Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2006
Publication Date: 4/16/2007
Citation: Veum, T.L., Ledoux, D.R., Raboy, V. 2007. Low-phytate barley cultivars improve nutrient utilization in diets fed to young swine. Journal of Animal Science. 85: 961-971
Interpretive Summary: A 28-d experiment was conducted using 45 crossbred barrows with initial averages of 9.5 kg BW and 35 d of age to evaluate low-phytate barley (LPB) mutants M422, M635, and M955 that were hulled near-isogenic progeny of the normal barley (NB) Harrington, and had 47, 66, and 96% 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 pig 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 of diet were equalized in all diets. Diets were: NB, M422, M635, and M955 without added inorganic P (iP); NB, M422, and M635 with added iP; and M422-H with or without added iP. Diets with added iP contained 0.30% available P (aP), the same concentration of aP provided by diet 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 utilization (g/d and % of intake) of P and Ca with increasing dietary concentration of aP from the LPB cultivars without added iP. There were linear decreases (P ' 0.02, g/d and %) in P and Ca excretion with increasing dietary aP from LPB. There were no linear responses for N or energy balance. Growth performance and bone response criteria did not differ for pigs fed diet M955 or the near-isogenic diets NB, M422, or M635 with added iP. However, pigs fed diet M955 had greater (P ' 0.02, g/d or %) utilization and less excretion of P, Ca, N, and energy than pigs fed the near-isogenic NB or LPB diets with added iP. When dietary aP was equalized with iP, the excretion of P in feces plus urine was reduced 20.0, 22.5, and 24.3%, respectively, by pigs fed diets M635+iP, M422+iP, or M955 compared with pigs fed diet NB+iP. Energy utilization did not differ for pigs fed diets with hulled or hull-less LPB when the ME/kg of diet 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 diet M955 also had greater utilization and less excretion of P, Ca, N, energy, and DM than pigs fed the near-isogenic NB or LPB diets with added iP to equalize aP at 0.30%.
Technical Abstract: Most of the phosphorus in grains and legumes is found as a compound called phytic acid. Non-ruminant animals such as poultry, swine and fish, as well as humans, do not digest phytic acid well. In addition, dietary phytic acid binds tightly to calcium and other mineral nutrients. As a result, when non-ruminants consume grain and legume-based diets, they excrete most of the phosphorus consumed, and in addition, the dietary phytic acid has a pronounced negative impact on calcium nutrition, and mineral nutrition in general. Furthermore, dietary phytic acid may negatively impact utilization of a diet's energy-containing compounds and other nutrients such as proteins. In this study growing pigs were fed a normal barley, or one of three different low phytic acid barley that contain 50%, 70% or 95% less phytic acid than normal barley. All the diets were supplemented so that they contained similar levels of nutritionally-available phosphorus, and were otherwise similar in all ways, except for their phytic acid contents. Pigs consuming diets prepared with the low phytic acid barleys gained more weight, had healthier bones, and utilized more of the phosphorus and calcium than did pigs consuming diets prepared with normal barley. In addition, pigs fed the diet prepared with M955 barley, which has the largest reduction in phytic acid, also had greater utilization of protein, energy, and dry matter than pigs fed the other diets containing normal barley or other low phytic acid barleys. This study adds further evidence that that the use of low phytic acid grains and legumes improves the utilization of phosphorus and other important nutrients in grains and legumes, and further shows that the use of low phytic acid grains and legumes can provide an overall improvement in animal health and productivity.