ESTIMATION OF FORAGE INTAKE BY LACTATING COWS

In the present study, the measurements of forage intake (grass, grass silage, maize silage, barley or wheat WPS, fodder beets, hay) and conc entrate intake of a total of 1102 single dairy cows with a experimenta l period of six weeks were used. Therefore, different animal and nutri tive factors were investigated by partial correlation analysis for the ir suitability estimating forage intake of lactating cows. A positive correlation was found between forage intake and live weight (r=0.31), milk yield (r=0.34), energy concentration of forage (r=0.20) and days in milk (0.18). A negative correlation existed between forage intake a nd concentrate intake (r=-0.49). The dry matter content of forage and the number of lactations were low correlated with forage intake (r=0.0 5 and r=0.07). In the present investigation a multifactorial, non line ar model with the parameters live weight (LW, kg), energy concentratio n of the forage (NEL, MJ NEL/kg DM) and concentrate intake (CI, kg DM/ d) was choosen to estimate forage intake (y, kg DM/d) y=0.009 (+/- 0.0 007) LW + 2.21 (+/- 0.40) NEL(0.67(+/-0.07))-0.07 (+/-0.003) CI1.63(+/ -0.20) The standard deviation for the different parameters was 4% to 1 8%. With rising live weight, the increase of forage intake was linear. An improved energy concentration increased the forage intake. The ris ing trend was declining, because the exponent was lower than one. The concentrate intake influenced forage intake negatively. After that the following equation for the intake of fresh grass (y, kg DM/d) was dev eloped. y=0.007 (+/-0.0006) LW + 1.79 (+/-0.23) NEL(0.93(+/-0.12))-0.1 8(+/-0.06) CI1.42(+/-0.17) The standard deviation for the different fa ctors was 8% to 32%. Again live weight had a positive linear influence on forage intake. Also with rising energy concentration of the grass the intake increased almost linear. An increasing concentrate intake d isplaced more and more grass.