Our objective was to model the effect of mean particle size (mPS) on in vitro rumen starch 
degradation (IVSD) and the kinetics of gas production for different starch-based feeds. For 
each feed, two batches of the same grains were separately processed through two different 
mills (cutter or rotor speed mills), with or without different screens to achieve a wide range of 
mPS (0.32 to 3.31 mm for corn meals; 0.19 to 2.81 mm for barley meals; 0.16 to 2.13 mm for 
wheat meals; 0.28 to 2.32 mm for oat meals; 0.21 to 2.36 mm for rye meals; 0.40 to 1.79 for 
sorghum meals; 0.26 to 4.71 mm for pea meals; and 0.25 to 4.53 mm for faba meals). The 
IVSD data and gas production kinetics, obtained by fitting to a single-pool exponential model, 
were analyzed using a completely randomized design, in which the main tested effect was mPS 
(n = 6 for all tested meals, except n = 7 for corn meals and n = 5 for sorghum meals). Rumen 
inocula were collected from 2 fistulated Holstein dairy cows that were fed a total mixed ration 
consisting of 16.2% crude protein, 28.5% starch, and 35.0% neutral detergent fiber on a dry 
matter basis. The IVSD, evaluated after 7 h of rumen incubation, decreased linearly with 
increasing mPS for corn, barley, wheat, rye, pea, and faba meals, and decreased quadratically 
with increasing mPS for the other meals. The y-axis intercept for 7h IVSD was below 90% 
starch for corn, barley, and rye feeds, but greater than 90% for the other tested feeds. The mPS 
adjustment factors for the rate of rumen starch degradation varied widely among the different 
tested feeds. There was a linear decrease in starch degradation with increasing mPS for barley, 
wheat, rye, and pea meals, while a quadratic decrease in starch degradation for the other tested 
meals. Further, there was a linear decrease in the rate of gas production (kd) with increasing 
mPS in each tested feed, except for pea meal, which had a quadratic relationship. For each 1 
mm increase in mPS, the kd was adjusted by -0.009 h-1 for corn, -0.011 h-1 for barley, -0.008 h- 
1 for wheat, and -0.006 h-1 for faba; while numerically greater adjustments were needed for oat (-0.022 h-1), rye (-0.017 h-1), and sorghum (-0.014 h-1). These mPS adjustment factors could be 
used to modify the starch-based feed energy values as a function of mean particle size, although in vivo validation is required.

In vitro rumen gas production and starch degradation of starch-based feeds depend on mean particle size / Gallo, Antonio; Giuberti, Gianluca; Atzori, Alberto Stanislao; Masoero, Francesco. - In: JOURNAL OF DAIRY SCIENCE. - ISSN 0022-0302. - 101:7(2018), pp. 6142-6149. [10.3168/jds.2017-13944]

In vitro rumen gas production and starch degradation of starch-based feeds depend on mean particle size

Atzori Alberto Stanislao;
2018-01-01

Abstract

Our objective was to model the effect of mean particle size (mPS) on in vitro rumen starch 
degradation (IVSD) and the kinetics of gas production for different starch-based feeds. For 
each feed, two batches of the same grains were separately processed through two different 
mills (cutter or rotor speed mills), with or without different screens to achieve a wide range of 
mPS (0.32 to 3.31 mm for corn meals; 0.19 to 2.81 mm for barley meals; 0.16 to 2.13 mm for 
wheat meals; 0.28 to 2.32 mm for oat meals; 0.21 to 2.36 mm for rye meals; 0.40 to 1.79 for 
sorghum meals; 0.26 to 4.71 mm for pea meals; and 0.25 to 4.53 mm for faba meals). The 
IVSD data and gas production kinetics, obtained by fitting to a single-pool exponential model, 
were analyzed using a completely randomized design, in which the main tested effect was mPS 
(n = 6 for all tested meals, except n = 7 for corn meals and n = 5 for sorghum meals). Rumen 
inocula were collected from 2 fistulated Holstein dairy cows that were fed a total mixed ration 
consisting of 16.2% crude protein, 28.5% starch, and 35.0% neutral detergent fiber on a dry 
matter basis. The IVSD, evaluated after 7 h of rumen incubation, decreased linearly with 
increasing mPS for corn, barley, wheat, rye, pea, and faba meals, and decreased quadratically 
with increasing mPS for the other meals. The y-axis intercept for 7h IVSD was below 90% 
starch for corn, barley, and rye feeds, but greater than 90% for the other tested feeds. The mPS 
adjustment factors for the rate of rumen starch degradation varied widely among the different 
tested feeds. There was a linear decrease in starch degradation with increasing mPS for barley, 
wheat, rye, and pea meals, while a quadratic decrease in starch degradation for the other tested 
meals. Further, there was a linear decrease in the rate of gas production (kd) with increasing 
mPS in each tested feed, except for pea meal, which had a quadratic relationship. For each 1 
mm increase in mPS, the kd was adjusted by -0.009 h-1 for corn, -0.011 h-1 for barley, -0.008 h- 
1 for wheat, and -0.006 h-1 for faba; while numerically greater adjustments were needed for oat (-0.022 h-1), rye (-0.017 h-1), and sorghum (-0.014 h-1). These mPS adjustment factors could be 
used to modify the starch-based feed energy values as a function of mean particle size, although in vivo validation is required.
2018
In vitro rumen gas production and starch degradation of starch-based feeds depend on mean particle size / Gallo, Antonio; Giuberti, Gianluca; Atzori, Alberto Stanislao; Masoero, Francesco. - In: JOURNAL OF DAIRY SCIENCE. - ISSN 0022-0302. - 101:7(2018), pp. 6142-6149. [10.3168/jds.2017-13944]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11388/205094
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