A modification to the isotope-dilution technique for estimating milk intake of pigs using pig serum

The aim of this study was to compare the measurement of deuterium oxide (D2O) directly in pig serum with that in sublimed whole blood. This was to assess whether excluding vacuum sublimation before analysis would cause any significant loss of accuracy in estimates of pig milk intake. Water and serum standards were made in deionized water and serum, respectively, and were assayed with samples under the same conditions on a fixed-filter, infrared spectrophotometer. The mean concentration of D2O in sublimed samples was 2,244 microg/mL of body water, and the mean concentration of D2O in serum samples was 2,184 microg/mL of body water. The mean ratio of D2O concentration in deionized water to the D2O concentration in serum was 1.0275, which was used as a correction factor to convert serum D2O concentration to D2O concentrations in body water. Using this method, the mean concentration of D2O in all serum samples was identical to that in sublimed samples (i.e., 2,244 microg/mL of body water). Mean milk intake of pigs based on sublimed samples was 1,006 g/d and that based on serum samples was 1,012 g/d. This confirms that milk intake determined from measurement of D2O directly in pig serum is sufficiently precise

Determining the valine requirement of the mgr-producing lactating sow

Two hundred-three large white x Landrace or large white x Chester White x Landrace sows (40 or 41/treatment, avg parity 3.7) were used in a 26 d lactation experiment to determine the valine requirement of high-producing sows. All diets were formulated to .9% lysine with all amino acids other than valine formulated to be at least 110% of their respective ratios relative to lysine. Synthetic valine replaced cornstarch to provide .75, .85, .95, 1.05, and 1.15% dietary valine. Corresponding valine:lysine ratios were 83, 94, 106, 117, and 128% of lysine. The experiment was conducted at two experiment stations from July, 1993 through January, 1994. Mean litter size of all treatments after adjustment was 10.33 pigs. Sow feed intake and grams of lysine intake were not different among treatments. Grams of valine intake increased linearly as dietary valine increased. Litter weight at d 21 and weaning increased linearly with increasing dietary valine. Litter weight gain from d 0 to 7 increased linearly as dietary valine increased to 1.15 %. Litter weight gain from d 0 to 21 and d 0 to weaning increased linearly as dietary valine increased, with the greatest portion of the response observed as valine increased to 1.05% of the diet. Dietary valine had no effect on sow weight change, 10th rib backfat (BF) change, or last lumbar BF change from d 0 to 21 or d 0 to weaning. Days to estrus postweaning were not affected by dietary valine. These results demonstrate that high-producing sows have a dietary valine requirement of at least 117% of lysine during lactation (66.4 g/d valine), much greater than is currently recommended by NRC (1988; 100% of lysine) or ARC (1981; 70% of lysine) to maximize litter weaning weight and litter weight gain