Effects of the Age of Newborn Pigs Receiving an Iron Injection on Effects of the Age of Newborn Pigs Receiving an Iron Injection on Suckling and Subsequent Nursery Performance and Blood Criteria Suckling and Subsequent Nursery Performance and Blood Criteria

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Introduction
Young pigs have more rapid growth rates that can lead to greater body blood volume. 4 Because of this rapid growth rate and sow colostrum containing low levels of Fe, newborn pigs are more susceptible to developing iron deficiency in the first week of life. 5 Due to this, intramuscular (IM) administration of 200 mg of Fe after birth is common in the swine industry and it is well established this practice prevents iron deficiency and anemia. 6 However, there are discrepancies in the optimal time after birth to provide the Fe injection to maximize growth and hematological criteria. Research has shown that providing a 180 mg Fe injection 1 d compared to 3 or 4 d after birth resulted in greater hematological criteria in the first week of life. 7 Kernkamp et al., on the other hand, observed that delaying a 150 mg Fe injection to 21 d after birth compared to administering a 150 mg Fe injection 7 d after birth revealed no evidence of difference in body weight or hematological criteria when pigs were weaned at 28 d of age. 8 GleptoForte (Ceva Animal Health, LLC., Lenexa, KS) is an injectable Fe source that contains gleptoferron. Gleptoferron is a macro-molecule complex that has the potential for increased bioavailability, which allows for improved Fe status at weaning for pigs 2016. An investigation of iron deficiency and anemia in piglets and the effect of iron status at weaning on post-weaning performance. J.  Egeli, A.K. and T. Farmstad. 1999. An evaluation of iron-dextran supplementation in piglets administered by injection on the first, third or fourth day after birth. Res. Vet. Sci. 66:179-184. doi:10.1053/ rvsc.1998.0223 8 Kernkamp, H.C.H., Clawson, A.J. and R.H. Ferneyhough. 1962. Preventing iron-deficiency anemia in baby pigs. J. Anim. Sci. 21:527-532. and potentially improved growth performance. Williams et al. 9 previously determined that a 200 mg Fe injection provided from GleptoForte on d 2 after birth maximized farrowing and nursery performance and Fe status. However, research is not available that describes the optimal injection timing of Fe from gleptoferron after birth that supports maximum pre-and post-weaning growth performance and Fe status. Therefore, the objective of this study was to determine the effects of increasing Fe injection time after birth in newborn pigs on preweaning and subsequent nursery performance and blood criteria.

Procedures
The Kansas State University Institutional Animal Care and Use Committee approved the protocol for this experiment. The study was conducted at the Kansas State University Swine Teaching and Research Center in Manhattan, KS.

Farrowing Performance
A total of 324 newborn pigs (DNA 241 × 600, initially 3.56 ± 0.10 lb BW) were used in a 80-d study. A total of 27 litters were utilized with number of pigs per sow equalized on each day of farrowing. Two days after birth, all piglets were weighed, and six barrows and six gilts were allotted in a randomized complete block design to 1 of 6 treatments such that there was 1 barrow and 1 gilt per treatment for each sow. Thus, there were 54 replications per treatment. The six treatments consisted of a negative control receiving no Fe injection or 200 mg of injectable Fe (GleptoForte, Ceva Animal Health, LLC., Lenexa, KS) provided in a single injection on d 2, 4, 6, 8, or 10 after birth. Piglets were weighed on d 2, 12, and weaning (d 21) to calculate ADG before weaning. Creep feed was not offered to suckling pigs.

Nursery Performance
Pigs were weaned at approximately 21 d of age and allotted to pens based on previous Fe treatment with BW balanced across all pens within a treatment with 5 or 6 pigs per pen and 10 pens per treatment. Each pen (4 × 4 ft) had metal tri-bar flooring, one 4-hole self-feeder, and a nipple waterer to provide ad libitum access to feed and water. Pigs and feeders were weighed on d 28,35,42,48,55,62, and 80 after birth to determine ADG, ADFI, and F/G.

Feed
Common diets were fed in all nursery phases ( Table 1). The phase 1 diet was prepared at a commercial feed mill located in central KS (Hubbard Feeds, Inc., Beloit, KS) and contained specialty protein ingredients fed in pellet form. Phase 2 and 3 diets were prepared at the Kansas State University O.H. Kruse Feed Technology and Innovation Center (Manhattan, KS). Phase 2 and 3 diets were formulated to include 50 mg/kg of carbadox (Mecadox, Phibro Animal Health Co., Stamford, CT) and were fed in meal form. All diets contained 110 mg/kg Fe from ferrous sulfate (FeSO 4 ) provided by the trace mineral premix. All diets were formulated according to the Nutrient Requirements of Swine 10 to be at or greater than the pigs' daily nutrient requirements so as not to limit growth performance. Feed samples in each dietary phase were collected directly from feeders and 6 pooled samples for each dietary phase were submitted for analysis of dry matter (DM), crude protein (CP), Ca, P, and Fe content (Ward Laboratories, Inc., Kearney, NE; Table 2).

Blood and Feed Analysis
Blood was collected via jugular venipuncture from one barrow per treatment per litter on d 2, 12, and 21 after farrowing as well as d 35 after birth. Blood criteria measured included Hgb and Hct using an ADVIA 2021i Hematology System (Siemens Healthcare Diagnostics, Tarrytown, NY) and serum Fe and total Fe binding capacity (TIBC) using a COBAS C501 Chemistry Analyzer (Roche Diagnostics, Indianapolis, IN). Blood samples were processed at the Veterinary Diagnostic Laboratory, College of Veterinary Medicine, Kansas State University, Manhattan, KS.

Statistical Analysis
Growth data of suckling piglets were analyzed as a randomized complete block design using the individual pig as the experimental unit and crate and gender as random effects. Nursery growth data were analyzed as a randomized complete block design using the PROC GLIMMIX procedure of SAS (version 9.4 SAS Institute, Inc., Cary, NC) with pen as the experimental unit and block as a random effect. Blood criteria from suckling and nursery pigs were measured as a repeated measure within pig with the individual pig as the experimental unit and crate as a random effect. Growth data and blood parameters were evaluated using linear and quadratic effects of Fe injection time point from d 2 to 10 after birth and a pairwise comparison of the negative control vs. all other treatments using preplanned CONTRAST statements. Blood criteria were also evaluated for treatment and day interactions using the PROC GLIMMIX procedure of SAS. Differences between treatments were determined by using least squares means. A P-value ≤ 0.05 was considered significant and 0.05 < P ≤ 0.10 was considered marginally significant.

Chemical Analysis
Results of the diet analysis indicated that DM, CP, calcium, and phosphorus met the pigs' nutrient requirement. 10 Iron analysis of the diets indicated that diets either met or exceeded the pigs' iron requirement. 10

Preweaning Growth Performance
From d 2 to 12, there was marginal evidence for an improvement (linear; P = 0.066) in ADG when increasing the age of piglets when receiving a 200 mg Fe injection (Table  2). From d 12 to 21, increasing the age that piglets receive a 200 mg Fe injection from 4 or 6 d after birth increased (quadratic; P = 0.024) ADG with a decrease in performance observed when the Fe injection was delayed until d 8 or 10. From d 12 to 21, pigs that did not receive an Fe injection after birth had decreased (P = 0.001) ADG compared to all other treatments. Overall, marginal evidence for a difference (quadratic; P = 0.065) in ADG was observed when increasing the age piglets received a 200 mg Fe injection to 4 or 6 d after birth, with a decrease in performance observed when delaying Fe injection until d 8 or 10. Not providing an Fe injection resulted in marginal evidence for a decrease (P = 0.070) in overall ADG and decreased (P = 0.001) d 21 BW compared to all other treatments.

Nursery Growth Performance
From d 21 to 35, there was marginal evidence for a difference (linear; P = 0.059) with increasing age after birth of a 200 mg Fe injection for an increase in ADFI (Table 3). Increasing the age when piglets that received a 200 mg Fe injection to d 4 after birth improved (quadratic; P = 0.028) d 35 BW with no further improvement observed when injections were provided at either d 6, 8, or 10 after birth. Also, the absence of a Fe injection after birth worsened (P = 0.001) ADG, ADFI, F/G, and d 35 BW compared to all other treatments.
From d 35 to 48, there was no evidence of a difference (P > 0.10) in growth performance by increasing the age when piglets received a 200 mg Fe injection. However, increasing time of a 200 mg Fe injection up to 4 d after birth improved (quadratic; P = 0.019) d 48 BW. Furthermore, not providing a Fe injection after birth decreased (P < 0.05) ADG, ADFI, and d 48 BW compared to all other treatments.
From d 48 to 80, there was marginal evidence for a difference (quadratic; P = 0.076) with increasing age after birth of a 200 mg Fe injection for an increase in ADFI. Increasing age when piglets received a 200 mg Fe injection from 2 to 4 or 6 d after birth improved (quadratic; P = 0.013) d 80 ending BW with a decrease in BW when pigs received Fe on d 8 or 10 of age. Marginal evidence for a reduction (P = 0.061) in ADFI was observed in pigs not receiving a Fe injection after birth compared to all other treatments. The absence of an Fe injection decreased (P = 0.001) d 80 ending BW compared to all other treatments.
Overall, there was no evidence of a difference (P > 0.10) in nursery growth performance by increasing the age when piglets received a 200 mg Fe injection. The absence of an Fe injection after birth decreased (P < 0.05) ADG and ADFI compared to all other treatments.

Hematological Criteria
As expected, there was no evidence of difference (P > 0.10) observed for any hematological criteria measured on d 2 prior to the Fe injection (Table 4) These results suggest that administering an injection of 200 mg Fe on d 4 or 6 after birth results in the greatest suckling and subsequent nursery performance. Up to weaning (d 21 post-farrow), there was no evidence of a difference in blood Fe status when a 200 mg Fe injection was administered up to d 6 of age with a decrease in blood Fe status observed thereafter. There was no evidence of difference in blood Fe status in the early nursery period among the pigs receiving a 200 mg Fe injection. The negative impact on growth performance and blood Fe status in pigs not receiving an Fe injection after birth is in agreement with previous research. These results suggest that producers should consider extending the time after birth before administering an Fe injection to maximize post-farrowing and subsequent nursery performance. In this study, providing a 200 mg Fe injection on d 4 after birth provided the greatest preweaning growth performance and ending nursery body weight.   A total of 311 nursery pigs (DNA 241 × 600) were used with 5 or 6 pigs per pen and 10 replicate pens with 5 or 6 pigs per treatment.   Represents 2 d after farrowing. Blood was drawn prior to Fe injection.