Table 7.

Carcass characteristics of pigs fed diets with either antibiotics or increasing levels of BA^1,2

		BA, %				P value
Item	PC3	0.00	0.50	1.00	SEM	PC vs. 0.00	Linear4	Quadratic5
Shrink weight, kg	105.3	93.7	101.3	97.3	5.4	0.004	0.362	0.093
Hot carcass weight, kg	80.4	70.9	75.7	73.8	2.1	0.002	0.331	0.209
Dressing, %	76.5	75.9	74.5	75.7	4.0	0.541	0.827	0.133
Backfat thickness, mm
First rib backfat	22.4	17.3	18.8	18.6	1.9	0.001	0.372	0.505
Last rib backfat	19.1	16.9	17.3	16.7	3.2	0.134	0.867	0.717
Last lumbar vertebra backfat	15.7	13.8	12.3	13.4	0.9	0.089	0.736	0.195
Loin eye area, cm2	43.41	35.34	45.26	38.23	3.34	0.088	0.545	0.045
Loin color6	3.00	3.09	2.90	2.40	0.21	0.746	0.020	0.542
Marbling score7	2.01	2.01	1.52	1.22	0.28	1.000	0.028	0.752
Lean %8	54.0	54.9	55.6	55.0	1.74	0.414	0.861	0.479
Drip loss, %	2.45	2.70	3.51	3.64	0.60	0.712	0.191	0.588

¹The experimental unit was a pen (1 pig representing the median BW was selected in each pen), and each least squares mean represents 11 observations.

²Pigs were moved to Texas Tech Meat Lab and euthanized after overnight fasting.

³PC = a basal diet with antibiotics (chlortetracycline at 100 mg/kg [450 mg/kg of Aureomycin 100] during phases 1 to 3, and tylosin at 44 mg/kg [200 mg/kg of Tylan 100] during phases 4 to 6).

⁴Linear = linear effect of increasing levels of BA.

⁵Quadratic = quadratic effect of increasing levels of BA.

⁶NPPC Scoring System (1: pale, pinkish gray; 5: dark, purplish red).

⁷NPPC Scoring System (1: devoid to practically devoid; 5: moderately abundant or greater).

⁸Lean, % = fat-free lean weight (kg)/hot carcass weight (kg) × 100; fat-free lean weight (kg) was determined using the average of 2 equations: 1) equation 1, kg = 8.59 + (1.03 × hot carcass weight, kg) − (0.863 × last rib backfat, mm) + (0.466 × loin eye area, cm²); 2) equation 2, kg = 23.6 + (1.11 × hot carcass weight, kg) − (0.841 × last rib backfat, mm).