Effect of Arachidonic Acid on Growth, Crosslaps, and Lipocalin-2 in Nursery Pigs.

Bone derived Lipocalin-2 can regulate feed intake and its expression may be modulated by Arachidonic Acid (ARA). Therefore, a total of 96 pigs (6.1 ± 0.8 kg initial body weight at 3 wk of age) were used in a 42 d trial to evaluate the effects of dietary ARA on growth performance and indicators of bone metabolism. Pigs were individual housed and randomly allotted to one of four treatments in a 2 x 2 factorial arrangement of treatments (n=24, 0% or 0.5% ARA of total dietary fat % and adequate or deficient (-15%) digestible phosphorus (DigP)). Pigs were fed in a 3 dietary phase system and total dietary fat was 4.6, 4.7, and 5% for phases 1-3, respectively. Weights and feed intake were measured at d 7, 21, and 42. Blood was collected at d 14 for the measurement of calcium, phosphorus, Crosslaps, and Lipocalin-2. Diets deficient in DigP tended to decrease ADG (335 vs. 311 g, P<0.1) in the first 3 weeks. No other effects of DigP were detected on performance. Inclusion of ARA decreased ADFI (391 vs. 356 g P<0.05) and ADG (338 vs. 308 g, P<0.05) in the first three weeks of the trial. Similarly, ARA decreased the overall ADG (467 vs. 435 g, P<0.05) and ADFI (643 vs. 602 g, P<0.05) for the 42 d trial. There were no interactions of ARA and DigP detected. Deficient DigP increased serum calcium (2.67 vs. 2.80 mM, P<0.05) and decreased serum phosphorus (2.95 vs. 2.73 mM, P<0.05). However, there was no effect of ARA or an interaction of ARA and DigP on serum calcium and phosphorus. Inclusion of ARA tended to decrease serum Alkaline Phosphatase activity (314 vs. 273 U/L, P<0.1). Alkaline Phosphatase activity was not affected by DigP nor was there an interaction of ARA and DigP on Alkaline Phosphatase. Deficient DigP decreased serum Crosslaps (0.21 vs. 0.17 ng/mL, P<0.05). This parameter was not affected by ARA nor was there an interaction of ARA and DigP. An effect of DigP or ARA on serum Lipocalin-2 was not detected. Collectively, this data indicates that inclusion of ARA at 0.5% of total diet fat negatively affects post-weaning growth performance, but has limited effect on markers related to bone metabolism measured in this study. Additionally, the effect of ARA on parameters measured did not differ when the pigs were fed diets adequate or deficient in DigP.