Arginine and omega-3 fatty acids for enhancing reproductive performance of sows

Ideal sow productivity characteristics include maximizing live litter size, farrowing rate and lactation yield while also optimizing piglet birth weight, sow longevity, and health. The modern sow’s potential to produce larger litter sizes and with fetal growth rates greater than before is encouraging in making these ideals possible. However, in order to achieve these goals, the provision of necessary nutrients is an important requirement. Current research is now going on with the objectives of re-evaluating certain important nutrients and their impact on sow productivity. One of the nutrients of interest is arginine, an amino acid with numerous metabolic functions and play important roles in reproduction and health. Further, rapidly growing young animals have a high requirement for arginine. However, arginine from sow’s milk as well as endogenous arginine synthesis by the neonate are lower than needed for maximal neonatal growth.

Polyunsaturated fatty acids (PUFA) such as the parent molecules of both the omega-6 (O6FA) and omega-3 family of fatty acids (O3FA) are known as essential nutrients because pigs lack the capacity to synthesize them. These PUFA play important roles in immune functions by regulating gene expression and by acting as precursors for various eicosanoids. They are also components of cell membranes making them crucial during rapid tissue formation. Although conventional diets contain high amounts of O6FA, they contain less appreciable amounts of O3FA. Current research in humans suggests that the ratio between O6FA and O3FA should be balanced. In this regard, although studies have been limited, increasing intakes of O3FA by sows have shown great potential for improving sow productivity and health. In addition, recent reports suggest that modern sows provided higher levels of protein during both late gestation and lactation may reduce catabolism of body nutrient stores which may occur during late gestation due to the dramatic increase in fetal growth rates and during lactation when milk demand is high and both feed intake and body nutrient stores are low.

This dissertation covers the areas of: 1) determining effects of arginine supplementation on both gestation and lactation performance of first-parity sows; 2) determining the effects of O3FA and high protein supplementation on both gestation and lactation performance of first-parity sows including the effects of O3FA on subsequent parity; and 3) determining the effects of long-term supplementation of both arginine and O3FA on the expression of immune-related genes in leukocytes of first-parity lactating sows.

The first study was conducted to test the hypothesis that dietary arginine supplementation improves reproductive performance of pregnant gilts. Fifty-two pregnant gilts with body weight (BW) of 167.6 ± 1.8 kg and backfat (BF) thickness of 13.3 ± 0.2 mm were assigned at d 30 of gestation to corn-soybean meal based diets supplemented with 1.0% L-arginine-HCl or 1.7% L-alanine (isonitrogenous control). Body weight and BF thickness were measured and blood samples were obtained periodically throughout gestation. At d 110 of gestation, pregnant gilts were transferred to individual farrowing crates. The numbers of total piglets born and born alive, as well as birth weights of piglets were recorded immediately after farrowing. Throughout gestation, BW or BF thickness of pregnant gilts did not differ between treatment groups. Plasma urea concentration was lower and both plasma insulin and arginine concentrations were higher in arginine-supplemented than in control gilts during the later parts of gestation (P < 0.05). Compared with the control group, arginine supplementation increased the number of pigs born alive by 22% (P < 0.05) and live litter birth weight of piglets by 24% (P < 0.05). This finding provides evidence for a marked increase of live-born piglets from arginine supplementation in pregnant gilts.

The effect of arginine supplementation on lactation performance was then further tested using a 2 x 2 factorial arrangement of treatments in a randomized block design on 38 first-parity sows. Litter size was standardized to a minimum of 9 piglets by cross-fostering within 24 h post-farrowing depending on piglet availability. No main or interaction effects (P > 0.05) were noted for BW, BF thickness, average daily feed intake (ADFI), and days until return-to-estrus among the different treatment groups during the 21-d lactation period. On d 7 of lactation, plasma concentrations of arginine and insulin in sows, as well as concentrations of most amino acids in milk were higher (P < 0.05) in response to arginine supplementation during lactation compared to the control. Piglet weight gain from sows fed the arginine-supplemented diet during lactation was greater between d 0 and 7 (P < 0.01) and between d 0 and 21 (P < 0.05) of lactation compared to piglets from sows fed the control diet during lactation. Collectively, results from this study show the potential beneficial effects of arginine supplementation in improving lactation performance of first-parity sows.

The third study was conducted to test the hypothesis that O3FA and high protein supplementation improves both gestation and lactation performance of first parity sows. The effects of O3FA were further tested on subsequent parity. Sixty-four pregnant gilts (BW 195.0 ± 2.1 kg BW, 12.9 ± 0.16 mm BF) were randomly assigned to 4 dietary treatments from 60 d of gestation to 21 d of lactation. Dietary treatments were: 1) corn-soybean meal-based control diet (CON); 2) high protein (HP); 3) CON + 0.2% O3FA (O3); and 4) HP + O3 (HPO3). The CP for CON and O3 were 12.3% for gestation and 17.9% for lactation while HP and HPO3 were 18.4% for gestation and 19.5% for lactation. Body weight, BF thickness, and ADFI did not respond (P > 0.10) to treatments either during gestation or lactation. Likewise, no differences (P > 0.10) in days until return-to-estrus were noted among treatment groups. First-parity gestation performance (P > 0.10) did not differ among treatment groups. Piglet BW at d 10 and 21 were higher (P < 0.05) for the O3 compared to both CON and HPO3 groups. A similar pattern was also noted for piglet weight gain between d 0 and 21 of lactation. Piglet growth of the HP group did not differ (P > 0.10) from other treatment groups. Second-parity live piglet birth weight tended (P = 0.065) to be higher for the O3 compared to the CON group. Compared to the CON group, O3 piglet performance showed a similar pattern as that of the previous parity. In summary, results indicate that O3FA alone during lactation improved growth of nursing piglets regardless of parity. However, O3FA supplemented with or without high protein did not affect first-parity pregnancy outcome, although O3FA alone may improve subsequent piglet birth weight.

The fourth study was conducted to investigate the effects of arginine supplementation on immune-related gene expression in leukocytes of first-parity sows. Differential blood counts were determined on whole blood samples obtained periodically throughout the study. Separate blood samples were collected into RNA blood tubes, via jugular venepuncture at 21 d of lactation. Expression of immune-related genes was determined using an immune system targeted microarray, the results of which were validated by quantitative PCR. Arginine supplementation resulted in increased (P < 0.05) numbers of neutrophils at 110 d of gestation and throughout lactation. Expression analysis showed that long-term feeding of arginine to sows significantly altered (P < 0.05) the expression of immune related genes including those with antigen-binding, antigen-presentation, enzyme, chemotaxis, and neurotransmitter related functions. Similarly, gene expression and differential blood count analyses were also conducted with O3FA supplementation using the same procedures described in the fourth study. Supplementation of O3FA resulted in lower (P < 0.05) monocyte counts at 110 d of gestation and throughout lactation. Expression analysis indicated that O3FA supplementation leads to an increase not only in anti-inflammatory genes but also pro-inflammatory genes mainly related to antigen cell presenting and antigen binding function. Results also showed a decrease in the expression of a number of potentially pro-inflammatory genes including IL-2 receptor, PKC-á, Toll-like receptor-á, and resistin. These alterations in immune- related gene expression may result in a balance between potentially pro- and anti-inflammatory gene actions.

In summary, results from these studies indicate that both arginine and O3FA supplementation to maternal diets may be considered as nutritional strategies for enhancing reproductive performance and possibly health of sows. However, further studies are required to confirm and to elucidate how improvements were brought about. In addition, the extent to which altered gene expression may affect the animal’s response to actual immune challenge conditions should be determined.