A milk production system based on alfalfa (Medicago sativa) and corn (Zea mays) silage in the south-central zone. II Forage intake and quality

Ernesto Jahn B.1, Agustín Vidal V., Patricio Soto O.

For two consecutive years a milk production system was evaluated at Humán Experiment Station, Los Angeles, Chile (37º 28` Lat. S y 72º 23`Long. W.). Four hectares of alfalfa were used under intensive rotational grazing at the prebud stage and alternatively as hay cuttings at the 10% bloom stage. Corn silage (1.8 ha) and alfalfa hay were used during the winter. As well, concentrates were supplemented throughout the year with the composition being varied according to the season of the year, forage quality and production level of the cows. Sixteen Holstein cows with calving dates concentrated during May and August were used. This work presents data on forage intake and changes in forage quality during different seasons. Intake of alfalfa decreased as stem length and forage availability decreased, with intake ranging from 3.03 to 0.0 kg DM cow-1 h-1 between the start and the end of the grazing period. With stem length below 25cm, intake was less than 0.5 kg DM cow-1 h-1. Pasture quality decreased as forage availability reduced and the cows showed a high selective capability. Protein content was 18.8% + 2.3 and 13.3% + 1.3 at the start and end of the grazing period, respectively. Acid Detergent Fiber values were 34.1% + 4.2 and 50.8% + 3.5 for the same periods, respectively. A high variability of alfalfa quality at the start of the grazing period was found.

Keywords: feed intake, forage quality, dairy cows, grazing.
1 Instituto de Investigaciones Agropecuarias, Centro Regional de Investigación Quilamapu, Casilla 426, Chillán, Chile. E-mail: ejahn@inia.cl.