The effects of group size and subtherapeutic antibiotic alternatives on growth performance and morbidity of nursery pigs: a model for feed additive evaluation

Olsen, Kristin M; Gabler, Nicholas K; Rademacher, Chris J; Schwartz, Kent J; Schweer, Wesley P; Gourley, Gene G; Patience, John F

One room of a commercial wean-to-finish research barn was populated with 1,300 barrows and gilts (6.14 ± 0.18 kg BW) derived from PIC 1,050 females and four different sire lines (PIC Duroc, DNA Genetics Duroc, Genesus Duroc or PIC Pietrain) for a 42-d nursery study. The pigs were selected from a study evaluating sire lines, thus explaining the larger than normal number of sires represented in the experiment. All pigs used in the experiment came from the same sow source and were weaned at 21 d of age. On day 1 after birth, all pigs were given iron and gentamicin injections. Before weaning, pigs were treated on an individual basis with injectable antibiotics (gentamicin, ceftiofur, or enrofloxacin) as needed. At weaning, pigs were vaccinated for porcine circovirus type 2 and Mycoplasma hyopneumoniae (Circumvent PCV-MG2, Merck Animal Health, Madison, NJ), and ileitis (Porcilis Ileitis, Merck Animal Health). Due to the flow schedule at the sow source, approximately half of the pigs were weaned 4 d prior to the start of the experiment and held at the sow farm while the other half was weaned 2 d prior to the start of the experiment. For the duration of the experiment, pigs were housed in a tunnel-ventilated barn. Each pen was equipped with a 4-space automatic dry selffeeder and nipple water drinker, fully slatted concrete floors, and metal rod penning and gates. Pigs were given ad libitum access to feed and water for the duration of the experiment. An automatic feeding system (Big Dutchman, Holland, MI) was used to deliver a specified amount of feed to each pen. Air temperature in the room averaged 28.5 °C ± 1.4, 28.7 °C ± 1.2, 27.1 °C ± 0.5, 24.5 °C ± 1.1, 25.8 °C ± 0.9, 26.5 °C ± 2.2, in weeks 1-6, respectively.