A cooperative study assessing the effects of a second iron injection administered before weaning on growth performance, hematological status, and tissue mineral concentrations of nursery pigs*

Objective: A study involving 7 experiment stations evaluated the effects of a second iron injection adminis- tered before weaning on growth and hematological mea- sures of pigs. Materials and Methods: Pigs (n = 514) were given an iron injection (100–200 mg) on the first day of life. Piglets were then allotted to pairs of similar-weight, same- sex siblings 3 to 5 d before weaning (on d 18–24) with one piglet from each pair receiving a second iron injection. All pigs received common station-specific postweaning diets. Data were subjected to ANOVA with the model contain- ing the terms treatment, station, pair within station, and treatment × station interaction. Results and Discussion: Postweaning ADG was greater for the added-injection group during during 0 to 14 d after weaning, but the response (212.5 vs. 202.6 g) was largely influenced by a single station as evidenced by a treatment × station interaction. The tendency for a treatment × station interaction for overall ADG (d −4 to 28) indicated that iron status was not the most limiting factor for growth at all stations. Hemoglobin concentra- tion was greater for the added-injection group at weaning and d 14 after weaning. Implications and Applications: An additional iron injection before weaning may lead to improved early nursery growth; however, the beneficial effects of an additional iron injection are not universal and are likely dependent on unique herd characteristics including timing and total dosage of iron injections as well as nursery diet supple- mentation.