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Energy and Nitrogen Metabolism and Performance Responses of Lactating Sows Fed Thyroprotein¹

Iowa Agriculture and Home Economics Experiment Station, Ames 50010^,4

Abstract

The influence of thyroprotein on sow lactation performance was determined using 32 sows, fed an average of 4.77 kg per sow per day during a three week lactation period. Litters were equalized to eight pigs at day 3 postpartum. Milk yield of sows was measured on days 5, 12 and 21. Eight of the 16 sows per treatment were used in two nitrogen and energy balance trials from days 6 to 11 and days 15 to 20 postpartum. Milk samples were collected on days 7 and 15 and blood samples were taken by vena cava puncture on days 1, 8, 15 and 22 postpartum.

The addition of 220 ppm thyroprotein to the diet significantly increased average 21-day pig gain. Milk production estimates were higher for the thyroprotein-fed sows at each weekly determination, but the differences were not significant. The milk from the thyroprotein-fed sows was significantly higher in dry matter, crude protein and energy content. Thyroprotein-fed sows lost significantly more weight and had a significantly greater reduction in backfat thickness. Blood glucose and blood urea nitrogen levels were not significantly affected by treatment. Effective thyroxine ratio was significantly increased by adding thyroprotein to the diet. Thyroprotein treatment significantly increased sow heart rates but not respiratory rate or rectal temperature. The control sows had larger net nitrogen retention in both balance trials, but the difference was significant only in the second balance period. The digestible and metabolizable energy coefficients were lower for the thyroprotein-fed sows than for the control sows, though the differences were not significant in either balance trial. Thyroprotein-fed sows produced smaller litters at their subsequent farrowings.

¹ Journal Paper No. J-7585 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 1757. This work was supported in part by U.S.D.A., C.S.R.S. Special Grant No. 916-15-01.

² Present address: Department of Animal Science, University of Alberta, Edmonton, Alberta, Canada.

³ The authors wish to express appreciation to Dr. R. C. Ewan, Dr. W. C. Wagner, Mr. P. Halmagean and Mr. E. J. Kleinwort for their assistance in this work.

⁴ Department of Animal Science.