Effects of Dietary Calcium Propionate Supplementation on Hypothalamic Neuropeptide Messenger RNA Expression and Growth Performance in Finishing Rambouillet Lambs.

The objective of this experiment was to evaluate the effects of feeding different levels concentrations of dietary calcium propionate (CaPr) on lambs' growth performance; ruminal fermentation parameters; glucose-insulin concentration; and hypothalamic mRNA expression for neuropeptide Y (NPY), agouti-related peptide (AgRP), and proopiomelanocortin (POMC). Thirty-two individually fed lambs were randomly assigned to four treatments: (1) control diet (0 g/kg of CaPr), (2) low CaPr, (30 g/kg dry matter (DM)), (3) medium CaPr, (35 g/kg DM), and (4) high CaPr (40 g/kg DM). After 42 days of feeding, lambs were slaughtered for collecting samples of the hypothalamus. Data were analyzed as a complete randomized design, and means were separated using linear and quadratic polynomial contrast. Growth performance was not affected (p ≥ 0.11) by dietary CaPr inclusion. The ruminal concentration of total volatile fatty acids (VFA) increased linearly (p = 0.04) as dietary CaPr increased. Likewise, a linear increase in plasma insulin concentration (p = 0.03) as dietary CaPr concentration increased. The relative mRNA expression of NPY exhibited a quadratic effect (p < 0.01), but there were significant differences in the mRNA expression of AgRP and POMC (p ≥ 0.10). Dietary calcium propionate did not improve lamb growth performance in lambs feed with only forage diets. Intake was not correlated with feed intake with mRNA expression of neuropeptides.