Effects on pre- and post-weaning growth performance, hematocrit level
By Sarah Albers, Clara Lemanski and Young Dal Jang Newborn piglets are susceptible to iron-deficiency anemia since they are born with low iron reserves and sow milk contains a low level of iron. A single iron injection given to newborn piglets is a common practice in the swine industry to improve iron and hematological status.
However, as piglets grow fast during the suckling period and weaning weight increases with increasing weaning age up to 28 days, a single iron injection at birth may not be sufficient to meet iron requirements during the entire suckling period when piglets are weaned at the age of over 21 days, which may result in post-weaning growth retardation.
A second iron injection before weaning could be a useful way to boost the iron status of piglets and thereby improve their hematological status. However, it has not been demonstrated yet whether the second iron injection enhanced the growth of piglets and how the effectiveness of additional iron injection could be accurately measured.
Therefore, the two research trials evaluated the effects of additional iron injection before weaning on pre- and post-weaning growth performance and hematocrit level of piglets weaned around 25 to 27 days of age.
Effects of second iron injection to suckling piglets Two experiments were carried out to assess the effects of second iron injection to suckling piglets on pre- and post-weaning growth performance and hematocrit level.
In Experiment 1, a total of 20 piglets were allotted into two treatments within the litter based on body weight and gender at day 1 to 2 of age. Treatments were:
An additional 200 mg of iron-dextran was injected to all piglets intramuscularly at day 14 after the first injection (11 days before weaning). Body weight and hematocrit levels were measured at day 0, 14 and 25 after the first injection. Preweaning growth performance did not differ among treatments.
In day 14 and 25 after the first injection, the Iron200b treatment had greater hematocrit levels than the Iron100b treatment (P<0.06; Table 1). Hematocrit level changes were greater in the Iron200b treatment in day 0 to 14 (P=0.06) after the first injection but lower in day 14 to 25 (P<0.05) after the first injection than Iron100b treatment.
Hematocrit, %
d 0 post-injection
d 25 post-injection
Change, %
d 0-14 post-injection
d 14-25 post-injection
d 0-25 post-injection
Table 1. Hematocrit concentrations in Experiment 1.
* Treatments were: 1) Iron100b: 100 mg iron-dextran intramuscular injection at day 1 to 2 of age, and 2) Iron200b: 200 mg iron-dextran intramuscular injection at day 1 to 2 of age. An additional 200 mg of iron-dextran was injected to all piglets intramuscularly at day 14 after the first injection (11 days before weaning).
The result of the first experiment indicated that second iron injection did not affect the preweaning growth of piglets, but when the low level of iron (100 mg) was administered to piglets at birth, the efficacy of the second iron injection in increasing hematocrit level was more pronounced than when the high level of iron (200 mg) was administered.
In Experiment 2, a total of 22 piglets from four litters were allotted into three treatments at birth (day 1-3 of age) within the litter based on body weight and gender as follows:
The initial 150 mg of iron-dextran was injected intramuscularly on day 1-3 of age. Body weight and hematocrit levels were measured at day 0, 10 (second injection for Iron14 treatment), 17 (second injection for Iron7 treatment), 24 (weaning), 31 and 38 after the first iron injection.
The Iron14 treatment tended to have a greater final weight at 2 weeks post-weaning than the control treatment (P=0.07), and the Iron7 treatment had an intermediate value in the final weight. In hematocrit level, the Iron14 treatment had greater levels than the control treatment at day 17, 24, 31 (P<0.05), and 38 (P=0.10) of experiment whereas the Iron7 treatment had greater levels than the control treatment at day 24, 31 and 38 of experiment (P<0.05) and lower than Iron14 treatment at day 17 (P<0.05) of experiment.
The results of the second experiment indicated that although the second iron injection before weaning could increase hematocrit levels of piglets in pre- and post-weaning periods, the injection 14 days before weaning may be effective for improving early post-weaning growth.
In conclusion, the additional iron injection to suckling piglets could potentially improve early post-weaning growth performance and hematocrit levels.
However, the change in hematocrit levels was greater when piglets had low hematocrit levels. In order to observe the effect of the second iron injection in the post-weaning period, the second iron injection may need to happen early enough before weaning.
Albers is a former undergraduate, Lemanski is an undergraduate and Jang is an assistant professor, all at the University of Wisconsin – River Falls.
1 vs 2
2 vs 3
Body weight, kg
Table 2. Growth performance and hematocrit level in Experiment 2
*Treatments were 1) Control: no second injection, 2) Iron14: 100 mg iron-dextran intramuscular injection 14 days before weaning (day 10 of experiment), and 3) Iron7: 100 mg iron-dextran intramuscular injection 7 d before weaning (day 17 of experiment).