Individual mineral supplement intake by ewes swath grazing or confinement fed pea-barley forage

Abstract

Previous research has reported high variation in intake of self-fed protein and/or energy supplements by individual animals, however little is known about variation in consumption of mineral supplements. Sixty mature range ewes (non-pregnant, non-lactating) were used in a completely randomized design repeated 2 years to determine if feeding method of intercropped field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.) forage (swath grazed or fed as hay in confinement) affected individual ewe mineral consumption. Thirty ewes were allocated to 3 confinement pens (10 ewes/pen) and 30 ewes were allocated to 3 grazing plots (10 ewes/plot). Ewes had ad libitum access to feed, water, and a mineral supplement containing 1% titanium dioxide as an external marker. Forage dry matter intake (DMI) was calculated using estimates of fecal output, and in vitro 48-h forage DM digestibility. Ewe supplement intake was determined from fecal and supplement Ti concentrations, and fecal output. Forage and mineral intakes were analyzed using ewe as the experimental unit, and plot or pen as the experimental unit for intake variation. A year×treatment interaction (P<0.01) existed for DM forage and mineral intake. Ewes in confinement consumed more forage DM than grazing ewes in 2010, but less than grazing ewes in 2011. Mean mineral intake was highest (P<0.01) by grazing ewes in 2011 and 2010 (average 69g/day), intermediate by confinement ewes in 2010 (57g/day), and lowest by confinement ewes in 2011 (31g/day). A year×treatment interaction (P=0.05) existed for mineral intake CV which was higher (P=0.04) for confinement ewes in 2011 (67 vs. 34%), but was not different (P>0.05) between treatments in 2010. In this study, variation in individual ewe intake of mineral supplement was large in both grazing ewes and ewes fed hay in confinement.