Physico-chemical composition and nutritional value of UK wheat cultivars exhibiting a wide range of hardness

Study to test the physical and chemical compostion and nutritional value of UK grown wheat cultivars, exhibiting a wide range of hardness.

Year of Publication2009

Twenty-four wheat cultivars, grown in UK and selected from a wide range of hardness values, were assayed for their chemical (total and soluble pentosans content, activity of endogenous xylanase and endogenous xylanase inhibitors, rate of starch digestion RSD60) and physical parameters (viscosity, SKCS hardness value, mean particle size and particle size distribution). Subsequently, they were offered to broiler chickens using the precision feeding method, in order to carry out a rapid determination of their nutritional value. Wheat hardness values ranged from 15 to 85 (SKCS method). Twelve cultivars exhibited hardness values below 50 and were classified as soft, whereas the other 12 cultivars exhibited hardness values over 50 and were classified as hard. Mean particle size of wheat, as well as the ratio between coarse and small particles, was greater (P<0.05) for hard than for soft cultivars. There was a positive correlation (P<0.05) between SKCS hardness value and mean particle size. These findings are in accordance with previous observations (Abécassis et al., 1997; Hruskova et al., 2004). Despite showing higher (P<0.05) soluble pentosan content, there was no significant difference in viscosity between hard and soft cultivars. This could be due to the fact that hard cultivars had higher (P<0.05) endogenous xylanase activity. However, the activity of endogenous xylanase inhibitors also tended to be higher with hard cultivars. There was no significant difference in the rate of starch digestion between hardness classes, unlike previous data reported by Pirgozliev et al. (2001). When given to 42 day-old broiler chickens, hard wheat samples tended (P<0.10) to show lower dry matter digestibility, and tended to have lower AMEn and TMEn values (average reduction of 65 kcal/kg, DM basis) when compared to soft cultivars. The lack of statistical significance may be due to the feeding method which did not allow sufficient time for the animal to adapt to the wheat fed. It could also be associated with high variability between birds, as the ability of juvenile broilers to digest wheat is strongly influenced by genetics (Mignon-Grasteau et al., 2004). The negative effect of grain hardness on the nutritional value of wheat is supported by previous studies (Carré et al., 2002 & 2005; Péron et al., 2006) and can be linked to an increased number of coarse particles in the digestive tract and reduced starch digestibility due to steric hindrance on the enzymes and microbes responsible for the degradation of starch (Péron et al., 2005 & 2007).

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wheatbroiler chickensnutritional value
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