421
Effects of amino acid supplementation of reduced crude protein (RCP) diets formulated on a NE basis on the fatty acid composition of the LM and jowl subcutaneous fat
Samples (n = 108) of pork LM and jowl s.c. fat were used to test the effects of crystalline AA supplementation of reduced CP diets (formulated on a NE basis) on fatty acid composition. Pigs (n = 216) were blocked by BW, and pens (6 pigs/pen) within each block were assigned randomly to either corn-soybean meal diets (C) or 1 of 3 RCP diets supplemented with crystalline AA to meet SID AA ratios during each of the 5 feeding phases (23 to 41, 41 to 59, 59 to 82, 92 to 104, and 104 to 127 kg BW). Paylean (10 mg/kg) was included in all diets during the last 3-wk feeding phase. After slaughter and chilling, jowls and whole pork loins were collected from randomly selected carcasses (3 carcasses/pen). Jowl s.c. fat and LM samples were freeze-dried and analyzed for fatty acid composition. Proportions of palmitic acid (16:0) increased (linear, P=0.014) in jowl fat with decreasing CP, but percentages of stearic acid (18:0; P ≥ 0.265) and total SFA (P ≥ 0.117) in LM and jowl fat were similar among treatments. Percentages of all MUFA, especially oleic acid (18:1c9), increased with decreasing dietary CP in the LM (linear, P < 0.001) and jowl fat (linear, P ≤ 0.014). Total PUFA percentages were decreased (linear, P < 0.001) with decreasing dietary CP. More specifically, decreasing dietary CP reduced (linear, P ≤ 0.001) weight percentages of linoleic (18:2n6) and linolenic (18:3n3) acids in samples of LM (26.8 and 39.5%, respectively) and jowl fat (10.4 and 32.0%, respectively). The resulting IV for both the LM and jowl s.c. fat was decreased (linear, P < 0.001) as CP decreased in the diets. Results indicate that the fatty acid composition of pork lean and fat were altered by reducing dietary CP, and the pattern of increased MUFA composition, particularly in jowl s.c. fat, may imply enhanced de novo synthesis in pigs fed RCP diets supplemented with crystalline AA.
CP (added L-Lysine-HCL) of experimental diets for each feeding phase (% as fed) |
||||
Phase |
C |
RCP1 |
RCP2 |
RCP3 |
1 |
20.640 (0.350) |
18.825 (0.512) |
18.433 (0.549) |
16.678 (0.716) |
2 |
19.382 (0.334) |
16.852 (0.558) |
16.498 (0.590) |
14.697 (0.763) |
3 |
16.755 (0.285) |
14.683 (0.468) |
14.079 (0.523) |
12.482 (0.675) |
4 |
14.994 (0.253) |
13.051 (0.424) |
12.611 (0.464) |
11.109 (0.607) |
5 |
17.981 (0.300) |
16.596 (0.424) |
16.198 (0.462) |
14.599 (0.614) |
Keywords: Reduced Crude Protein, Net Energy, Fatty Acids