|Daniels, T - MONTANA STATE UNIVERSITY|
|Bowman, Janice - MONTANA STATE UNIVERSITY|
|Sowell, Bok - MONTANA STATE UNIVERSITY|
Submitted to: Journal of Animal Science Supplement
Publication Type: Proceedings
Publication Acceptance Date: July 1, 1998
Publication Date: N/A
Interpretive Summary: Supplementation programs for grazing cows have not always been shown to be cost-effective, primarily because measures such as subsequent pregnancy rate, calving interval, or calf growth have not been consistently improved. Some of this inconsistency may be due to variation in supplement intake by individual animals. In addition, delivery method has been shown to affect supplement intake. There may also be differences in intake between age groups that can be modified by supplement delivery method. The objectives of this study were to evaluate the effects of liquid supplement delivery method and cow age on forage and supplement intake by cows grazing native range. Supplying liquid supplement to cows grazing winter native range increased forage digestibility, and tended to reduce body condition score loss during two years. Forage intake was increased by 15% when cows had ad libitum access to liquid supplement, and by 47% when liquid supplement consumption was limited by a computer-controlled delivery system, compared to unsupplemented cows. Supplement intake increased with increasing cow age. Variation in supplement intake by individual cows was reduced by modifications in the liquid supplement delivery method and its dosing frequency.
Technical Abstract: One hundred eighty crossbred cows were assigned to one of six native range pastures during two winters to evaluate forage and supplement intake as affected by cow age and liquid supplement delivery method. Treatments were: 1) no supplement (Control); 2) a lick-wheel feeder containing liquid supplement (ADLIB); and 3) a computer-controlled lick- wheel feeder that dispensed 1 kg/head/d of liquid supplement (REGULATE). Each treatment was applied to two pastures. Supplement used in both tanks contained YbC1 to estimate individual supplement intake. Boluses containing Cr2O3 were used to estimate fecal output (FO). Data were analyzed as a split-plot design with treatment, and year as main plots, and cow age as sub-plot. Forage DMI was lowest (P=.07) by unsupplemented cows (12.9 kg), intermediate by cows on ADLIB (14.8 kg), and highest by cows on REGULATE (18.9 kg). Forage DMI as % BW was similar (P>.10) for all age groups (avg 3.1% BW). Forage digestibility was increased (P<.01) by supplementation both years. Supplemented cows tended to lose less (P=.14) body condition (1-9 scale) than Control cows (-.3 vs -.6). Supplement intake (as-fed) was higher (P<.01) by cows on ADLIB (1.9 kg/d) than those on REGULATE (.7 kg/d). Supplement intake (as-fed) was lowest (P<.01) for 2-yr-old cows (.8 kg/d), intermediate for 3-yr-olds (1.2 kg/d), and greatest for 4-, 5-, and 6-yr-olds (avg 1.5 kg/d). Liquid supplement increased forage intake, and forage digestibility, and tended to reduced body condition score loss.