Ration digestibility and mineral balance in lactating cows fed rations containing dried whey.

Including dried whey in rations of nonruminants usually increases digestibilities and mineral retention, presumably because of the lactose in the whey. A trial with total collection had five lactating cows per treatment to determine the effects of 5% dried whey product in the concentrate on digestibility of the ration and on absorption and retention of calcium, magnesium, and phosphorus. Rations included corn silage ad libitum, 3 kg alfalfa hay, and either control or dried whey product in concentrate ration at 1 kg/3 kg milk produced. Rations were balanced for content of nitrogen, calcium, magnesium, and phosphorus. Digestibilities of dry matter, nitrogen, and energy were not increased with dried whey product in the ration. Apparent absorption of calcium, magnesium, and phosphorus was not affected significantly by inclusion of whey in the ration. Productive (milk plus retained) calcium and magnesium were not increased when dried whey product was in the ration although productive phosphorus was slightly higher with the dried whey product. Adding small amounts of dried whey to a ruminant's ration will not increase mineral absorption and retention probably because tthe lactose in dried whey is fermented in the rumen and unavailabe for aiding absorption from the small intestine.