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

Energy and protein requirements of 3/4 Zebu × 1/4 Holstein crossbreds fed different calcium and phosphorus levels in the diet

The aim of this study was to determine the nutritional requirements of energy and protein for maintenance and weight gain of crossbred cattle, as well as their efficiencies. Fifty 3/4 Zebu × 1/4 Holstein crossbred bulls with initial weights of 214±4kg and aged 11±0.2 months on average were used in this experiment. Four animals were used in the reference group; ten bulls were fed at the maintenance level; and the remaining 36 bulls were fed ad libitum and distributed in a completely randomized design in a 3×3 factorial arrangement, which had three feedlot periods (56, 112 or 168 days) and three calcium and phosphorus levels (low, medium and normal) in the diet. Four of the maintenance animals had their heat production measured by respirometry at the Laboratory of Metabolism and Calorimetry of UFMG. After slaughter, composite samples, referred to as carcass and noncarcass samples were obtained from each animal. The net energy requirements for maintenance (NEm) and metabolizable energy for maintenance (MEm) were 68.9 and 90.1 kcal/EBW0.75/day, respectively. The efficiency (km) was 76.41%. The NEm requirement determined in the respirometry chamber was 85.5 kcal/kg0.75. The following equations were obtained for net energy for gain (NEg) and net protein for gain (NPg): NEg (Mcal/day) = 0.0505±0.000986 × EBW0.75 × EBWG1.095 and NPg (g/day) = 162.79±18.2546 × EBWG - 1.30±5.3010 × RE. The efficiencies of fat and protein deposition were 70.04 and 15.12%, respectively. In conclusion, the requirements of NEm for growing and finishing non-castrated 3/4 Zebu × 1/4 Holstein crossbred cattle are 68.9 kcal/EBW0.75/day. Requirements of NEg and NPg can be obtained by the following equations: NEg (Mcal/day) = 0.05050.000986 × EBW0.75 × EBWG1.095 and NPg (g/day) = 162.79±18.2546 × EBWG - 1.30±5.3010 × RE