Supplementation of mid-gestation swine grazing alfalfa

For four years (1991-1994), gestating gilts rotationally grazing alfalfa were compared to gilts in a drylot fed 1,800 g/d of a corn-soy diet (control). The dietary supplementation treatments for the grazing gilts were 1,260 g, 720 g, and 180 g of ground corn (70, 40, and 10% of the gilts' energy needs) plus 45 g of monosodium phosphate and 9 g of salt (sodium chloride) per day. All gilts were fed individually. In 1991 and 1992, the gilts were fed daily. In 1993 and 1994, the gilts were fed their weekly feed ration in three equal feedings on Monday, Wednesday, and Friday. Alfalfa paddocks were grazed for one week with a stocking rate of 62 gilts/ha/wk. All gilts had rings in their noses to minimize rooting. For the 42-d mid-gestation trial, the weight gain of the control gilts did not differ from the gain of the grazing gilts daily fed 720 g corn (40%) (P < .05). The interval feeding reduced gains compared to the daily feeding. Gilts daily fed 1,260 g corn/d (70%) gained more than the other grazing treatments (P < .05). The gilts daily fed 180 g corn/d (10%) gained less than all other treatments (P < .05) and had the greatest backfat loss (P < .05) for the 42-d trial. No major trends were noted in number of pigs born per litter or pig birth weight. After one week of grazing, alfalfa height decreased 14.7 cm and DM content of the remaining alfalfa increased 9%. Each grazing season, the alfalfa stand decreased 3.8 plants/m(2). Daily alfalfa intakes per gilt were calculated at 11.5 kg (3.2 kg DM) for 1991 and 1992, and increased to 16.3 kg (4.2 kg DM) for 1993 and 1994. These are composite intakes because all grazing gilts were commingled. Mid-gestation gilts rotationally grazing alfalfa need 720 g of corn per day plus phosphorus and salt to match weight gains of gestating gilts in a drylot fed 1,800 g/d of a corn-soy diet. Daily feeding, rather than interval feeding, resulted in greater weight gains and lower alfalfa intakes. The practice of grazing gestating sows has the advantages of no manure to haul, reduced purchased feed inputs, and inclusion of a soil-building crop like alfalfa in the crop rotation.