Comparative nutrient digestibility in horses fed a fat-supplemented, high-fiber diet

Abstract

Eight mature stock-type mares averaging 481.4 kg were used in a 4 x 2 switchback arrangement of treatments to determine nutrient density of an experimental diet. The horses were blocked by age into groups of four and then randomly assigned to a treatment from a group. The treatments were 1) control - feeding oats with alfalfa hay in a 50:50 ratio and 2) experimental - feeding an experimental high-fat, high-fiber concentrate in a 50:50 ratio with grass hay. Daily feed intakes were similar in both groups, averaging approximately 1.5% of body weight. Following 10 d of adjustment to the diets, the horses underwent 4 d of total collections of feces. Feed and fecal samples were analyzed for dry matter, neutral detergent fiber (NDF), acid detergent fiber (ADF), nitrogen, ether extract and gross energy concentrations. Dry matter digestibility was higher when horses were fed the control diet (P < 0.01). Likewise, crude protein intake, apparent protein digestibility and digestible protein intake were higher when the horses were fed the control diet (P < 0.01). Ether extract intake and digestibility were similar (P > 0.10) when feeding both diets. Total NDF intake was higher when horses were fed the experimental diet (P < 0.01), but NDF digestibility was higher when the horses were fed the control diet (P < 0.01). Still, digestible NDF intake was higher when the horses were fed the experimental diet (P < 0.05). Total ADF intake was higher (P < 0.01), but ADF digestibility was lower when the horses were fed the experimental diet (P < 0.10). Thus, digestible ADF intake was greater when horses were fed the experimental diet (P < 0.05). Energy digestibility was higher when the horses were fed the control diet (P < 0.01), thus digestible energy (DE) intake was higher when the horses were fed the control diet (P < 0.01) than when fed the experimental diet. In summary, feeding the experimental diet resulted in higher digestible fiber intake, but the digestible ether extract and protein intake was not sufficient to equal the DE intake of the control, higher carbohydrate, higher protein diet.