Both USDA and the CME Group's Daily Livestock Report noted harsh winter weather is having an impact on cattle weights at slaughter.

In its World Agricultural Supply and Demand Estimates report, USDA said cattle outside feedlots are believed to be close to last year, which led USDA to raise its forecasts for cattle placements, marketings and slaughter.

"However, partly offsetting the increase in expected slaughter, cattle weights are reduced for early 2010 due to severe weather, which has impacted weight gain," the report stated.

Statistics published in Tuesday's DLR supported USDA's statement.

Steer and heifer carcass weights have drifted lower in recent weeks due too poor feedlot conditions, and possibly poor feed quality, according to the DLR. For the week ending Jan. 23, steer weights were down 16 pounds, or 1.9 percent, compared to a year ago, while heifer weights were down 8 pounds, or 1 percent, compared to last year.

Live cattle weights for the week ended Feb. 6 were reported down some 19 pounds, or 1.45 percent, from a year ago. Cattle carcass weights for the same week were 15 pounds, or 1.9 percent, lower than a year ago.

"We suspect that USDA will further lower its live and carcass weight estimates in a couple of weeks to reflect the poor performance of feedlot animals as well as beef cows," predicted the DLR. It said the reported weight declines are the equivalent of 15,000 fewer cattle coming to slaughter each week, and thus will compound the impact of already light slaughter levels.

There might also be another factor at play. The DLR cited studies indicating a crop with mold has a lower nutritional value, thus requiring more feed to produce the same amount of beef.