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Influence of Supplemental Lighting during Periods of Increasing or Decreasing Daylength on the Onset of Puberty in Gilts^1,2,

Purdue University^,5, West Lafayette, IN 47907

³ Address reprint requests to this author.

Abstract

Sixty-four crossbred gilts were assigned randomly to one of four treatments at 9 to 11 wk of age: (1) supplemental lighting and boar exposure, (2) supplemental lighting without boar exposure, (3) no supplemental lighting with boar exposure and (4) no supplemental lighting and no boar exposure. Gilts in all treatment groups received natural daylight through windows of a growing and finishing house from February to July (Exp. 1) or from August to January (Exp. 2). Gilts in treatment groups 1 and 2 received supplemental lighting from a 250 w incandescent bulb (300 lx) from 0520 and 0830 h and from 1630 to 2020 h, for atotal daily photoperiod of 15 h. No differences in weight gain or feed efficiency were found among any of the treatments. In Exp. 1, the proportion of gilts displaying estrus by 8 mo of age were 77, 13, 79 and 31% for treatments 1, 2, 3 and 4, respectively. As expected, the proportion of gilts that reached puberty was greater (P<.01) in gilts that had received boar exposure than gilts that did not receive boar exposure. However, supplemental lighting given during periods of increasing natural daylength did not increase (P>.05) the proportion of pubertal gilts or reduce the age of puberty. In Exp. 2, the proportion of gilts displaying estrus by 8 mo of age were 75, 7, 80 and 12% for treatments 1, 2, 3 and 4, respectively. Boar exposure increased the proportion of gilts reaching puberty by 8 mo of age. In addition, gilts exposed to boars and supplemental lighting (Exp. 2) attained puberty an average of 20 d earlier (P<.01) than gilts that received boar exposure alone. Incidence of secretory spikes of luteinizing hormone (LH) or serum concentrations of follicle stimulating hormone (FSH), prolactin (PRL), or LH in thrice weekly bleedings were similar in all treatments for both experiments. These data indicate that the effectiveness of supplemental lighting on the age of puberty in gilts was dependent upon season. However, supplemental lighting did not affect serum concentrations of LH, FSH or PRL. Furthermore, the lack of an effect of supplemental lighting on serum concentrations of PRL in gilts contrasts with published results from studies on cattle and sheep.

¹ Journal Paper No. 9208, Purdue Univ. Agr. Exp. Sta.

² The authors gratefully acknowledge G. D. Niswender, Colorado State Univ., for supplying antisera to luteinizing hormone and progesterone; P. V. Malven, Purdue Univ., for supplying antisera to porcine prolactin, and R. J. Ryan, Mayo Clinic, for supplying radioiodination grade porcine follicle stimulating hormone. The technical assistance of D. Blair and D. Elftman is greatly appreciated.

⁴ Present address: Dept. of Anim. Ind., Univ. of Connecticut, Storrs 06268.

⁵ Dept. of Anim. Sci.

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