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United States Department of Agriculture

Agricultural Research Service

Research Project: Improving the Efficiency of Sheep Production in Western Rangeland Production Systems

Location: Range Sheep Production Efficiency Research

Title: Feeding low-phytic acid corn grain to finishing wethers does not alter phosphorus digestion

Authors
item Taylor, Joshua
item Leytem, April
item Raboy, Victor

Submitted to: Journal of Animal Science Supplement
Publication Type: Proceedings
Publication Acceptance Date: April 1, 2013
Publication Date: June 17, 2013
Citation: Taylor, J.B., Leytem, A.B., Raboy, V. 2013. Feeding low-phytic acid corn grain to finishing wethers does not alter phosphorus digestion. Journal of Animal Science Supplement. 64:392-395.

Interpretive Summary: Low-phytic acid (LPA) feed grains contain similar concentrations of phosphorus as do standard grains, but the majority of phosphorus exists as inorganic phosphate rather than phytic acid. Although ruminant animals can completely digest phytic acid and utilize the phosphorus, LPA grains are being promoted as tools to improve overall phosphorus management in ruminant production systems. Data are limiting to support such claims. Our objective was to determine the extent of phytic acid degradation in sheep fed a finishing diet that was formulated with LPA corn grain. Based on the results from this study, we conclude that LPA corn grain did not improve phosphorus digestion in finishing sheep. Therefore, LPA grains may not improve efficiency of phosphorus utilization and management in ruminant productions systems.

Technical Abstract: Low-phytic acid (LPA) feed grains contain similar concentrations of P as do standard grains, but the majority of P exists as inorganic phosphate rather than phytic acid. Research has shown that LPA feeds can be used to improve overall efficiency of P utilization in swine, poultry and aquaculture production. Unlike simple-stomached animals, ruminants can digest and utilize phytic acid because of microbial phytases in the rumen. Nevertheless, LPA grains are being promoted as tools to improve overall P management in ruminant production systems. Data are limiting to support such claims. Our objective was to determine the extent of phytic acid degradation in sheep fed a finishing diet that was formulated with LPA corn grain. Crossbred wether lambs (n = 14; BW = 41.4 ± 2.5 kg), pre-adapted (35 d) to a finishing diet, were placed indoors (d 0) and assigned randomly and equally to 1 of 2 treatment finishing diets. Diets included ground corn grain (83.0% DM basis) from either LPA (LPG) or standard-phytic acid (SPG; control) hybrids. Diets were fed individually for 21 d; Cr2O3 was included as an indigestible marker. Wethers were slaughtered and contents from the duodenum were collected for analyses. Phosphorus flow at the duodenum was estimated from the product of the daily Cr intake and the duodenal P:Cr concentration ratio. Chemical composition of P was determined using 31P nuclear magnetic resonance spectroscopy. Total P intakes for SPG and LPG treatment groups were 4.18 and 3.75 ± 0.20 g/d (DM basis), respectively. Inorganic phosphate was 22.1 and 76.2% and monoester phosphate was 76.2 and 18.7 % of dietary P in SPG and LPG diets, respectively. Daily P flow at the duodenum and composition of duodenal P were similar between treatments (P = 0.34 to 0.42). Duodenal P flow was 10.63 and 9.10 ± 1.19 g/d for SPG and LPG, respectively. Inorganic phosphorus was 64.6 and 70.0 ± 4.3% and monoester phosphate was 34.1 and 27.7 ± 4.2 % of duodenal P for SPG and LPG treatments, respectively. We conclude that LPA corn grain did not improve P digestion in finishing sheep. Therefore, LPA grains may not improve efficiency of P utilization and management in ruminant productions systems.

Last Modified: 12/21/2014
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