Performance and nutrient balance in growing swine fed low-protein diets supplemented with amino acids and potassium.

Five experiments, using 216 barrows and gilts (initial weight 19.9 to 23.7 kg), were conducted to evaluate the effects of improving amino acid balance by supplementing low-protein corn-soybean meal diets with essential amino acids. Three experiments were growth studies lasting approximately 3 wk, and the other two were 4-d metabolism trials. The control diets in each of the experiments were formulated to contain .80% lysine and contained approximately 17% CP. The other diets were formulated from a basal diet containing a 10.9% CP, fortified corn-soybean meal mixture, which included crystalline L-lysine.HCI, L-tryptophan, L-threonine, L-isoleucine, DL-methionine and L-valine to correct amino acid deficiencies. Nonessential N (glutamic acid or urea) also was added to some of the diets to increase the CP equivalent to 12 or 13%. Supplemental K (as a salt of bicarbonate or glutamate) was included in selected diets to increase the K concentration to the same level as that of the control diet. Growth rate of pigs fed the basal diet was similar (P greater than .05) to that of the control diets in only one growth study. Added glutamic acid and urea did not improve either growth rate or N retention. Added K improved K digestibility but did not increase K retention, N retention or growth rate. Improving amino acid balance by adding essential amino acids to low-protein diets did not benefit performance beyond that of a typical corn-soybean meal diet. Under our conditions, K, N, and nonessential N were not limiting.

Development of liver metabolism and serum hormones and metabolites in the perinatal pig.

In vitro glucose and pyruvate utilization by perinatal pig liver was determined at 90, 100, 110, and 114 days fetal age, and at 1 and 24 hours postpartum. The in vitro response of newborn pig liver to elevated glucose and insulin in vivo was also determined. Temporal patterns of increasing CO2 and total lipid and decreasing fatty acid production from glucose were associated with a decrease and subsequent increase in total liver DNA and protein at 110 days. A low capacity for gluconeogenesis from pyruvate was evident at 90 days fetal age, but doubled by 100 days then increased four-fold between 1 and 24 hours postpartum. In newborn pigs, the in vitro rate of glucose incorporation into CO2 and total lipids was increased by glucose feeding one hour before sacrifice, whereas fatty acid synthesis was increased by glucose feeding and/or intraperitoneal insulin injection. The in vivo glucose and/or insulin treatments also decreased serum growth hormone and cortisol levels. The results indicate that developmental changes in glucose utilization and synthesis by perinatal pig liver might be associated with changes in liver DNA content, whereas short-term changes at birth are related to serum concentrations of glucose and insulin.