Effects of prepartum treatment with monensin or propylene glycol mixed with concentrate on milk yield and blood NEFA and BHBA levels in dairy cows

Sixty multiparous Holstein-Friesian dairy cows made up the study sample. Group M (n = 20) received 300 mg/day monensin (Kexxtone, Elanco) for 21 days prior to the expected calving date. Group PGC (n = 20) received propylene glycol, mixed with concentrate and fed separately from total mixed ration (TMR) twice a day in the last 21 days of gestation. The control group, Group C(n = 20) did not receive any treatment prior to parturition. Cows in all three groups received PG (300 mL/day) for 5 days after parturition. Blood samples were collected 21 and 7 days prior to the expected calving date, as well as 7 and 14 days after parturition. NEFA and BHBA levels did not differ between the treatment groups. However, milk yield of Group M was significantly higher than that of Group C during weeks 3, 4, and 5 of lactation. Although NEFA and BHBA levels were similar in both treatment groups, higher milk yield in monensin-treated cows could be related to an increase in glycogenic precursors resulting from favorable effects of monensin on ruminal bacterial flora