Influence of liquid supplement delivery method on forage and supplement intake by grazing beef cows

In Experiment 1, 28 heifers were individually fed on low quality hay ad lib itum along with one of seven levels of liquid supplement (0, 0.23, 0.45, 0. 68, 0.90, 1.13, and 1.36 kg/day) during a 24-day trial to evaluate the use of YbCl3 and Cr2O3 as external markers to estimate forage and supplement in take. A linear relationship was found between supplement DM intake predicte d by the dual marker technique and actual supplement DM fed (p < 0.001; r(2 ) = 0.92). In Experiment 2, 60 crossbred 2- and 3-year-old pregnant cows we re assigned to one of the three native range pastures to evaluate forage an d supplement intake, and supplement feeding behavior as affected by cow age (2 versus 3 years) and liquid supplement delivery method. Treatments were: (1) no supplement (control); (2) ad libitum access to a liquid supplement feeder (ADLLB); and (3) ad libitum access to Regulate(R) liquid feed delive ry system (REGULATE; Agri-Beef, Boise, Idaho, USA). The REGULATE feeder was computer controlled to dispense 18 kg/day liquid supplement. Liquid supple ment (28.5% CP as-fed) used in both feeders contained ytterbium chloride. C hromic oxide boluses were used to estimate fecal output (FO). Forage intake was estimated from FO, and 48 h DM indigestibility of extrusa samples coll ected using ruminally cannulated cows, and incubated in situ. Forage 48 h D M and NDF digestibility values were greater (p < 0.01) for ADLIB and REGULA TE than for Control (average 67.1 versus 49.4% for DM; average 63.7 versus 42.7% for NDF). Three-year-old cows consumed 11% more (p < 0.05) forage DM than 2-year-old cows (15.3 versus 13.8 kg/day), but no differences (p > 0.1 0) were significant when expressed on a g/kg body weight basis. Cows receiv ing REGULATE and ADLIB consumed 49% more (p < 0.01) forage DM than control cows (average 16.3 versus 11.0 kg/day). Individual supplement DM consumptio n ranged from 0.002 to 2.54 kg/day. A cow age by treatment interaction was detected for supplement consumption. Two- and 3-year-old cows on REGULATE a nd 2-year-old cows on ADLIB consumed less (p < 0.01) supplement DM than 3-y ear-old cows on ADLIB. Liquid supplement increased forage intake and digest ibility by cows grazing fall native range. A computer controlled liquid sup plement feeder equalized supplement intake by 2- and S-year-old cows. Scien ce B.V. All rights reserved.