The effects of porcine somatotropin and dietary lysine on growth performance and carcass characteristics of finishing swine.
Seventy-two finishing pigs (initial weight = 57.6 kg) were utilized to determine the effects of porcine somatotropin (pST) and dietary lysine level on growth performance and carcass characteristics. Pigs were injected daily with 4 mg pST in the extensor muscle of the neck and fed either a pelleted corn-sesame meal diet (.6% lysine, 17.8% CP) or diets containing .8, 1.0, 1.2 or 1.4% lysine provided by additions of L-lysine.HCl. All diets were formulated to contain at least twice the required amounts of other amino acids. Control pigs received a placebo injection and the .6%-lysine diet. Increasing levels of dietary lysine resulted in increased ADG and improved feed conversion (quadratic, P less than .01) for pST-treated pigs. The calculated daily lysine intake was 16.6, 13.6, 19.6, 25.1, 29.6 and 33.6 g for the control and pST-treated pigs fed .6, .8, 1.0, 1.2 and 1.4% lysine, respectively, over the entire experiment. Breakpoint analysis indicated that cumulative ADG and feed conversion were optimized at 1.19 and 1.22% lysine, respectively. Longissimus muscle area and trimmed ham and loin weights increased as dietary lysine was increased among pST-treated pigs (quadratic, P less than .01). Breakpoint analysis indicated that 1.11% lysine maximized longissimus muscle area, whereas trimmed ham and loin weights were maximized at .91 and .98% lysine, respectively. Adjusted backfat thickness was not affected by dietary lysine, but pST-treated pigs had less backfat (P less than .05) than control pigs did. Percentage moisture of the longissimus muscle increased (linear, P less than .05), as did percentage CP (quadratic, P less than .05), whereas fat content decreased (linear, P less than .05) as lysine level increased. Similar trends in composition were observed for muscles of the ham (semimembranosus, semitendinosus, and biceps femoris). Shear-force values from the longissimus and semimembranosus were lowest for control pigs, but they increased as dietary lysine level increased among pST-treated pigs. Sensory panel evaluations indicated that juiciness and tenderness decreased (linear, P less than .05) as dietary lysine level increased. Plasma urea concentrations decreased linearly (P less than .01) on d 28 as lysine level increased, whereas plasma lysine and insulin were increased (quadratic, P less than .01). Plasma glucose and free fatty acid concentrations on d 28 tended to increase (quadratic, P less than .10) with increasing dietary lysine level.(ABSTRACT TRUNCATED AT 400 WORDS)
Goodband
R D
RD
Dept. of Anim. Sci. and Ind., Kansas State University, Manhattan 66506.
Nelssen
J L
JL
Hines
R H
RH
Kropf
D H
DH
Thaler
R C
RC
Schricker
B R
BR
Fitzner
G E
GE
Lewis
A J
AJ
D000273:Adipose Tissue / Q000254:growth & development; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001823:Body Composition; D004032:Diet; D004435:Eating; D005260:Female; D013006:Growth Hormone / Q000097:blood / Q000494:pharmacology*; D008239:Lysine / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D008297:Male; D024510:Muscle Development; D009929:Organ Size; D013552:Swine / Q000254:growth & development*; D014508:Urea / Q000097:blood; D015430:Weight Gain
D000596:Amino Acids; D014508:Urea; D013006:Growth Hormone; D008239:Lysine