Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2016
Publication Date: 3/21/2016
Citation: Veum, T.L., Raboy, V. 2016. Hulled and hull-less barley cultivars with the genetic trait for low-phytic acid increased the apparent digestibility of phosphorus and calcium in diets for young swine. Journal of Animal Science. 94(3):1000-1011. Interpretive Summary: Phosphorus (phosphate) is an essential nutrient for animals. It has multiple functions that include skeletal mineralization, bone growth, protein synthesis, energy metabolism, cell membrane phospholipid, DNA and RNA structure, signal transduction, and gene expression. Most of the P in cereal grains is found in a single chemical form called phytic acid (myo-inositolhexaphosphate). Swine and other non-ruminant animals lack the ability to digest dietary phytic acid. As a result, the digestibility and utilization of P in cereal grains by swine is poor. However, animal trials have shown that cereal grains with the low-phytic acid (LPA) genetic trait have a marked increase in P digestibility and utilization, resulting in less excretion of P in swine manure compared with normal grain. The objective of this experiment was to evaluate the efficacy of the LPA genetic trait in hulled and hull-less barley cultivars in diets for young swine. Criteria were growth performance, serum phosphatase enzyme activity, bone measurements, bone breaking strength, and apparent total-tract digestibility of P, Ca, energy, and “dry matter” (DM). Results demonstrated that the LPA genetic trait was effective in enhancing P digestion and utilization, and reducing P waste, when introduced into either hulled and hull-less barley cultivars. For example, pigs fed one LPA barley (M955) consumed 31% less P and excreted 78% less fecal P, yet displayed equal or better growth and performance, than pigs fed a diet prepared with normal barley and supplemented to have a similar level of available P. Therefore, LPA barley cultivars have the potential to markedly reduce the use of phosphate in swine diets and to reduce environmental P pollution from swine manure, which will contribute to the goal of achieving global P sustainability.
Technical Abstract: A 35-d experiment was conducted using 63 crossbred pigs (35 barrows and 28 gilts) with an average initial BW of 7.0 kg and age of 28 d to evaluate the efficacy of the low-phytic acid (LPA) genetic trait in hulled and hull-less barley cultivars. The hulled cultivars were Harrington normal barley (NB) and the near-isogenic LPA mutant M955 with P availabilities of 36 and 95%, respectively. Hull-less cultivars were produced by crossing NB and M422 with a hull-less cultivar, producing hull-less NB (HNB) and hull-less M422 (HM422) with P availabilities of 41 and 66%, respectively. Barrows were in individual metabolism cages and gilts were in individual pens. Seven isocaloric diets were made for Phase 1 (d 0 to 14) and Phase 2 (d 14 to 35). Diets 1 to 4 contained cultivars NB, HNB, HM422, and M955, respectively, with no added inorganic P (iP). Calculated available P (aP) concentration for diets 1 to 4, respectively, were 0.27, 0.28, 0.35, and 0.40% for Phase 1, and 0.15, 0.17, 0.23, and 0.31% for Phase 2. Diet 4 with M955 was adequate in aP. Diets 1 to 3 were deficient in aP. Therefore, diets 5 to 7 were made by adding iP to diets 1 to 3, respectively, to increase aP to equal that in diet 4 in both Phases. Criteria were growth performance, serum phosphatase activity, metacarpal and radius bone breaking strength, and apparent total-tract digestibility of P, Ca, energy, and “dry matter” (DM). Overall (d 0 to 35), pigs fed diets 3 to 7 had greater (P < 0.01) ADG and G:F than pigs fed diet 1, with pigs fed diet 2 intermediate. Serum tartrate-resistant acid phosphatase (TRAP) activity on d 34 was greater (P < 0.01) for pigs fed diets 1 or 2 than for pigs fed diets 4 to 7, with pigs fed diet 3 intermediate. Apparent P absorption (g/d) was greater (P < 0.01) for pigs fed diets 4 to 7 than for pigs fed diets 1 to 3. Pigs fed diet 4 absorbed greater (P < 0.01) percentages of P and excreted less (g/d, P < 0.01) fecal P than pigs fed any of the other diets. In conclusion, the LPA genetic trait was effective with hulled and hull-less barley cultivars in isocaloric diets for young pigs. Pigs fed diet 4 with LPA barley M955 consumed 31 % less P and excreted 78% less fecal P than pigs fed diet 5 with NB+iP with aP equal to diet 4. Therefore, LPA barley cultivars have the potential to markedly reduce the use of iP in swine diets and to reduce environmental P pollution from swine manure, which will contribute to the goal of achieving global P sustainability.