759
The effects of dietary zinc oxide and chlortetracycline on nursery pig growth performance
A total of 240 weaned pigs (PIC 1050; initially 6.08 ± 0.60 kg) were used in a 47-d study to compare the effects of added Zn from ZnO, alone or in combination with a low or high dose of chlortetracycline (CTC) on nursery pig growth performance. Pigs were allotted to pens at weaning (d 0) and fed a common starter diet with no antimicrobial for 5 d before the start of the experiment. On d 5, pens of 5 pigs were allotted to 1 of 6 dietary treatments, balanced on average pen weight in a randomized complete block design with 8 replications per treatment. Dietary treatments were arranged in a 2 × 3 factorial with main effects of added ZnO (0 vs. 2,500 ppm of Zn) and CTC (0, 55, or 441 mg/kg feed). Pigs were fed experimental diets from d 5 to 26 after weaning followed by a common corn-soybean meal-based diet without antimicrobial from d 26 to 47. Pigs on the 55 mg/kg treatment received CTC continuously from d 5 to 26; however, to comply with FDA guidelines, CTC was removed from the diets of pigs fed 441 mg/kg CTC on d 15, then added again from d 16 to 26. All diets contained at least 110 ppm of Zn from ZnO in the trace mineral premix. No ZnO × CTC interactions were observed. Pigs fed added ZnO had increased (P=0.001) ADG, ADFI, and BW during the treatment period but decreased G:F (P=0.025) from d 26 to 47 when a common diet was fed. Overall (d 5 to 47), pigs fed added ZnO had increased (P<0.05) ADG and ADFI. Pigs fed CTC had increased (linear, P<0.05) ADG, ADFI, and BW during the treatment period. Overall, pigs fed CTC tended to have increased (linear, P<0.10) ADG and ADFI, but G:F tended (quadratic, P=0.070) to increase then decrease as CTC increased. In summary, ZnO and CTC increased ADG and ADFI but had a minimal effect on feed efficiency.
Table 1. Effect of zinc oxide and chlortetracycline on pig growth.
Added Zn, ppm |
0 |
0 |
0 |
2,500 |
2,500 |
2,500 |
|
CTC, mg/kg |
0 |
55 |
441 |
0 |
55 |
441 |
SEM |
d 5 to 26 |
|
|
|
|
|
|
|
ADG, g |
355 |
378 |
386 |
397 |
397 |
417 |
7.9 |
ADFI, g |
504 |
514 |
528 |
549 |
542 |
570 |
11.9 |
G:F |
0.705 |
0.737 |
0.731 |
0.725 |
0.734 |
0.732 |
0.0128 |
Keywords: nursery pig, zinc, chlortetracycline