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Publication type: Doctoral Thesis

Year: 2014

Author(s): Deckardt, Kathrin

Title: Chemical and thermal processing of barley grain in ruminant nutrition.

Source: Dissertation, Vet. Med. Univ. Wien, pp. 126.


Zebeli Qendrim

Wagner Martin

Vetmed Research Units:
Institute of Animal Nutrition and Functional Plant Compounds

Graduation date: 27.06.14

Resistant starch (RS) is that fraction of starch which cannot be degraded in the duodenum of monogastrics. Hence, RS is fermented in the large intestine. However, in ruminants RS (called ruminally resistant starch, RRS) is not fermented in the rumen but in the small intestine. Resistant starch can reduce the risk of cardiovascular disease, diabetes and colon cancer in humans, rumen acidosis in ruminants, cholesterol levels in chicken as well as colonic inflammation and metabolic disorders in pigs. Therefore finding new methods to increase the amount of RS in grains is of global interest. The first aim of this thesis was to investigate the RS content of native barley genotypes as well as morphological differences of starch granules with scanning electron microscopy. Barley starch granules did not differ in size and shape, although representing different genotypes. Content of RS ranged from 0.3 to 1.1% of dry matter (DM). Another objective was to test 28 chemical and thermal grain processing techniques, including water and different lactic (LA) and tannic acid (TA) concentrations, steeping durations, with or without heat (55°C) and post-cooling conditions on their potential to enhance RS content. Treating barley grain Eufora with 5% LA for 48 h was the most efficient method to enhance RS (3.1% of DM) content, which was 5 times higher than that of the control (native Eufora). The third aim was to examine the most promising processing techniques (with higher RS content) and native barley Eufora, in view of practical reasons, for their potential to modulate ruminal fermentation, nutrient degradation and microbiological composition in vitro with a rumen stimulation technique (Rusitec). Those 5 treatments included: Eufora enriched with 1% LA (1% LA); Eufora enriched with 5% LA (5% LA); Eufora enriched with 1% LA plus oven-heated at 55°C (1% LAH), Eufora enriched with 1% TA plus oven-heated at 55°C (1% TAH), Eufora enriched with 5% TA (5% TA). Besides daily measurement of gas formation (CH4, CO2), pH-value, redox potential, ammonia and nutrient degradation were analysed. Rumen microbiota and short chain fatty acids (SCFA) were measured using quantitative PCR and gas chromatography, respectively. Clostridium cluster XIV species , which may be involved in RS- metabolism, were increased with 1% LA and 1% LAH treated barley by 11 and 47 % compared to control (P = 0.042). Non- fiber carbohydrates (NFC) degradability was decreased by 4.5 and 5.4% with 1% TAH and 1% LAH (P = 0.009) as well as with TA (P = 0.013) compared to control. Neutral detergent fiber (NDF) degradation was enhanced by LA (P = 0.037), TA (P = 0.013) and heat treatment (P = 0.002). Total SCFA amount was linearly decreased from 133.4 to 121.6 mmol/L by LA treatment in comparison with control (P = 0.026). Moreover processing barley grain with 1%LAH and 1%TAH lowered gene copy numbers of total protozoa (P = 0.032), which are involved in starch degradation, and lipopolysaccharide (LPS) concentration (P = 0.032). In conclusion, all results of these studies are a good basis for further in vivo studies. On the one hand barley grain processed with mild organic acids is environmentally friendly, easy applicable and non-hazardous for farmers, consumers and animals. On the other hand decreasing the concentration of total SCFA, LPS and NFC degradation as well as increasing fiber degradation and Clostridium cluster XIV in the rumen, is auspicious concerning the improvement of the rumen ecosystem, feed conversion efficiency and the prevention of ruminal acidosis.

Publication(s) resulting from University thesis:

Deckardt, K; Metzler-Zebeli, BU; Zebeli, Q (2016): Processing barley grain with lactic acid and tannic acid ameliorates rumen microbial fermentation and degradation of dietary fibre in vitro. J Sci Food Agric. 2016; 96(1):223-231

Deckardt, K; Khiaosa-ard, R; Grausgruber, H; Zebeli, Q (2014): Evaluation of various chemical and thermal feed processing methods for their potential to enhance resistant starch content in barley grain. Starch-Stärke (66), 5-6 558-565.

Deckardt, K; Khol-Parisini, A; Zebeli, Q (2013): Peculiarities of enhancing resistant starch in ruminants using chemical methods: opportunities and challenges. Nutrients. 2013; 5(6):1970-1988
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