Effects of pelleting and expanding of vegetable feeds on <i>in situ</i> protein and starch digestion in dairy cows

Abstract

In situ digestion of protein and starch in barley, oats, wheat, wheat bran, maize, sorghum, peas, and soyabeans was evaluated in dairy cows after milling (untreated), pelleting (ca. 81 o C) and expander processing at two different temperatures (110 or 130 o C). Effective degradation of crude protein (EPD) and starch (ESD) in the rumen, as well as total tract indigested protein (IP) and starch (IS) fractions, were determined by in situ methods. Pelleting significantly decreased EPD of wheat and wheat bran by 14 and 10 percentage units, respectively, and increased ESD in maize by 10 percentage units. Expander treatment efficiently protected protein from rumen degradation in all feeds evaluated, except maize. The ESD of maize, sorghum, peas and oats increased with 31, 18, 22 and 5 percentage units, respectively, after expander treatment at 130 o C. The IP fraction of sorghum and peas increased after expander treatment. In maize, sorghum and peas the IS fraction decreased by heat treatment. It is concluded that protein and starch digestion of vegetable feeds in dairy cows can be modified by different heat treatment.

Effect of extrusion on in situ ruminal protein degradability and in vitro digestibility of undegraded protein from different feedstuffs

“…Whereas in maize extrusion produced an increase in protein solubility and degradability up to 24 h of incubation in the rumen and thus in the effective degradability, in barley this effect was limited to the first 2 h, changing its sign from 4 h onwards, which resulted in a decrease in the effective degradability. Ljøkjel et al 12 also observed an increase in protein degradability of maize when it was expanded, whereas in barley the opposite effect was recorded. McNiven et al 9 did not find significant differences in the fractional rate of degradation and effective CP degradability of maize after roasting at 74, 118 or 163…”

“…Whereas some authors 9,10 have found a reduction, others have not 11 or have observed different effects among feedstuffs. 12 These latter found a decrease in the effective crude protein degradability of barley, sorghum, oats and wheat after expansion, but not of maize.…”

In vitro gas production profiles and fermentation end‐products in processed peas, lupins and faba beans

“…These effects are in agreement with the findings of other researchers. 6,10 Compared with the R samples, the lower NGR and higher propionate due to the fermentation of the E and EP samples in lupins and faba beans can be explained by the elevated R max S 1 . It is very well documented that a fast fermentation leads to the production of more glucogenic VFA.…”

“…The results of the current study are in fair agreement with some in situ trials where it was found that expander treatment increased ruminal degradation of starch in legume seeds such as peas. 10 Heat treatment, which is often associated with an increased level of gelatinised starch, 34,35 is generally thought to increase both the rate and extent of starch degradation in vitro and in situ. Indeed, in the current study the increased R max G 1 in the E-and EP-treated peas and faba beans was concomitant with the increase in gelatinised starch (Table 3).…”

“…Such processing manipulates the site of digestion in ruminants by reducing the size of feed particles, 5 protecting the proteins from being degraded in the rumen 6,7 and making the starch granules more accessible for microbial digestion. 7,8 The effects of expander processing and/or pelleting on ruminal degradation of starch 8 -10 and protein 6,10,11 of feedstuffs have been intensively studied, mostly in situ. This technique fractionates feed material into a washable fraction, a potentially degradable fraction and an undegradable fraction.…”