Table 3.

Calcium and P balances for sows in late gestation fed diets containing different levels of Ca¹

	Ca level, % of the requirement2				P-value 3
Item	25	50	75	100	SEM	Lin.	Quad.
Feed intake, kg/d	3.05	3.09	3.05	3.08	0.13	0.834	1.000
Fecal excretion, kg DM/d	0.29	0.31	0.30	0.32	0.02	0.116	0.884
Urine excretion, kg/d	3.99	4.76	7.87	4.80	1.39	0.380	0.177
ATTD of DM, %	89.11	88.80	88.82	88.47	0.54	0.156	0.955
Ca balance
Ca intake, g/d	5.7	10.8	16.0	21.0	0.5	<0.001	0.935
Fecal Ca output, g/d	6.2	9.3	12.8	16.5	1.0	<0.001	0.571
Absorbed Ca, g/d	−0.4	1.6	3.3	4.7	0.8	<0.001	0.601
ATTD of Ca, %	−7.49	14.34	20.59	22.04	5.95	<0.001	0.039
Urine Ca output, g/d	0.1	0.1	0.1	0.1	0.04	0.300	0.581
Ca retention, g/d	−0.5	1.6	3.2	4.6	0.7	<0.001	0.592
Ca retention, % of intake	−9.33	13.53	19.83	21.45	5.87	<0.001	0.034
Ca retention, % of absorbed4	—	99.88	99.80	96.08	5.29	0.491	0.705
P balance
P intake, g/d	18.6	18.8	18.6	18.8	0.8	0.822	0.967
Fecal P output, g/d	11.5	13.1	13.2	14.4	0.9	<0.001	0.673
Absorbed P, g/d	7.0	5.7	5.3	4.3	0.6	<0.001	0.680
ATTD of P, %	39.02	31.26	29.72	23.97	3.01	<0.001	0.677
Urine P output, g/d	4.9	3.8	2.2	1.3	0.3	<0.001	0.770
P retention, g/d	2.3	2.0	3.2	3.3	0.5	0.031	0.704
P retention, % of intake	12.33	10.90	17.87	17.86	3.19	0.026	0.755
P retention, % of absorbed	28.39	29.49	50.83	69.03	7.93	<0.001	0.093

¹Each least squares mean represents 9 observations.

²The requirement estimate is based on the requirement for Ca by gestating sows that are in their third parity and in late gestation (NRC, 2012).

³Lin. = linear effect of Ca level; Quad. = quadratic effect of Ca level.

⁴Regardless of calculated value, Ca retention was assumed to be close to zero. Therefore, the first diet was excluded to test the linear and quadratic effects of dietary Ca.