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An optimal balance of intestinal microbiota is necessary for digestive and immune health. Poor performance, susceptibility to infections, and decreased growth rate can be signs of an imbalanced microbiome. Dietary strategies to establish and maintain an optimal balance of microbiota include prebiotics (food for indigenous microbiota in the gastrointestinal tract) and probiotics (beneficial microbiota consumed by the animal). Recent research regarding use of probiotics and prebiotics in reproducing and growing livestock and companion animals is summarized. Documented benefits include prevention of diarrhea, decreased mortality, establishment of a healthy microbiota balance, and improved immune function.

Experiments were conducted to determine effects of isolated lignin and intact lignin in foods on bioavailability of intrinsic iron in lignin-containing foods and of supplemental iron (FeSO4.H20). Standard curve and slope ratio methodology were employed to determine iron bioavailability to chicks. In one experiment, lignin content of foods ranged from 2 to 25% and iron bioavailability ranged from -20 to 140%, but no association between lignin content and bioavailability existed. In other experiments, increasing dietary lignin concentration from some natural sources reduced total iron availability, whereas increasing isolated lignin concentration had no effect. These results suggest that lignin structure or other unidentified factors determine intrinsic iron availability. No lignin source significantly decreased supplemental iron bioavailability.

There has been an increase in vitamin A fortification of livestock feeds resulting in increased residual vitamin A in organ meats, which are often used in canned dog foods. The effect on bone density of feeding various concentrations of vitamin A in a canned dog food product was investigated. Thirty-two random-source dogs were assigned to four treatments in a randomized complete block design. The diets contained 15,000, 50,000, 116,000, or 225,000 IU vitamin A/1,000 kcal ME. Diets were fed up to 1 yr. Computed tomography was used to determine bone density of the right tibia at 0, 3, 6, 9, and 12 mo. Computed tomography is a more sensitive technique for determining bone density in vivo than conventional x-rays. There were no differences (P > .10) in tibia bone or marrow density in any of the dogs fed the various concentrations of vitamin A. There was no interaction of time x diet on bone density (P > .05) or bone marrow density (P > .05). In addition, there were no changes in serum alkaline phosphatase, calcium, or phosphorus. These results indicate that concentrations of vitamin A three times the recommended maximum safe amount (71,429 IU/1,000 kcal ME) are not detrimental to normal bone health in dogs. Therefore, these data support the hypothesis that canines are less sensitive to excess vitamin A in the diet than some other mammals.