Effect of different dietary protein sources on skeletal muscle growth characteristics and stem cell activity of young piglets
Type of DegreeMaster's Thesis
Restriction TypeAuburn University Users
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Neonatal period of pigs is distinguished by a rapid growth as a result of a high protein synthesis, influenced by amino acid availability. Nutrients necessary for immune system function are redirected from growth and negatively impact growth performance. To evaluate how different protein sources supplemented to young piglets affect muscle fiber size, fiber number, and satellite cell proliferative activity, a randomized complete block design experiment utilizing a 4 × 2 factorial treatment arrangement was conducted. A total of 123 piglets (66 males and 57 females) from 5 different farrowing groups assigned to 1 of 4 treatments consisting of a control group and three dietary treatments were utilized. The 3 liquid diets were: whey only (MLK), MLK + spray dried plasma (SDP), and MLK + soy protein concentrate (SPC). After birth, piglets were left with the sow for a minimum of 36 h to ensure adequate colostrum intake. Then, piglets assigned to one of the three dietary treatments were transferred to Rescue Decks® and reared until tissue collection on experimental d 6, 14, 19, and 25. The control group of piglets was left in the farrowing crate and nursed the sow until sampling (SOW). On sampling days, pigs were injected with 5’-bromo-2’-deoxyuridine (BrdU) to label proliferating cells. One-hour post-injection pigs were euthanized by CO2 asphyxiation and tissue samples from longissimus dorsi (LD) and biceps femoris (BF) were collected and stored until further immunofluorescence analysis. Depending on the marker combinations, cell populations were classified as the following: mitotically-inactive myogenic SC (MyoD+; Pax7+; MyoD+:Pax7+), mitotically-active non-myogenic cells (BrdU+), or mitotically-active myogenic SC (MyoD+:BrdU+; Pax7+:BrdU+; MyoD+:Pax7:BrdU+). Data were analyzed as a 2-way ANOVA using SAS V9.4 PROC GLIMMIX, and treatment means were separated using PDIFF at P ≤ 0.05. Tendencies were declared when 0.0501 < P ≤ 0.10. At d 25, male SPC-fed piglets tended to have a higher BWG than all other treatments (P = 0.0699) and d 14 and 19 BWG was lower in MLK-fed piglets (P ≤ 0.0810). On d 14 and 19, MLK-fed piglets had a greater muscle fiber density and lower CSA (P ≤ 0.0439), while d 6 and 25 fibers where unaffected by dietary treatment (P ≥ 0.4649). Muscle SC mitotic activity was not affected by dietary treatment and sex interaction on d 6 and 19 (P ≥ 0.1462). Day 14 Pax7+ SC tended to be more abundant on female piglets from MLK and SPC treatments and males from SOW treatment (P ≤ 0.0919). Also, d 14 MyoD+ SC were more abundant on female piglets from SOW (P = 0.0584). On d 25, females from SOW and males from SPC had the greatest amount of LD MyoD+ and Pax7+ SC, respectively (P ≤ 0.0495). Finally, d 25 MyoD+ SC of females form SPC treatment were more abundant than piglets from SDP and MLK treatments (P = 0.0437). These data indicates that dietary protein source may impact mitotically active cells and muscle fiber number and size of neonatal piglets.