SEW prices and new nursery designs

Pork producers are beginning to act nervous about profit prospects this fall. SEW prices continue to decline, both on the contract and spot market as the Chicago futures continue to gradually decline in value. This past week USDA reported SEW prices as low as $27.50/pig delivered. The last time SEW pig spot market prices dropped this low was last November.

The current week to week decline in average price is now steeper than the last years decline. As a point of reference, SEW pig prices typically decline from a high around years end (representing pigs destined for early summer markets) to week 33 of the year (mid-August).

There is still quite a bit of interest in new facilities for construction this summer. Producer calls this week dealt with both wean-finish and nursery construction projects. There does appear to be renewed interest in nursery facilities. In some cases it’s driven by concern about higher heating costs for large wean-finish facilities, sometimes by the desire for better environments for challenged health status pig flows and sometimes by siting issues. A nursery for 2500 pigs is relatively small and doesn’t come close to any animal unit limit that often restricts grow-finish facilities.

The challenge for both nursery and grow-finish facilities is sizing attic inlets large enough to get sufficient air into the attic to supply the large number of ceiling inlets being installed. Producers are asking for more ceiling inlets (usually actuated) so they can get better air quality to all parts of rooms.

Curtain sided grow-finish barns are now often sized for 42 cfm/pig ceiling inlet, nurseries at 45 cfm/pig and tunnel ventilated barns at approximately 50 cfm/pig. If there are 1200 pigs in the room, the number of ceiling inlets is similar in all 3 situations. Since the nursery is generally 50% or more smaller than grow-finish facilities, attic inlet area becomes a critical design issue.

In general, designers want one square foot of attic inlet per 400 cfm of ventilation air. If they go with one square foot per 800 cfm of air, this adds approximately 0.04” of static pressure to the ventilation system. At 800-1000 fpm ceiling inlet velocity we already have 0.04-0.05” of static pressure to get air thru the inlet. If anything causes inlets to be partially plugged such as inlet doors, dirty soffit, incorrect soffit materials, etc., the static pressure on the fan increases and fan performance declines. As fan output declines in response to higher pressures, electricity usage goes up to move the same amount of air, resulting in higher operating costs and potentially higher fan maintenance costs.

I recently worked on a nursery ventilation design for a 100 x 100 nursery that would be 2 rooms of 1250 pigs each (100 x 50 rooms). If one of the soffits is closed in winter weather due to concerns with snow drifting into the attic, the remaining soffit must be sized large enough to supply air for both nursery rooms. In this case, the soffit (and associated clearance above the installed insulation chute at the plate) needed to be almost 18 inches wide/tall. The solution in this case was to add a gable end inlet and even then sizing was a concern.

6 thoughts on “SEW prices and new nursery designs

  1. Do you think removing half of the dust and H2S and ammonia from the air in the production room will help elevate some of these sizing concerns? Especially for those facilities already built with improper ventilation.

    Ionization treatment of the air can help.

  2. Removing pollutants won’t change the sizing requirements since we are dealing with the large increase in heat production by today’s improved pigs. The target for summer ventilation is to move enough air so room temperatures stay with 2-3F of outside temperatures.

  3. Mike, is it ever possible to have a nursery design that is curtain sided, with the thought of getting enough air to the pigs especially in the summer and cutting down on electricity costs?

  4. Curtain sided nurseries are quite common in the southeast. However, in the upper midwest we stay in heating mode and minimal ventilation much of the year and getting curtain sided barns tight enough is always a problem. In addition, curtains have almost no insulation capability so you would end up having to devise strategies to reduce heat loss thru the curtain wall that become time consuming to install/remove, etc.

  5. Ventilation is obviously important in nursery facilities, especially with pigs having longer turns in the nursery. Taking into consideration that the ventilation is sized correctly, does having 4 square feet per pig have a positive effect on pig growth over the old rule of 3 feet per pig space?

  6. All of the available data on space for growing pigs suggests that 3.0 sqft/pig is adequate until pigs weigh about 52 pounds. Thus, if pigs are removed from a nursery or over-stocked wean-finish where they are housed at 3.0 sqft/pig prior to 50 pound liveweight, pen space would not be a limit to feed intake and daily gain. Four sqft/pig is thought to be adequate for pigs up to 77 lb bodyweight. In general, a small amount of space restriction is generally used as total weight gain per unit of space is higher even if daily gain begins to slow down. The general rule of thumb is that there is a 1% reduction in daily gain and daily feed intake with each 3% decrease in space allocation below the requirement for maximum pig performance on fully slatted floors.

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