SUMMARY
Influence of amino acid content of grower and finisher diets
on quality characteristics of pork from Duroc pigs selected for
lean growth efficiency.
Lonergan, S. M., E. Huff-Lonergan, L. I. Chiba, L. T.
Frobish, S. B. Jungst, and D. L. Kuhlers.
Indirect selection for lean growth efficiency has generated
a line of Duroc pigs (S) that is leaner than a randomly selected
control line (C). An investigation designed to determine the
effect of selection and dietary lysine levels during the grower
(20-50 kg) and finisher (50-112 kg) phases on fresh pork quality
was conducted. Barrows (n=32) and gilts (n=32) were pen fed
in pairs by treatment combination of select line (C or S),
grower diet (0.421 or 0.762 lysine:DE, g/MJ), and finisher
diet (0.421 or 0.656 lysine:DE, g/MJ). Carcass composition
data and quality attributes of longissimus dorsi (LD), semimembranosus
(SM), semitendinosus (ST) and bicep femoris (BF) were documented.
Carcasses from the S line had less backfat and higher percent
muscle than the C line carcasses. Neither diet nor selection
affected LD subjective color or marbling scores. Hunter L values
were higher in the S line BF and SM chops and Hunter a values
were higher in the S line ST, LD and BF chops when compared
to the C line chops. Selection for lean growth efficiency resulted
in lower pH in SM and LD muscles at 45 minutes, but not at
24 hours post mortem. LD chops from the S line pigs had lower
subjective firmness scores, higher percent moisture and protein
lost as purge, and tended to have higher Warner-Bratzler shear
values (WBS) than LD chops from the C line. BF chops from the
S line had greater drip loss than the C line. Napole yields
in SM, BF, and LD were not affected by line or diet. Within
the S line LD, the high lysine finisher diet group had higher
percent moisture lost as drip than the low lysine diet. The
high lysine grower diet resulted in higher WBS in LD than the
low lysine grower diet within the S line pigs.
The line of pigs selected for lean growth efficiency produced
poorer quality pork regardless of the dietary treatment. Line
by diet interactions indicate that pork quality traits may
be influenced by production practices in specific genetic lines
of pigs.
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