Sixteen steers were used to investigate the efficacy of the sustained-release implant of bovine somatotropin (bST) in improving growth and feed:gain ratio during 12 weeks. Administration of the 400 mg bST implant resulted in a 16.1% increase in growth rate, and this increase was significant (p less than .05). The use of the sustained-release implant did not alter (p greater than .05) feed intake and feed:gain ratio. Thirty-four cows were used to investigate the efficacy of the sustained-release implant of bST in milk production during 4 weeks. Administration of the 200 mg bST implant resulted in an 8.7% increase in milk production, and this increase was significant (p less than .05). Twenty-four barrows were used to investigate the efficacy of the sustained-release implant of porcine somatotropin (pST) in improving growth, feed:gain ratio and backfat thickness during 6 weeks. Administration of the 120 mg pST implant resulted in a 11.4% increase in feed:gain ratio and a 60% decrease in backfat thickness, and these results were significant (p less than .05). But the use of the sustained-release implant did not alter (p greater than .05) growth rate and feed intake.

Present study was undertaken in order to evaluate the lead contents of various feedstuffs produced in Korea and the effect of the burning of gasoline by automobiles on the lead contents. Ninty-one samples near and 95 far road were collected from 9 regions(Do). All of the samples were washed, dry-ashed and analyzed for lead content using atomic absorption spectrophotometer. The mean values obtained were checked for significance of difference using computer. The lead content in micro g/g of agriculture-byproducts were measured with the following mean values and ranges (in parenthesis). Rice bran:2.07+-1.67 (0-5.00), rice hull : 1.84+-1.18 (0-3.71), rice straw:1.27+-1.09(0-3.62), soybean pod; 4.55+-3.13 (1.13+-10.43), and wheat bran: 1.69+-0.86 (0-3.65). The lead content in micro g/g of pasture plants were measured with the following mean values and ranges. Kudzu:2.71+-1.74 (0.38+-8.75), leed: 2.03+-1.61 (0-4.54), lespedeza:4.73+-5.93 (0-31.25), sagebrush: 4.08+-3.75 (0-12.18), Korean-grass: 2.11+-1.38 (0-5.50), maizestalk: 2.62+-2.35 (0-8.65), clover: 3.83+-2.97 (0-12.19), alfalfa: 7.14+-0.97 (4.46-9.25), and timothy: 5.86+-4.79 (0-9.25). Fourteen samples (22.2%) out of 63 agriculture-byproduct samples and 42 (34.2%) out of 123 pasture plant samples showed lead content of more than 3 micro g/g which are said to be the upper limit value for cattle. No significant difference between the mean lead contents of near road, and those of far road was recorgnized. The regional mean values for all kinds of samples collected in Kyungbuk and Kyungnam were significantly (p0.05, p0.10) higher compared to those in Chungnam and Chejudo. From these results it may be concluded that the buring of gasoline by automobiles did not affect the lead contentes of washed feedstuffs produced in Korea at present

Nickel toxicity and interactions of nickel with zinc, copper and lead were studied in growing chicks fed supplement diet. Feed intake and growth rate of the chick were reduced by 250 mg nickel as a sulfate salt per kg of feed. The toxicity of nickel was decreased by zinc or copper supplementation, but not lead. High nickel feed increased nickel level in kidney and decreased zinc levels in tibia and plasma. However, low zinc levels in tibia and in plasma were reversed by zinc supplementation. Hemoglobin, packed cell volume, and aortic elastin content were increased in chicks fed nickel