Ad libitum versus step-up feeding during late lactation: The effect on feed consumption, body composition and production performance in dry fed loose housed sows

The aim of this study was to compare the effect of ad libitum feeding versus a step-up feeding strategy during late lactation on sows' feed consumption, body composition and production performance. This on-farm study was conducted on 155 loose housed Norwegian Landrace×Swedish Yorkshire sows and their litters, originating from three batches of farrowing. The lactation feed contained 9.86 MJ NE/kg feed and 8.26 g lysine/kg feed and daily feed allowance was recorded. Measurements of sow body weight, body condition score, litter size and litter weight were taken within 24 h after birth and at weaning. Body weight, litter size and litter weight were also recorded on day 21 for sows farrowing in batches 2 and 3. Sows in batches 1 and 2 were backfat measured prefarrowing and at weaning. The study design was a randomized block design with 1st parity, 2nd parity and ≥3rd parity as blocks. Within block sows were randomly allotted to feeding strategy. “Feed refusal” was defined as a drop in feed intake of >3 kg for ≥3 days. Feeding strategy did not affect daily or total feed consumption, weight loss, backfat loss or litter gain. The ad libitum group had a lower feed consumption in week four of lactation (p<0.05) and more feed refusals (p<0.01). The relative backfat loss (%) tended to be higher in the ad libitum group (p<0.1), and backfat loss in the loin was higher in older sows (≥3rd parity) in this group (p<0.05). Parity affected daily, weekly and total feed consumption, with 1st and 2nd parity sows consuming less than older sows (p<0.0001). First parity sows had more feed refusals (p<0.01), higher weight loss (p<0.05) and lower litter gain (p<0.001) than older sows. The relative weight loss (%) was higher in 1st and 2nd parity sows compared to older sows (p<0.05). Positive correlations were found between total feed consumption and litter gain (r=0.45, p<0.0001), body condition and weight loss (r=0.46, p<0.0001), backfat before parturition and total backfat loss (r=0.67, p<0.0001) and body condition and backfat (r=0.55, p<0.0001). A negative correlation was found between total feed consumption and weight loss during the three first weeks of lactation. (r=−0.66, p<0.0001). Parity affects feed consumption, body composition and production, and caution should be taken not to overexert young sows during lactation. A higher risk of feed refusal and more individual variation in the ad libitum group favours the step-up strategy.