Abstract
Effects of Hydrolyzed Feather Meal as a Source of Extra Dietary
Nitrogen on Growth Performance and Carcass Traits of Finisher
Pigs.
Lee I. Chiba, Henry W. Ivey, Keith A. Cummins, and Brian
E. Gamble
Background Information & Objectives
As the dietary protein content increases, a greater proportion
of total energy is provided by protein rather than non-protein
energy sources, thus reducing energy available for pigs. In addition,
a possible increase in the energy expenditures because of increased
mass of internal organs and(or) whole-body protein turnover may
further reduce energy status of pigs fed diets high in protein.
Furthermore, the suppressing effect of high-protein diets on
the rate of lipogenesis has been reported in swine. All these
factors may imply that leanness of pigs can be improved by increasing
the nitrogen (N) component of the diet above the requirement,
even though it is costly. To improve the carcass quality, however,
providing adequate amounts of extra protein might be more important
than the quality of protein sources, indicating that inexpensive
protein supplements can be used for this purpose. The lysine
requirement for the population of crossbred pigs was estimated
in the first experiment. The second experiment was designed to
evaluate the value of hydrolyzed feather meal (FM) as a source
of extra dietary N to enhance leanness of finisher pigs.
Experimental Procedures, Results & Conclusions
In Experiment 1, 15 pens containing crossbred
gilts and castrated males (six pigs per pen) averaging 53.7 +/-
1.9 kg were randomly assigned to five soybean meal (SBM) diets
containing 4.8 to 9.8 lysine/kg in each of two trials. Pigs responded
to the increase in lysine up to 7.3 g/kg, and there was little
or no improvement in the growth performance or carcass traits
with further increases. The results of the broken-line analysis
indicated that weight gain was optimized at 6.9 g lysine/kg,
whereas corresponding values were 7.6, 7.2 and 7.3 g lysine/kg
for longissimus muscle area, specific gravity and lean accretion,
respectively. Therefore, the lysine concentration of 7.3 g/kg
was chosen as the basis for the second experiment. In Experiment
2, 21 gilts and 21 castrated males averaging 57.1 +/- 4.5 kg
were randomly assigned within sex to seven diets. Two SBM diets
were formulated to contain 7.3 g lysine and 150 g crude protein
(CP)/kg (Med) or 8.5 g lysine and 167 g CP/kg (High). An additional
SBM diet containing 6.0 g lysine and 132 g CP/kg (Low) was also
included as part of dietary treatments. Two FM diets were formulated
to be iso-lysinic (Iso-Lys) to the Med and High SBM diets. Two
additional FM diets were formulated to be iso-nitrogenous (Iso-N)
to the Med and High SBM diets. Corn and SBM provided 6.0 g lysine
or 132 g CP/kg to the Iso-Lys and Iso-N diets, respectively,
and additional lysine and CP were supplied by FM. Corn starch
and(or) dried fat product were used to achieve similar energy
content of all diets (3.45 Mcal DE/kg). A fundamental assumption
of the experimental design was that providing extra lysine and(or)
CP (i.e., above the optimum level) would have no effect on the
rate of protein accretion, but it would reduce the rate of fat
accretion, thus improving leanness of pigs. Pigs were housed
and fed individually, and they were slaughtered at an average
weight of 108.5 +/- 5.5 kg. As expected, weight gain of pigs
generally decreased (P < .05) as dietary
lysine and CP levels increased from medium to high. Pigs fed
the High diets had lower carcass backfat (P < .05), larger longissimus
muscle area (P = .08) and higher specific gravity (P < .05) and
proportion of lean (P < .05) than those fed the Med diets. The
improved carcass quality in response to the increased dietary
lysine and CP levels from medium to high was independent of the
source (SBM or FM) or method of incorporating FM in the diets
(Iso-Lys or Iso-N). Pigs fed the Med and High diets had heavier
liver (P < .05) and kidneys (P < .01) than those fed the Low
diet. On the average, pigs fed diets containing FM tended to
have heavier liver (P = .10) and kidneys (P = .07) than those
fed the Med and High SBM diets. The results indicate that providing extra dietary N may be a viable method
to enhance leanness of finisher pigs, even though a possible increase in urinary
N excretion is a potential environmental concern. In addition, the low quality
protein sources for pigs such as FM may be used effectively as a source of
extra dietary N to enhance leanness of finisher pigs.
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