Table 4.

Least square means for growth performance of nursery pigs fed increasing standardized total tract digestible (STTD) P from 11- to 23-kg body weight (BW), Exp. 1¹

	STTD P2, %
	0.26	0.30	0.33	0.38	0.43	0.48	0.53		Probability, P
Item2  % of NRC3	80	90	100	115	130	145	160	SEM	Linear	Quadratic
Days 0 to 21
ADG, g	513	510	533	532	566	563	573	11.6	<0.001	0.718
ADFI, g	782	764	776	780	818	824	828	19.4	0.004	0.603
G:F, g/kg	656	667	687	682	692	684	693	7.4	<0.001	0.066
STTD P, g/d	2.03	2.29	2.56	2.97	3.52	3.95	4.39	0.082	0.001	0.418
STTD P, g/kg gain	3.85	4.41	4.89	5.53	6.31	7.19	7.68	0.067	0.001	0.579
BW, kg
d 0	11.4	11.4	11.4	11.4	11.4	11.4	11.4	0.29	0.935	0.933
d 21	22.2	22.2	22.6	22.7	23.3	23.3	23.5	0.92	0.001	0.759

¹A total of 1,080 barrows and gilts (PIC; 337 × Camborough, initial pen average BW of 11.4 ± 0.29 kg) were used in a 21-d growth trial with 23 to 27 pigs per pen and 6 pens per treatment. Two groups of pigs were weaned at approximately 21 d of age, fed a common phase 1 and phase 2 diet for 21 or 24 d postweaning, then fed experimental diets. Low (0.26% STTD P) and high (0.53% STTD P) diets were blended at the farm by a robotic feeding system to create the 0.30%, 0.33%, 0.38%, 0.43%, and 0.48% STTD P dietary treatments.

²STTD P = Standardized total tract digestible phosphorus.

³ADG = average daily gain; ADFI = average daily feed intake; G:F = gain-to-feed ratio; BW = body weight.

⁴The NRC requirement estimate for nursery pigs from 11 to 25 kg, expressed as a percentage of the diet, is 0.33% STTD P. Therefore, treatment concentrations represented 80%, 90%, 100%, 115%, 130%, 145%, and 160% of the NRC (2012) requirement.