Abstract
ABSTRACTThirty-six British Saanen female kids, born between either 20 March and 6 April (E) or 10 April and 16 June (L), were reared under three different patterns of lighting — a constant 18-h light: 6-h dark (C); or a weekly step-wise reduction from 18-h to 10-h light: 14-h dark over 10 weeks, commencing at either 6 (R6) or 10 (R10) weeks of age. Vasectomized males were used to test for oestrus; blood samples were collected to determine plasma progesterone concentration. Thirty-three goats attained puberty; all but two kids showed oestrus at first ovulation. The mean ( ± s.d.) age and live weight at puberty were 174·6 (± 4·1) and 141·7 (± 4·3) days (P < 0·001), and 28·6 (± 0·9) and 22·8 (± 1·0) kg (P < 0·001), for E and L treatments, respectively. For R6, R10 and C treatments, the ages and weights wer e 151·6 (± 4·7), 160·4 (± 5·2) and 164·7 (± 4·9) days (NS), respectively, and 24·5 (± 1·1), 25·3 (± 1·2) and 27·8 (± 1·1) kg (NS), respectively. A significant date of birth × lighting-pattern treatment interaction was found for date at puberty (P < 0·001), with puberty occurring earlier for E than L kids only when a reduction in daylength occurred. Puberty occurred earlier on R6 than R10 treatments only for L kids.
Publisher
Cambridge University Press (CUP)
Subject
Animal Science and Zoology
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