EN LOS CABRITOS MACHOS DE REGIONES SUBTROPICALES, LA EXPOSICIÓN A DÍAS LARGOS ARTIFICIALES ESTIMULA UNA MAYOR TASA CRECIMIENTO, UN MEJOR DESARROLLO E INCREMENTA LA GLUCEMIA

Abstract

<p><strong>Background.</strong> Small ruminants from subtropical regions are sensitive to respond physiologically to natural photoperiodic changes. In some subtropical goat production systems as located in semi-arid areas of México, the main objective is to obtain in the shortest possible time, males with a suitable weight and body development for sale. <strong>Objective.</strong> The present study determines if the exposure to artificial long day photoperiod could promote a growth rate, body development and an increased glycemia in male goat kids compared with those under natural short days. <strong>Methodology.</strong> Starting on late September, 21 creole male goat kids (13 ± 0.1 week aged; mean ± SEM) were assigned to one of the two experimental groups. In the natural short days group, males remain under natural short days from autumn-winter (GDC, n = 10). In the artificial long days group, males were exposed to artificial photoperiod consisting in 16 h light and 8 h darkness (GDL, n = 11). The study lasted until the animals had 35 weeks of age. All animals were fed according their nutritional requirements. <strong>Results.</strong> During the study, the body weight of the GDL animals was higher than that of the GDCN males (P < 0.05). Due to this, the daily weight gain (GDP) obtained at 23 weeks of age was higher in the GDL males (165 g/day) than that registered in the GDC males (143 g/day; P <0.05). In some periods, the males of the GDL had higher body mass index (IMC) than the males of the GDC (P < 0.05). Thoracic perimeter at week 32 was greater in the GDL males than in the GDC males (P <0.05). The height at the withers did not reach significant differences in the comparisons between groups in the different weeks measured (P > 0.05). However, the total height at the withers gained during the study was significantly higher in the GDL males than in the GDC males (P < 0.01). Under fasting conditions, GDL males had higher levels (P < 0.05) of blood glucose in some periods than GDC males. <strong>Implications.</strong> The present study demonstrate that artificial long days stimulates growth in goats as occurs in other ruminants<strong>. Conclusion.</strong> Exposure of the male goat kids from subtropical regions to artificial long days, promotes a higher growth rate, better body development and increased glycemia compared to kids maintained under natural short-day photoperiods.</p>