Amino Acid Boosts Litter Size and Piglet Growth

Research at North Carolina State University shows that feeding extra arginine to young sows during pregnancy and lactation can increase litter size and piglet growth, writes Jackie Linden, editor of ThePigSite.

17 October 2008

5 minute read

Dr Sungwoo Kim, North Carolina State University

Arginine is an essential amino acid and, as Dr Sungwoo Kim of North Carolina State University explains, "It plays multiple roles in animal metabolism by serving as a substrate for protein synthesis, as in intermediate in the hepatic urea cycle, and as a precursor for the synthesis of various metabolic molecules, including nitric oxide (NO) and polyamines."

These multiple roles make arginine particularly interesting to Dr Kim, whose focus is researching the role of amino acids in sows and neonatal pigs. He has recently joined the Swine Nutrition Group at North Carolina State University.

He says that other researchers have found nitric oxide to play a vital role in enhancing blood flow during pregnancy in ewes, which helps to deliver more nutrients to the developing embryos. Polyamines are involved in the earliest development of the embryo (embryogenesis) as well as the growth of the placenta, which delivers nutrients to the embryos.

Dr Kim found that porcine amniotic fluid, which surrounds the developing embryos - contains an unusually high concentration of arginine (4-6mmol/litre)

Table 1. Reproductive Performance of Gilts Fed a Control Diet or One Supplemented with 1% L-Arginine HCl¹ ^{(Mateo et al., 2007)}
Parameter	Control	Arginine	SEM
Total piglets born alive per litter, n	11.27	11.94	0.96
Total piglets born alive per litter, n	9.37	11.40*	0.56
Birth weight of all piglets born, kg	1.39	1.43	0.04
Birth weight of all piglets born alive, kg	1.41	1.46	0.04
Litter weight of all piglets born, kg	15.54	16.85	1.31
Litter weight of all piglets born alive, kg	13.19	16.38*	0.74
Piglets born dead per litter, n	1.86	0.66*	0.147
Birthweight variation for all piglets born², kg	0.293	0.257	0.021
Birthweight variation for all piglets born alive³, kg	0.240	0.253	0.017

This discovery led Dr Kim and his colleagues to a study to see what effects additional arginine in the diet would have on reproduction in pigs. Using 52 pregnant gilts, they fed half of the animals an extra 1% arginine from days 30 to 114 of gestation. The results are shown in Table 1.

They found that the supplemented group had two extra piglets born alive (11.40 versus 9.37 for the control). The difference was statistically significant (P<0.05) The piglets born (both in total and born alive) tended to be heavier were heavier and more even in size in the group of gilts fed extra arginine.

These promising results led to a follow-up experiment with 38 sows in their first parity. The trial was a 2x2 factorial design, with two diets in late pregnancy (from 30 days of gestation to farrowing) and in lactation: these were an unsupplemented control diet or one with an extra 1% arginine hydrochloride).

Table 2. Lactation Performance of Sows Fed Fed a Control Diet or One Supplemented with 1% L-Arginine HCl¹ ^{(Mateo et al., 2008)}
Parameter	Control Gestation Diet		Supplemented Gestation Diet		SEM
	Control Lactation Diet	Suppl. Lactation Diet	Control Lactation Diet	Suppl. Lactation Diet	SEM
No. of sows	8	9	10	11
Piglet weight - day 0, kg	1.43	1.43	1.45	1.42	0.025
Piglet weight - day 7, kg	2.42	2.62	2.48	2.80	0.049
Piglet weight - day 14, kg	3.81	4.14	3.91	4.22	0.069
Piglet weight - day 21, kg	5.26	5.66	5.46	5.86	0.089
Body weight gain - 0 to 7d, g	140.0	170.0	147.1	191.4	0.046
Body weight gain - 7 to 14d, g	202.9	220.0	202.9	208.6	0.036
Body weight gain - 14 to 21d, g	205.7	217.1	221.4	234.3t	0.050
Body weight gain - 0 to 21d, g	182.9	202.4t	191.0	211.4	0.093

The results are shown in Table 2. The author notes that piglets whose dams received the extra arginine during lactation gained about 20g more weight per day during the 21-day lactation (P<0.05) than those fed the control diet.

It is interesting to note that although supplemental arginine in the lactation diet had a significant effect on the bodyweight of the piglets, these parameters also benefitted from supplementation during the sow's pregnancy. The effects of extra arginine during the two periods tended to be additive despite piglet birth weights being similar for all treatments.

The extra arginine did not affect the sows in terms of bodyweight changes, back fat, feed intake or the days taken to return to oestrus.

"Collectively," Dr Kim concludes, "results from this study indicate the beneficial effects of dietary arginine supplementation in improving the lactation of first-parity sows."