2. Materials and methods
2.1. Animals and housing
The experimental subjects were 22 Yorkshire × Norwegian Landrace, individually loose-housed sows which had farrowed at the Pig Research Unit at the Norwegian University of Life Sciences in 2009. Four of these sows were excluded from the study due to health problems (birth difficulties, MMA). All sows were inseminated with semen from Duroc × Landrace boars and moved from the indoor group gestation unit to the indoor farrowing unit at Day 110 post-insemination. Parities ranged from 1 to 7 (2.5 ± 1.8, mean ± SD). All farrowing pens were in the same building and each pen had a total area of 8.9 m2, where part of the pen accessible to the sow measured 7.0 m2 (resting area with solid floor measured 3.3 m2, plastic, slatted floor measured 3.7 m2). The creep area (1.9 m2), inaccessible to the sow, had floor heating with a wooden triangular roof and was separated by a diagonal wall with a 0.20 m gap along the bottom for piglets to enter (Fig. 1). Two metal farrowing rails were fixed in the resting area and above the slatted floor to avoid piglet crushing (Fig. 1). The cleaning was conducted manually twice a day and 2.0 kg of straw was provided on a daily basis from Day 113 until farrowing. Thereafter the solid floor of the resting area and creep area were covered by 2 cm of fresh, clean sawdust every day. Water was available ad libitum from nipple drinkers placed over the slatted floor area both for the sow and her piglets. Commercial lactation diet and 0.5 kg of roughage (hay from the first harvest which was placed on the floor) were provided to the sows at 8.00 h and 14.00 h daily. The farrowing unit was automatically ventilated and the air temperature was maintained at around 16 °C. In order to enable the non-stop continuous video recording the artificial dim lights were kept on during the night. During the day-time natural light entered through windows. During the first 24 h after farrowing cross-fostering was carried out; piglets from large litters were moved to small litters, however no attempt to balance for piglet size within litter was made. Litter size was calculated as number of live born piglets minus piglets fostered off plus piglets fostered on from other sows. Litter size ranged from 5 to 17 (mean ± SD: 13 ± 2.9). Piglets had their teeth ground and received an oral dose of iron at 24 h old.
2. วัสดุและวิธีการ2.1. สัตว์และที่อยู่อาศัยThe experimental subjects were 22 Yorkshire × Norwegian Landrace, individually loose-housed sows which had farrowed at the Pig Research Unit at the Norwegian University of Life Sciences in 2009. Four of these sows were excluded from the study due to health problems (birth difficulties, MMA). All sows were inseminated with semen from Duroc × Landrace boars and moved from the indoor group gestation unit to the indoor farrowing unit at Day 110 post-insemination. Parities ranged from 1 to 7 (2.5 ± 1.8, mean ± SD). All farrowing pens were in the same building and each pen had a total area of 8.9 m2, where part of the pen accessible to the sow measured 7.0 m2 (resting area with solid floor measured 3.3 m2, plastic, slatted floor measured 3.7 m2). The creep area (1.9 m2), inaccessible to the sow, had floor heating with a wooden triangular roof and was separated by a diagonal wall with a 0.20 m gap along the bottom for piglets to enter (Fig. 1). Two metal farrowing rails were fixed in the resting area and above the slatted floor to avoid piglet crushing (Fig. 1). The cleaning was conducted manually twice a day and 2.0 kg of straw was provided on a daily basis from Day 113 until farrowing. Thereafter the solid floor of the resting area and creep area were covered by 2 cm of fresh, clean sawdust every day. Water was available ad libitum from nipple drinkers placed over the slatted floor area both for the sow and her piglets. Commercial lactation diet and 0.5 kg of roughage (hay from the first harvest which was placed on the floor) were provided to the sows at 8.00 h and 14.00 h daily. The farrowing unit was automatically ventilated and the air temperature was maintained at around 16 °C. In order to enable the non-stop continuous video recording the artificial dim lights were kept on during the night. During the day-time natural light entered through windows. During the first 24 h after farrowing cross-fostering was carried out; piglets from large litters were moved to small litters, however no attempt to balance for piglet size within litter was made. Litter size was calculated as number of live born piglets minus piglets fostered off plus piglets fostered on from other sows. Litter size ranged from 5 to 17 (mean ± SD: 13 ± 2.9). Piglets had their teeth ground and received an oral dose of iron at 24 h old.
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