SUMMARY
Growth performance and carcass traits of pigs subjected to
marginal dietary restrictions during the grower phase.
Chiba, L. I., H. W. Ivey, K. A. Cummins, and B. E. Gamble.
Sixty-four, individually-housed pigs
were used to investigate the effect of amino acid content
of finisher diets on growth performance of pigs subjected
to marginal dietary amino acid restrictions (80% of the 1988
NRC lysine recommendation) during the grower phase. In each
of the two trials, low- and high-amino acid grower diets
(.421 and .765 g lysine/MJ DE, respectively) and four finisher
diets (.421, .516, .612, and .707 g lysine/MJ DE) were randomly
assigned within sex to 16 gilts and 16 castrated males weighing
23.0 ± 2.0 kg in a 2 x 4 factorial arrangement
of treatments. The average weight of pigs after a completion
of diet change was 50.4 ± 2.1 kg. All pigs were slaughtered
at an average weight of 105.2 ± 4.1 kg. Ultrasound backfat
thickness was measured at the time of diet change and before
slaughter. Pigs were allowed ad libitum access to feed and
water.
During the grower phase, pigs fed the
high-amino acid diet grew faster (P < .001) and more efficiently (P < .001), and
had less ultrasound backfat (P < .001) than those fed the low-amino
acid diet. The grower diet had no effect on weight gain during
the finisher phase. Consequently, pigs fed the high-amino acid
grower diet had better overall weight gain (P < .01) than those
fed the low-amino acid diet. The rate of lean accretion was,
however, similar between the two groups of pigs. Furthermore,
pigs fed the low-amino acid grower diet seemed to have better
carcass quality as indicated by less ultrasound backfat (P < .01)
and larger carcass longissimus muscle area (P < .05). Average
and 10th rib carcass backfat decreased linearly (P < .05)
and lean accretion rate improved linearly (P < .05) as the
amino acid content of finisher diets increased, but there was
no grower x finisher diet interaction in these and other response
criteria.
Although no evidence of compensatory weight gain was observed,
it is possible that the compensatory lean tissue growth may
have occurred in pigs subjected to early amino acid restrictions
at the expense of fatty tissue growth.
Built: 5/24/01 |
