Photoperiod Manipulation on the Melatonin Secretion and Fiber Fineness of Capra hircus laniger in Highland Cold Deserts

Abstract

Photoperiod is a critical environmental cue regulating endocrine responses and fiber production in small ruminants, particularly under the harsh conditions of highland cold deserts. This study assesses the effects of controlled photoperiod manipulation on melatonin secretion patterns and fiber fineness in Capra hircus laniger. A controlled field experiment was conducted in a high-altitude cold desert region, where animals were subjected to altered light–dark cycles simulating extended and reduced daylight conditions, alongside a natural photoperiod control. Results revealed that photoperiod manipulation significantly influenced circulating melatonin levels, with extended dark periods enhancing melatonin secretion, thereby modulating follicular activity associated with fiber growth. Animals exposed to optimized light regimes exhibited improved fiber fineness and uniformity, indicating a direct link between endocrine regulation and fiber quality traits. Additionally, the treatment contributed to better physiological adaptation and reduced environmental stress in extreme climatic conditions. While analytical tools were employed to monitor hormonal fluctuations and fiber characteristics, the primary emphasis remained on understanding biological responses and improving animal production systems. The findings demonstrate that strategic photoperiod management can serve as an effective, non-invasive approach to enhance fiber quality in cold desert goat production systems. This research contributes to sustainable livestock production by integrating environmental management practices that improve product quality while supporting animal welfare and adaptation in fragile agroecosystems.