Effect of live yeast products on performance, digestion, thermoregulation, and immune response of lactating cows during summer

Abstract

This experiment evaluated if the supplementation of lactating dairy cows with products containing different strains of live Saccharomyces cerevisiae would induce differential response in lactation performance, digestibility, plasma niacin concentration, evaporative heat loss, and immunity during Brazilian summer (THI > 68 for 86.4% of time). Thirty Holsteins (169 ± 87 DIM) were individually fed on TMR for a 2-week covariate period and then paired blocked before assignment to a treatment for 56 d. Treatments were products containing strains SC 47 or NCYC 996 (PhileoLesaffre) or Control (CTL). Pre-planned contrasts were: C1) CTL vs. SC 47 + NCYC 996 and C2) SC 47 vs. NCYC 996. Yeast products (10 g/cow/d) were mixed to a cup of ground corn and top dressed to the TMR in the morning. Viable and non-viable cells/g were: 1.00 x 1010 and 1.03 x 1010 for SC 47 and 1.76 x 1010 and 0.93 x 1010 for NCYC 996, respectively. Yeast products did not affect the yields of milk (35.8 kg/d) and solids (1.048 kg/d protein, 0.953 kg/d fat and 1.572 lactose) and DMI (19.4 kg/d). Plasma niacin concentration did not differ. The rectal temperature at 1900 h tended to be lower (39.1 vs. 39.4oC) on NCYC 996 relative to SC 47 and the frequency of rectal temperature ≥ 39.2oC was reduced at 1300 h (37.5 vs. 48.1%) and 1900 h (41.8 vs. 58.1%) on NCYC 996 relative to CTL. The respiratory frequency and sweating rate did not change. The Linear SCC scores were 4.94 for CTL (384,000 cells/mL), 4.17 for SC 47 (225,000 cells/mL), and 4.37 for NCYC 996 (258,000 cells/mL) (P < 0.01 for C1). The cell-mediated immune response was evaluated on days - 1, 7, and 15 and the humoral response on days - 1, 7, and 23 relative to vaccination with an inactivated rabies vaccine on d 35. The titer of rabies antibodies in serum and Interleukin-4 (IL-4) were increased and Interferon Gamma (IFNγ) was reduced in response to vaccination. Monocytes in blood were reduced by NCYC 996 relative to SC 47 on d - 1 and were increased on d 15. Compared to SC 47, NCYC 996 also tended to increase IL-4 on d - 1 and reduced IL-4 on d 15. The titer of rabies antibodies and IFNγ were not affected by treatment. The total tract apparent digestibility of nutrients and the daily urinary allantoin excretion did not differ. Yeast products increased ingestion time per day and per unit of DMI and meal duration relative to CTL, at similar DMI. Cows on NCYC 996 showed selective sorting behavior in favor of feed particles > 19 mm at night and SC 47 induced rejection of long feed particles. Glucose and urea-N concentrations in plasma did not differ. Yeast supplementation had no impact on animal performance and diet digestibility, but reduced milk SCC. The effect on cell-mediated immune response and thermoregulation differed between the yeast products evaluated. Yeast supplementation tended to increase IL-4 after vaccination, tended to reduce blood monocytes before vaccination, and reduced milk SCC.