Phosphorus digestibility and metabolizable energy concentrations of contemporary cereal grain varieties fed to growing pigs

This study was conducted to determine apparent total tract digestibility (ATTD) of phosphorus (P) and metabolisable energy (ME) concentrations for pigs of 32 different genotypes ( n = 8 per grain species) of barley, rye, triticale and wheat. All genotypes were grown at the same location under the same field conditions and were fed to growing castrated crossbred pigs (initial body weight: 31.1 ± 6.95 kg) using a series of duplicate 3 × 3 Latin square designs. A basal ration, which was deficient in P, and 32 experimental rations containing 400 g/kg DM of the basal ration and 600 g/kg DM of the corresponding cereal grain were mixed. Pigs were kept in metabolism crates and the total collection method was used for separate faeces and urine collections with 7-d adaptation and 7-d collection periods. The mean ATTD of P was greater ( p < 0.05) for wheat than for triticale, rye or barley (59.4%, 50.4%, 44.9% and 44.4%, respectively, for the mean of each grain species). Within-grain species differences ( p < 0.05) among genotypes were obtained for ATTD of P of barley and triticale. The concentrations of ME of triticale and wheat were higher ( p < 0.05) than that of barley and rye (16.1 and 16.2 vs. 14.9 and 14.8 MJ ME/kg DM, respectively). Differences in ME concentration among genotypes within a grain species ( p < 0.05) were found for barley, triticale and wheat. No differences were found for rye. Compared to literature data the present study showed, in part, considerable differences in ATTD of P and ME concentration. These results should be taken into account for accurate pig ration formulation with regard to minimised P output and efficient use of ME. No significant relationships were detected between ATTD of P and phytic acid concentration or phytase activity in the grain genotypes in this study . Abstract A study was conducted to validate an in vitro method for the estimation of the digestible phosphorus (dP) content in plant feedstuffs fed to growing pigs. In total, 65 different samples were examined in vitro and in vivo , both following a strictly standardised trial protocol. Male castrated crossbred pigs (initial body weight ± standard deviation; 30.3 ± 5.6 kg) were fed a basal ration with a deficient P supply or an experimental diet containing a specified amount of the basal ration mixed with the corresponding plant feedstuff. Pigs were kept in metabolic crates, and faeces were collected quantitatively with 7-day adaptation and 7-day collection periods for calculation of apparent total tract digestibility (ATTD) of P. For determination of hydrolyzed P (hP) as part of total P, an enzymatic digestion of the feedstuff was simulated using a three-step in vitro system including xylanase, pepsin and pancreatin. Calculation of dP was by linear regression analysis. Comparison of all 65 in vivo and in vitro values revealed a linear correlation (dP all (g/kg DM) = –0.125 ( P > 0.10) + 1.482 ( P < 0.01) • hP (g/kg DM), R ² = 0.880, P < 0.001, residual standard deviation (RSD) = 0.652). The data was extended with additional feedstuffs and corrected for outliers, i.e., when hP-values were greater than dP-values, and regression analysis was repeated without intercepts (dP without outliers (g/kg DM) = 1.469 ( P < 0.01) • hP (g/kg DM), R ² = 0.923, P < 0.001, RSD = 0.442, n = 52). The applied in vitro method is a rapid and suitable instrument for estimating dP-values in plant feedstuffs for pigs. With precise estimation of dP-values, diet formulation can be optimised and excretion of excess P in animal manure can be minimized. vitro pig,