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Effect of Environmental Temperature and Thiouracil Feeding upon Growing-fattening Pigs¹

Michigan State University, East Lansing

Abstract

The effects of environmental temperature and thiouracil feeding upon rate and efficiency of gains, blood lipid levels, the weight of some endocrine glands and body organs and certain carcass characteristics of growing-fattening pigs were investigated. A total of four trials were conducted using 54 Chester White and Yorkshire pigs at an average initial weight of approximately 70 kg. They were slaughtered at an average weight of about 90 kg. The environmental temperatures were either 4° C. (cold) or 27° C. (warm), and the rations were identical except that one group was fed 0.15% thiouracil.

The feeding of thiouracil beyond 30 days caused a marked decrease in activity, and after 40 days there was a marked decline in appetite. The thiouracil-fed pigs lost their bloom and developed a mottled appearance in some areas of the skin, similar to one of the symptoms of Addison's disease in man. The thiouracil-fed pigs made slower gains and had higher blood lipid levels, a lower 24-hr, off-feed shrink, shorter carcasses, heavier thyroid glands and livers than control pigs. The cold environmental temperature increased blood lipid levels, resulted in heavier thyroid glands and liver weights, but decreased feed efficiency, average backfat thickness and percent of fat trim. Although data on the average height of the thyroid acinar cells were obtained for control pigs only, height was increased significantly by the cold environments, indicating greater thyroid activity at the low temperature.

The Yorkshire pigs had higher blood lipid levels, less backfat, a lower percent of fat trim, a greater percent of lean and primal cuts, longer carcasses and a higher specific gravity of the ham than the Chester White pigs.

¹ Michigan Agricultural Experiment Station Journal Article 3795.

² Department of Food Science.

³ Department of Physiology.

⁴ Department of Animal Husbandry.