This study was conducted with the objective to evaluate the effects of corn and sorghum processing methods on the expression of genes involved in volatile fatty acids (VFA) transport of finishing bulls. Five rumen cannulated Nellore bulls (260 ± 23 kg of body weight) were used in a 5x5 Latin square arrangement with five periods of 23 d, with 14 d for adaptation and 9 d for sample collection. Diets contained 72% concentrate (Dry matter basis) and treatments were four energy sources (Dry-ground corn; dry-ground sorghum; high-moisture corn; high-moisture sorghum), plus a control (55% concentrate diet). Bulls were fed twice daily at 0800 and 2000 h. Total and ruminal digestibilities of organic matter (OM) were determined from day 15 to 19. On day 22, 20 mL of ruminal fluid were sampled and preserved with metaphosphoric acid solution (5 mL, 25% w/v) for later determination of VFA. On day 23, samples of rumen epithelium from ventral sac were rapidly excised and stored at -80°C until total RNA isolation and qPCR analysis. Data were analyzed using SAS 9.4 with α = 0.05. Bulls fed high-moisture grains presented greater OM total digestibility and lower OM ruminal digestibility (
P < 0.01). The concentration of total VFA, acetate, and propionate were greater (
P < 0.01) for animals fed corn. There was an interaction
(P = 0.03) between ingredient and grain processing method for mRNA abundance of
DRA, which was lowest in high-moisture corn treatment (Table 1). The mRNA abundance of
AE2,
MCT1,
MCT4,
NHE1,
NHE2, and
PAT1 did not differ (
P > 0.05) among treatments. These results may suggest that changes in corn processing may impact the VFA transport throughout rumen epithelium of finishing Nellore bulls.
Table 1. Relative mRNA abundance (Arbitrary units) of target genes
Item
|
|
Dry-ground
|
|
High-moisture
|
SEM
|
P-value
|
Control
|
Corn
|
Sorghum
|
|
Corn
|
Sorghum
|
Control x Remain treatments
|
Ingredient
|
Grain processing
|
Ingredient x Grain processing
|
AE2
|
3.36
|
3.67
|
3.17
|
|
2.84
|
3.07
|
0.76
|
0.82
|
0.83
|
0.49
|
0.59
|
DRA
|
2.70a
|
3.02a
|
2.99a
|
|
1.80b
|
3.17a
|
0.55
|
0.90
|
0.04
|
0.10
|
0.03
|
MCT1
|
1.79
|
1.97
|
1.77
|
|
1.56
|
1.62
|
0.36
|
0.83
|
0.78
|
0.27
|
0.61
|
MCT4
|
1.59
|
1.82
|
2.03
|
|
1.72
|
1.95
|
0.31
|
0.38
|
0.46
|
0.75
|
0.97
|
NHE1
|
1.58
|
1.84
|
1.74
|
|
1.22
|
1.68
|
0.25
|
0.86
|
0.39
|
0.10
|
0.19
|
NHE2
|
2.05
|
2.24
|
2.05
|
|
1.50
|
2.07
|
0.42
|
0.72
|
0.36
|
0.10
|
0.09
|
PAT1
|
3.07
|
3.25
|
3.25
|
|
2.58
|
3.17
|
0.34
|
0.95
|
0.13
|
0.06
|
0.12
|
a,b Within a row, different subscripts differ at P < 0.05.
