Abstract:
A total of 880 weanling pigs (initially 15.6 lb and 16 to 20 d of age) were used in a 41-d
experiment to compare the effects of different antibiotic regimens on growth performance
and economic return in the nursery phase. Pigs were alloted to 1 of 5 treatment
groups based on weight within gender. The antibiotic regimens included: (1) control
diets containing no antibiotic throughout the trial, (2) a combination of Denagard
(Novartis Animal Health, Greensboro, NC) at 35g/ton and chlortetracycline at
400g/ton (Denagard/CTC) for the entire 41-d trial, (3) a Pulmotil (Elanco, Greenfield,
IN) regimen of 363g/ton from d 0 to 10 followed by 181g/d from d 10 to 41,
(4) Denagard 200 from d 0 to 10 followed by Denagard/CTC from d 10 to 41, and
(5) Denagard/CTC from d 0 to 10, Denagard 200 from d 10 to 20, and Denagard/
CTC from d 20 to 41. From d 0 to 10, ADG, ADFI, and F/G were similar (P > 0.40)
between the pigs fed nonmedicated diets and the mean of the groups fed diets containing
antibiotics. However, from d 10 to 20, 20 to 41, and for the overall trial, pigs fed
diets containing antibiotics had greater (P < 0.05) ADG and improved (P < 0.04) F/G
than pigs fed the control diet without antibiotics. Pigs fed diets containing Denagard/
CTC had greater (P < 0.02) ADG and ADFI than pigs fed Pulmotil for d 0 to 10,
20 to 41, and the overall trial. No differences were found (P > 0.18) between pigs fed
Denagard/CTC and Denagard 200 during any phase. Final pig weights were greater
for pigs fed diets containing antibiotics compared with the control (P < 0.01) and for
pigs fed Denagard/CTC compared with pigs fed Pulmotil (P < 0.05). Adding antibiotics
to the diets increased (P < 0.01) feed cost per pig; however, income over feed cost
(IOFC) also increased for pigs fed Denagard/CTC compared with the control (P <
0.01) and compared with pigs fed Pulmotil (P < 0.01). These results demonstrate that
adding antibiotics to the nursery diet improved pig performance and economic return.