Growth Rate and Feed Efficiency of Rats Fed Yogurt and Other Fermented Milks

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Abstract
Fermented milks, including yogurt, 3 types of acidophilous milk, lactic buttermilk, Bulgarian buttermilk and directly acidified milk, were compared to unfermented milk in rat feeding trials to determine if they offered any nutritional advantage to healthy, growing rats. Fresh product was fed daily, and daily feed consumption and weekly weights were used to calculate mean weight gains and feed efficiency. Starter viability was maintained in all diets. In 6 different trials yogurt gave greater weight gains than uninoculated control and other fermented milks. Its feed efficiency ratio was greater than the control in low fat milks but not in full fat milks. Rats fed directly-acidified milk had less growth than rats on regular milk diets. Although additional vitamines stimulated growth in both yogurt and the control, the superiority of the yogurt was maintained. None of the other fermented milks gave improved growth or feed efficiency. Although Lactobacillus bulgaricus was frequently in the intestinal tract (small intestine, cecum, colon) during feed trials, it disappeared after 3 days when on longer fed. Streptococcus thermophilus never was isolated below the upper small intestine. Lactobacillus acidophilus was usually present and persisted when no longer in the diet.