Periparturient nest building: Implications for parturition, kit survival, maternal stress and behaviour in farmed mink ( Mustela vison)

Abstract

Several types of nesting materials with different capacity as substrate for nest building are currently supplied to farmed mink. We investigated whether different nesting resources and possibility of performing periparturient nest-building influenced (a) the parturition, (b) the vitality and survival of neonates, and (c) maternal stress and behaviour. Individually housed female mink (all provided with wood shavings in the nest box) had either (1) restricted possibility of nest building (NON; n = 60), (2) restricted possibility of nest building, but an artificial plastic nest available (ART; n = 60), (3) full possibility of nest building using straw (STR; n = 60), or (4) full possibility of nest building using straw and an artificial plastic nest available (ART + STR; n = 60). The experimental period began on average 11 days before the deliveries (range: 5–21 days) and lasted until 7 days after birth of each individual litter. The access to straw for nest building reduced the variation in inter-birth intervals between kits ( P = 0.044; S.D. STR: 36 min versus NON: 58 min and ART: 53 min), but did not affect the total duration of parturition. The average body weight of kits was significantly reduced in NON litters after 7 days ( P = 0.025), with no differences on Day 1 after delivery. In addition, the mortality of live-born kits was highest in the NON litters ( P < 0.001). Female stress hormone metabolites, measured non-invasively in faeces, tended to differ between treatment groups after delivery ( P = 0.064), with a lower concentration in ART and ART + STR than in NON. In a maternal reactivity test, ART + STR females were quicker than NON females to retrieve their 5-day-old kit to the home nest ( P = 0.027). In conclusion, an artificial nest alone or in combination with ad libitum access to straw tended to reduce maternal stress postpartum, and the combination significantly enhanced maternal kit retrieval. For the kit vitality and survival, an artificial nest appeared as good as a nest of straw created by the dam, due to an improved in-nest climate postpartum. However, access to straw for nest building resulted in a less variable parturition, whereas the feedback from an artificial nest had no such effect.