Table 2.

Productive performance of broilers added with increasing levels of humic substances in the feed, probability level, and type of effect associated with humic substances.

		Level of Humic Substances, %						Effect of Humic Substances
Response Variables a	Positive Control	0.00	0.15	0.30	0.45	SEM b	p-Value	Lin	Quad	Cub
Body weight, g
Day 1	44.5	44.7	44.5	44.3	44.0	0.259	0.33	0.24	0.94	0.92
Day 14	418.4	432.9	431.6	426.3	421.6	6.122	0.40	0.19	0.80	0.88
Day 28	1323	1327	1313	1295	1314	15.504	0.65	0.44	0.31	0.55
Day 42	2600	2497	2555	2491	2510	25.682	0.29	0.74	0.28	0.14
Productive performance from 1–14 days of age
Feed intake, g/d	40.5	41.9	41.6	40.8	40.1	0.573	0.17	0.05	0.78	0.78
Weigh gain, g/d	26.7	27.7	27.6	27.3	27.0	0.436	0.42	0.22	0.80	0.88
Feed conversion ratio	1.52	1.51	1.50	1.50	1.49	0.024	0.93	0.48	0.94	0.94
Productive performance from 15–28 days of age
Feed intake, g/d	122.1	118.4	119.0	118.8	119.1	1.658	0.53	0.80	0.95	0.86
Weigh gain, g/d	64.6	63.8	63.0	62.1	63.8	1.062	0.51	0.81	0.23	0.57
Feed conversion ratio	1.89	1.86	1.89	1.92	1.87	0.026	0.58	0.65	0.17	0.60
Productive performance from 29–42 days of age
Feed intake, g/d	218.5 c	215.8 c	204.5 d	199.3 d	203.8 d	3.097	0.05	0.05	0.01	0.44
Weigh gain, g/d	91.2	83.6	88.7	85.4	85.4	1.582	0.12	0.47	0.10	0.23
Feed conversion ratio	2.40 c	2.58 d	2.31 e	2.34 c,d	2.39 c,d	0.045	0.01	0.05	0.01	0.10
Productive performance from 1–42 days of age
Feed intake, g/d	127.0 c	125.4 c,d	121.7 d,e	119.6 e	121.0 e	1.458	0.01	0.05	0.10	0.79
Weigh gain, g/d	60.8	58.4	59.8	58.3	58.7	0.577	0.29	0.72	0.28	0.14
Feed conversion ratio	2.09 c,d	2.15 c	2.04 d	2.05 d	2.06 d	0.019	0.01	0.05	0.01	0.05
Overall mortality, %	7.08 c,d	13.33 c	5.42 d	1.67 d	3.75 d	2.370	0.05	0.05	0.01	0.86

^a Data are means of eight replications (pens) per treatment. ^b Standard error of the mean. ^c–e Values within rows with different superscripts differ significantly, p ˂ 0.05.