Effect of increasing dietary lysine level on transcriptomic profile in pig longissimus dorsi muscle following a period with dietary protein restriction after weaning

Thus, in the present study the objective was to determine whether increasing dietary Lys levels after a period of dietary protein restriction would lead to distinct muscle transcriptomic profiles in weaner pigs. It was hypothesized that increased dietary Lys levels would lead to increased expression and enrichment of, respectively, genes and pathways regulating muscle protein synthesis. Overall design: Sixty-seven Swiss Large White piglets from 20 litters of one farrowing series were used in the experiment, where 33 were females and 34 were male castrates. Of the 67 piglets 60 piglets were randomly pre-allocated on the day of weaning to one of 4 dietary treatments implemented from week five to eight (W5-8) after weaning. Remaining seven piglets were not further used in the present study. From weaning and until four weeks after weaning (W1-4), pigs were divided into two groups, a control (STD, N = 18) receiving a diet with standard CP content and a group receiving a diet with a low protein CP content (LP, N = 42). The LP diet was 81/79% (total/digestible) of the CP in the STD diet to force a reduced protein intake during the first four weeks after weaning, while maintaining digestible AA at requirement level in both diets (Table 1). Pigs had ad libitum access to feed. In the period W5-8 the four dietary treatments were a control (STD-STD, N = 12), standard (LP-STD, N = 12), STD + 10% Lys (LP-STD10+, N = 12) and STD + 20% Lys (LP-STD20+, N = 12), where STD-STD and LP-STD treatments received the standard diet, and Lys10 and Lys20, respectively, STD with 10% and 20% greater digestible Lys content and remaining digestible essential amino acids (EAA) above requirement level (Table 1). Pigs in the STD-STD group only included pigs from the STD group from W1-4, whereas the LP-STD, LP-STD10+ and LP-STD20+ groups only included pigs from the LP group of W1-4. Tissue samples from the longissimus dorsi (LD) muscle were collected, snap frozen in liquid nitrogen and subsequently stored in -80 °C until further analysis.