TABLE 8.

Evaluation of essential oils (EO) and herbal betaine on broiler breast myopathy scores and breast myopathy percent incidence of broiler chickens exposed to cyclic heat stress at day 43^a.

	Thermoneutral	Heat stress	Heat stress + EO1	Heat stress + EO2
Woody Breast1
Average	0.74 ± 0.04a	0.21 ± 0.04b	0.32 ± 0.04b	0.27 ± 0.04b
0 Occurrence	47.50 ± 5.09b	98.00 ± 4.55a	94.00 ± 4.55a	98.00 ± 4.55a
1 Occurrence	52.50 ± 5.09a	2.00 ± 4.55b	6.00 ± 4.55b	2.00 ± 4.55b
2 Occurrence	—	—	—	—
White Striping2
Average	1.18 ± 0.05a	0.96 ± 0.04b	1.03 ± 0.04 ab	0.95 ± 0.04b
0 Occurrence	5.00 ± 4.12	16.00 ± 3.69	8.00 ± 3.69	14.00 ± 3.69
1 Occurrence	80.00 ± 5.03	82.00 ± 4.50	86.00 ± 4.50	84.00 ± 4.50
2 Occurrence	15.00 ± 3.11a	2.00 ± 2.78b	6.00 ± 2.78 ab	2.00 ± 2.78b

^a Data are expressed as the mean ± SE., ab Indicates significant differences between the treatments within the rows (p < 0.05). Cyclic heat stress started at day 10. EO1: essential oil of Lippia origanoides, thymol chemotype (45 ppm) and herbal betaine (150 ppm). Administration dose: 350 g/Ton food. EO2: essential oil of Lippia origanoides, phellandrene chemotype (45 ppm) and herbal betaine (150 ppm). Administration dose: 350 g/Ton food. For average myopathy scores, thermoneutral treatments only consisted of an n = 40. All remainders had an n = 50. For percent incidence, scores were broken out on a pen basis and consisted of an n = 24. 1Breast fillets were considered a score of 0, 1, or 2 for woody breast if the fillet was flexible throughout, stiff in cranial region, or stiff in the cranial and caudal regions, respectively. 2Breast fillets were considered a score of 0, 1, or 2 for white striping if the fillet displayed no visible stripes, stripes less than 1 mm, or stripes larger than 1 mm, respectively.