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Health and performance of dairy calves supplemented with prebiotics: A systematic review.

R. Branco Lopes




Health and performance of dairy calves supplemented with prebiotics: A systematic review.
R. Branco Lopes*, N. Silva-del-R�o. Veterinary Medicine Teaching and Research Center, University of California-Davis Tulare, CA.

The objective of this study was to systematically review and summarize the current literature on the effect of prebiotic supplementation on performance and health of dairy calves. A review protocol was developed in accordance with PRISMA-P guidelines. The literature search was performed on Oct-2018 and updated on Dec-2019 using 5 electronic databases (CAB Abstracts, PubMed, Science Direct, Scopus and Web of Science). Eligible studies were non- and randomized controlled trials available in English, Portuguese, and Spanish, that evaluated the effect of prebiotic supplementation on dairy calves' performance and health. For randomized trials, the risk of bias was assessed at the outcome (average daily gain; ADG) level, using the Cochrane Collaboration's tool. A total of 2,199 publications were retrieved, and 27 manuscripts (32 trials) met the inclusion criteria. Twenty-one studies were randomized controlled trials; among those assessed for risk of bias, most did not report the randomization method. Forty-eight percent of the studies received financial support or were affiliated with a prebiotic industry. Trials size ranged from 4 to 60 calves/treatment group; none of the studies included sample size calculations. All the studies used HO or HO crossed calves (n = 1458) with age at enrolment ranging from 0 to 162 d (mean � SD = 14 � 28). The prebiotic supplementation was mostly via milk replacer (n = 15) or whole milk (n = 7) during 7 to 143 d (52 � 33). Twenty studies investigated oligosaccharides; mainly fructo- (n = 5) and mannan-oligosaccharides (MOS; n = 5). Among the manuscripts evaluating performance (n = 21), 16 did not observe effect on ADG. Only 5 studies (n = 2 inulin; n = 1 galacto-oligosaccharides; n = 1 MOS; n = 1 polysaccharides) reported a positive effect of prebiotic supplementation on growth. Two of those studies presented a high risk of detection bias; BW was estimated with measuring tape and the personnel was not blinded. Sixty percent of studies evaluating fecal consistency (n = 6/10) did not report positive effect. To allow proper knowledge summary, future research should adhere to guidelines for performance and health measurements.

Keywords: calves, review.