Production and use of renewable fuels has increased dramatically in the United States, according to S.J. Schieck of the University of Minnesota in St Paul and co-authors there and at USDA-ARS Ames, Southern Research and Outreach Center in Waseca and West Central Research and Outreach Center in Morris.

In their paper published in the Journal of Animal Science, they explain that although the production and use of renewable fuels has many benefits, there are challenges associated with utilisation of the co-products. Expansion of biodiesel production has caused an influx of crude glycerol that is not needed for further purification in food, pharmaceutical and cosmetic industries.

They conducted an experiment to evaluate the effect of dietary crude glycerol in lactating sow diets on sow and litter performance under heat stress conditions. Mixed parity (range = 0 to 13) sows (n = 345; 253 ± 24kg bodyweight) were assigned randomly within gestation housing location and parity to 1 of 4 dietary treatments. Treatments consisted of a corn- and soybean-based control diet (CON) and three, six or nine per cent glycerol added at the expense of corn and soybean meal.

The researchers explained that liquid crude glycerol was incorporated in the complete diet at the time of mixing. Dietary treatments were imposed on day 109 of gestation (2.25kg per day) when sows were moved into farrowing rooms. Heat index during lactation in farrowing rooms exceeded 25°C for all sows. At farrowing, sows were allowed ad libitum access to feed throughout lactation. Dietary treatment tended (P = 0.08) to influence average daily feed intake (ADFI) of sows (control = 6.04kg/day; 3 per cent = 6.21kg/day; 6 per cent = 5.69kg/day; 9 per cent = 6.00kg/day; pooled SE = 0.18). Up to 9 per cent crude glycerol in the diet had no effect on sow body weight and backfat loss, weaning-to-oestrus interval, pre-weaning mortality of piglets and ADG of piglets. Increasing dietary glycerol linearly reduced (P = 0.10) litter size at weaning (CON = 9.50; 3 per cent = 9.60; 6 per cent = 9.36; 9 per cent = 9.39; pooled SE = 0.08). Daily water consumption was not affected by dietary treatment.

Crude glycerol did not affect respiration rates or rectal body temperatures, indicating no efficacy in reducing heat stress of sows.

Plasma glycerol concentrations increased linearly (P<0.05) as dietary crude glycerol increased (CON = 1.21µM; 3 per cent = 1.69µM; 6 per cent = 7.21µM; 9 per cent = 29.04µM; pooled SE = 1.58) but plasma glucose concentrations were not affected.

Crude protein content of the milk of sows was not affected (P = 0.16) by dietary treatment. Dry matter (P = 0.07) and crude fat (P = 0.09) content of the milk of the sows tended to increase linearly (DM basis: CON = 17.84 per cent; 3 per cent = 18.43 per cent; 6 per cent = 18.98 per cent; 9 per cent = 18.48 per cent; pooled SE = 0.34; crude fat: CON = 4.78 per cent; 3 per cent = 4.91 per cent; 6 per cent = 5.50 per cent; 9 per cent = 5.24 per cent; pooled SE = 0.30), whereas milk ash concentration tended (P = 0.09) to decrease linearly with increasing dietary glycerol (CON = 0.77 per cent; 3 per cent = 0.79 per cent; 6 per cent = 0.74 per cent; 9 per cent = 0.74 per cent; pooled SE = 0.02).

Increasing dietary crude glycerol linearly increased (P<0.05) lactose concentration in the milk of sows (CON = 5.16 per cent; 3 per cent = 5.30 per cent; 6 per cent = 5.43 per cent; 9 per cent = 5.46 per cent; pooled SE = 0.10).

Results from this study indicate that lactating sows fed diets containing up to 9 per cent crude glycerol perform similarly to sows fed a standard corn-soybean meal diet, concluded Schieck and co-authors.

Reference

Schieck S.J., B.J. Kerr, S.K. Baidoo, G.C. Shurson, and L.J. Johnston. 2010. Use of crude glycerol, a biodiesel coproduct, in diets for lactating sows. Journal of Animal Science, 88:2648–2656. doi:10.2527/jas.2009-2609

Further Reading

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