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Steam-flaking conditions affect starch availability of barley grain

TAGS: Beef
DarcyMaulsby/iStock/Thinkstock Cattle in feedlot
Decreasing flaking density increased starch reactivity of barley grain.

Grain processing techniques, such as steam flaking, are meant to improve nutrient availability when included in livestock rations.

University of Saskatchewan researchers J.A. Johnson, K. Burakowska, L.A. Radke and G.B. Penner conducted a study to determine how steam-flaking conditions affect the starch availability of barley grain.

Johnson et al. obtained barley grain from five independent sources for the trial that, which was arranged as a 3 x 3 + 1 factorial, with main effects of steam conditioning duration (five, 20 or 35 minutes) and flaking density (targeting 0.43, 0.34 and 0.25 kg/L) compared with samples that were not processed (control).

The researchers analyzed samples for seven-hour in vitro digestibility, amyloglucosidase reactive soluble starch (AGR) and six-hour amylase reactive insoluble starch (ARIS). Insoluble reactive starch, digestive insoluble starch and predicted ruminal starch digestion (PRSD) were calculated.

According to Johnson et al., actual flaking densities obtained were 0.47 + 0.031 kg per liter for the high treatment, 0.37 + 0.021 kg per liter for the mid treatment and 0.32 + 0.010 kg per liter for the low treatment.

The control barley had less AGR, ARIS, insoluble reactive starch and predicted ruminal starch digestion (P < 0.01) but greater digestive insoluble starch (P < 0.01) relative to flaked barley, the researchers reported.

Extending conditioning duration tended to increase AGR (P = 0.06) but did not affect predicted ruminal starch digestion or seven-hour in vitro digestibility, Johnson et al. said.

They noted, though, that reducing the flaking density increased AGR, which was 9.26%, 12.75% and 21.41% for the high, mid and low treatments, respectively (P < 0.01); ARIS, at 51.15%, 57.26% and 61.52%, respectively (P < 0.01); predicted ruminal starch digestion, at 95.89%, 97.32% and 99.20%, respectively (P < 0.01), and seven-hour starch digestibility, at 86.3%, 83.8% and 78.9%, respectively (P < 0.01).

Johnson et al. concluded that, relative to non-processed barley grain, steam conditioning increased starch reactivity, but conditioning durations of longer than five minutes had minimal additive effects. Also, decreasing the flaking density of steam-flaked barley grain increased its starch reactivity.

The research was published in Applied Animal Science.

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