Effect of Dietary Protein Deficiency on Gene Expressions of Amino Acid Transport Systems at Peak Lactation in Procine Mammary Tissue

Abstract

The objectives of this study were to determine the mRNA expressions of amino acid transport system A; ATA2, system B[subscript 0,+]; ATB[subscript 0,+], system L; LAT2 and 4F2hc (heterodimer), and system y⁺ ; CAT2B in porcine mammary tissues and to determine the effects of dietary protein deficiency on growth performance, individual plasma amino acid concentrations in sows and their piglets, physical and histological changes of mammary glands, and the expression level of amino acid transporter genes in mammary tissues at peak lactation (d 18 of lactation). Eleven multiparous crossbred sows were allocated into 2 groups; 5 sows for deficient protein diet group and 6 sows for normal protein diet group. The experimental period started from farrowing (d 0) until weaned day (d 28). Sows were fed 4 kg per day. Two experimental diets differed only in the crude protein (CP) levels; normal protein diet contained 18.2% CP and deficient protein diet contained 8.2% CP. The sows fed with deficient protein diet had significant increase in the body weight losses throughout lactation period (P≤0.05), significant decrease in the body weight and average daily gain (ADG) of their piglets (P≤0.05), significant decrease in plasma amino acid concentrations notably for neutral and cationic amino acids in sows and proline in their piglets (P≤0.05), appearance of visible physical change of mammary glands, and histological change of mammary tissues. Moreover, sow mammary gland expressed mRNA of system A; ATA2, system B[subscript 0,+]; ATB[subscript 0,+], system L; LAT2 and 4F2hc (heterodimer), and system y⁺ ; CAT2B. In addition, the quantitative mRNA expressions of ATB[subscript 0,+] and LAT2 were down regulated significantly (P≤0.05) when compared to the sows fed with normal protein diet. In conclusion, the present study showed that dietary protein deficiency had the effects on increase in body weight losses of sows, impairment of mammary gland conformation during lactation, decrease in plasma amino acid concentrations, and down regulation of mRNA expression levels of ATB[subscript 0,+] and LAT2. These important factors lead to the decrease in growth performance of piglets.