Deprivation of straw bedding alters PGF - induced 2 a nesting behaviour in female pigs

Sows are highly motivated to build a maternal nest on the day preceding parturition. A model for nest building has been established in pigs, in which exogenously administered prostaglandin Ž . F PGF may be used to elicit nesting behaviour in cyclic, pseudopregnant and pregnant pigs. 2a 2 a The aim of this experiment was to examine the effects of deprivation of straw bedding on PGF -induced nest building in pseudopregnant Large White gilts. Oestradiol valerate injections 2a Ž . 5 mgrday were given on days 11–15 of the oestrous cycle to induce pseudopregnancy. The pigs Ž . were housed individually in a pen 2.8=1.7 m and provided with 2-kg fresh straw each day. On the test day, on day 46 or 47 of pseudopregnancy, half of the pigs were deprived of straw Ž . Ž substrate effect and they were injected intramuscularly with saline or 15 mg of PGF Lutalyse, 2a . Ž . Upjohn treatment effect allocated in a Latin-square design. Behaviour was recorded onto video tapes for 1 h either side of treatment for analysis using a computerised event recorder. PGF -treated pigs housed in bare or strawed pens showed significantly higher frequencies of 2a pawing and rooting, and stood for longer than saline-treated controls. This treatment effect has been previously shown to be comparable to pre-partum nest building. The removal of straw significantly reduced the frequency of pawing and the duration of rooting by PGF -treated pigs. 2a The results demonstrate that nesting behaviour can be initiated by exogenously administered PGF and is further modified by the provision of straw. This suggests that PGF -induced 2a 2 a nesting behaviour is subject to environmental feedback. q 2000 Elsevier Science B.V. All rights reserved.