Effect of feeding brown rice instead of corn on lactation performance and blood metabolites in periparturient dairy cows

The objective of this study was to evaluate the effect of replacing corn with brown rice (BR) on dry matter intake (DMI), milk production, blood metabolites and energy balance (EB) in cows during the periparturient period. Twenty-four nonlactating multiparous Holstein cows in late gestation were studied from 3 week before the expected calving date through 6 week after parturition. The cows were divided into one of two dietary treatment groups based on parity and the expected calving date. The treatments were a diet containing steam-flaked corn and a diet containing steam-flaked BR. Prepartum DMI and body weight (BW) and postpartum DMI, BW, milk yield, milk protein and lactose yield were not affected by the dietary treatment. However, the milk fat content and fat yield were higher (P = 0.02 and P = 0.01) for cows fed BR than for cows fed corn. Thus, cows fed BR-based total mixed ration (TMR) tended to have more negative EB in early lactation (P = 0.06) compared with cows fed corn-based TMR. During the prepartum period, the plasma concentrations of glucose, insulin, β-hydroxybutyrate (BHBA), nonesterified fatty acids (NEFA), aspartate transaminase (AST) and Ca were not affected by dietary treatments. On the other hand, the postpartum plasma glucose and insulin concentrations were decreased (P < 0.01 and P = 0.02) and the BHBA and AST concentrations were increased (P < 0.01 and P = 0.02) by replacing corn with BR with no dietary effect on postpartum plasma NEFA and Ca concentrations. These results show that feeding BR instead of corn does not affect DMI or milk yield, but increases milk fat production and leads to a more negative EB state in early lactation. Replacing corn with BR during the periparturient period has adverse effects on the metabolism and energy status in early lactating cows.