When regulations in the Netherlands required that ammonia emissions be cut by 50%, animal scientists at Wageningen University looked at phase-feeding sows a low-protein, low-phosphorus diet.

Gestating sows account for about 85% of phosphorus and nitrogen excretion, and lactating sows, 55%, says Martin Verstegen, an animal nutrition professor at Wageningen. Nitrogen is a bigger issue in his country, he adds.

Addressing the Minnesota Nutrition Conference on parity and phase feeding, Verstegen presented results of the study.

Sows were fed a control diet or phase-fed diet for four parities in the 185-sow study. The control group received a conventional gestation diet containing 13.5% protein and 4.7 grams of phosphorus per kg. The phase-fed group received a diet of 11.8% protein and 4.1 g/kg. phosphorus in the beginning of gestation. Sows of Parities 1, 2, 3 and 4 were fed the low-protein, low-phosphorus diet during the first 4, 8, 10 and 12 weeks of gestation, respectively. All lactating sows received the same commercial diet containing 16.5% protein and 6.0 g/kg. phosphorus.

Gestating sows were housed in cubicle, free-access stalls or in groups with an electronic sow-feeding system. Sows were locked in the cubicles during feeding.

Results of the study showed:

• Phase feeding does not affect culling rate.

• Phase feeding does not affect body weight or backfat thickness over four parities.

• Phase feeding did not affect numbers born live, still-borns, birth weight, number weaned, weaning weight and wean-to-estrus interval.

• In Parity 1 and 2 sows, phase-feeding increased the percentage that recycled after first breeding. In Parity 1, recycles increased from 9.1 to 17%. In Parity 2, it increased from 14 to 24%.

• In Parities 3 and 4, the percentage of sows that returned to estrus was similar between groups.

• Phase feeding reduced nitrogen and phosphorus excretion by 4.5%/sow/year.

• Replacement rate, which averages 45-48% in the Netherlands, was lower for phase-fed females.

The return-to-estrus issue in early parity females makes a low-protein diet unadvisable, notes Verstegen. Sows are still gaining weight at that age and need more protein. In Parity 3 and 4 sows, however, a low-protein diet during early gestation did not hurt performance. Keep in mind, the Dutch scientist says, that if only Parity 3 and older sows are phase-fed, the reduction in nitrogen and phosphorus excretion will be lower than the 4.5% found in their research.