Abstract #T250

# T250
Supplementation of lactating dairy cows with strains of live yeast during summer.
K. T. Silva1,2, F. F. Cardoso1, E. F. Barbosa1, J. C. Silva1, L. J. Lara1, E. A. Garcia3, M. Aronovich3,4, A. P. Peconick1, R. A. N. Pereira2,5, M. N. Pereira*1,5, 1University of Lavras, Lavras, Brazil, 2Minas Gerais Ag Research Enterprise (Epamig), Lavras, Brazil, 3Phileo Lesaffre Animal Care, Lille, France, 4Rio de Janeiro State Ag Reasearch Enterprise (Pesagro), Rio de Janeiro, Brazil, 5Better Nature Research Center, Ijaci, Brazil.

This experiment evaluated if strain type would induce differential response of lactating cows to Saccharomyces cerevisiae supplementation during Brazilian summer (THI >68 for 86.4% of time). Thirty Holsteins (169 ± 87 DIM) were milked 3x/d and individually fed on TMR for a 2-week covariate period and blocked by parity (1 vs. > 1) and milk yield before assignment to a treatment for 56 d. Treatments were: strains SC 47 or NCYC 996 (Phileo Lesaffre) 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 × 1010 and 1.03 × 1010 for SC 47 and 1.76 × 1010 and 0.93 × 1010 for NCYC 996, respectively. Yeast products did not affect milk yield (35.8 kg/d, P ≥ 0.69), solids (1.048 protein, 0.953 fat, and 1.572 lactose. kg/d. P ≥ 0.37), and DMI (19.4 kg/d, P ≥ 0.62). 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). Immune response was evaluated on d −1, 7, and 15 relative to vaccination with an inactivated rabies vaccine on d 35. Total leukocytes and interleukin-4 (IL-4) increased in all treatments in response to vaccination. Compared with SC 47, NCYC 996 tended to increase IL-4 on d −1 (P = 0.10 for C2) and reduced it on d 15 (P = 0.03 for C2). Gamma-interferon was not affected by treatments (P ≥ 0.19). Total-tract apparent digestibility of nutrients and the daily urinary allantoin excretion did not differ (P ≥ 0.20). Yeast increased ingestion time per day and per DMI and meal duration (P ≤ 0.02 for C1). Plasma niacin concentration on d 14 and 56 did not differ (P ≥ 0.62). Rectal temperature at 7 p.m. tended to be lower on NCYC 996 than SC 47 (39.4 vs. 39.1°C, P = 0.06 for C2), but respiratory frequency and sweating rate did not change (P ≥ 0.32). Plasma glucose concentration at 0, 2, 4, and 12 h post-feeding did not differ (P ≥ 0.22). Live yeast supplementation reduced milk SCC and affected immunity, but had no impact on animal performance, diet digestibility, and plasma niacin concentration and thermo-regulation.

Key Words: heat stress, immune function, yeast