Kallikrein proteoforms and reproductive parameters in stallion are conditioned by climate

Horses are seasonal polyoestrous animals, and the photoperiod is the main factor modulating their reproductive activity. There is no consensus on the andrological and biochemical factors that influence breeding seasonality. To assess the involvement of climate in reproduction, Mangalarga Marchador stallions were monitored over 1 year regarding semen quality and seminal plasma proteome. Here, we show that kallikrein (KLKs) proteoforms in seminal plasma are involved in climate conditioning of reproduction. During the breeding season, greater abundance and different types of KLKs occurred simultaneously to lower sperm motility, greater semen volumes and higher concentrations of glucose and cholesterol. Considering that vasodilation due to activation of the kallikrein-kinin system and the consequent inhibition of the renin-angiotensin system may be associated with lower sperm motility, unravelling the involvement of KLK proteoforms in reproductive seasonality is a priority in horse breeding.

Nonlinear Models to Describe the Testicular Size Growth Curve of Mangalarga Marchador Stallions

This study aimed to describe the testicular growth curve in Mangalarga Marchador stallions fitting nonlinear models to data of total scrotal width (TSW) and testicular volume (TV). A cross-sectional study was conducted with 120 stallions, aging from 1.75 to 21.93 years. The parameters of nonlinear models (Brody, Gompertz, Hill, Logistic I and II, Meloun I and II, Michaelis-Menten, Mitscherlich, and von-Bertalanffy) were estimated by Gauss-Newton iterative process. Goodness of fit was evaluated by the corrected Akaike (AICc) and Bayesian (BIC) information criteria, adjusted R², error sum of square, mean absolute deviation and average prediction error. Based on the goodness of fit, the Logistic I model fitted better for TSW while Logistic II fitted better for TV growth curve. The inflection point (IP) of TSW growth was estimated in 5.23 cm at 0.76 years; the IP of TV growth was estimated in 139.36 cm³ at 2.57 years. The TV growth curve reached a plateau later than TSW growth curve, mainly because testicular height maintains growth for a longer period. In addition, there were moderate and positive correlations between whiter height and TSW and TV (r = 0.51 and r = 0.53, respectively). Findings suggest that TV is more associated with sexual maturity than sexual precocity. In addition, the moderate and positive correlations between whiter height and TSW and TV indicate that testicular traits can be included in selection programs of Mangalarga Marchador stallions with the same relevance as the morphometric traits.

Use of nonlinear mixed models for describing testicular volume growth curve in Nellore bulls

This study aimed to describe longitudinal testicular volume (TV) data of Nellore bulls by using nonlinear mixed models. Dataset consisted of 2,294 TV measurements from 505 bulls with ages ranging from 563 to 4,307 days. Nine nonlinear models were evaluated: Brody, Gompertz, Hill, Logistic I and II, Meloun, Michaelis-Menten, Mitscherlich and von Bertalanffy. Goodness of fit was evaluated by Akaike's information criterion (AIC), Bayesian information criterion (BIC), adjusted R², percentage of convergence, error sum of squares (ESS), mean absolute deviation (MAD), and average prediction error (APE). These criteria were used to select the best model, then the absolute growth rate (AGR) for TV was estimated by the first derivate of the adjusted model related to time (∂Y/∂t). The values of adjusted R², ESS, MAD and APE were similar among models. Percentage of convergence was higher for the Logistic I (76.8%), Logistic II (75.5%) and Mitscherlich (78.6%) models, but Logistic I and II showed the lowest values of AIC and BIC, indicating a better fit, so the Logistic I model was chosen for subsequent analyses. The TV growth occurred at a high rate until the inflection point, which was estimated at approximately 22 months of age; it stabilized and reached a plateau at approximately 2,500 days of age. This may suggest that TV is more related to sexual maturity than precocity. Additionally, the Logistic I model was used to estimate the growth curve and the AGR of the testicular length and width. As a result, testicular length increased at a higher rate than testicular width until approximately 1,600 days of age, indicating that the testes become longer with increasing age.

In vitro evaluation of cryopreserved bovine sperm and its relation to field fertility in fixed-time artificial insemination

This study aimed to assess characteristics of bovine cryopreserved sperm and evaluate its relation to field fertility in fixed-time artificial insemination (FTAI). Semen samples of 16 bulls were used to inseminate 811 Nellore cows, and four of these bulls were also used to inseminate 101 Nellore heifers. Samples of the same ejaculate used for FTAI from each bull were analysed in the laboratory after thawing. Sperm motility and vigour were subjectively assessed by light microscope, and integrity of the plasma and acrosome membranes, and H₂ O₂ production were evaluated by flow cytometer. Relation among sperm characteristics and pregnancy rate of cows and heifers were evaluated by univariate and multivariate logistic regression. Subjective sperm motility and vigour did not affect the probability of pregnancy in cows or heifers. In univariate analysis for pregnancy in cows, sperm traits related to acrosome injury positively affected probability of pregnancy mainly when associated with plasma membrane integrity; H₂ O₂ production seems to be less important than plasma membrane integrity in affecting probability of pregnancy. In multivariate analysis, sperm traits related to injured acrosome positively affected probability of cow and heifer pregnancies while intact acrosome was negatively related to cow pregnancy. Intact plasma membrane and high H₂ O₂ production were positively related to cow pregnancy but negatively related to heifer pregnancy. Results suggest that a capacitation-like status of the acrosome may benefit probability of pregnancy in cows.

How to build a specialty MSO

The specialty-based management services organization (MSO), with its focus on management support, contracting, information systems and related benefits, is intended to help preserve specialist physician access to patients. It does this by enabling the MSO's physicians to clearly differentiate themselves from other specialist providers. To be successful, however, an MSO must be built on a shared vision of its goals. Considerations of structural, operational, ownership, antitrust and governance concerns should all follow from that ground. All parties should recognize that MSOs are best in the long-term; they are not short-term solutions.