Influence of the duration of photoperiod on growth, testicular characteristics and endocrine function of boars

• Published in: Domestic animal endocrinology Vol. 2; no. 1; pp. 53 - 59
• Main Authors: Minton, J.E., Fent, R.W., Wettemann, R.P.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 1985
• Subjects: BOARS; CRECIMIENTO; CROISSANCE; DURACION; DURATION; DUREE; FOTOPERIODISMO; GROWTH; HORMONAS; HORMONE; HORMONES; PERFORMANCE DE REPRODUCTION; PHOTOPERIODICITE; PHOTOPERIODICITY; REPRODUCTIVIDAD; REPRODUCTIVITY; VERRACO; VERRAT
• ISSN: 0739-7240; 1879-0054
• DOI: 10.1016/0739-7240(85)90026-8

Crossbred boars were used to evaluate the influence of exposure to 8 or 16 hr of light daily from 75 to 175 days of age on growth rate, testicular characteristics and endocrine function. At 160 days of age, concentrations of testosterone in serum (P<.10), the areas under plotted 12 hr testosterone profiles (P<.10) and the number (P<.05) and magnitude (P<.10) of testosterone secretory spikes were increased in boars exposed to 16 hr of light compared to boars in 8 hr light, but concentrations of LH in serum were similar in boars exposed to both treatments. Treatment with GnRH resulted in similar concentrations of LH in serum for both groups of boars. Testosterone in serum after GnRH-mediated LH release was greater at .5 (P<.05) and 1.0 (P<.10) hr following GnRH in boars exposed to 16 hr of light compared to boars at 8 hr, but concentrations of testosterone were similar for both treatments from 1.5 to 4.0 hr after GnRH. Growth rate and testicular and epididymal weights and sperm reserves at 175 days of age were not significantly altered by duration of photoperiod. Boars exposed to 8 hr of light had more hair per unit area than boars exposed to 16 hr of light. We conclude that exposure of prepubertal boars to longer daily photoperiods results in increased concentrations of testosterone in serum at 160 days of age.