When heifers are on a nutrient-dense, limit-feeding program, they still need a low-nutritive forage source to promote rumen function and satisfy foraging needs. The preferred form of that forage recently was evaluated by researchers at the University of Guelph, and published in the Journal of Dairy Science.
The research team, led by Trevor DeVries, compared the consumption preferences of 10 Holstein heifers, 8 to 10 months of age, over two successive, 7-day treatment periods. The heifers were allowed four days to adapt to the new ration, and their consumption was measured the next three days after that.
The two forage sources evaluated were:
- Long-particle oat straw (85% of particles longer than 8 mm); and
- Short-particle oat straw (45% of particles longer than 8 mm).
Throughout the trial period, all heifers were fed a consistent, nutrient-dense TMR at 2.05% of bodyweight. Following the “either-or” evaluation, heifers were given access to both types of straw during an additional 2-day preference period.
The researchers found that dry-matter intake of both the TMR and straw was similar regardless of which length of straw was fed. Rumen temperature also did not vary between treatments.
However, feeding longer straw meant heifers spent more time feeding throughout the day than when short straw was fed (197.7 vs. 175.2 minutes/day). When both forms of straw were offered, heifers showed a strong preference for long straw.
The researchers concluded that limit-fed heifers will consume similar amounts of supplementary long or short straw when fed alongside a nutrient-dense TMR. Limit-fed heifers do, however, show a clear preference for long straw when offered the choice, suggesting that they find long straw to be more satisfactory for achieving rumen fill and/or meeting their behavioral foraging needs.