Abstract
The transition period is a metabolically demanding time for dairy animals because of the increased nutrient requirements for milk production. The objective of this study was to investigate the effect of feeding a commercial direct-fed microbial (DFM) supplement in multiparous and primiparous dairy cows on productive measures, blood metabolites, and immune status markers during the transition period. Primiparous heifers, (n=33) and multiparous cows (n=35) were fed a close-up TMR before calving and a lactation TMR postpartum. Three weeks before expected calving, all animals were blocked to balance parity and body weight, then randomly assigned to either control group (CTRL; n=34) or an active dry yeast (ADY; n=34). The ADY animals received a top-dressed ADY (Saccharomyces cerevisiae boulardii, CNCM I-1079) fed daily at 12.5 g per head. Dry matter intake (DMI) was measured by subtracting the weight of refusals from the amount of feed given daily during both pre- and post-calving periods. All animals were weighed weekly for the duration of the study. Blood samples were collected weekly and were analyzed for glucose, non-esterified fatty acid (NEFA), and β – Hydroxybutyrate (BHBA) concentrations. Colostrum samples were collected at calving and analyzed for IgG, IgA, and IgM content and somatic cell count (SCC). Milk samples were collected once per week postpartum, and all of the milk samples were analyzed for protein percentage, fat percentage, lactose percentage, urea nitrogen (MUN), and somatic cell count. All results were analyzed using PROC MIXED in SAS with significance defined as P ≤ 0.05. All covariate models were selected based on the lowest AIC value. Results showed that the interaction of treatment, parity, and time affected DMI (P < 0.01). Supplemented cows were maintained a heavier body weight overall (P = 0.05). The supplementation of the DFM had aiii
significant effect on milk yield as the ADY animals produced more milk overall (P = 0.04); also, there was a tendency for ADY multiparous animals to produce more energy corrected milk (ECM) over time (P = 0.06). Also, there was a tendency for ADY animals to be more efficient (kg ECM/kg DMI) over time (P = 0.06). There was a significant interaction of treatment, parity, and time on milk protein percentage as the multiparous ADY animals had a greater percentage of protein at day 0 (P = 0.03). There was also a significant interaction of treatment, parity, and time on MUN as the DFM primiparous cows had a greater MUN at days 0 and 21 (P < 0.01). There was not, however, a significant difference in milk fat percentage (P = 0.34), milk lactose (P = 0.54), somatic cell count (P = 0.98), IgG concentration (0.47), IgA concentration (0.94), IgM concentration (0.92), colostrum somatic cell count (0.98), peak milk production (0.31), plasma glucose (P = 0.73), serum NEFA (P = 0.89), or plasma BHBA (0.96) by treatment effect. Supplemented animals also had a greater circulating concentration of haptoglobin (P = 0.03). Supplementation of an active dry yeast showed a significant effect on DMI, milk yield, gross feed efficiency, milk protein percentage, increased MUN, and increased haptoglobin concentration. Overall, feeding an ADY improved some productive measures, but there needs to be more research conducted to fully understand all of the mechanisms that occur during this time.