[en] Efficient exploitation of grass for cattle requires the application of appropriated grassland management strategies to maximize pasture dry matter intake (PDMI) while maintaining high sward quality by allocating cows to an adequate pasture allowance (PA). The aim of this study was to investigate the effect of two PA, low (L) vs. high (H), on sward quality, PDMI and milk performance of Holstein-Friesian cows (n=72) at two lactation stages (LS), early (E) vs. middle (M). Cows were randomly assigned to four groups (LE, LM, HE and HM) in a 2×2 factorial design. The low PA treatments completed 5 rotations, with more grazing days (+13), lower pre- (14.3) and post-grazing (5.3) sward heights (cm) and higher herbage utilization (81.7%). The low PA had higher stocking rate than the high PA treatments (4.8 vs. 3.9 cows ha-1)and lower PDMI (13.4 kg vs. 14.4 DM cow-1 day-1) with higher (p&lt;0.05) (g kg-1 DM) protein (149.1), carbohydrates (166.7) and digestibility (746.8) while lower (p&lt;0.05) DM (18.4%), acid (283.5) and neutral detergent (508.6) fibers (g kg-1 DM). Sward quality is deteriorated (p&lt;0.05) from rotation 1 to 5, lower decrease was found on low PA treatments. Milk yield (MY) was higher (p&lt;0.05) in cows at early LS (24.8 kg cow-1 day-1), with the lowest (p&lt;0.05) protein (28.9) and fat (36.9) content (g kg-1). No differences were found on MY between PA treatments, but higher protein and fat content were observed on low PA. Decreasing PA resulted in higher sward and milk quality without penalizing MY.

[es] Un uso eficiente de la hierba por el ganado requiere de la aplicaci&oacute;n de apropiadas estrategias de manejo del pasto para maximizar la ingesti&oacute;n de materia seca (PDMI) mientras se mantiene una alta calidad del pasto con una adecuada disponibilidad de hierba (PA). El objetivo de este estudio fue investigar el efecto de dos PA, baja (L) vs. alta (H), sobre la calidad del pasto, PDMI y producci&oacute;n de leche de vacas Holstein-Friesian (n=72) en dos estados de lactaci&oacute;n (LS), inicio (E) vs. mitad (M). Los animales fueron asignados al azar a cuatro grupos (LE, LM, HE y HM) en un dise&ntilde;o factorial 2&times;2. Los grupos con baja PA completaron 5 rotaciones, con m&aacute;s d&iacute;as de pastoreo (+13), menores alturas de la hierba (cm) pre- (14,3) y post-pastoreo (5,3) y mayor utilizaci&oacute;n del pasto (81,7%). Los tratamientos con baja PA mostraron una carga ganadera mayor que los de alta PA (4,8 vs. 3,9 vacas ha-1) y una PDMI menor (13,4 vs. 14,4 kg MS vaca-1 d&iacute;a-1) con mayores (p&lt;0,05) contenidos (g kg-1 MS) en prote&iacute;na (149,1), carbohidratos (166,7) y digestibilidad (746,8) pero menores (p&lt;0,05) MS (18,4%), fibra &aacute;cido (283,5) y neutro (508,6) detergente (g kg-1 MS). La calidad del pasto disminuy&oacute; (p&lt;0,05) de la rotaci&oacute;n 1 a la 5, siendo el descenso menor con baja PA. Las vacas de inicio de lactaci&oacute;n (24,8 kg vaca-1 d&iacute;a-1) produjeron m&aacute;s leche (MY) (p&lt;0,05), pero con menores (p&lt;0,05) contenidos de prote&iacute;na (28,9) y grasa (36,9) (g kg-1). No se observaron diferencias en MY entre tratamientos, pero la baja PA mostr&oacute; mayores contenidos de prote&iacute;na y grasa. La disminuci&oacute;n en PA provoc&oacute; mayor calidad del pasto y de leche sin penalizar MY.