Reproductive characteristics of ligth and semi-heavy roosters submitted to different photoperiods / CaracterÃsticas reprodutivas de galos leves e semi-pesados submetidos a diferentes fotoperÃodos.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

With the objective of evaluating the effects of differents photoperiods on the reproductive parameters in roosters of light and semi-heavy strains, an experiment was conducted in the Animal Science Department of the Federal University of Lavras. 24 roosters of the Lohman LSL strain (light) and 24 roosters of the Lohman Brown strain (semi-heavy), aged 19 weeks were utilized, they themselves being submitted to 3 treatments: a)Photoperiod 1: Continuous; b) Photoperiod 2: Intermittent and c) Photoperiod 3: growing natural light. The birds were housed in a shelter divided into 3 environments, so that the lighting of one did not interfere upon the that of the other. The experimental period lasted 140 days and the measures were taken at 168, 203, 238 and 273 days of age of the roosters. The animals were allotted to a completely randomized experimental design in a split plot scheme, taking into account the evaluations in the different ages as measures in time. For the measures of body weight, feed intake, seminal performance and parameters, 8 animals of each strain per treatment were utilized, the experimental unit being made up of 1 animal. The variables evaluated were: feed intake (g/bird/day), body weight (g), seminal volume (ml), spermatic motility (%) and vigor (0 to 5), spermatic concentration (number of cells x 109), number of total spermatic cells (NCT- volume x concentration) and spermatic morphology (alterations of head, tail and total alterations). For the evaluations of the testicular development and histology and of the semen collected in the deferent duct, 4 animals of each strain per treatment were utilized, the experimental unit being constituted of 1 animal. The following variables were evaluated: body weight, weights of the right and left testes, total testicular weight in grams; diameter of the seminiferous tubules (DTS) and thickness of the seminiferous epithelium (EES) in m; number of cells of the seminiferous tubules (Sertoli cells; rounded spermatogonia and spermatids); motility (%), vigor (0 to 5) and spermatic concentration (number of cells x 109). The differences between treatments were compared by the Scott Knott test (5%) and the ages submitted to the analysis of regression. The light roosters submitted of continuous light showed increased ration consumption (P<0,05), there being no significant influence (P>0.05) of the photoperiods on the other variables. The semi-heavy roosters submitted of the natural photoperiod presented decreased semen production, NCT, testicular weights, EES and number of rounded spermatids. It follows that the photoperiods continuous, intermittent or growing natural light (210 14â de south latitude) can be utilized in open shelters for light roosters over the reproductive period without harming the reproductive parameters. Semi-heavy roosters can be bred under either continuous or intermittent photoperiods, but when these animals are submitted only to growing natural light, they have their reproductive parameters wronged.

ASSUNTO(S)

luz intermitente zootecnia reproduÃÃo roosters fotoperÃodo sÃmen photoperiod intermittent lighting reproduction, semen galos

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