Date of this Version
Proceedings, Western Section, American Society of Animal Science Vol. 60, 2009
Two consecutive summer grazing studies were conducted to quantify the effect of supplementing cows with wet distillers grains (WDGS) mixed with low quality forage on 1) grazed forage intake and 2) cow and calf performance. During exp. 1, twenty-four three year old lactating cows rotationally grazed for 56 d and were assigned to one of three treatments: 1) the recommended stocking rate of 1.48 AUM/ha with no supplementation (CON1), 2) double the recommended stocking rate (2.96 AUM/ha) and supplemented 6.64 kg/hd daily of 45% grass hay and 55% WDGS (DM) to replace 50% of estimated total intake (SUP), and 3) grazing at 2.96 AUM/ha with no supplementation (2X). In exp. 2, forty two-year old lactating cows rotationally grazed the same paddocks as in exp. 1 for 56 d and were assigned to one of four treatments grazing at: 1) recommended stocking rate (1.48 AUM/ha) with no supplementation (CON2), or double the recommended stocking rate and receiving 5.8 kg/hd daily of wheat straw and WDGS mixed at: 2) 70:30 (LOW), 3) 60:40 (MED), or 4) 50:50 (HIGH). Supplemented groups were fed at 50% of estimated total intake. For both studies forage utilization was determined by clipping twenty, 1- m2 quadrats pre- and post-grazing. For exp. 1, SUP cows had higher ADG (0.25 kg/d; P < 0.01) than CON1 and 2X (-0.45 and –0.52 kg/d, respectively). Calf daily gain was higher for SUP than for CON1 and 2X (1.07, 0.82, and 0.75 kg/d; P < 0.01). Forage utilization (% standing green) for CON1 was 51.1 and 68.0% less than SUPP and 2X, respectively (P < 0.01). For exp. 2, HIGH cows were the heaviest at the end of the study (P = 0.04). Forage utilization was less for CON2 than for HIGH or MED (34.4, 45.9, and 44.3%, respectively; P < 0.02), but was similar for CON and LOW (38.4%; P = 0.18). Grazing cows supplemented wheat straw and 45% or greater WDGS gained more weight. Grazing intake was reduced the most when wheat straw was 70% of the mix.