Effects of dietary fiber from forage of advanced maturity on performance of lactating goats.

Although the term quality is ambiguous when applied to the forage in ruminant nutrition it is highly correlated with intake and digestibility. Both chemical and physical changes occur in forage as a result of plant maturity affecting, as a consequence, the dynamics of digestion and passage of rumen digesta, resulting in filling effects, reduction of feed intake and decrease of milk production. The effect of the inclusion of neutral detergent fiber levels from forage (fNDF) with advanced maturity (86.24% NDF; 6.47% CP) was evaluated in goat diets. Feed intake, digestibility of dry matter and of nutrients, nitrogen balance, milk production, efficiency of use of metabolizable energy consumed (ME), and feeding behavior were used as dependent variables. Five dairy goats were assigned to a 5 x 5 Latin square design, using dietary fNDF levels of 20, 28, 35, 43 and 49% as independent variables. The intakes of dry matter (DMI), of nutrients, and of net energy (NEl) were reduced (p<.05) as fiber was added to ration. Conversely, intake of NDF increased (p<.01)suggesting ability for accommodation of fiber in the rumen despite the negative effect on intake. The fNDF level influenced (p<.05) the digestibility coefficients of dry matter, organic matter, crude protein and nonfibrous carbohydrates. Intake of nitrogen (g/day) was influenced in a quadratic manner with no effect on retained nitrogen. Quadratic effects were observed for the nitrogen excreted in the feces and urine, and a linear effect on nitrogen produced in the milk. No influence of fNDF levels was observed for milk constituents (fat, protein and lactose). A quadratic effect of fiber in diet was observed for milk yield with higher values obtained at 28% of fNDF. The levels of forage fiber studied did not influence values of efficiency of use of ME consumed for milk production. A variation on feeding behavior was noticed by increased time of rumination and mastication with a reduction on idle time as fiber from forage increase in diets. [ABSTRACT FROM AUTHOR]