Valor nutricional de silagens do capim-tifton 85 em diferentes idades

The objective was to determine the potential of ensilage of Tifton 85 Bermudagrass and indicate the moment of harvest to ensure balance between productivity, nutritional and fermentation quality of silage, intake and protein and energy retention by sheep. The Tifton 85 Bermudagrass was grown at Santa Helena farm, Bom Despacho, MG, between October and December 2007 and was harvested at ages 27, 45, 56, 74 and 90 days of regrowth. There was a variation of dry matter production among the ages and highest production of dry matter and digestible dry matter were observed at 45 days of age (9.2 and 5.9 t/ha). The increasing age of regrowth jeopardized the nutritional quality and fermentation kinetics of the plant. The effects were more pronounced after 74 days. There was a linear decrease in leaf: stem ratio with increasing age (. = 0.7845-0.0041**x, where x is the age of regrowth). The nutritional and fermentation quality of silages were also influenced by the moment of ensiling, with the best fermentative pattern obtained at ages 45 and 56 days. The silage produced at the extremes age (27 and 90 days) showed signs of undesirable fermentation affecting the nutricional protein fraction and dry matter losses. The dry matter intake did not differ between silages (mean of 2.27 g/100g body weight (BW) and 59.04 g/kg BW0.75), but the intake of digestible dry matter was superior to the age of 45 day (29.49 g / kg BW0.75). Nitrogen balance was positive for silage produced at 45, 74 and 90 days of age (3.26, 0.32 and 2.83 g/day, respectively) and urinary losses was the main nitrogen loss. The energy intake was lower and higher, respectively, for the silage produced at 27 days (101.26 kcal/BW0.75) and 45 days (162.19 kcal/BW0.75) regrowth. The silage produced between 45 and 90 days showed similar net energy intake and highest than silage 27 days (89.59 vs. 51.24 kcal/BW0.75), resulting in positive energy balance. Energy losses in urine, methane and caloric increment did not differ between treatments with mean values of 2.43, 4.35 and 14.66 kcal/100kcal gross energy consumed. Methane production was similar between silages (17.33 g/day, 16.90 g/kg dry matter intake). The net energy content of silages was similar, with an average of 1.33 Mcal/kg dry matter. The ensiling of Tifton 85 should occur 45 days of regrowth.

Objetivou-se determinar o potencial de ensilabilidade do capim-tifton 85 e indicar o momento de colheita que garanta equilibrio entre produtividade, qualidade nutricional e fermentativa das silagens, consumo e retencao proteica e energetica pelos ovinos. O capim-tifton 85 foi cultivado na Fazenda Santa Helena, municipio de Bom Despacho, MG, entre outubro e dezembro de 2007 e os cortes foram realizados nas idades de 27, 45, 56, 74 e 90 dias de rebrota. A producao de materia seca variou entre as idades e as maximas producoes de materia seca e materia seca digestivel foram observadas aos 45 dias de rebrota (9,2 e 5,9 t/ha). O avanco na idade de rebrota comprometeu a qualidade nutricional e a cinetica de fermentacao da planta, sendo os efeitos mais pronunciados a partir de 74 dias. Houve reducao linear na relacao folha:colmo como o avanco da idade (.= 0,7845 - 0,0041**x, onde x e a idade de rebrota). A qualidade fermentativa e nutricional das silagens tambem foram influenciadas pelo momento de ensilagem, com os melhores padroes fermentativos obtidos nas idades de 45 e 56 dias. As silagens produzidas nos extremos de idade (27 e 90 dias) apresentam indicios de fermentacoes indesejaveis com comprometimento nutricional da fracao proteica e perdas de materia seca. O consumo de materia seca nao diferiu entre as silagens (media de 2,27 g/100g peso vivo (PV) e 59,04 g/kg PV0,75), mas o consumo de materia seca digestivel foi superior para a idade de 45 dias (29,49 g/kg PV0,75). O consumo medio de fibra detergente neutro foi de 1,38 g/100g PV. O balanco de nitrogenio foi positivo para as silagens produzidas aos 45, 74 e 90 dias de rebrota (3,26; 0,32 e 2,83 g/dia, respectivamente) e as perdas urinarias foi a principal perda de nitrogenio. O consumo de energia metabolizavel foi inferior e superior, respectivamente, para as silagens produzidas aos 27 dias (101,26 kcal/PV0,75) e 45 dias (162,19 kcal/PV0,75) de rebrota. As silagens produzidas entre 45 e 90 dias apresentaram consumos de energia liquida semelhantes entre si e superiores a silagem de 27 dias (89,59 vs. 51,24 kcal/PV0,75), resultando em balancos positivos de energia. As perdas de energia na urina, metano e incremento calorico nao diferiram entre as silagens, com valores medios de 2,43; 4,35 e 14,66 kcal/100 kcal de energia bruta consumida. A producao de metano foi semelhante entre as silagens (17,33 g/dia; 16,90 g/kg materia seca consumida). Os conteudos de energia liquida das silagens foram semelhantes, com media de 1,33 Mcal/kg de materia seca. A ensilagem do capim-tifton 85 deve ocorrer os 45 dias de rebrota.