Arginine supplementation increases weight gain, depresses antibody production, and alters circulating leukocyte profiles in preruminant calves without affecting plasma growth hormone concentrations.

The hypothesis that dietary L-arginine (L-Arg) supplementation would increase growth hormone (GH) secretion and antibody production in preruminant calves was tested. Sixteen newborn calves were randomly assigned to either Arg+ or Arg- treatment groups. Both groups were fed a single dose of Colostrx within 6 h after birth followed by milk replacer twice daily until weaning. Beginning with the Colostrx feeding, calves in the Arg+ group were supplemented with L-arginine at 500 mg kg x BW(-1) x d(-1), and the Arg- group received equivalent, but unsupplemented, diets. All calves were immunized against keyhole limpet hemocyanin (KLH) on d 4 and received a booster vaccination on d 14. The Arg+ treatment increased (P < .05) plasma L-Arg and urea concentrations an average of 2.8-fold and 26%, respectively, during the 4-wk supplementation period. Average daily gain (ADG) of Arg+ calves was increased (P < .10) during wk 1, 3, and 5 of life. The Arg+ treatment depressed (P < .05) total and KLH-specific IgG concentrations in plasma and caused a decrease (P < .01) in circulating leukocyte numbers. Differential counts revealed that the decrease in circulating leukocyte numbers was due to decreases in absolute numbers of lymphocytes, monocytes, and neutrophils. The Arg+ diet did not affect mean plasma GH concentrations during the first 3 wk of life, but GH mean concentrations were decreased (P < .01) during wk 4 due to depressed (P < .10) pulse amplitudes. The decrease in GH mean concentrations during wk 4 was paralleled by lower (P < .10) plasma IGF binding protein-3 concentrations. These data show that supplementary L-Arg does not increase plasma GH concentrations, but it increases ADG, depresses KLH antibody production, and alters circulating leukocyte populations in preruminant calves.

Insulin-like growth factor (IGF)-I and -II and IGF binding proteins in serum and mammary secretions during the dry period and early lactation in dairy cows.

Concentrations of IGF-I and IGF-II, and IGF binding proteins (IGFBP) in serum and mammary gland secretions were surveyed during the dry period and early lactation of 30 Holstein cows. Although there was a threefold drop in the concentration of IGF-I in serum from the last week of the dry period to parturition (81 +/- 7 to 24 +/- 3 ng/ml, P less than .01), there was no significant change in serum IGF-II concentration during this period (150 +/- 17 vs 173 +/- 13 ng/ml, P greater than .05). Furthermore, a 57% increase in serum IGF-I was observed from the last week of lactation to the second week of drying off (100 +/- 5 to 157 +/- 8 ng/ml, P less than .05). Changes in serum IGF-II were not observed (126 +/- 11 vs 150 +/- 10 ng/ml, respectively; P greater than .05). Although IGF-I, IGF-II, and IGFBP concentrations in mammary secretions peaked 2 wk before parturition (2.95 +/- 1.1, 1.83 +/- .6, and 7.27 +/- .76 micrograms/ml, respectively), total output/quarter was highest in colostrum (394 +/- 119, 295 +/- 132, and 2,680 +/- 1,967 micrograms/quarter, respectively). Weekly milking of two individual quarters during the dry period did not affect (P greater than .05) IGF-I or IGF-II concentration (ng/ml) or total output (microgram/quarter) and milk yield in colostrum and milk (2 wk and 7 wk) compared with the ipsilateral quarter. The data support the hypothesis that IGF-I may be transported by the mammary gland epithelium. Furthermore, the secretion mechanisms of IGF-I, IGF-II, and IGFBP by the gland may be related to each other.