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.