DIETARY CALCIUM-PHOSPHORUS LEVELS FOR GROWTH AND REPRODUCTION IN GILTS AND SOWS
The effect of feeding barley-wheat-soya finisher, gestation and lactation diets containing (A) 1979 National Research Council (NRC) recommended calcium-phosphorus (Ca-P) levels or (B) 150% of NRC levels from 65 kg body weight (Bwt) on growth and reproduction was studied in two experiments using Lacombe (L) and Yorkshire (Y) gilts. The number of gilts used were 299 (148 L + 151 Y) and 107 (53 Y + 54 Y) in exp. 1 and 216 (106 L + 110 Y) and 101 (49 L + 52 Y) in exp. 2 during finishing and gestation-lactation periods, respectively. The reproductive performance during second parity was measured only in exp. 2 using 85 (36 L + 49 Y) primiparous sows. All pigs were housed in confinement except during breeding and gestation, when they were housed in outside dirt-lot pens. Average daily gain, feed intake, and feed conversion were similar for gilts fed finisher diets A or B in both experiments. In exp. 1, both L and Y gilts fed gestation diet B had more (P < 0.05) total (9.5 ± 0.3 vs. 8.6 ± 0.3) and live pigs (9.2 ± 0.3 vs. 8.2 ± 0.3) born and weaned (7.7 ± 0.3 vs 6.9 ± 0.2) with lower piglet weight gains at 3 wk (3.5 ± 0.1 vs. 3.9 ± 0.1 kg) and 5 wk (6.9 ± 0.2 vs. 7.5 ± 0.2 kg) when compared to gestation diet A group. These differences were not significant in exp. 2. Higher dietary Ca-P levels elevated the serum P during both gestation (7.3 ± 0.1 vs. 7.0 ± 0.1 mg/dL) and lactation (6.2 ± 0.1 vs. 5.9 ± 0.1 mg/dL) periods in exp. 1 but not in exp. 2. The changes in body weight during gestation and lactation, piglet birth weights, and weaning to estrus interval were similar for both treatment groups. These results indicated that the 1979 NRC recommended dietary Ca-P levels may be adequate to support the maximum growth and reproduction in gilts during finishing and lactation but are too low for gestation. Key words: Calcium, phosphorus, gilts, sows, growth, reproduction