This study determined impacts of a commercial blend of microencapsulated
essential oils (EO), fed at increasing dose levels to high
yielding primiparous dairy cows, on milk yield and composition.
Eight pregnant Holstein heifers, selected to have their parturition
within a period of 30 d, were kept in tie stalls equipped for individual
feeding, and with free access to water, from the 7th month of
gestation. At an average of 40 d postpartum, cows were assigned to
one of four dietaryEOlevels in a replicated 4×4 Latin square design.
The experimental diets (i.e., corn silage, fescue hay and a compound
feed, 6.5, 4.4 and 8.7 kg DM/d respectively) differed only in the addition
level of a microencapsulated EO supplement (RumaXol Feed)
mixed at different levels into the compound feed (fed at 1 kg/cow
day) in order to provide 0, 0.32, 0.64 and 0.96 g/d of the EO mixture.
The experiment had four experimental periods of 21 d, with the
last 5 d used for collection of faeces and urine, for milk yield and
composition recording and measurement of cow biometric data.
The dietary EO supplementation had no effect on dry matter (DM)
intake, water consumptions or faecal DM, while urine density was
(P=0.01) lower at the intermediate EO dosages. Digestibility and
biometric measures of cows were not modified by EO feeding. The
protein content of milk tended (P=0.06) to be higher at the intermediate
EO dosages, as did (P=0.05) the milk energy concentration.
However milk and milk component yields were not affected by EO
feeding level.