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Title: Identification of alpha-1 acid glycoprotein (AGP) as a potential marker of impaired growth in the newborn piglet

Author
item Caperna, Thomas
item Shannon, Amy
item Blomberg, Le Ann
item Stoll, Margo
item Ramsay, Timothy

Submitted to: Reproduction, Fertility and Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2013
Publication Date: 8/1/2013
Citation: Caperna, T.J., Shannon, A.E., Blomberg, L., Stoll, M.J., Ramsay, T.G. 2013. Identification of alpha-1 acid glycoprotein (AGP) as a potential marker of impaired growth in the newborn piglet. Reproduction, Fertility and Development. 25:1126-33.

Interpretive Summary: A major hindrance to profitability in the swine industry is the variability in growth performance in feeder and finishing pigs. Piglets with low initial growth rates become poorly performing grower-finishing pigs and reduce the overall efficiency of production by increasing the cost and time of meat production. Therefore, identification of pigs with poor growth potential, at birth would allow early intervention to enhance growth in such pigs. Two studies were conducted to investigate the relationship between the blood levels of two proteins, haptoglobin (HP) and alpha-1 acid glycoprotein (AGP), which might serve as markers for growth rate and growth potential in neonatal pigs. In runts, the circulating level of AGP, but not HP in serum of newborn piglets was higher than average-sized littermates. In contrast, at one or three weeks of age, total protein, AGP and HP levels in blood were similar among control and runt piglets. These results led to the idea that AGP levels at birth might be correlated with future weight gain. To determine the nature of the association between AGP and growth rate, blood was collected between the first and second day after birth in all piglets from ten average litters. Birth weight was positively correlated with growth rate through 21 days of age in males and females, as expected. Plasma levels of AGP were higher in poorer growing pigs and was linearly related with growth rate through 21 days of age. When the blood level of AGP was calculated on a per kg of birth weight basis, the correlation for growth rate improved by 25 and 34% in males and females, respectively, compared to birth weight alone. HP in blood collected at birth, was neither positively nor negatively associated with growth rate in pre-weaning piglets. These studies show that the level of AGP at birth may serve as a very early biomarker for growth which could also be potentially used as a genetic selection marker.

Technical Abstract: Two studies were conducted to investigate the relationship between the circulating levels of the acute phase proteins haptoglobin (HP) and alpha 1 acid glycoprotein (AGP) and growth potential in neonatal pigs. In runts, the circulating level of AGP, but not HP in serum of newborn piglets was higher (p< 0.001) than average-sized littermates. Additionally, total serum protein was lower at birth in runts. In contrast, at one or three weeks of age, total protein, AGP and HP levels in serum were similar among control and runt piglets. To determine the nature of the potential association between AGP and growth rate, blood was collected between the first and second day after birth in all piglets (n=95) from ten average litters (8-11 live births). Birth weight was positively correlated with growth rate through 21 days of age [linear regression correlation coefficient, 0.43 (p< 0.006); and 0.299 (p< 0.003)] in males (n=41) and females (n=54), respectively. Plasma levels of AGP were negatively correlated with growth rate through 21 days of age [correlation coefficient,-0.429 (p< 0.006); and -0.351 (p< 0.01)] in males and females, respectively. When the levels of AGP were calculated on a per kg birth weight basis (ug/ml/kg), the correlation coefficient for growth rate improved by 25 and 34% in males and females, respectively, compared to birth weight alone. In contrast, the concentration of HP in blood collected at birth, was neither positively nor negatively associated with growth rate in pre-weaning piglets. These data suggest the levels of AGP at birth are reflective of growth conditions in utero and/or fetal maturation which may serve as a very early biomarker for growth and could potentially be used as a genetic selection marker for breeding programs.