Higher light intensity and mat temperature attract piglets to creep areas in farrowing pens.

Loose farrowing pens have been considered as alternatives to crates to enhance sow welfare. A major concern with pen systems is often higher piglet pre-weaning mortality, especially due to crushing by the sow. An optimal management of light and mat surface temperature may promote greater piglet use of the creep, which has been associated with reduced piglet crushing. A total of 108 sows and their piglets were studied in sow welfare and piglet protection pens on a commercial piggery, across two replicates. Sows were randomly assigned to pens arranged within two creep treatments (bright creep: 300 lx v. dark creep: 4 lx), considering mat temperature as a covariate. Twelve sows and their litters in each treatment (24 in total) had their behaviour continuously recorded for 72-h postpartum (pp), and four focal piglets per litter were weighed on the first and third days pp. In situ behaviour observations were performed daily (from 0800 to 1700 h) on all sows and their litters, every 15 min over 72-h pp to record piglet time spent in the creep, latency to enter the creep for the first time, latency for the litter to remain in the creep for at least 10 min, and piglet and sow use of pen areas immediately in front of (A2) and farthest from the creep (A3). Piglets with access to bright creeps spent on average 7.2% more time (P<0.01) in the creeps than piglets in pens with Dark creeps. In addition, for each degree increase in mat temperature, piglets spent on average 2.1% more time (P<0.01) in the creep. Piglets in pens with bright creeps spent less time in A2 (P=0.04) and the least time in A3 (P=0.01). Light or mat temperature did not affect sow use of pen areas or piglet weight gain. Piglets with bright creeps tended (P=0.06) to take longer to enter the creep for the first time after birth, but the latency for 30.0% of the litter to remain clustered for 10 min tended (P=0.08) to be shorter in bright compared to dark creeps. Overall, piglet use of the creep increased with warm mat temperatures and brightness, which should be further investigated as potential strategies to promote piglet safety and reduce crushing in pen farrowing systems.

Determining the effects of early gestation in utero heat stress on postnatal fasting heat production and circulating biomarkers associated with metabolism in growing pigs.

The study objective was to characterize effects of early gestation in utero heat stress (IUHS) on postnatal fasting heat production (FHP) and blood biomarkers associated with metabolism in growing pigs. Based on previous observation of increased postnatal core body temperature set point in IUHS pigs, we hypothesized that FHP would be altered during postnatal life because of IUHS. Pregnant first-parity gilts were exposed to thermoneutral (TN; = 4; 17.8 ± 0.1°C) or heat stress (HS; = 4; cyclical 28 to 38°C) conditions from d 30 to 60 of gestation. At weaning (21 d of age), 2 median-weight male pigs (1 barrow and 1 boar) were selected from each litter ( = 8 in utero TN [IUTN] and 8 IUHS pigs) and then housed in TN conditions based on age. Blood samples were collected at 8, 9, and 10 wk of age when pigs were in a fed state to analyze thyroxine (T4) and triiodothyronine (T3) concentrations. Pigs were trained to enter an indirect calorimeter from wk 8 through 10 of life and then acclimated over a 24-h period 1 wk prior to testing. At 12 wk of age, pigs were fasted for 24 h, and then indirect calorimetry was performed on individual pigs over a 23-h testing period to determine FHP and the respiratory quotient in 3 intervals (0900 to 1700 h, 1700 to 0000 h, and 0000 to 0800 h). Body weight was determined before and after testing and was similar for all pigs ( = 0.77; 37.0 ± 0.5 kg BW). Data were analyzed using PROC MIXED in SAS 9.4. No boar vs. barrow differences were observed with any analysis. Overall, FHP per kilogram BW was greater ( = 0.03; 12.1%) in IUHS pigs compared with IUTN pigs. Fasting heat production per kilogram BW was greater ( < 0.01; 19.8%) from 0900 to 1700 h compared with 1700 to 0000 h and 0000 to 0800 h and was greater (10.9%) from 1700 to 0000 h compared with 0000 to 0800 h. The RQ did not differ by in utero treatment ( = 0.51; 0.72 ± 0.01); however, the RQ was increased ( < 0.01; 13.0%) from 1700 to 0000 h compared with 0900 to 1700 h and 0000 to 0800 h. No other FHP and RQ differences were detected. Although no in utero treatment differences were observed for T4 ( = 0.11; 52.2 ± 6.2 ng/mL), T3 was greater overall ( = 0.04; 19.5%) in IUHS pigs than in IUTN pigs. In summary, FHP and circulating T3 were increased in IUHS pigs, and this may have implications for postnatal production efficiency in pigs gestated during hot summer months.