Should I give my child zinc to prevent gastroenteritis?

Probiotics. Agree with dr. C. Zinc has been shown to help kids with zinc deficiency or malnourished kids with gastroenteritis but we don't know about other kids. But probiotics [include lactobacillus] may prevent gastroenteritis in adults and kids. Here's to healthy tummies!
No evidence. There is no evidence that zinc is effective in preventing gastroenteritis. The best preventative is proper hygiene and food preparation.
May help if zinc low. Several reports from developing countries have demonstrated zinc supplements provide significant reduction in stool output and duration, persistency and severity of diarrhea. The use of zinc as adjunctive therapy to oral hydration has been thought as a way to manage diarrhea. The who supports the use of zinc in pediatric patients. A 2009 trial however did not find any benefit from supplementation.