Peer review

The objective was to evaluate the response of New Zealand Holstein cows to concentrate supplementation at contrasting times of the day on herbage intake and ingestive behavior. Two experiments were conducted in winter and spring-summer in a grazing dairy production system of Medicago sativa L. with Dactylis glomerata L. pastures. Three moments of supplying 5.0 kg DM concentrate cow(-1) d(-1) were used: AM after morning milking, PM after afternoon milking, and the AM-PM control equally dividing that amount after both milkings. The experimental units were groups of six cows in winter (a total of 18 cows) and five cows in spring-summer (a total of 15 cows), additionally their respective grazed areas were also considered as experimental units. The design used was a three x three (treatments x periods) cross-over; the allotment of groups to the treatments was consecutive and randomized. The management criterion of rotational grazing was 8 cm of residual forage height for all treatments. Each time the target height of residual herbage was reached, the portable electric fence was manually moved forward allowing on average 36 m(2) fresh pasture. In winter, intake was not different (P < 0.5) between treatments; however, during spring-summer it was 8% lower (P < 0.005) with AM supplementation. There was no effect (P > 0.5) of treatments on total grazing time, rumination and other activities. In conclusion, AM supplementation in spring-summer resulted in dominant evening grazing, and herbage was utilized at its time of highest nutrient concentration.

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Consejo Nacional de Humanidades, Ciencia y Tecnología (CONAHCyT) Universidad Autónoma Chapingo (UACh)