Table 2.

Carcass and cuts yield (%) of broiler chickens fed with different vitamin A supplementations at d 42.

		Vitamin A supplementation (IU/kg)
	Supplementation1	0	6,000	16,000	26,000	36,000	46,000	Average2	SEM	P (Anova)	P (Test F)	P (Regression)
Carcass	T – 21	72.918	73.388	73.388	73.906	72.771	72.344	73.1191	1.39589	0.3288	0.3337	0.0829
	T – 42	72.046	72.862	72.795	72.900	73.193	73.050	72.8076	1.23125	0.5803		0.4376
Wing	T – 21	5.23	5.55	5.35	5.67	5.60	5.70	5.51666	0.34208	0.0182	0.4575	0.0088 (L)
	T – 42	5.35	5.64	5.49	5.49	5.54	5.38	5.48166	0.46097	0.0006		0.0392 (Q)
Legs	T – 21	39.654	39.556	40.050	39.455	39.762	39.308	39.6308	1.1452	0.8593	0.0286	0.4954
	T – 42	39.917	40.257	39.605	40.366	40.429	40.279	40.1421	1.07259	0.7092		0.8619
Breast	T – 21	27.265	28.063	28.012	28.238	27.570	27.696	27.8073	0.99573	0.4022	0.0109	0.1108
	T – 42	26.754	27.399	27.561	27.013	27.450	27.061	27.2063	1.14569	0.7570		0.3640
Tenderloins	T – 21	5.23	5.544	5.346	5.665	5.596	5.527	5.48466	0.40144	0.2764	0.6541	0.3049
	T – 42	5.347	5.640	5.489	5.490	5.317	5.381	5.444	0.39883	0.6403		0.5182

L: linear; Q: Quadratic.

Carcass: relative weight (%); Wing: relative weight (%); Legs: relative weight (%) to legs with a portion of the back; Breast: relative weight (%); Tenderloins: relative weight (%).

Wing (T-21 d): 0.00000841 vit A + 9.30975; R²: 0.13; Wing (T-42d): 0.0000000000660904 vit A² - 0.00004650 vit A + 10.10156; R²: 0.28; Vit. A for minimum response: 35,179 UI /kg; Minimum response: 9.29.

¹T-21d: birds supplemented with treatments in the period from 4 to 21 days of age; T-42 d: birds supplemented with treatments in the period from 4 to 42 days of age;

²Test F (P ≤ 0.05) for comparing the averages of vitamin A supplementation times.