Altura pré-pastejo para o capim massai sob lotação rotativa com ovinos no trópico úmido brasileiro no período chuvoso

Abstract

The objective was to evaluate the height of entry of the animals adequate to the physiology of the plant and to the performance of sheep in the pasture of Massai grass. We used 18 Dorper x crossbred sheep with no defined racial pattern (SPRD) grazing at three pre-grazing heights in Massai grass, being heights of 45 cm, 35 cm and 25 cm. The rotational grazing method was adopted with a fixed period of 12 and 4 days of rest and occupation, respectively. Prior to entry of the animals into the area, the animal stocking rate was estimated to be approximately 50% of the initial height. The values of real height, the productivity of the Massai grass and the structural composition of the plant were obtained and, finally, these variables were correlated. The morphogenic characteristics, the forage composition and the performance of the animals were evaluated. Ingestive behavior observations were made from 6 h to 18 h in the second and third evaluation cycles, at the entrance and exit of the animals from the pickets, adding four days of observation. Grazing times, rumination times and other activities were also observed. In that question, these observations were grouped and analyzed in three periods of the day, from 6 h am to 10 h a.m., 10 h a.m. to 2 h p.m. and 14 h a.m. to 6 h p.m. The time to perform bites, the time of rumination of the food bolus, the number of merciful chews and the bit rate and grouped in the periods of entry and exit of the animals of the area were counted. The treatment with 35 cm showed higher forage density, higher yields of total dry mass, leaf blade and dead fodder, greater amount of forage available, greater forage supply and higher rate of daily accumulation. The treatment with 25 cm showed a higher leaf: stem ratio and a higher percentage of leaves in the forage structure. On the other hand, the treatment with 45 cm presented higher percentages of stalk and dead forage, resulting in less seizure of leaves by the animals. Leaf appearance rate, defoliation severity and number of live leaves were higher for the 25 cm treatment, not differing from the 35 cm treatment in the latter variable. The height of 25 cm reduced stem elongation, phyllochron, and sheath length. The highest levels of protein and total digestible nutrients were observed in the treatment with 35 cm followed by treatment with 25 cm. The highest acid detergent fiber content was observed in the 45 cm treatment. The highest consumption was obtained by treatment with 35 cm, as well as the higher stocking rate that triggered the highest weight gain per area. The highest behavioral activity was grazing, followed by rumination and other activities, and the period from 6 h a.m. to 10 h a.m. showed the highest grazing activity. At the other periods of the day the animals in the treatment with 35 cm grazed less than the animals of the other treatments. Rumination in all treatments was more significant in the period from 2 h p.m. to 6 h p.m., but the animals in the treatment with 45 cm were the ones that spent more time doing this activity and had less time for other activities. The animals in the treatment with 45 cm presented greater time of rumination of the food bolus and more number of mericics chews. The bite rate was higher for the 25 cm treatment, followed by the 45 cm and 35 cm treatment respectively, the inverse occurred for the time needed to make the bites. Based on the results presented, the height of 35 cm, among the pre-grazing heights evaluated, is the best indicated for the Massai grass used in the rearing of sheep from grass to pasture, due to the greater availability of food, with a good quality and for allowing greater weight gain of the animals per area.