Short Communication: The effect of seed hardness and malting characteristics on in situ dry matter digestibility of barley grain in beef heifers

Estimation of the net energy value of barley for finishing beef steers

The objective of this study was to identify barley grain characteristics measured by laboratory procedures that could be used to predict barley energy content for finishing beef steers. Twenty-eight different barley genotypes were evaluated including 18 cultivars and 10 experimental lines. Laboratory analysis of barley samples included bulk density, particle size, N, ADF, starch, and ISDMD (in situ DM disappearance after 3 h of ruminal incubation). Animal performance data (BW, DMI, ADG, steer NE_m, and NE_g requirements) were collected from 26 feedlot experiments conducted in Montana and Idaho during a 10-yr period and were used to estimate barley NE_m and NE_g content. A total of 80 experimental units were available with each experimental unit being a diet mean from an individual feedlot experiment. Fifty-eight of the 80 experimental units were randomly selected and used in the development data set and the remaining 22 experimental units were used in the validation data set. Forward, backward, and stepwise selection methods were used to identify variables to be included in regression equations for NE_m using PROC REG of SAS. Barley samples in the model development data set represented a wide range in concentrations (DM basis): N (1.6% to 2.8%), ISDMD (25.7% to 58.7%), ADF (3.6% to 8.0%), starch (44.1% to 62.4%), particle size (1,100 to 2,814 µm), and bulk density (50.8 to 69.4 kg/hL). The barley grain characteristics of particle size, ISDMD, starch, and ADF were the most important variables in six successful models (R ² = 0.48 to 0.60; P = 0.001). The six prediction equations gave mean predicted values for NE_m ranging from 1.99 to 2.05 Mcal/kg (average 2.04 Mcal/kg; 0.45% CV). The mean actual NE_m values from animal performance trials ranged from 1.75 to 2.48 Mcal/kg (average 2.03 Mcal/kg; 6.5% CV). The mean bias or difference in predicted vs. actual values ranged from -0.001 to 0.005 Mcal/kg. Barley NE_g values calculated from animal performance ranged from 1.13 to 1.78 Mcal/kg (average 1.39 Mcal/kg; 8.4% CV). Average predicted barley NE_m and NE_g were 0.02 and 0.01 Mcal/kg less, respectively, than the 2.06 Mcal/kg NE_m and 1.40 Mcal/kg NE_g reported by NRC. Barley NE can be predicted from simple laboratory procedures which will aid plant breeders developing new feed varieties and nutritionists formulating finishing rations for beef cattle.

Effect of diastatic power and processing index on the feed value of barley grain for finishing feedlot cattle

The objective of this study was to assess the nutritional value of barley grain differing in diastatic power (DP; high vs. low; a malt trait) and processing index (PI; 75 vs. 85). One hundred sixty Angus × Hereford crossbred yearling steers (467 ± 38 kg; 144 intact and 16 rumen cannulated) were used in a complete randomized 2 × 2 factorial experiment. Steers were assigned to 16 pens, 8 of which were equipped with the GrowSafe system to measure individual feed intake. Cannulated steers (2 per pen) were randomly assigned to the 8 GrowSafe pens. Diets consisted of high- or low-DP barley grain (80.0% of diet DM) processed to an index of either 75 or 85% (PI-75 and PI-85, respectively). Ruminal pH in cannulated steers was measured over four 5-d periods using indwelling electrodes. Fecal samples were collected every 28 d from the rectum of each steer to assess digestibility using AIA as a marker. No differences ( > 0.10) in rumen pH were observed among cattle as measured by the indwelling pH meters. However, lower ( < 0.05) rumen pH was observed for steers fed low- as opposed to high-DP barley in rumen samples collected just prior to feeding and measured in the laboratory. Intake of DM and OM were not affected ( ≥ 0.24) by DP but were lower ( < 0.01) with more severe processing (PI-75 vs. PI-85). Low-DP barley tended to exhibit higher ( = 0.09) total tract DM digestibility than high-DP barley. Steers fed PI-75 barley also had higher ( = 0.06) G:F and NEg. Digestibility of DM, OM, CP, NDF, and starch was higher ( < 0.05) for PI-75 barley than for PI-85 barley. Low-DP barley increased ( < 0.05) carcass dressing percentage by 0.5% compared with high-DP barley, with a lower PI tending to increase ( = 0.06) rib eye area. Compared with steers fed high-DP diets, steers fed low-DP diets had more ( = 0.01) total (41.7 vs. 19.4%) and severe liver abscesses (22.2 vs. 9.7%). Results suggest that although low-DP barley increased liver abscesses, differences in DP did not alter digestion or growth performance but low-DP barley did improve dressing percentage. Barley with different DP responded similarly to processing, with more intensive processing (PI-75) of barley improving starch digestion, feed efficiency, and NEg without negatively affecting rumen pH.