Effect of specific weight on the metabolizable energy content of four cultivars of wheat grain in ewes

In situ starch and crude protein degradation in the rumen and in vitro gas production kinetics of wheat genotypes

The objective of this study was to determine the variation of in situ ruminal degradation characteristics of dry matter (DM), crude protein (CP) and starch (ST), and to determine the effective degradation (ED) of wheat genotypes. Further, multivariate associations of these in situ values with their corresponding in vitro gas production (GP) kinetics and laboratory measurements were evaluated using correlation and multiple linear regression analyses. Grains of 20 genotypes of wheat were characterized by proximate constituents, amino acid (AA) composition and physical characteristics. Ruminal degradation kinetics were determined by in situ degradation of DM, CP and ST, and subsequent evaluation of in vitro GP relative to time courses. In situ and GP measurements were fitted to an exponential equation, and ED was calculated using passage rates in the rumen of 5%/h (ED5) and 8%/h (ED8). To predict ED8 of CP (EDCP8) and ST (EDST8), correlations were evaluated and stepwise multiple linear regression analyses were applied. Estimated degradation parameters varied considerably between wheat genotypes irrespective of the nutrient tested. Variance in a, b and c was not reflected in the variation of the ED, due to high degradation rates (c). The assumed passage rate also impacted estimation of the ED minimally. Estimated GP parameters varied only slightly among wheat genotypes. Nevertheless, regression models explained up to 80 and 99% of the variance in EDCP8 and EDST8, respectively, and associations between EDST8 and EDCP8 and chemical and physical characteristics of grains were detected. As ST is the primary nutrient in wheat grains and can comprise substantial portions of dairy rations, the total amount of ST as well as its ED in the rumen should be taken into account when wheat is incorporated into dairy rations. Conversely, variance in wheat grain CP degradation was very low and can largely be neglected in practical ration formulation for ruminants.

The effect of variety and growing conditions on the chemical composition and nutritive value of wheat for broilers

The aim of this study was to examine the effect of variety and growing conditions of wheat on broiler performance and nutrient digestibility. One hundred and sixty-four wheat samples, collected from a wide range of different sources, locations, varieties and years, were analyzed for a range of chemical and physical parameters. Chemical and physical parameters measured included specific weight, thousand grain weight (TG), in vitro viscosity, gross energy, N, NDF, starch, total and soluble non-starch polysaccharides (NSP), lysine, threonine, amylose, hardness, rate of starch digestion and protein profiles. Ninety-four of the wheat samples were selected for inclusion in four bird trials. Birds were housed in individual wire metabolizm cages from 7 to 28 d and offered water and feed ad libitum. Dry matter intake (DMI), live weight gain (LWG) and gain:feed were determined weekly. A balance collection was carried out from 14 to 21 d for determination of apparent metabolizable energy (AME), ME:gain, DM retention, oil and NDF digestibility. At 28 d the birds were sacrificed, the contents of the jejunum removed for determination of in vivo viscosity and the contents of the ileum removed for determination of ileal DM, starch and protein digestibility. The wheat samples used in the study had wide-ranging chemical and physical parameters, leading to bird DMI, LWG, gain:feed, ME:GE, AME content and ileal starch and protein digestibility being significantly (p<0.05) affected by wheat sample. A high level of N fertilizer application to the English and NI wheat samples tended to benefit bird performance, with increases of up to 3.4, 7.2 and 3.8% in DMI, LWG and gain:feed, respectively. Fungicide application also appeared to have a positive effect on bird performance, with fungicide treated (+F) wheat increasing bird DMI, LWG and gain:feed by 6.6, 9.3 and 2.7%, over the non-fungicide treated (-F) wheats. An increase (p<0.1) of 9.3% in gain:feed was also observed at the low seed rate of 40 compared to 640 seeds/m². It was concluded that the type of wheat sample and environmental growing conditions significantly affects bird performance when fed wheat-based diets.

Chemical and physical predictors of the nutritive value of wheat in broiler diets

The aim of this study was to establish relationships between chemical and physical parameters of wheat with performance and digestibilities of feed components in broiler chickens fed on wheat-based diets. Ninety-four wheat samples were selected for inclusion in four bird trials. Birds were housed in individual wire metabolism cages from 7 to 28 d and offered water and feed ad libitum. Dry matter intake (DMI), liveweight gain (LWG) and gain:feed were measured weekly. A balance collection was carried out from 14 to 21 d for determination of apparent metabolizable energy (AME), ME:gain, dry matter retention, oil and neutral detergent fibre (NDF) digestibility. At 28 d the birds were humanely killed, the contents of the jejunum removed for determination of in vivo viscosity and the contents of the ileum removed for determination of ileal dry matter, starch and protein digestibility. When wheat parameters were correlated with bird performance data, it was found that specific weight was not significantly (p>0.05) related to bird performance. Bird DMI, LWG and gain:feed were best correlated (p<0.05) with the rate of starch digestion, although the coefficients of correlation (r) were still low (0.246 to 0.523). A negative relationship (p<0.01) between AME and total (r = −0.432) and soluble (r = −0.304) non starch polysaccharide (NSP) was observed in this study. Thousand grain weight (TG) was positively correlated with DMI (r = 0.299), LWG (r = 0.343) and gain:feed (r = 0.371). When establishing multiple regression relationships, correlation coefficients greater than 0.8 were achieved for DMI, LWG, gain:feed and ileal crude protein digestibility. However, the economics involved in determining the parameters involved in the regressions make the process impractical.