Grow-finish pigs and summer heat

It has been a quiet week in my swine consulting business. As a result, I’ve had time to catch up on some of my reading of recently published scientific papers and conference proceedings.

One paper that caught my eye was some work from Europe that looked at the impact of temperature on space requirements of group housed finishing pigs. With summer heat approaching its time to put in place the strategies that will mitigate some of the impacts of summer heat.

It also increases the amount of time spent lying since the effort to stand and move generates heat so a first response to hot conditions is to spend more time lying. At the same time, it changes its posture in the lying position.

In cooler conditions, the pig prefers to lay with its sternum touching the floor (ventral posture). The amount of space required for lying is very similar to the amount of space required to stand. In cold conditions the pig huddles with other pigs and the amount of space required for lying is less than that required for the group of pigs to stand.

However, as conditions warm, the pig increasingly lies in a lateral position with its feet and legs spread away from the body. The result of this change in posture is increased surface exposure for heat loss. In European housing situations where the pig had the choice of a bedded kennel, solid surfaced pen area or slatted floor, it increasingly chose the slatted floor as the lying area as temperatures increased.

The use of sprinklers will impact this behavior as it provides a very effective means for the pig to lose heat well beyond what could be accomplished by postural changes. All of this brings us to what producers need to think about as summer heat approaches.

Because of interruptions in pig flows because of farrowing losses due to PEDv, there are many facilities that will be short of pigs this summer. I’m aware of producers who have rented some of these facilities for single turns in order to help maintain sale weights during summer months.

In the US, the most common space allocation in a pen is 7.2 sq ft/pig (0.67 sq m). A large number of facility permits are based on 7.5 sqft/pig stocking densities using overall building dimensions, including sidewall structural dimensions and aisles in the facility. This space allocation is adequate for the pigs needs in thermal neutral conditions up to about 195 lb, after which crowding begins to limit feed intake and daily gain.

The best estimate is that this space limitation is limiting US grow-finish daily gain to about 95% of what it would be if we gave the pigs adequate space based on pig removal to sale beginning when the pen average weight is 250 lb. The estimated requirement for space allocation on fully slatted floors for pigs taken to 250 lb before the first pig is removed to slaughter is around 8.5 sq ft/pig. If pigs were given this much space versus the current industry standard of 7.2 sq ft/pig, the data suggests daily gain from 50-250 lb would increase about 0.1 lb/d. Because there is very little impact of space allocation on feed conversion (the biggest production expense) the industry has chosen to reduce allocation so that more pounds of gain can be captured per unit of space per year to pay for this component of production.

All of the above suggests that producers who have the option to rent facilities for short term summer use can expect pig performance to improve if they put fewer pigs in their facilities (more space per pig) due to both the response to more space and the ability of the pig to adapt more aggressive postural changes to help it cope with summer heat.

In a future blog I’ll discuss the common myths of summer sprinkling management and grow-finish pigs.

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