T WO experiments involving 296 pigs from gilts fed diets containing low (2%) or adequate (17%) protein during gestation followed by 5% or 17% during lactation were conducted to determine the effect of maternal dietary protein level on performance of the progeny. Blood hematocrit, hemoglobin and plasma protein levels were not affected by the dietary treatments imposed on the dam during gestation. In the first experiment, pigs reared by dams fed adequate protein diets during gestation and lactation retained less (P<.01) of the absorbed nitrogen than pigs from gilts fed low protein. No significant differences in nitrogen utilization were observed in the second experiment. In experiment 1, rate of gain was greater (P<.05) and feed required per unit of gain was reduced in pigs reared by dams fed adequate protein as compared with the performance of pigs from dams fed an inadequate level of dietary protein, indicating that a lasting effect existed in progeny owing to the lactation treatment or gestation carryover effects in the rearing dam. The differences in gain and feed/gain responses in the second experiment were not statistically significant (P<.05).Low protein intake, 45 g per day, during gestation did not significantly (P<.05) affect postweaning performance of the pigs, although a trend toward slower gains by pigs from dams fed low protein during gestation did exist. However, gestation or gestation and lactation treatment apparently influenced quantity or quality of milk produced by the dam and therefore lactation treatment did affect subsequent growth of the progeny. It appears that swine are not as sensitive as rats to protein restriction during gestation and lactation.

The assay for melengestrol acetate (MGA) in cattle feed supplements was the subject of a collaborative study using 6 laboratories. Two feed formulations were each fortified with 0, 0.0625, 0.125, 0.500, 1.00, and 1.50 mg MGA/lb of supplement, and each laboratory assayed 4 samples of each level of each formulation by electron capture gas chromatography after liquid-liquid extraction of each sample followed by solvent partition and column chromatography cleanup procedures. Overall recovery was 83.2% with a pooled within-laboratory sample-to-sample standard deviation of 9.5%. This includes the variability due to formulation, batches, days, levels of MGA, samples, and their interactions. Including the collaborators as a source of variance results in an overall standard deviation of 15.0%. The major sources of variability were associated with collaborator, formulation, and level of MGA. Lower than expected recoveries were attributed to difficulty in recovering MGA from samples containing concentrations of MGA below the range of the method and the inadvertent substitution by some laboratories of ethanol-free chloroform for the ethanol-containing reagent grade chloroform specified in the methodology. On the basis of the collaborative results, the method has been adopted as official first action for MGA in cattle feed supplements at concentrations from 0.125 to 1.00 mg MGA/lb.