Effects of dietary level of barley hulls and fibre type on protein and energy digestibilities of Condor hulless barley in growing swine

Condor barley hulls were added by weight (0, 50, 100, 150 and 200 g kg−1) to Condor barley kernels to study the effect of added hulls and fibre level on apparent protein and energy digestibilities using the Mobile Nylon Bag Technique (MNBT) with growing castrates. Twenty-four 1-g samples of the hull-kernel mixtures and hulls alone were placed into nylon mesh bags and were inserted through a simple T-cannula in the duodenum of six growing pigs using a 6 × 6 Latin square design. Bags were collected from faeces approximately 24–36 h after insertion and cleaned. Samples were analysed for crude protein (CP), gross energy (GE), and acid-detergent (ADF) and neutral-detergent (NDF) fibre. The addition of hulls to Condor kernels linearly increased ADF and NDF levels in the kernel-hull mixtures. Condor kernels had a crude protein (CP) content of 142 g kg−1; the apparent digestibility of protein was 88.6%. The addition of hulls linearly decreased CP content (P < 0.01) and CP digestibility in a curvilinear fashion (P = 0.006). Condor kernels had a GE content of 17.6 MJ kg−1 and a digestibility of 87.4%. Energy digestibility coefficients decreased linearly (P = 0.27) as the proportion of hulls in the kernel/hull mixture was increased to 200 g kg−1. Regression models based on CP, GE, ADF and NDF were highly significant and produced accurate estimates of protein and energy digestibility in the six Condor kernel-hull mixtures. Correlation coefficients relating predicted CP and GE digestibilities in 25 barley samples using regression equations based on ADF or NDF and data from the kernel-hull mixtures and MNBT digestibilities were 0.53 (P = 0.006) and 0.79 (P = 0.0001) for CP and GE, respectively. Condor hulless barley represents a good source of digestible energy and protein for swine and digestibility coefficients could be reliably predicted from regression models using chemical components as independent variables.