Milk production of grazing Holstein x Zebu cows supplemented with Calliandra calothyrsus and Vigna unguiculata hays in Colombia

The effect of supplementing a low-quality Paspalum notatum pasture with hays of a tanniniferous and non-tanniniferous legume and mixtures thereof, on milk production and composition was tested at the CIAT Experiment Station, Cauca, Colombia during a dry season. Eight Holstein x Zebu cows were distributed among four treatments in a balanced change-over design with two animals per sequence. The treatments (supplements) were: T1: Calliandra calothyrsus 100%, T2: Vigna unguiculata 100%, T3: V. unguiculata/C. calothyrsus 67/33% and T4: C. calothyrsus/V. unguiculata 67/33%. The 3 ha pasture area consisted of two 1.5 ha paddocks, one for adjustment and the other for data collection, that were each grazed for 7 d during the four 14-d cycles of the 56-d experiment. The hay supplements were offered at milking time. Hay dry matter intake of 3.8 and 3.5 kg/d in T2 and T3 exceeded (P < 0.05) that of T4 (2.6 kg), which in turn exceed T1 (1.2 kg). Daily 4% fat-corrected-milk production followed the same pattern with corresponding means of 5.3, 4.7, 4.4, and 3.6 kg. Ureic nitrogen level in milk was higher (P < 0.05) for T2 and T3 (6.3 and 4.5 mg/dL) than for T1 and T4 (3.7 and 3.1 mg/dL). Milk total solids, fat and non-fat solids contents did no differ among treatments. It was concluded that tanniniferous legume hay alone depressed milk production, but its inclusion at 67% and especially 33% of the supplement had little effect