～18.75, 27.67～44.44, 75.48～79.97, 46.21～50.33 g/d,and that of the P were respectively 5.10～8.24, 11.18～17.96, 22.63～23.97, 13.80～15.03 g/d,the daily intake of the Se were respectively 0.10～0.16, 0.14～0.22, 0.28～0.29, 0.25～0.27 mg/d,the difference of minerals intake in different phenological phase was significant (p<0.05); 4. Leymus chinensis,Stipa baicalensis,Carex duriuscula were main forages of intake for grazing cow in different phenological phase,and the intaked proportion of above three kinds of forage were 53～63%, 55～62%, 73～80%, 88～93% in the phenological phase of green,green–grass,maturity and grass–withering respectively;5. The regression equation of forecasting feed intake of grazing dairy cow by linear regression analysis through the REG was as follows: Y= -14.6763+0.5475X1+0.2273X2+0.5004X3-0.2888X4-0.0286X5 (R2=0.9250) ;6. The digestibility of DM ,CP ,EE ,NDF ,ADF and OM in the phenological phase of green,which was the highest one,were respectively 66.76%, 64.59%, 31.64%, 50.61%, 50.11% and 71.48%;However,with the lapse of phenophase the digestibility of various nutrients were gradually decreased;In the phenological phase of grass–withering the digestibility of various nutrients,which was to the lowest,were respectively 47.11% , 45.54% , 17.31% , 34.50% , 41.36% and 53.78%.