Effects of a second iron-dextran injection administered to piglets during lactation on differential gene expression in liver and duodenum at weaning.

Six female littermate piglets 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). All piglets in the litter were administered the first 1 mL injection < 24 h after birth. On day 7, piglets were paired by weight (mean body weight = 1.72 ±â€…0.13 kg) and one piglet from each pair was randomly selected as control (CON) and the other received a second injection (+Fe). At weaning on day 22, each piglet was anesthetized, and samples of liver and duodenum were taken from the anesthetized piglets and preserved until mRNA extraction. differential gene expression data were analyzed with a fold change cutoff (FC) of |1.2| P < 0.05. Pathway analysis was conducted with Z-score cutoff of P < 0.05. In the duodenum 435 genes were significantly changed with a FC ≥ |1.2| P < 0.05. In the duodenum, Claudin 1 and Claudin 2 were inversely affected by + Fe. Claudin 1 (CLDN1) plays a key role in cell-to-cell adhesion in the epithelial cell sheets and was upregulated (FC = 4.48, P = 0.0423). Claudin 2 (CLDN2) is expressed in cation leaky epithelia, especially during disease or inflammation and was downregulated (FC = -1.41, P = 0.0097). 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 hepcidin antimicrobial peptide (HAMP) with a 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. Gene expression related to metabolic pathway changes in the duodenum and liver provides evidence for the improved feed conversion and growth rates in piglets given two iron injections preweaning with contemporary pigs in a companion study. In the duodenum, there is a downregulation of gene clusters associated with gluconeogenesis (P < 0.05). Concurrently, there was a decrease in the mRNA expression of genes for enzymes required for urea production in the liver (P < 0.05). These observations suggest that there may be less need for gluconeogenesis, and possibly 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.

Iron deficiency anemia (IDA) in neonatal piglets is a problem that occurs unless there is intervention with exogenous iron. The most common method to prevent IDA is with an iron injection within 48 h of birth. However, the iron from the first injection will only support normal iron status in the piglets for ~4 kg of growth. As a result, with faster-growing piglets and larger litters, many piglets weaned today are iron deficient which results in slower growth and poor immunity. Pigs never fully recover nor grow at the same rate as those that have sufficient iron status. The aim of this study was to evaluate the effects of one or two injections of iron dextran on the differences in gene expression and metabolic pathway changes in the small intestine and liver of nursing piglets. At weaning, samples of liver and duodenum underwent genome-wide RNA sequencing. The data obtained were statistically analyzed to determine which genes and metabolic pathways were affected. There were 362 and 435 genes significantly changed in the liver and duodenum, respectively, due to a second dose of iron dextran on day 7 after birth.

A second iron injection administered to piglets during lactation improves hemoglobin concentration, growth performance, and carcass characteristics at slaughter.

An experiment was conducted to evaluate the effects of a second injection of iron dextran administered on days 6 to 8 of age. A total of 144 crossbred pigs (equal barrows and gilts; initial age 6 to 8 d; initial body weight [BW] = 2.86 ± 0.01 kg) 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 an initial intramuscular (IM) injection of iron dextran (200 mg Fe) <24 h after birth. Pigs assigned to the +Fe treatment received a second IM injection of iron dextran (200 mg Fe) on days 6 to 8. All pigs were weaned at 22 to 25 d, housed 6 pigs/pen, and received a common corn-soybean meal diet. BW and feed disappearance were recorded every 2 wk. Hemoglobin (Hb) concentrations were measured at birth, initiation of experiment (days 6 to 8), weaning, and the end of the nursery and end of the study. At the end of the study, 1 pig/pen (n = 12 pigs/treatment), closest to the pen mean was selected and slaughtered for carcass characteristic measures. The individual pig served as the experimental unit for BW, Hb, average daily gain (ADG), and carcass characteristic data whereas the pen served as the experimental unit for average daily feed intake, and gain/feed ratio data. The +Fe pigs had a greater Hb at weaning (13.1 vs. 10.7 g/dL, respectively; P < 0.01) and end of the nursery (12.1 vs. 11.7 g/dL, respectively; P = 0.01) compared to CON pigs. During the finisher period, +Fe pigs had a greater ADG (0.94 vs. 0.91 kg, respectively; P = 0.05) compared to CON pigs. Overall, pigs receiving the second iron injection had an ~4% increase in ADG (P = 0.04) from weaning to the end of study. The cumulative improvement in ADG from weaning to the end of study observed for +Fe group resulted in +Fe pigs having a heavier BW at the end of the study (~3 kg; P = 0.04). Following slaughter, +Fe pigs had ~7.2% heavier trimmed loin (P = 0.04) compared to the CON pigs. In conclusion, administering a second iron injection resulted in greater Hb at weaning and the end of the nursery as well as improved growth performance from weaning to the end of study weight and increased carcass weight at slaughter.

The study aimed to evaluate the effects of a second iron dextran injection administered to piglets before weaning on hemoglobin concentration (Hb), growth performance, and carcass measures. Treatments included: a single iron injection administered within 24 h after birth (CON) and two iron injections (+Fe), one administered within 24 h after birth followed by a second iron injection administered 6 to 8 d after birth. Administering a second iron injection before weaning resulted in increased Hb at weaning and the end of the nursery period. Furthermore, pigs receiving a second iron injection had a greater average daily gain from weaning to final market weight which resulted in a final bodyweight difference of ~3 kg. The increased slaughter weight observed for pigs receiving a second iron injection was associated with an increase in trimmed loin yield. In the current study, providing a second iron injection before weaning was a practical method to improve weaning Hb in early life and resulted in a faster overall growth from weaning to the end of the study.

Assessment of visceral organ growth in pigs from birth through 150 kg.

Visceral organs (VO) are essential for their role in the metabolism and distribution of consumed nutrients as well as other life functions in animals. Two experiments were conducted to assess the natural longitudinal changes that the VO undergo from birth through 150 kg body weight (BW). In Experiment 1, a total of 96 crossbred pigs were euthanized at birth (pre-suckle), d 1, 2, 3, 5, 7, 14, 21 (weaning), 22, 23, 24, 26, 28, 42, 49, and 63 of age. In Experiment 2, a total of 48 crossbred pigs were euthanized at 30, 50, 75, 100, 125, and 150 kg of BW. The absolute weight of VO, and the volume and length of the gastrointestinal tract (GIT) were measured. In both experiments, the absolute weight of VO, GIT length, and their volume increased (linear, quadratic, and/or cubic, P < 0.05) as BW and age increased. In Experiment 1, the relative weight of VO (liver, kidney, heart, and lung) decreased after initially increasing within the first week of life (linear, quadratic, and/or cubic, P < 0.05), whereas the relative weight of all VO decreased as BW increased in Experiment 2 (linear and/or quadratic, P < 0.05). The relative length of small intestine decreased and that of large intestine increased as age increased in Experiment 1 (linear and quadratic, P < 0.05), whereas the relative length of the small and large intestine in Experiment 2 were relatively constant at 80% and 20% of the total length of the intestine, respectively. As age and BW increased, the relative volume of the large intestine to the total volume of the GIT increased (linear and/or quadratic, P < 0.05), while the relative volume of the small intestine decreased (linear and/or quadratic, P < 0.05). In conclusion, results showed that both absolute and relative measurements (weight, volume, and length) of VO were dependent on the BW (age) of the pig.