The effect of various diet nutrient densities and electrolyte balances on sow and litter performance during two seasons of the year.

An experiment involving 289 farrowings during a 2-yr period was conducted to determine the effect of increasing dietary nutrient concentration, electrolyte balance, and season of the year on the lactational performance of sows. Experimental diets were corn-soybean meal-based. The basal diet was formulated to meet or exceed the NRC requirements and the high-nutrient diet was formulated to contain approximately 20% higher levels of the nutrients than the basal diet, with or without adjustment of the electrolyte balance (Na+K-Cl) to 250 mEq/kg. Experimental diets were fed in both the warm (May through October) and cool (November through April) seasons of the year, resulting in a 2 x 2 x 2 factorial arrangement of treatments. There were no season x treatment interactions for any of the indices measured. During the first 21 d of lactation, sows farrowing in the cool season consumed more feed (P < .001) and produced heavier (P < .001) pig weights and litter weight gains than sows farrowing in the warm season. Increasing nutrient density from 100 to 120% of the NRC requirements resulted in decreased (P < .05) daily feed consumption, but it increased (P < .001) daily CP and GE intake, 21-d pig weights, and litter weight gains. Adjusting the dietary electrolyte balance from normal (130 mEq/kg) to 250 mEq/kg tended to increase (P < .07) 21-d pig weights, but it had no effect on other indices measured. These data indicate that under the environmental and management conditions of this experiment, the nutrient requirements of the lactating sow are higher than the current NRC standards.