2 HAY - CONCENTRATE RATIOS IN TOTAL MIXED RATIONS FOR COWS AT DIFFERENT STAGES OF LACTATION

Different proportions of forage to concentrate in total mixed rations (TMR), for cows in earlier and later lactation, were tested in a two-p hase (I and II) experiment. During phase I (120 days), nine control co ws rotationally grazed unfertilized, dry season, grass pastures and we re group-fed supplemental concentrates (treatment A), while their pair mates in confinement received a TMR of 40% grass hay, 25% of which wa s finely ground (FG) and 15% coarsely chopped (CC), and 60% concentrat es (treatment B). During phase II (37 days), the TMR was 50% hay (35% FG, 15% CC) and 50% concentrates; control (A) as previously. Mean resu lts for A and B in I were: daily yield of milk, 16.1 vs. 17.8 kg, and of 4% fat-corrected milk (FCM), 11.4 vs. 14.9 kg; percentage concentra tion of milk fat (NIF), 2.05 vs. 2.91 and protein, 3.13 vs. 3.19; dail y liveweight (LW) gain, 0.20 vs. 0.03 kg. Treatments differed (P = 0.0 1) in FCM yield and MF. Dry matter intake (DMI) in B was 18.2 kg/day a nd feed efficiency (FCM yield/DMI), 0.82; for A, DMI from concentrates was 7.3 kg/day and partial efficiency (FCM yield/concentrate DMI), 1. 57. In II, A and B means were: milk yield, 13.7 vs. 15.5 kg/day; FCM y ield, 11.7 vs. 13.6 kg/day; MF, 3.07 vs. 3.22; LW gain, 0.30 vs. 0.75 kg/day, without significant differences. Feed efficiency and partial e fficiency were 0.77 (B) and 1.71 (A). These TMR resulted in satisfacto ry animal performance, but should be used with higher producing cows f or better feed efficiency.