ABSTRACT
The objective of this study was to evaluate the effect of substituting sweet potato flour for ground corn in rations fed to lactating dairy on milk yield and composition, blood metabolites, and feeding behavior. Twenty lactating Holstein cows from 30 to 60 days postpartum were randomly assigned to one of two groups (n = 10 each) and used in a cross-over design trial with two treatments: a standard concentrate with ground corn as an energy source or experimental concentrate with sweet potato flour (SPF) replacing all of the ground corn. Each of the 35-day periods consisted of 14 days for adaptation to diet and 21 days for data and sample collection. Milk yield, dry matter intake (DMI), and feeding behavior were evaluated daily throughout the trial. Milk samples were collected weekly and blood samples were collected every 3 days. Milk was analyzed for fat, protein, lactose, and total solid constituents. Blood was analyzed for glucose, non-esterified fatty acid (NEFA), gamma-glutamyl transferase (GGT), aspartate aminotransferase (AST), total protein (TP), albumin, and urea concentrations. Milk yield (P = 0.62) and composition (fat: P = 0.71; protein: P = 0.12; lactose: P = 0.82; total solids: P = 0.56) were not affected by dietary treatments. There were no differences between treatments in DMI or meal frequency, but total eating time (P = 0.001), feeding time (P = 0.001), and meal duration (P = 0.001) was higher for control compared with SPF. However, feeding rate (P = 0.001) and serum urea concentration (P = 0.001) were higher for SPF compared with control. No differences were observed in serum metabolites and enzymes measured among treatments. The results of this trial indicate that SPF can be substituted for ground corn without impairing the performance, feeding behavior, and metabolism in dairy cows.
