Search

IntroductionThe charge given is to describe and discuss that livestock research accomplished during the past 100 yr which is deemed to be most significant.Significance lies largely in the mind of the observer. Each person has his/her own reference points, priorities, concerns, values and perceptions.One would ask, “Should significance be to the livestock industry, to consumers, to total economic activity, or to the sciences? Should judged significance be based on precision and credibility of the research itself, the degree to which the perceived accomplishment was accepted and implemented, economic consequence, social consequence, or the degree to which the research accomplishment served as a base for later discoveries?” We did not select a single response to either of these questions.There is no effort in this paper to repeat or to summarize previously published reviews of livestock research. Such reviews represent a large repository and provide generous coverage of livestock research activities of the past 100 yr.

Corn-soybean oil meal rations containing 12% and 14% protein were supplemented with four levels of L-lysine and/or four levels of DL-methionine and, in a 2 × 4 × 4 factorial arrangement of treatments, fed to pigs weighing 23 lb. until they reached a weight of 100 lb. The 32 ration treatments were imposed on pens of two pigs, one barrow and one gilt, in each of two replicates.On the 12% protein ration, rate of gain and feed efficiency were improved by L-lysine, up to the 0.10% supplemental level. Lysine supplementation of the 14% protein ration exerted no consistent effect. The protein level × supplemental lysine interaction was statistically significant for both rate of gain and feed conversion.Methionine supplementation of the 12% ration exerted no apparent effect on either gains or feed conversion. Methionine supplementation of the 14% ration gave indication of improvement in rate of gain and feed efficiency, up to the 0.05% supplemental level; however, differences were not statistically significant.

Measurements on length of carcass, specific gravity, percent lean cuts, cross-section area of the loin muscle, live probe, depth of backfat, and weight of leaf fat from 102 swine carcasses are reported in this study. The test rations were fed to the pigs throughout the feeding period without alteration of composition.While there were some discrepancies in the uniformity of response to the imposed experimental treatments in the two experiments in this study, the results are in close agreement. They give no indication that the inclusion of the antibiotics, aureomycin or terramycin, at 5 mg. per lb. of ration in a corn-soybean oil meal ration fed to pigs from weaning to 200 lb. liveweight had an important effect on hog carcass quality.Feeding pigs protein levels over the range from 10 to 20 percent of the ration resulted in carcasses with a significantly greater proportion of lean as the level of protein increased. This increment in proportion of lean per interval of protein (two units percent) increase is of such small magnitude, however, as to be of minor consideration when a choice must be made between two adjacent protein levels.

Protein levels of 10, 12, 14, 16, 18 and 20 percent, with and without 5 mg. of aureomycin or terramycin per lb. of ration, were fed in two experiments (numbers 536 and 554) to a total of 288 pigs. The fortified corn-soybean oil meal rations were fed in concrete drylot to pigs weighing from 31 to 36 lbs. to 200 lbs.The level of protein in the ration significantly affected the rate of gain made by the pigs in both experiments as measured by the linear and quadratic components. In general, the average daily gains of the pigs reached a maximum between 16 and 18 percent protein without antibiotics and at 14 percent protein with antibiotics (effect not statistically significant) and then leveled off or declined. Feed efficiency was not significantly affected by the level of protein fed in the first experiment. However, in the second experiment, the protein level had a significant effect on feed requirements which paralleled the performance in daily gains.In the first experiment, terramycin (but not aureomycin) significantly increased the rate of gain of the pigs during the 36- to 75-lb. period. However, this effect had disappeared by the time the pigs reached 200 lbs. Although the pigs fed aureomycin or terramycin required 21 and 18 lbs. less feed per 100 lbs. of gain respectively, these differences were not statistically significant.In the second experiment, the feeding of aureomycin significantly increased the daily gains and feed efficiency of the pigs for the entire feeding period, but not for the 31- to 75-lb. period.The effect of protein levels and antibiotic feeding on carcass measurements will be reported separately.