|Abstract or Summary
- Tests using paired pens of barrows were conducted during a 13 month
period to determine the influence of protein level of the ration on
production traits of market barrows. One member of each pair of six to
ten full- and half-sib pairs was randomly allotted to each pen group;
thus, pen groups designated as controls had sibs or half sibs in a
counterpart treatment pen group. From 27 to 57 kg, designated as phase
1, all pen groups were fed a 14% crude protein ration. One pen group of
each set of paired pens was switched to an 11% protein ration at approximately 57 kg mean weight while its contemporary comparison group remained
on the 14% protein ration. The two levels of dietary protein resulted
from manipulation of the corn-soybean oil meal ratio in the ration.
Ration energy contents were similar. From 57 to 91 kg (phase 2), the
paired pen groups were maintained on their respective diets. Carcass
data were obtained following slaughter at approximately 91 kg live weight,
Similar average daily gains (ADG), feed efficiencies (F/G), and
daily feed intakes (DFI) were observed for the paired groups during
phase 1 in which both groups were fed the 14% protein ration. Phase 2
gains of pigs fed the control ration (14% protein) were significantly affected by ambient temperature whereas ambient temperature did not
significantly affect gains of pigs fed the 11% ration.
Means, from the 11 groups per ration were 3.62 and 4.08 for F/G
and 2.96 and 2.92 kg for DFI. Means for ADG, based on individual animal
gains, were .83 ± .13 and .72 ± .11 kg for 14% and 11% protein rations
Dietary protein level did not significantly affect weights of any
of the primal cuts of the carcass, backfat thickness, dressing percent
or carcass length. Although the means for loin eye area were not significantly different, loin eye area tended to be smaller for pigs fed the
11% protein ration.
Estimates of heritability for growth on the two rations lack sufficient precision to be conclusive and were more variable on the 11% ration
than on the 14% ration. For both rations, correlations among ADG, LEA
and backfat thickness were not significantly different from zero.
Economic analysis based on feed and overhead costs tends to favor
feeding the 14% protein ration in months of mild and warm temperatures
and the 11% protein ration in the coldest months.