Effect of starch content and processing method on in situ ruminal and in vitro intestinal digestion of barley grain in beef heifers

doi:10.1016/j.anifeedsci.2016.03.025

Animal Feed Science and Technology

Volume 216, June 2016, Pages 121-128

https://doi.org/10.1016/j.anifeedsci.2016.03.025 Get rights and content

Highlights

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In situ rumen degradation and in vitro intestinal digestibility of barley grain were evaluated.
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Particle size distribution of processed barley grains varied with starch content and processing.
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Starch content and processing method were not interacted in rumen degradation kinetics.
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Processing method affected in situ degradation kinetics and in vitro digestibility of barley grain.

Abstract

Rate of barley starch digestion in the rumen is critical issue in high-grain fed beef cattle because it is associated with growth performance and health. The digestion rate of starch varies with variety, grain processing or starch content. The objectives of this study were to evaluate the effect of starch content and processing method of barley grain on in situ ruminal dry matter (DM) and starch digestion kinetics, and to develop a model to predict the rate of DM digestion of barley grain. The study was a 2 × 2 factorial arrangement of treatments: starch content (low vs. high) and processing method (PM; grinding vs. dry rolling). Ten barley samples with 5 low (571 ± 17 g/kg) and 5 high (660 ± 7 g/kg DM) starch were either ground 2 mm or dry-rolled with processing index (PI) of 0.75 (PI = bulk density processed/bulk density whole). Three beef heifers (650 kg body weight) fitted with rumen cannulas and fed diet consisting (g/kg DM) of 700 barley silage and 300 barley grain were used for in situ incubation. In situ degradation kinetics of DM, starch, neutral detergent fibre (NDF) and crude protein (CP) were estimated after 0, 2, 4, 8, 12, 24, and 48 h of ruminal incubation. Data from DM, starch, NDF and CP degradation at different times of incubation were fitted to a model y = a + b(1 − e^−c(t−L)). In vitro intestinal disappearances of DM, starch, NDF and CP of ruminal residue after 12 h of incubation were determined using a modified three-step procedure. Interactions between starch content and PM on the degradation kinetic parameters of DM, starch, NDF and CP were seldom observed. High starch barley had greater (P < 0.01) a and effective degradability (ED) of DM and starch, but it had less (P = 0.03) b of starch versus low starch barley. Ground barley had greater (P < 0.01) a, c and ED of DM and starch, and lower (P < 0.01) b compared with dry-rolled barley. Intestinal disappearance DM and starch of rumen residues were affected by both starch content and PM. Starch content of barley grain and manipulating processing method could effectively alter rumen digestion of barley grain.

Introduction

Barley grain is the major energy source used in the diets of dairy and beef cattle in western Canada. As much as 0.80 of all barley grain grown in Alberta enters the feed chain for cattle and swine Alberta Agriculture and Rural Development (2010). Barley grains from different sources are diverse in their chemical composition and estimated metabolizable energy contents due to geographical, environmental and genetic variations as well as their interactions (Dehghan-banadaky et al., 2007). This inherent variability in barley chemical composition leads to differences in animal performance (Yang et al., 2013). The rate of barley starch digestion in the rumen is critical in high-grain fed cattle since it is associated with growth performance and animal health (Mathison et al., 1991, Ramsey et al., 2002). The degradation of starch varies with variety, processing method (PM) or starch content (Ramsey et al., 2002, Yang et al., 2014). Because of rapid digestion of barley starch in the rumen, we hypothesized that starch content of barley grain can influence both rates of dry matter (DM) and starch digestion.

Digestibility of whole barley in cattle is much less than its potential because of its fibrous hull and intact pericarp which are resistant to bacterial attachment and digestion in the rumen (McAllister et al., 1994). Hence, barley grain needs to be processed prior to feeding to expose the endosperm, encased within indigestible pericarp and hull layers, to the microbial population in the rumen (Wang and McAllister, 2000). Physical processing techniques such as grinding or rolling increase digestibility of grain (Hironaka et al., 1992) and the advantages and disadvantages of these PM are well documented (Mathison, 1996). Dry rolling is widely used in barley processing by the western Canadian feedlots. Beauchemin et al. (2001) reported that the optimal degree of dry rolling is around 0.75 of processing index (PI) for barley fed to finishing beef cattle. The PI is widely used by feed industry or feedlot operators to quantify the degree of barley processing; it is expressed as fraction of bulk density after processing to the bulk density before processing (Yang et al., 2000). However, Yang et al. (2014) recently found some advantages of grinding processing over dry-rolling to evaluate digestion characteristics of barley in batch culture. For instance, ground barley had similar starch disappearances after 24 h of incubation to in vivo values, low variability in DM digestibility, better correlation between chemical composition and in vitro digestibility, and no concern on processing quality associated with kernel uniformity compared with dry-rolled barley.

In addition, commercially, feed barley is often marketed as a blend from different varieties or locations during handling and transport. Yang et al. (2014) reported large variability of physical and chemical constituents, and in vitro gas production and DM digestibility of commercial feed barley collected from different locations and year. This finding emphasizes the challenge in precision feeding of commercial feed barley, and suggests a need to develop a simple way to rapidly and concisely determine the feed value of blend barley. The objective of this study was to evaluate the effect of starch content and PM of commercial blend barley on the in situ ruminal digestion kinetics and in vitro intestinal digestibility.

Section snippets

Barley sample collection and processing

Barley samples (n = 120) were collected monthly from ten commercial feedlots in southern Alberta for one year from November 2012 to October 2013. All 120 samples were analyzed for starch content, ranked them, and then used the samples with lowest and highest concentration for the experiment. Ten barley samples with 5 low (571 ± 17.5 g kg⁻¹) and 5 high (660 ± 7.3 g kg⁻¹ of DM) starch were selected. Subsequently, each sample was divided into two equal parts: one part was ground through 2 mm sieve (Arthur

Characteristics of barley grain

Apart from starch content, the contents of aNDF, ADF and CP were slightly greater (P < 0.05) in low versus high starch barley (Table 1). Considerable variation was noted in ADF of the low starch barley samples with CV of 0.209 but much less variations for starch contents of the high starch samples with CV of 0.011. Particle size distribution was affected by starch content and PM (Table 2). The particles retained on the 3.35-mm sieve were less (P < 0.01) but the particles on 2.36-mm sieve were

Chemical composition and particle size distribution

The differences in the contents of CP, ADF, and aNDF were reflected to the relative difference in starch content between the low and high starch barley. The chemical compositions of barley with low or high starch content were consistent with previous study (Stevnebø et al., 2009) that negative correlation between starch and NDF or starch and CP was reported (Salo, 1978). Commercially, the bulk density (BD; g L⁻¹) of barley is used as a measure of the feed value of barley with the assumption that

Conclusion

Starch content (high versus low) had significant effect on in situ ruminal soluble fraction of DM and starch but no effect on the rate of DM and starch disappearance. Effective digestibility of DM and starch in the rumen and in vitro digestibility of starch and DM in the intestine were increased by the starch level. Results showed that grinding versus dry-rolling increased the extent and rate of disappearance of DM and starch. These results indicated that manipulating starch content of barley

Conflict of interest

The authors declare that no conflict of interest, financial or other, exists.

Acknowledgements

This study was financially supported by the Alberta Crop Industry Development Fund (Grant #2012C070R, Lacombe, Alberta, Canada). The authors thank Mr. Alastair Furtado for his technical assistance and Research Centre Barn staff for their management of animal.

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Effect of starch content and processing method on in situ ruminal and in vitro intestinal digestion of barley grain in beef heifers☆

Highlights

Abstract

Introduction

Section snippets

Barley sample collection and processing

Characteristics of barley grain

Chemical composition and particle size distribution

Conclusion

Conflict of interest

Acknowledgements

Anim. Feed Sci. Technol.

Anim. Feed Sci. Technol.

Anim. Feed Sci. Technol.

J. Dairy Sci.

Anim. Feed Sci. Technol.

Anim. Feed Sci. Technol.

Anim. Feed Sci. Technol.

J. Dairy Sci.

Anim. Feed Sci. Technol.

J. Dairy Sci.

J. Dairy Sci.

J. Dairy Sci.

Anim. Feed Sci. Technol.

The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passage

J. Agric. Sci.

Official Methods of Analysis

Understanding the Barley Future Contract

Effects of barley grain processing on the site and extent of digestion of beef feedlot finishing diets

J. Anim. Sci.

Guidelines On: The Care and Use of Farm Animals in Research, Teaching and Testing