# Feline Testicular Biometry and Gonadosomatic Index: Associations Among Conventional Measurements, Mathematical Estimates, and Seminal Parameters

## TL;DR

This study shows that testicular measurements in domestic cats correlate with reproductive traits, helping select better breeders for feline conservation.

## Contribution

The study identifies consistent and useful biometric methods for assessing feline testicular traits linked to reproductive success.

## Key findings

- Three testicular measurement methods showed consistent results for area, volume, weight, and GSI.
- Moderate positive correlations were found between testicular weight/GSI and reproductive parameters.
- Larger body biometrics are associated with improved seminal and reproductive traits in domestic cats.

## Abstract

The refinement of reproductive science in domestic models is useful for developing breeding programs for threatened species. To apply such biotechnologies in wild felines, the physical characteristics of the animals and behavior of gametes must first be verified in domestic cats. However, several instruments have been developed for measuring testicular characteristics; thus, researchers must determine the most appropriate instrument and whether the measurements are representative of reproductive capacity. The present study identified three suitable methods for testicular measurement and various formulas for estimating the physical parameters of the body and testes. In addition, the association between the biometrics and semen characteristics was verified. We concluded that physical characteristics can be used as the primary selection criteria in wild animals.

The development of biometric techniques in domestic animals has greatly advanced scientific practices in wildlife research. The association between seminal characteristics and body and testicular biometry enables the selection of suitable breeders, though appropriate measurement techniques are required. The present study assessed differences among conventional methods and formulas for estimating testicular parameters. Testicular length, width, and thickness were measured using three methods in 13 adult male domestic cats. Testicular area, volume, and weight were estimated, from which the gonadosomatic index (GSI) was calculated. Sperm were collected using an alpha-2 adrenergic agonist and urethral catheterization, and characterized in terms of volume, vigor, total motility, progressive motility, concentration, plasma membrane integrity, and morphology. The three methods were consistent in terms of testicular area, volume, weight, and GSI. Moderate positive correlations were observed for testicular weight (r = 0.61, p < 0.05) and GSI (r = 0.58, p < 0.05). Testicular parameters showed strong positive correlations among each other (r > 0.80, p < 0.05). We observed a moderate positive correlation between head length and progressive motility (r = 0.65, p < 0.05). In conclusion, all testicular measurement and estimation techniques showed comparable performance. Therefore, testicular biometry is useful for selecting breeding males in feline conservation programs, wherein larger body biometrics are related to improved seminal and reproductive parameters.