Se-yeast has numerous advantages over selenite,
but the question remains, “Is it more profitable to
use Se-yeast?” In situations where antagonists are
not a concern, inorganic Se is probably the most
cost-effective option for lactating cows. If
antagonists are present, some or all of the Se should
be provided by Se-yeast. To ensure adequate Se
status of calves, providing a portion of the
supplemental Se as Se-yeast in dry cow diets is a
good idea. Current regulations permit using a
combination of Se sources as long as the total
supplemental Se does not exceed 0.3 ppm in the
total diet. Usually using a combination of nutrient
sources is better than relying on a single ingredient.
Some data with other trace minerals show benefits
when a combination of inorganic and organic sources
are used compared with either all organic or all
inorganic. The same may be true for Se. In my
opinion, if antagonists are not present in feed or
water, lactating cows should be supplemented with
Se that is predominantly from inorganic sources. If
antagonists are present, the predominant Se source
should be Se-yeast. Because of potential benefits
to the newborn calf, a larger proportion of Se
(maybe 50%) in dry cows diets should come from
Se-yeast, even when antagonists are not present.