Genetic parameters of morphometric measurements in Criollo horses.

The aim of this study was to estimate the genetic parameters for the morphometric measurements of withers height (WH), thoracic circumference (TC) and cannon bone circumference (CBC) of Criollo horses, stratified for maternal and paternal effects. Statistical genetic design of factor crossings was used to evaluate the offspring of full siblings and half-siblings. Fifty stallions were selected (n = 50) who had been crossed with six mares each (n = 6), to provide 300 parental pairings in which two offspring were born per mare (n = 600). WH in females and TC in males were highly influenced by additive genetic effects, while the other morphometric measures were found to be closely related to the general effects of the environment. WH had the greatest additive genetic influence on female offspring (47.06%), while TC presented the greatest additive genetic influence on male offspring (58.73%). When comparing the parental influence on the morphometric characteristics evaluated, TC and CBC had greater additive genetic influence from maternal effects, regardless of offspring sex. However, the WH in female offspring showed greater maternal additive genetic contribution, while in males this characteristic presented greater paternal additive genetic influence. For WH in male offspring, narrow sense heritability ( h r 2 : 0.26) was more influenced by paternal effects, while for WH in females ( h r 2 : 0.47), TC in females ( h r 2 : 0.08) and males ( h r 2 : 0.59), and CBC in females ( h r 2 : 0.07) and males ( h r 2 : 0.05) the maternal effects were the most important. Therefore, the phenotypic expression of WH in males and females and TC in males is influenced by the additive genetic effect of the genes. On the other hand, the TC in female progenies and CBC in progenies of both sexes are closely related to the effects of the environment. The results obtained in this study could be useful in the selection process of Criollo horses.

Immunolocalization of Leptin and its Receptor (ObR-b) in Equine Placenta at Term and Plasma Level Measurement in the Late Gestation.

Placental tissues from humans, rodents, and farm animal contain leptin and its receptor. Expression of leptin has already been described in horses, although there is no description about immunolocalization of leptin and its receptor. The aim of the present study was to investigate the presence and distribution of leptin and ObR-b in the equine placenta at term by immunofluorescence staining, and the changes on plasma leptin concentrations during late gestation. The present study involved eight Criollo-type mares carrying healthy pregnancies. Blood samples were collected during the third trimester of gestation, at foaling, and at 24 hours after foaling. Leptin concentrations were analyzed via radioimmunoassay. Plasma leptin concentrations did not change from the 8th to the 10th month of gestation and displayed a discrete decrease 24 hours after parturition (P = .07). The expression of leptin and ObR-b was observed in the cytoplasm of pseudostratified epithelial cells in the areolar region and in the epithelium of microcotyledons. Also, leptin receptor was allocated in the apical surface of the cells. The presence of leptin and its receptor (ObR-b) in the placenta of mares at term supports an endocrine and autocrine/paracrine action of leptin within this organ.