Dos sistemas para la alimentación de vacas lecheras pastoreando gramíneas fertilizadas intensivamente

Abstract

Forty-eight Holstein cows were alternately assigned to one of the two following treatments: (T1) A stocking rate of 2.5 cows/ha on grass pastures fertilized with 2,270 kg (15-5-10)/ha/yr, plus 1 kg of concentrate/2.15 kg of milk above 10 kg/d; (T2) A stocking rate of 3.125 cows/ha on pastures fertilized with 1,700 kg/yr, plus 1 kg of concentrate/2 kg of milk. Through 180 days post-partum, cows in T1 produced more milk (17.1 vs. 14.3 kg/d; P < 0.01) and more 4% fat-corrected-milk (FCM; 14.8 vs. 12.9 kg/d; P < 0.02) than in T2, in spite of consuming only about half (3.8 vs. 7.4 kg/d) as much concentrate. Body weight losses were extensive, more so for cows in T2 at both 30 (4.9 vs. 6.8%; P < 0.03) and 90 days post-partum (6.4 vs. 9.6% of calving weight; P < 0.05). Feed and land costs per unit of milk produced were greater for T2 than for T1 (22.7 vs. 18.7 cents/kg). However, milk yield and income over feed and land costs per hectare grazed were greater for T2; therefore, system T2 represents a better alternative for intensive utilization of limited pasture resources.