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Effect of Porcine Growth Hormone on Growth and Carcass Composition of the Pig^{1, 2, 3,}

Monsanto Company, St. Louis, Missouri 63166

Abstract

DAILY injection of 0.22 mg and 1.10 mg per kilogram body weight of porcine growth hormone (PGH) into pigs weighing 47 kg resulted in some mortality. Liver and kidney degeneration, hemorrhage of the stomach, edema and arthritis were the most common histopathological observations. Injection of 0.13 mg per kilogram body weight or less had no effect on mortality or pathology. Since extremely high levels of the same preparation were not toxic in the rat, it was concluded that the pig is uniquely sensitive to high levels of GH.

In two other experiments, daily injection of 0.13 mg PGH per kilogram body weight into pigs weighing 45 kg resulted in significant improvements in average daily gain, feed conversion and all parameters of lean mass (i.e., percent lean cuts, loin eye area, percent protein of ham). The back fat thickness and percent fat of the ham were reduced while the specific gravity of the ham was increased.

In a fourth experiment, graded levels of PGH were injected. With 0.033 mg of PGH per kilogram body weight, specific gravity of the ham was significantly increased; with 0.066 mg both specific gravity and percent lean cuts were improved and with 0.132 mg these parameters as well as loin eye area were increased. In every experiment PGH improved feed conversion.

When 95 kg pigs were fed a restricted amount of a high protein diet, the average daily gain for the 3-week, experimental period was 0.23 kg compared to 0.82 kg in control pigs fed ad libitum. Daily injection of 0.13 mg per kilogram body weight of a PGH preparation purified by DEAE chromatography and devoid of lipolytic activity resulted in a gain of 0.67 kg per day. The data obtained in this experiment suggest that lipolytic activity is not essential for the growth activity of PGH. Furthermore, it is possible that caloric restriction might inhibit endogenous GH production in the pig.

¹ The assistance of Ben Smith, M. Niebruegge and R. Logan of the Hunter Packing Co., East St. Louis, for their role in maintenance of the animals and assessment of the carcass is gratefully acknowledged.

² The assistance of Drs. B. Guerin and P. Vardiman of the Ralston Purina Company, St. Louis, for maintenance of the animals and for the autopsy of pigs postmortem is gratefully acknowledged.

³ The author acknowledges the assistance of Dr. Martha Moseley for preparation of the highly purified porcine growth hormone and of Miss Gloria Johnston for carrying out the lipolytic assays.

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