Amino Acid Case Study - (Growth In Pigs)
SUMMARY
Effect of selection for lean growth efficiency on growth performance, nutrient digestibility, blood profile, and carcass and meat quality.
Fabian, J., L. I. Chiba, D. L. Kuhlers, L. T. Frobish, K. Nadarajah, W. H. McElhenney, J. Lin, and B. L. Anderson.
Eight select line (SL) and eight control line (CL) Duroc pigs were used to determine the effect of six generations of selection for lean growth efficiency on growth performance, nutrient digestibility, serum profiles, and carcass and meat quality. At 20 kg, pigs were placed in pens individually. Three corn-soybean meal diets [grower (G), finisher 1 (F1), and finisher 2 (F2)] were formulated to meet the NRC nutrient requirements. Pigs were allowed ad libitum access to feed and water. At the end of the G and F2 phases pigs were fed diets containing 0.25 % Cr2O3 to determine apparent digestibility of CP and DM. Three blood samples were taken from each pig at 20, 50 and 105 kg for glucose, triglyceride (TG), and urea N (BUN) analyses. Pigs were subjected to ultrasound backfat (UBF) measurement at 50 kg and at the end. At 105 kg, each pig was slaughtered.
The SL pigs grew faster and more efficiently (P < 0.05) during G (ADG: 812 vs 733 g/day; G/F: 429 vs 402 g/kg) and the F1 phases (ADG: 931 vs 804 g/day; G/F: 330 vs 296 g/kg), but there was no effect of line during the F2 phase and overall. The SL pigs had lower UBF (P < 0.05) at 50 (7.15 vs 9.04 mm) and 105 kg (17.59 vs 22.89 mm), and had higher initial serum TG (5.49 vs 3.23 mg/L; P < 0.001) and lower initial BUN (0.95 vs 1.17 mg/L; P < 0.05) than the CL pigs. The SL pigs had heavier heart (342 vs 298 g; P < 0.05), liver (1459 vs 1359 g; P = 0.08), and kidneys (298 vs 249 g; P < 0.01). Lower 10th rib backfat (21.66 vs 31.62 mm; P < 0.01) and larger longissimus muscle area (32.84 vs 30.02 cm2; P = 0.1) were reflected in higher estimate daily lean gain (279 vs 238 g/day; P < 0.01) in the SL pigs. The SL pigs had lower meat color (2.02 vs 2.29; P < 0.05), firmness (2.45 vs 3.23; P < 0.01), and marbling (2.82 vs 3.55; P < 0.1) scores.
These results indicate that selection for lean growth efficiency has changed the growth rate and body composition of the SL pigs.
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