I have an 8 year data series of Iowa/Southern Minnesota barrow and gilt live weight at slaughter as reported by USDA. Live weights in the past two weeks declined 5.7 pounds, the largest 2 week decline in my data set. The only other decline similar was the 5.5 pound drop in weights for the 2 week period ending on July 4 in 2009.

In 2009, weights went from 268.7 lb for the week ending on June 20 to 263.2 lb for the week ending on July 4. This year, weights have fallen from 266.6 for the weeks ending on July 9 and July 16 to 260.9 lb for the week ending on July 30.

This year we’ve gone from the heaviest weekly live weights on record in January, February and March to falling within 1.2 lb of the 2004-2008 average weekly weight for week 30 of the market year. We’ve gone from an average live weight of 275.8 lb for the week ending January 8 to the 260.9 weight last week, a reduction of 14.9 lb/pig delivered to slaughter plants. This is a 5.4% reduction in pork supplies just from a change in live weight, assuming constant carcass yield and similar pig numbers delivered both weeks.

Some of this decline in sale weight is due to producer reaction to historic feed ingredient prices and now the record heat. In tunnel barns with very detailed records, I’ve seen over 0.1lb/d difference in adg between the curtain end of the barn where the highest daily gains occurred and the fan end of the barn which was the warmest part of the barn, even with fans running and pigs being wetted down. Summer heat has really impacted pigs in Iowa and Southern Minnesota

Sale weights rebounded quickly in 2009 when the summer turned cool and rainy. I don’t think that will happen this year. In a normal year, weights continue to remain low for another 3-4 weeks before they begin their rapid fall rise in response to cooler weather and new crop corn.

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