Intake, milk production and weight change curves for lactating Holstein x Zebu cows under grazing

The purpose of this study was to evaluate feed intake and develop lactation and weight change curves for Holstein x zebu cows under grazing. Eighteen F1 cows were used, divided into three treatments; 6 were Holstein x Gir (HGI), 6 were Holstein x Guzerat (HGU), and another 6 were Holstein x Nelore (HNE), under the feeding conditions of pasture plus concentrate with 22% of crude protein (CP). To estimate individual feed intake at pasture, 2 markers were used: titanium dioxide to estimate fecal dry matter (DM) excretion, and the indigestible acid detergent fiber (iADF) to estimate individual pasture intake. The Wood (1967) model was used to evaluate milk yield and the parameters were estimated for each genetic group, as follows: HGI = 17.2667*t0.0652*e-0.00424t; HGU = 18.1470*t0.0332*e-0.00408t; and HN = 14.2836*t0.1059*e-0.00552t. The NEFA contents varied according to different genetic groups (P<0.001). It was concluded that the estimated peak DMI occurs during the sixth week of lactation, when the DMI by the different genetic groups was stabilized. The HGI cows have greater cumulative production at 305-d.