Forage yield of annual grasses seeded on the summer/Producao de forragem de gramineas anuais semeadas no verao

In the Rio Grande do Sul (RS) state, southern Brazil, the forage foundation of beef and dairy cattle operations is pasture of warm-season grasses, with high nutritive value (NV) during spring and part of summer seasons, if managed frequently. However, during cool-season, forage NV is very low and worsen by frosts. A 2-yr split-plot experiment on randomized complete block design with three replications compared yield, yield distribution, and nutritive value in three seeding dates (January, February, and March) allocated on main plots, and five forage grasses cultivars (common pearl millet, teosinte, sudangrass, and BRS 800 and AG 2501C sorghum hybrids) on subplots. The two first seeding dates had the highest forage yield, about 6.0Mg [ha.sup.-1] of DM than March seeding date of high nutritive value forage (>150g [kg.sup.-] MS). Sorghum-hybrids genotypes yield more than teosinte and sudangrass. Pearl millet, sudangrass and teosinte had more tillering. Pearl millet had high CP (200g [kg.sup.-] DM), and lower FDA (350g [kg.sup.-] DM) concentrations on leaf blades compared to sorghums and teosinte. It is possible minimize fall forage shortage seeding annual forage grasses until end of February in the Planalto region of RS state, and extend the productive period, an additional 30 to 60-d, during a time of year when warm-season perennial grasses have low forage allowance or low nutritive value, and annual winter forages are not established. Key words: seeding date, forage shortage, teosinte, sudangrass, pearl millet, BRS 800 and AG 2501C. No Rio Grande do Sul, a base forrageira para bovinos de corte e de leite e constituida, basicamente, por pastagens de gramineas perenes de verao, com bom valor nutritivo (VN) durante a primavera e parte do verao, quando manejadas adequadamente. Entretanto, a forragem no outono e inverno tem baixa concentracao de nutrientes, o que ainda e agravado pelas geadas. Um experimento com dois anos de avaliacao com parcelas divididas no delineamento em blocos casualizados, com tres repeticoes, comparou rendimento, distribuicao de forragem e valor nutritivo em tres epocas de semeadura (janeiro, fevereiro e marco), alocadas nas parcelas principais, e cinco genotipos (milheto comum, capim-sudao ou aveia de verao, teosinto e os hibridos de sorgo BRS 800 e AG 2501C) nas subparcelas. As duas primeiras epocas de semeadura resultaram em maior rendimento de forragem (mais de 6,0Mg [ha.sup.-1] de MS) que a semeadura de marco, com elevado valor nutr