1567
Interactions between levels and source of energy supplementation in beef cattle
The objective of this trial was to evaluate the effect of two levels and two sources of energy on voluntary intake and ruminal parameters of Nellore steers grazing intensively managed tropical pasture during the rainy season. Treatments corresponded to two levels of supplementation (0.3 and 0.6% of BW, as fed) combined with two sources of energy concentrate (fine ground corn and pelleted citrus pulp). Eight 24-month-old rumen-cannulated steers (356 kg BW ± 9.8) were assigned to two 4x4 Latin squares and allocated in 2 ha of Brachiaria brizantha cv. marandu (Palisadegrass), managed in a rotational grazing system. Chromium oxide was used as an indigestible marker. Concentration of purine derivatives in the urine was used to estimate microbial synthesis. Total DMI was not affected by treatments. Feeding 0.6% of BW of energy supplement decreased forage intake (P<0.05) and increased (P<0.01) digestible DMI. There was interaction (P<0.05) for ruminal pH between source and level of supplementation, with lower pH for steers fed citrus pulp and for steers supplemented at 0.6% of BW. Energy supplementation at 0.6% BW decreased ruminal N-NH3 (P<0.05) due to greater microbial synthesis (P<0.05), resulting in greater N retention. No differences between ground corn and citrus pulp were observed as an energy supplement for growth cattle. Feeding 0.6% BW of energy supplement is an effective to increase digestible dry matter intake in grazing cattle.
Table 1 – Forage and total intake, ruminal parameters, microbial synthesis and nitrogen retention
|
Energy Source |
Supplementation, %of BW |
P value |
SEM |
||||
Corn |
Citrus Pulp |
0.3 |
0.6 |
ES |
S |
ES*S |
||
Total DMI, %BW |
1.77 |
1.76 |
1.74 |
1.78 |
ns |
ns |
ns |
0.27 |
Forage DMI, %BW |
1.32 |
1.31 |
1.44 |
1.18 |
ns |
* |
ns |
0.26 |
Digestible DMI, %BW |
1.19 |
1.18 |
1.08 |
1.29 |
ns |
** |
ns |
0.16 |
Forage digestibility, % |
58.00 |
58.08 |
57.88 |
58.2 |
ns |
ns |
ns |
0.94 |
pH |
6.46a |
6.38b |
6.47a |
6.37b |
* |
* |
* |
0.09 |
NH3,mg/dL |
6.12 |
5.96 |
6.65a |
5.43b |
ns |
* |
ns |
0.85 |
Microbial synthesis, g/d |
537.88 |
511.18 |
460.87 |
588.19 |
ns |
* |
ns |
67.39 |
Nitrogen retention, % N % intake |
29.74 |
21.88 |
16.58 |
35.04 |
ns |
** |
ns |
5.18 |
SEM= Standard error of the mean, *=significant, ns=not significant, ES= energy source, S=supplementation
Keywords: energy source, forage intake, supplementation