Low-phytate barley cultivars improve the utilization of phosphorus, calcium, nitrogen, energy, and dry matter in diets fed to young swine

¹ Department of Animal Sciences, University of Missouri, Columbia 65211
² USDA - ARS, National Small Grains Germplasm Research Facility, Aberdeen, ID 83210

^* To whom correspondence should be addressed. E-mail: veumt{at}missouri.edu.

	Abstract

A 28-d experiment was conducted using 45 crossbred barrows with an average initial BW of 9.5 kg and 35 d of age to evaluate low-phytate barley (LPB) mutants (M) M422, M635, and M955, that were hulled near-isogenic progeny of the normal barley (NB) Harrington, and had 47, 66, and 80% less phytic acid, respectively, than NB. A hull-less LPB, M422 - H, not near-isogenic to the other cultivars, was also evaluated. Apparent nutrient balance, bone measurements, and growth performance were the response criteria. Pigs were fed the diets to appetite in meal form in individual metabolism crates. Barley and soybean meal were the only sources of phytic acid. Dietary protein supplementation and ME/kg were equalized in all diets. Treatments were diets containing NB, M422, M635, or M422 - H without or with added inorganic P (iP), or M955 without added iP. Diets with added iP contained 0.30% available P (aP), the same concentration of aP provided by the diet containing M955 without added iP. There were linear increases (P 0.02) in ADG, G:F, metacarpal and radius bone strength and fat-free dry weight, and the absorption and retention (g/d and % of intake) of P and Ca with increasing dietary concentration of aP from the near-isogenic cultivars NB, M422, M635, or M955 without added iP. There were linear decreases in the grams (P 0.02) and percentages (P < 0.001) of P and Ca excreted per day with increasing dietary concentration of aP without added iP. There were no linear responses for N or energy balance. Growth performance and bone response criteria did not differ for pigs fed the diet containing M955 or the near-isogenic diets containing NB, M422, or M635 with added iP. However, pigs fed the diet containing M955 had greater (P 0.02) percentages of P, N, and energy absorption and retention, Ca absorption, and DM digestibility; and less (P 0.02, g/d and %) excretion of P, N, energy, and Ca (g) per day than pigs fed the diets containing the near-isogenic NB or LPB cultivars with added iP. When dietary aP was equalized with iP, the excretion of P in feces plus urine (g/d) was reduced 20.2, 27.9, and 44.6%, respectively, by pigs fed the diets containing M422 + iP, M635 + iP, or M955 compared with pigs fed the diet containing NB + iP. Energy utilization did not differ for pigs fed the diets containing hulled or hull-less LPB when ME/kg was equalized with lard. In conclusion, the apparent utilization of P and Ca, bone strength and fat-free dry weight, and growth performance increased with increasing dietary concentration of aP provided by LPB, with linear decreases in P and Ca excretion. Pigs fed the diet containing M955 also had greater utilization and less excretion of P, Ca, N, energy, and dry matter than pigs fed the diets containing the near-isogenic NB or LPB cultivars with added iP to equalize aP at 0.30%.

Key Words: barley, nutrient absorption, nutrient excretion, phytate, pig, swine

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