1766
Ruminal parameters of confined steers fed with diets containing virginiamycin and monensin sodium
Ionophore and non-ionophore antibiotics are known for their abilility to manipulate rumen fermentation and increase efficiency of high concentrate diets. The aim of this trial was to evaluate the effects on ruminal parameters of confined Nellore steers fed with diets using isolated and combined levels of virginiamycin (VM) and monensin sodium (MON). Fifteen Nellore steers (536 kg of BW) with ruminal cannula were used in a randomized complete block design with five treatments and three replicates. The blocks were defined by initial BW. The animals were kept in feedlot in individual pens for 28-d. Ruminal ammoniacal nitrogen (NH3-N), short-chain fatty acids (SCFA) and ruminal fluid pH were measured before feeding (T0) and 6 and 12 hours after feeding (T6 and T12, respectively). Treatments were defined by levels of VM and MON (mg/ kg of dry matter) as follows: 30MON; 15VM+30MON; 25VM+30MON; 34VM+ 30MON and 34VM. Animals were fed ad libitum twice daily with isonitrogenous and isoenergetic diets, with a 88:12 concentrate:forage (sugarcane bagasse) ratio. Data are shown in Table 1. There were not effects (P>0.05) on NH3-N concentration between treatments. However, pH and SCFA presented differences in T0 for the treatments, with lower SCFA concentration in 34VM+30MON than in 34VM. Acetate:propionate ratio (A:P) did not show differences (P>0.05) between treatments. In conclusion, the different levels of isolated and combined associations of VM and MON did not affect pH, NH3-N, SCFA and A:P ratio, except for pH and SCFA measured at T0, when we observed differences between treatments. Supported by Phibro/Minerva/FAPEG.
Table 1- Ruminal parameters of steers fed with diet containing different levels of feed additives.
Treatments |
30MON |
15VM+30MON |
25VM+30MON |
34VM+30MON |
34VM |
SEM |
NH3-N (mg/ dL) |
||||||
T 0 |
16.16 |
16.71 |
14.96 |
14.97 |
17.11 |
1.1 |
T 6 |
16.51 |
18.23 |
16.27 |
19.13 |
20.80 |
2.8 |
T 12 |
18.46 |
21.32 |
19.45 |
19.03 |
21.72 |
3.1 |
SCFA (mM) |
||||||
T 0 |
105.27ac |
113.08ab |
97.72bc |
93.45c |
116.03a |
5.6 |
T 12 |
148.98 |
138.60 |
135.03 |
139.37 |
140.74 |
7.1 |
A:P ratio |
|
|
|
|
|
|
T 0 |
3.34 |
3.48 |
3.10 |
3.46 |
4.03 |
0.3 |
T 12 |
3.30 |
3.27 |
3.22 |
3.58 |
4.04 |
0.3 |
Ruminal pH |
|
|
|
|
|
|
T 0 |
6.68ab |
6.67ab |
6.78a |
6.85a |
6.54b |
0.1 |
T 6 |
5.94 |
6.24 |
6.24 |
6.23 |
6.08 |
0.1 |
T 12 |
5.67 |
5.80 |
5.88 |
5.91 |
5.81 |
0.1 |
Different superscripts indicate differences among treatments by t test at 5% of probability
Keywords: feed additives, feedlot, ruminal fermentation