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An experiment was conducted to evaluate the effects of an additional injection of iron dextran (Uniferon, Pharmacosmos Inc.) administered at d 6 to 8 of age. Crossbred pigs [n = 144; equal barrows and gilts; initial body weight (BW) = 2.86 ± 0.01 kg] from 21 litters were assigned to either the control (CON) or an added-injection treatment (+Fe). Pigs were paired by sex and BW within a litter and randomly assigned to the iron treatment within each pair. All pigs had received a 200 mg Fe intramuscular (IM) injection < 24 h after birth. All pigs were weaned at 22 to 24 days, housed 6 pigs/pen for a total of 12 pens/treatment, and received a common corn-soybean meal diet formulated to meet or exceed the NRC (2012) requirement estimates relative to BW until slaughter. Body weight and feed disappearance were recorded at least biweekly to determine average daily gain (ADG) and feed intake (ADFI). Hemoglobin (Hb) concentrations were measured at birth, initiation of experiment (d 6 to 8), weaning, and at the end of the nursery and finisher periods. At the time of slaughter, 1 pig/pen (n = 12 pigs/treatment) was selected and slaughtered for carcass characteristic measures. Data were subjected to ANOVA by the GLM procedure of SAS; the individual pig served as the experimental unit for BW, Hb, ADG, and carcass characteristics whereas pen served as the experimental unit for ADFI, and gain/feed ratio data. The statistical model included sex, treatment, sex × treatment, and allotment pair for Hb and ADG. There were expected sex effects for ADG but no sex × treatment interactions for any response measures. The +Fe pigs had a greater Hb at weaning (13.1 vs. 10.7 g/dL, P < 0.0001) and end of the nursery (12.1 vs. 11.7 g/dL, P = 0.01) compared with CON pigs (Table 1). During the finisher period, +Fe pigs had a greater ADG (P = 0.05) compared with CON pigs. Overall, pigs receiving the added iron injection had an ~ 4% increase in ADG (P = 0.04) from weaning to slaughter. The cumulative improvement in ADG from weaning to slaughter observed for +Fe group resulted in +Fe pigs having a heavier BW at the end of the experiment (115.77 vs. 112.79 kg; P = 0.04). Following slaughter, +Fe pigs had ~ 2.5% heavier cold carcass weight (82.99 vs. 80.93 kg; P = 0.34) and trimmed loin (10.67 vs. 9.95 kg; P = 0.04) compared with the CON pigs. In conclusion, administering an additional iron injection resulted in greater Hb at weaning and the end of the nursery as well as improved growth performance from weaning to slaughter weight and increased carcass measures at slaughter. [ABSTRACT FROM AUTHOR]

Six female littermate pairs were used in an experiment to evaluate the mRNA expression in tissues from piglets given one or two 1 mL injections of iron dextran (200 mg Fe/mL, Uniferon, Pharmacosmos Inc. Watchung, NJ). All pigs in the litter were administered the first 1 mL injection < 24 hours after birth and on d 7, pigs were paired by body weight (BW; 1.72 ± 0.13 kg) and one pig from each pair was randomly selected as control (CON) and the other received a second injection (+Fe). At weaning on d 22, each piglet was anesthetized, and samples of liver and duodenum were taken from the anesthetized piglets and placed in DNA/RNA Shield (Zymo, Irvine, CA) for preservation until mRNA extraction. RNA-Seq libraries were sequenced to a depth of at least 30 million read pairs (150 bp paired-end sequencing) per sample. Differential Gene Expression data were analyzed with GeneSpring (Agilent, Santa Clara, CA) with a foldchange (FC) of |1.2| P < 0.05 (Table 1). Pathway analysis was conducted with Ingenuity Pathway Analysis (IPA QIAGEN, Redwood City, CA) software with Z-score cutoff of P < 0.05. In the duodenum 435 genes were significantly changed with a FC =|1.2| P < 0.05. Most notably, Claudin 1 and Claudin 2 were inversely affected by the second dose of iron. Claudin 1 (CLDN1, FC = 4.48, P = 0.0423) is responsible for cell-to-cell adhesion in the epithelial cell sheets and serves as a barrier to prevent water and solutes from passing through the paracellular space. Claudin 2 (CLDN2, FC = -1.41, P = 0.0097) was down regulated because it is expressed in cation leaky epithelia. In the liver 362 genes were expressed with a FC =|1.2| P < 0.05. The gene most affected by a second dose of 200 mg Fe was HAMP (Hepcidin Antimicrobial Peptide) with an FC of 40.8. HAMP is a liver-produced hormone that is the main circulating regulator of Fe absorption and distribution across tissues. It also controls the major flows of Fe into plasma by promoting endocytosis and degradation of ferroportin (SLC4A1). This leads to the retention of Fe in Fe-exporting cells and decreased flow of Fe into plasma. Metabolic pathway changes in the duodenum and liver provide evidence for the improved feed conversion and growth rates in pigs given two iron injections pre-weaning. In the duodenum, there is a down regulation of gluconeogenesis (P < 0.05). Concurrently, there is a decrease in the production of urea in the liver (P < 0.05). These observations show that there is less need for gluconeogenesis, thus less urea production from deaminated amino acids. The genomic and pathway analyses provided empirical evidence linking gene expression with phenotypic observations of piglet health and growth improvements. [ABSTRACT FROM AUTHOR]

A cooperative study utilizing 514 weanling pigs from 7 experiment stations was conducted to determine the effects of an additional iron injection administered to piglets before weaning on growth performance and hematological measures. All pigs received an initial iron injection at the time of processing postfarrowing. At each station, pigs were assigned to either the control or an added-injection treatment by pairing two samesex pigs with a BW difference = 0.453 kg within a litter. One pig within each pair received the additional iron injection (same dose received at processing) 3 to 5 days preweaning. Once weaned, both the control and addedinjection group received common station-specific nursery diets. Body weight was recorded weekly by all stations. Blood samples were also collected at second injection, weaning, 14 and 28 days postweaning by 3 of the 7 stations. All data were subjected to ANOVA with the model containing the terms treatment, station, and treatment by station interaction. Average daily gain (Table 1) was greater for the added-injection group during d 0 to 14 (212.5 vs. 202.6 g, P = 0.03) which resulted in an increase in d 14 BW (P = 0.05). Although there was no treatment effect for overall ADG (d -4 to d 28), the tendency for a treatment by station interaction (P = 0.09) illustrated both responsive and nonresponsive stations, indicating that iron status was not the most limiting factor for growth at all stations. Hemoglobin concentration was greater (P < 0.0001) for the added-injection group at weaning and d 14 postweaning. In conclusion, an additional iron injection administered before weaning may lead to early success in the nursery resulting in a heavier BW in subsequent periods; however, the beneficial effects of an additional iron injection are likely dependent on herd status and characteristics. [ABSTRACT FROM AUTHOR]