Effect of partial dehulling of two- and six-row barley varieties on precaecal digestibility of amino acids in pigs

Abstract

Five barrows (German Landrace; initial BW 58 kg, final BW 80 kg) fitted with an ileo-rectal anastomosis were used to determine the effect of partial dehulling and addition of barley hulls of two- and six-row barley varieties on the precaecal digestibility (pD) of CP and amino acids. The following diets were provided according to a standardized diet formulation and tested in seven consecutive periods (repeated group-period design): two-row barley (TRB) + casein (C), dehulled TRB + C, TRB + C + 10% hulls, six-row barley (SRB) + C, dehulled SRB + C, SRB + C + 1% hulls, and wheat starch + C. The diets were supplied at daily rates of 79 – 86 g DMI · kg BW^−0.75 in barley containing diets and at 49 g DMI · kg BW^−0.75 in the casein diet. The digestibility of amino acids in barley varieties was determined by the difference method (casein as basal diet) using quantitative digesta collection.

In both varieties of barley the pD of CP and amino acids did not differ. The pD of CP was unchanged in regard to the treatments in both barley varieties. Due to dehulling in TRB the pD was improved significantly for most indispensable amino acids and in SRB for Met and Cys. Addition of 10% hulls to TRB led to equivalent pD of Arg, His, Leu, Tyr, and Trp compared to TRB, but the pD of Lys, Phe, Thr and Val was significantly decreased below the levels of TRB. Addition of even 1% hulls to SRB impaired the pD of Lys below the level in SRB. In conclusion, addition of barley hulls to pig diets impairs amino acids absorption in the small intestine. The pD values, measured under standardized experimental conditions (without a correction using basal endogenous amino acids), are similar to the values of true digestibility published by NRC (1998).

Keywords:

• Amino acids
• precaecal digestibility
• barley
• dehulling
• pigs

Acknowledgements

The authors acknowledge Dr agr. Hans-Joachim Wustrack, Gülzow, for supply of the barley batches. The authors acknowledge R. Gaeth for preparation of diets, animal care, and sample collection. We are grateful to Ch. Voigt, U. Lüdtke, and M. Gratopp for performing analyses of nitrogen and amino acids.