Effect of fiber digestibility on methane emission, milk production and quality in dairy cattle ; Efecto de la digestibilidad de la fibra sobre la emisión de metano, producción y calidad de la leche en ganado bovino productor de leche

International audience ; It is known that dairy cows' enteric methane emission (CH4) increases as diet fibre content increases. However, this positive linear relationship may not work in some tropical regions where dietary fibre is high and has low quality, which may reduce dry matter intake (DMI) and digestibility. The present study evaluated the effect of increasing dietary fibre levels (>40% of neutral detergent fibre; NDF) and its digestibility on DMI, milk production and composition, and CH4 emission from lactating dairy cows. Eight Holstein cows were randomly assigned to four treatments of four dietary NDF levels= 40.2, 43.3, 46.5 and 50.5%, in a 4x4x2 Latin square experimental design; the experimental periods lasted 21 days each. Cows were fed TMR of corn-alfalfa silage and concentrate with a forage:concentrate ratio = 60:40. To reach increasing contents of NDF, part of the silage was replaced with corn stover. During 14 days of each period, cows were adapted to diet in individual pens and then moved to respiration chambers where DMI, nutrient digestibility, milk and CH4 production were measured. No effect on NDF, DMI and milk production was observed. However, CH4 production and CH4 yield decreased (P < 0.0001) as NDF increased (421, 409, 362 and 336 l CH4/day and 32.1, 28.1, 23.1 and 21.3 l CH4/kg DMI, respectively). The fat content in milk was greater in cows fed higher fibre than in the control treatment (3.95 vs 3.65, respectively). Decreasing DM digestibility was found as NDF increased (73.6, 66.4, 62 and 58.5, respectively). The NDF digestibility explained better (P < 0.0001) CH4 variability than DM digestibility (Pearson correlation coefficient= 0.89 vs 0.54, respectively). The increasing fibre content in experimental cows' diets reduced DM and fibre digestibility, which means reduced digestible substrate in the rumen and hence CH4 emission. ; El presente estudio evaluó el efecto de niveles crecientes de fibra en la dieta (>40% de fibra detergente neutra; FDN) y su digestibilidad sobre ...