Productivity, behavior, and environmental impact of outdoor gestating sows

From ancient times, the pig has been a scavenger, living and foraging in forests, woods, and orchards. However, in the recent past, the need for specialization and increasing food demand has seen all stages of sow production move towards confinement units. A number of challenges including high costs of initial investment on facilities, animal welfare, public perception, odor, waste management, and issues of sustainability, face indoor production systems. Outdoor production systems are favorable in terms of low capital investment, flexibility, and perceived welfare advantages. Outdoor production systems are becoming popular due to stringent regulatory procedures and guidelines for producers directed towards confinement systems, especially in European countries and some parts of the United States. However, because of environmental concerns, the need to ensure that this method of production is sustainable still remains. Studies reported herein assess potential nutrient accumulation in soil on pastures occupied by sows, changes in percentage ground cover and botanical composition, productivity of sows and their litters, preference and use of selected forages by pregnant gilts. Dynamic assimilation model was performed for behavioral activities of outdoor pregnant sows as influenced by ambient temperature changes as well as time of day.

The first study compared soil-nitrate nitrogen (NO3") and phosphorus (P) accumulation, change in percentage of ground cover and botanical composition of burned and non-burned pastures with four replicates, each measuring 0.4 ha and occupied by seven pregnant gilts for 150 d. Productivity of sows and their litters were also evaluated, as well as effects of temperature on behavioral activities. Soil NO3' tended (P 0.05) to accumulate during dry periods when grass was dormant with no precipitation, but this changed with the onset of rains and forage re-growth. Soil NO3 were higher (P < 0.05) on outside sections of pastures were feeding took place. There were no differences in soil P between burned and non-burned pastures; however, levels tended to be higher (P < 0.08) on the non-burned pastures by the end of the study. Higher (P < 0.05) levels of P were noted on feeding area. Sows rooted more (P < 0.02) on cold d, whereas wallowing activity was higher (P < 0.001). Rooting holes and sizes increased as days increased, especially for the non-burned pastures. Sows on non-burned pastures lost more (P < 0.002) weight than those on burned pastures, however there were no differences in other measures of productivity.

Two stocking rates and two protein diets, in a factorial arrangement, were compared in the second study. Pastures (0.4 ha) that were occupied by 35 sows/ha lost more (P < 0.001) percentage of ground cover than those that had 17.5 sows per ha. More (P < 0.01) piglets were weaned per sow from the higher stocking rate than the lower one. No significant effects were noted in either soil nitrate concentrations or change in percentage of ground cover as a result of diet. Stocking rate is a management tool that can be used effectively to minimize loss of ground cover, especially from areas that tend to have less vegetative cover or have been more denuded. Diets given to sows can be tailored so that excessive nutrients are not excreted in the soil in this production system.

Preference and use of forages by sows was evaluated using alfalfa (Medicago sativa), tall fescue (Festuca arundinacea), white clover (Trifolium repens) and buffalograss (Buchloe dactyloides). In the first study, two gilts had free access to each block of the four forages (four replicates) for 48 h. Clover and alfalfa were preferred more (P < 0.01) for grazing and rooting than fescue and buffalograss, and clover was rooted more than other forages. In second study where clover was excluded, gilts were randomly confined individually on single forages with six replicates. Alfalfa was grazed more (P < 0.01) than fescue and buffalograss. When the objective is to provide sows with an extra source of nutrition from forages, alfalfa may be a good choice, whereas when ground cover is the priority, either buffalograss or fescue might be better choices than clover depending on the geographical region, prevailing environmental conditions, and water availability.

Behavior of 91 pregnant outdoor sows were evaluated during 24 h, 10-min scan observations in winter, spring, and summer to determine effects of ambient temperature and time of day on behavioral changes as well as sow location within pasture. Mutually exclusive behaviors included standing, lying, rooting, drinking, and feeding, whereas locations were around the hub, middle section, around the wallow, inside hut, outside, and feeding area. Dynamic models were developed for active, wallowing, rooting sow behaviors, as well as use of hut. During low temperatures sows were more active in the middle of the day while warm temperatures caused a morning as well as evening peaks in active behaviors. Wallowing activity increased (P < 0.01) as temperatures increased, while rooting activity was higher during cooler than warmer temperatures. Sows used the hut more (P < 0.001) during cool and high temperatures to shelter from harsh conditions. The models help recognize changes in sow behavioral activities with shifts in ambient temperatures and thus could facilitate management decision making.