Effect of rates and extent of ruminal barley grain dry matter and starch disappearance on bloat, liver abscesses, and performance of feedlot steers

Processing index of barley grain and dietary undigested neutral detergent fiber concentration affected chewing behavior, ruminal pH, and total tract nutrient digestibility of heifers fed a high-grain diet

The objective of this study was to investigate the effects of processing index (PI) of barley grain and dietary undigested neutral detergent fiber (uNDF) concentration on dry matter (DM) intake, chewing activity, ruminal pH and fermentation characteristics, total tract digestibility, gastrointestinal barrier function, and blood metabolites of finishing beef heifers. The PI was measured as the density after processing expressed as a percentage of the density before processing, and a smaller PI equates to a more extensively processed. Six ruminally cannulated heifers (average body weight, 715 ± 29 kg) were used in a 6 × 6 Latin square design with three PI (65%, 75%, and 85%) × 2 uNDF concentration (low and high; 4.6% vs. 5.6% of DM) factorial arrangement. The heifers were fed ad libitum a total mixed ration consisting of 10% barley silage (low uNDF), or 5% silage and 5% straw (high uNDF), 87% dry-rolled barley grain, and 3% mineral and vitamin supplements. Interactions (P < 0.01) of PI × uNDF were observed for DM intake, ruminating and total chewing time, and DM digestibility in the total digestive tract. Intake of DM, organic matter (OM), starch, and crude protein (CP) did not differ (P > 0.14) between low and high uNDF diets, but intakes of NDF and acid detergent fiber were greater (P = 0.01) for high uNDF diets regardless of barley PI. Heifers fed high uNDF diets had longer (P = 0.05) eating times (min/d or min/kg DM) and tended (P = 0.10) to have longer total chewing times (min/kg DM) than those fed low uNDF diets. Additionally, heifers sorted (P = 0.01) against long particles (>19 mm) for high uNDF diets but not for low uNDF diets. Altering PI of barley grain did not affect (P > 0.12) total volatile fatty acid (VFA) concentration, molar percentages of individual VFA, or duration of ruminal pH < 5.8 and <5.6. Total VFA concentration was less (P = 0.01), acetate percentage was greater (P = 0.01), and duration of ruminal pH < 5.8 and <5.6 was less (P = 0.05) for high compared with low uNDF diets. Digestibility of DM, OM, and CP was greater (P = 0.02) for low vs. high uNDF diets with PI of 65% and 75%, with no difference between low and high uNDF diets at PI of 85%. Blood metabolites and gastrointestinal tract barrier function were not affected (P ≥ 0.10) by the treatments. These results suggest that increasing dietary uNDF concentration is an effective strategy to improve ruminal pH status in finishing cattle, regardless of the extent of grain processing, whereas manipulating the extent of barley processing did not reduce the risk of ruminal acidosis.

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.

Effects of rumen-escape starch and coarseness of ingredients in pelleted concentrates on performance and rumen wall characteristics of rosé veal calves

The objective was to study the effect of rumen-escape starch and coarseness of ingredients in pelleted concentrates on performance, carcass quality and rumen wall characteristics in rosé veal calf production. Two alternative concentrates (Coarse and Slow) were compared with a traditional (Control) concentrate. Control was based on finely ground ingredients, whereas in Coarse, the same ingredients were coarsely ground resulting in a mean particle size before pelleting of 1.5 in Coarse and 0.6 mm in Control. Slow compared with Control and Coarse contained finely ground sorghum and corn instead of barley and wheat which increased the amount of rumen-escape starch to 59 compared with 22 g/kg in Control and Coarse. All concentrates had the same total starch (362 g/kg), NDF (168 g/kg), CP (154 g/kg) and DE (15.5 MJ/kg DM) content and a pellet diameter of 3.5 to 4 mm. Use of an 'indicator of starch digestibility' method gave a value of 98.6% for Control and Coarse and 91.1% for Slow (P < 0.001). A total of 57 Holstein bull calves (n = 19 per treatment) were offered one of the three concentrates ad libitum from weaning (2½ months of age) to slaughter (<10 months of age). Concentrate intake was recorded individually. Barley straw was available ad libitum but intake was not recorded. Average daily gain (1.43 kg/day), concentrate conversion efficiency (3.7 kg DM concentrate/kg gain), LW at slaughter (386 kg), carcass weight (194 kg) and EUROP conformation (3.9) were not affected by type of concentrate (P > 0.05). Papillae length and shape evaluated in atrium ruminis and the cranial part of the ventral rumen sac at slaughter were not affected by type of concentrate (P > 0.05). Rumen wall characteristics showed degrees of plaque formation (i.e., papillary aggregation), hyperaemia and necrotic areas in all treatment groups, but with no general difference between type of concentrate (P > 0.05). Incidence of liver abscesses (LAs, 16%) was not affected by type of concentrate (P > 0.05). There were no differences in performance or rumen wall characteristics between liver-abscessed and non-abscessed calves. The results show a high level of production performance with the three types of pelleted concentrates and indicates that neither the more coarse ingredients nor the additional rumen-escape starch tested, when fed ad libitum, could improve rumen wall characteristics or reduce LAs of rosé veal calves.