Effect of irrigation, during dry and rainy season, on stocking rate, intake and performance of steers grazing 'Mombaca' guineagrass and 'Napier' elephantgrass

The research was carried out comprising one rainy season and two dry seasons. The objective was to evaluate the influence of irrigation on stocking rate (SR), weight gain (WG) intake, nutrient intakes and in vivo digestibility in elephantgrass and mombacagrass, under rotational grazing. Combinations of the two grasses and two irrigation levels (with and without) were evaluated. Data from dry season and rainy season were analyzed separately. Irrigation was performed restore up 100% mean evapotranspiration (ET0) of the last ten-year. A total of 40 and 16 crossbred steers European x Zebu was used as tester experimental animals in the rainy and dry seasons, respectively. Similar put-and-take animals were used as to adjust grazing pressure of the green leaves biomass. In the rainy and dry seasons, irrigation has enabled the rise in the stoking rate in both forages. In the dry season, irrigation reduced the weight gain in both forages, while in the rainy season, increased the weight gain in the mombacagrass. Irrigation did not affect intake in any of the periods evaluated, but affect the digestibility of dry matter, which reduced in the rainy season and increased in the dry season. The highest stocking rates were obtained in the mombacagrass, while, in the elephant grass, higher values were obtained for weight gain, intake and digestibility. The means stocking rates during the rainy and dry season for the elephant grass with and without irrigation and for the mombacagrass with and without irrigation were 5.6, 4.5, 7.7, and 4.9 anim/ha and the values of WG of 0.64, 0.68, 0.50 and 0.60 kg/day. The effect of irrigation is more evident in the stocking rate than in weight gain of animals, and in intensive grazing production systems, animal productivity (kg/ha) is similar for mombacagrass and elephantgrass.