# Allometric Coefficients for Body Measurements and Morphometric Indices in Young Huacaya Alpacas from the Peruvian Highlands

## TL;DR

This study examines how young Huacaya alpacas grow in body size and shape in the Peruvian highlands, identifying key traits influenced by birth month and sex.

## Contribution

The study provides the first allometric coefficients for young Huacaya alpacas at high altitude, aiding in breeding and management decisions.

## Key findings

- Birth month significantly affects certain morphometric indices like compactness and body side index.
- Thoracic perimeter strongly correlates with body weight and has low variability, making it a key predictor of body size.
- Head traits show low allometric coefficients, while torso traits like dorsal length and abdominal perimeter show higher coefficients.

## Abstract

(1) Background: Alpacas play a crucial role in the livelihood and cultural heritage of Andean communities, yet limited scientific information exists regarding their morphometric growth patterns under high-altitude conditions. Understanding how environmental and biological factors influence their body development is essential for optimizing management and genetic improvement programs. (2) Methods: This study aimed to characterize the morphometric profile and allometric growth patterns of young Huacaya alpacas, evaluating the influence of sex, birth month, and fiber color on 18 linear body measurements and 6 morphometric indices from 146 animals. (3) Results: General linear models revealed that birth month had a significant effect (p < 0.05) on the compactness index, body side index, and body index while sex, fiber color, and their interaction did not significantly affect most indices. Allometric analysis showed that head traits exhibited low allometric coefficients (0.08–0.23), whereas torso-related measures such as dorsal length and abdominal perimeter showed higher coefficients (0.33 and 0.36, respectively). The compactness index showed marked sexual dimorphism in the allometric coefficient (0.83 in females, 0.95 in males). Thoracic perimeter exhibited a strong relationship with body weight and low variability, highlighting this measure as a key predictor of body size. (4) Morphometric and allometric analyses provide the first growth coefficients for young Huacaya alpacas at high altitude, offering a scientific basis for phenotypic selection of animals with superior meat potential and adaptability, thereby directly improving breeding efficiency and management in Andean production systems.