Ruminal starch digestion characteristics in vitro of barley cultivars with varying amylose content

Evaluation of pineapple stem starch as a substitute for corn grain or ground cassava in a cattle feedlot for 206 or 344 days: feedlot performance, carcass characteristics, meat quality, and economic evaluation

The pineapple stem starch substituted for ground cassava or corn as a carbohydrate source in the concentrate diet. The experiment used 36 Holstein crossbred steers (aged 22 months) with an average initial body weight of 453.0 ± 35.3 kg. The experimental units were randomly assigned to three different starch sources of concentrate diets: ground corn (GC), ground cassava (CA), or pineapple stem starch (PS) with two different feeding periods: (1) period 1 for 206 days or (2) period 2 for 344 days with six replicates per treatment (two steers per replication), arranged in a completely randomized design. The animals were slaughtered at the end of the experimental periods. After that, the feedlot performance, carcass characteristics, meat quality, and economic return were evaluated. The results showed that the steers fed PS had a greater weight gain, average daily gain, and lower feed: gain ratio when fed for 206 days than when fed for 344 days, but dry matter intake, carcass characteristics, meat quality, and fatty acids profile did not differ between treatments in both periods of feeding except C14:1 and C18:0. The steers fed PS showed the greatest economic return. As a substitute for cassava or corn, pineapple stem starch had no negative impact on the feedlot performance, carcass characteristics, and meat quality. These results indicate that pineapple stem starch could be a useful feedstuff for the feedlot steers diets as an alternative starch source.

Effect of pineapple stem starch feeding on rumen microbial fermentation, blood lipid profile, and growth performance of fattening cattle

Pineapple stem starch (PS) was evaluated for its suitability as a new starch source in concentrate for fattening cattle, based on the growth performance, blood profile, and rumen parameters of 36 steers in a 206-day feeding study. PS was formulated as a 40% concentrate and fed with forage in comparison with ground corn (GC) and ground cassava (CA) formulated at the same level. PS feeding improved weight gain and feed conversion ratio without affecting feed intake. PS did not obviously influence blood lipid profiles throughout the experiment. Ruminal concentration of total short-chain fatty acids (SCFA) increased with PS without affecting SCFA composition throughout the feeding study. Rumen amylolytic group, especially Ruminococcus bromii, was dominant in the rumen microbial community, and showed increased abundance by PS feeding throughout the experiment. These results clearly indicate the potential of PS as a useful starch source for fattening cattle in terms of rumen fermentation and growth performance.

Effect of starch properties and zein content of commercial maize hybrids on kinetics of starch digestibility in an in vitro poultry model

BACKGROUND

The kinetics of starch digestion is a key determinant of poultry performance. Research so far has shown that starch digestibility kinetics depends on the molecular structure of starch but also on the properties of the complex matrix in which starch granules are embedded in most feedstuffs. However, the manner in which genotype differences in the same plant affect starch digestibility kinetics has not yet been addressed. The present study explored the extent to which the starch digestibility rate in commercial high-yielding maize hybrids depended on amylose / amylopectin content, starch granule size and shape, and zein in total starch (TS) content.

RESULTS

Hybrids differed in all the traits examined, giving the following ranges: amylose content, 165-207 g kg^-1 DM; zein in TS content, 70-89 g kg^-1 DM; starch granule equivalent diameter, 11.5-12.3 μm, and in vitro starch digestion rate, 1.22-1.44 h^-1 . The starch digestion rate correlated negatively with zein in TS content (r = -0.36) and positively with equivalent diameter (r = 0.45). The negative correlation between starch digestion rate and zein in TS suggests that some zein remained after grinding and pepsin incubation and acted as a barrier to amylolytic enzymes.

CONCLUSIONS

When starch granules are embedded in a complex protein matrix, zein limits their accessibility to enzymes and affects the starch digestibility rate. Surprisingly, our results suggest that when enzymes reach starch granules, they digest a greater proportion of the starch when the granules are larger. © 2019 Society of Chemical Industry.

Effects of different starch source of starter on small intestinal growth and endogenous GLP-2 secretion in preweaned lambs

The objective of this study was to investigate the effects of different sources of starch in starter feed on small intestinal growth and endogenous glucagon-like peptide 2 (GLP-2) secretion in preweaned lambs. Twenty-four 10-d-old lambs were divided into three groups that were treated with different iso-starch diets containing purified cassava starch (CS, n = 8), maize starch (MS, n = 8), and pea starch (PS, n = 8). At 56 d old, there was no significant difference in final body weight (BW) of lambs among the three groups. However, different starch source in starter significantly affected the average daily feed intake (ADFI) and average daily gain (ADG) of lambs among three groups. Compared with the CS and MS diets, the PS diet significantly increased the GLP-2 concentration in blood plasma (P < 0.001), the crypt depth of the jejunum (P = 0.006), and the villus height of the ileum (P = 0.039). Meanwhile, PS diet significantly increased the mRNA expression of proglucagon and the glucagon-like peptide 2 receptor (GLP-2R) in the jejunum and ileum (P < 0.001). Furthermore, the PS diet significantly upregulated the mRNA expression of cyclin D1 (P < 0.001), cyclin E (P = 0.006), and cyclin-dependent kinases 6 (CDK6) (P = 0.048) in the jejunum and cyclin A (P < 0.001), cyclin D1 (P < 0.001), and CDK6 (P = 0.002) in the ileum. Correlation analysis showed that endogenous GLP-2 secretion was positively related to the mRNA levels of cell cycle proteins in small intestinal mucosa. In summary, all results showed that PS in starter feed promoted small intestinal growth that may, in part, be related to cell cycle acceleration and endogenous GLP-2 secretion in preweaned lambs. These findings provide new insights into nutritional interventions that promote the development of small intestines in young ruminants.

Lactobacilli Are Prominent Members of the Microbiota Involved in the Ruminal Digestion of Barley and Corn

The chemical composition of barley grain can vary among barley varieties (Fibar, Xena, McGwire, and Hilose) and result in different digestion efficiencies in the rumen. It is not known if compositional differences in barley can affect the microbiota involved in the ruminal digestion of barley. The objective of this study was to characterize the in situ rumen degradability and microbiota of four barley grain varieties and to compare these to corn. Three ruminally cannulated heifers were fed a low (60% barley silage, 37% barley grain, and 3% supplement) or high grain (37% barley silage, 60% barley grain, and 3% supplement) diet. One set of bags was used to estimate dry matter (DM), starch and crude protein (CP) degradability. A second set was used to extract DNA from the adherent microbiota and visualize grain after incubation using scanning electron microscopy (SEM). DNA was subjected to amplicon 16S rRNA gene sequencing followed by analysis using QIIME. In the low grain diet, McGwire had the highest effective degradability (ED) of DM (P < 0.01). The ED of starch was highest (P < 0.01) for Fibar, McGwire, and Xena, but the ED of CP was not affected by variety. For the high grain diet, Xena and McGwire had the highest ED of DM (P < 0.01). The ED of starch was highest (P < 0.01) for Xena and Fibar. The ED of protein was highest (P < 0.01) for Xena and McGwire. Although the microbiota did not differ among barley varieties, they did differ from corn and with incubation time. Lactobacilli were dominant members of the mature biofilms associated with corn and barley and were accompanied by a notable increase in the lactic acid utilizing genera, Megasphaera. As none of the cattle exhibited subclinical or clinical acidosis during the study, our results suggest that lactobacilli play a more prominent role in routine starch digestion than presently surmised.

Influence of barley grain treated with alkaline compounds or organic extracts on ex vivo site and extent of digestion of starch

Objective

Two ex vivo experiments were conducted to verify the effect of barley grain (Nusrat cultivar) treated with alkaline compounds (AC) including alum, ammonium, and sodium hydroxide or cation-exchanged organic extracts (OE) prepared from alfalfa hay, sugar beet pulp and Ulva Fasciata, on extent and digestion of starch.

Methods

In the first study, the in vitro first order disappearance kinetic parameters of dry matter (DM), crude protein (CP) and starch were estimated using a non-linear model (D_(t) = D_(i) · e^{(−k_d · time)} + I, where: D_(t) = potentially digestible residues at any time, D_(i) = potentially digestible fraction at any time, k_d = fractional rate constant of digestion (/h), I = indigestible fraction at any time). In the second experiment, the ruminal and post-ruminal disappearance of DM, CP, and starch were determined using in situ mobile nylon bag.

Results

Barley grains treated with alum and alfalfa extract had a higher constant rate of starch digestion (0.11 and 0.09/h) than others. Barley grain treated with OE had a higher constant rate of CP digestion and that of treated with AC had a higher constant rate of starch digestion (0.08 and 0.11/h) compared with those of the other treatments. The indigestible fraction of starch treated with alum and sugar beet pulp extract was higher than that of the control group (0.24 and 0.25 vs 0.21). Barley grain treated with AC and OE had significant CP disappearance in the rumen, post-rumen and total tract, and also starch disappearance for post-rumen and total tract compared with the untreated (p<0.001).

Conclusion

This study demonstrated that AC and OE might have positive effects on the starch degradation of the barley grain. In addition, treating barley grain with alum and sugar beet pulp extract could change the site and extend digestion of protein and starch.

In situ and in vitro ruminal starch degradation of grains from different rye, triticale and barley genotypes

In recent years, advances in plant breeding were achieved, which potentially led to modified nutritional values of cereal grains. The present study was conducted in order to obtain a broad overview of ruminal digestion kinetics of rye, triticale and barley grains, and to highlight differences between the grain species. In total, 20 genotypes of each grain species were investigated using in situ and in vitro methods. Samples were ground (2 mm), weighed into polyester bags, and incubated in situ 1 to 48 h in three ruminally cannulated lactating dairy cows. The in vitro gas production of ground samples (1 mm) was measured according to the 'Hohenheim Gas Test', and cumulative gas production was recorded over different time spans for up to 72 h. There were significant differences (P<0.05) between the species for most parameters used to describe the in situ degradation of starch (ST) and dry matter (DM). The in situ degradation rate (c) and effective degradability (assuming a passage rate of 8%/h; ED8) of ST differed significantly between all grains and was highest for rye (rye: 116.5%/h and 96.2%; triticale: 85.1%/h and 95.0%; barley: 36.2%/h and 90.0% for c and ED8, respectively). With respect to DM degradation, the ranking of the species was similar, and predicted c values exhibited the highest variation within species. The in vitro gas production rate was significantly higher (P<0.05) for rye than for triticale and barley (rye: 12.5%/h; triticale: 11.5%/h; barley: 11.1%/h). A positive relationship between the potential gas production in vitro and the maximal degradable DM fraction in situ was found using all samples (r=0.84; P<0.001) as well as rye (P=0.002) and barley (P<0.001) alone, but not for triticale. Variation in ruminal in situ degradation parameters within the grain species resulted from the high c values, but was not reflected in the ED estimates. Therefore, the usage of mean values for the ED of DM and ST for each species appears reasonable. Estimated metabolisable energy concentrations (ME, MJ/kg DM) and the estimated digestibility of organic matter (dOM, %) were significantly lower (P<0.05) for barley than for rye and triticale. Rye and triticale dOM and ME values were not significantly different (P=0.386 and 0.485).

Estimation of the in situ degradation of the washout fraction of starch by using a modified in situ protocol and in vitro measurements

The in situ degradation of the washout fraction of starch in six feed ingredients (i.e. barley, faba beans, maize, oats, peas and wheat) was studied by using a modified in situ protocol and in vitro measurements. In comparison with the washing machine method, the modified protocol comprises a milder rinsing method to reduce particulate loss during rinsing. The modified method markedly reduced the average washout fraction of starch in these products from 0.333 to 0.042 g/g. Applying the modified rinsing method, the fractional degradation rate (k d ) of starch in barley, oats and wheat decreased from on average 0.327 to 0.144 h-1 whereas for faba beans, peas and maize no differences in k d were observed compared with the traditional washing machine rinsing. For barley, maize and wheat, the difference in non-fermented starch in the residue between both rinsing methods during the first 4 h of incubation increased, which indicates secondary particle loss. The average effective degradation of starch decreased from 0.761 to 0.572 g/g when using the new rinsing method and to 0.494 g/g when applying a correction for particulate matter loss during incubation. The in vitro k d of starch in the non-washout fraction did not differ from that in the total product. The calculated ratio between the k d of starch in the washout and non-washout fraction was on average 1.59 and varied between 0.96 for oats and 2.39 for maize. The fractional rate of gas production was significantly different between the total product and the non-washout fraction. For all products, except oats, this rate of gas production was larger for the total product compared with the non-washout fraction whereas for oats the opposite was observed. The rate of increase in gas production was, especially for grains, strongly correlated with the in vitro k d of starch. The results of the present study do not support the assumption used in several feed evaluation systems that the degradation of the washout fraction of starch in the rumen is much faster than that of the non-washout fraction.