For fast gains, pigs need more water available to them at all times- in winter as well as summer. One of the least expensive ways in both money amd labor is to supply water with electrically heated waterers.
Altman, Landy B. Jr.; Ashton, Gordon C.; and Catron, Damon
"Your Pigs May Need More Water,"
Iowa Farm Science: Vol. 7
, Article 5.
Available at: https://lib.dr.iastate.edu/farmscience/vol7/iss3/5