Abstract #T122

# T122
Probiotics supplementation for dairy calves: A systematic review.
R. Branco Lopes*1, N. Silva-del-Río1, 1Veterinary Medicine Teaching and Research Center, University of California-Davis, Tulare, CA.

The objective of this study was to systematically review the current literature on probiotics for dairy calves. In October 2018, 5 electronic databases (CAB Abstracts, PubMed, Science Direct, Scopus and Web of Science) were used to retrieve manuscripts. The literature search strategy was defined based on population, intervention, and outcome. An a priori protocol was developed, including screening and data extraction forms. Descriptive statistics were performed on Microsoft Excel. A total of 2,177 publications were retrieved, 1,808 abstracts were screened and 90 manuscripts (corresponding to 97 trials) met the inclusion criteria. The earliest manuscript included was published in 1991, and most studies (n = 65) were performed between 2008 to 2018. Studies took place in 22 different countries, mostly in Asia. Ninety-three trials had an untreated group and 4 a positive control group (applying antimicrobial). Lactobacillus spp. (n = 37), Bacillus spp. (n = 10) and Saccharomyces spp. (n = 11) were the most evaluated genera; 69% of trials tested a single strain probiotic and 31% a multi-strain product. The average study sample size was 58.3 ± 113.8 dairy calves. Studies ranged from 6 to 770 calves; 52 studies used less than 30 calves. The age of calves enrolled on the trials varied from 1 to 180 d (10.6 ± 24.9). Trials enrolling newborns calves administered probiotics in colostrum. For older calves (>1d), probiotic administration was via milk replacer, milk, concentrate, syringe, drench, or esophageal tube. Holstein and its crossbreeds (n = 67) were the breeds most assessed; only 1 study used Jersey calves. The duration of probiotic supplementation varied from 1 to 364 d (64.2 ± 75.8); most studies evaluated preweaned calves (n = 80). Calves performance was consistently evaluated across trials; however, studies reporting health outcomes used multiple and non-standardized measurements. Substantial research has examined the effect of probiotics on performance and health of calves, but experimental design varied across studies. Future studies should adhere to guidelines for health measurements. Funding provided by CDFA–AUS project.

Key Words: calf, probiotic, systematic review