Investing.com -- Bank of America released its monthly protein monitor showing mixed performance across U.S. animal protein markets over the past four weeks, with beef prices relatively stable while pork and chicken face continued pressure.

Trailing four-week boxed choice beef prices averaged $368 per hundredweight, down 0.7% year-over-year, while select beef prices averaged $354 per hundredweight, up 1.0% year-over-year, according to United States Department of Agriculture data. Live cattle prices averaged $237 per hundredweight, up 0.2% year-over-year.

Beef packer margins averaged negative $251 per head on a trailing four-week basis according to Hedgers Edge, compared to negative $177 per head in the same period last year.

The USDA announced a phased reopening of the U.S./Mexico border for cattle imports beginning August 24. Tyson (NYSE: TSN) noted on its third-quarter earnings call that resumed imports should improve cattle availability over time and provide a modest tailwind to industry margins. The company said it will take at least a year to see the impact and is not enough on its own to offset current cattle cycle headwinds. Mexico accounts for approximately 5% of U.S. slaughter supply.

In pork markets, trailing four-week boxed pork prices averaged $102 per hundredweight, down 12% year-over-year, and lean hog spot prices averaged $98 per hundredweight over the trailing four weeks, down 9.3% year-over-year. Pork packer margins averaged negative $0.63 per head on a trailing four-week basis compared to negative $4.28 per head a year ago.

June cold storage data showed pork inventories, particularly hams and bellies, building counter-seasonally, signaling that spring export and foodservice demand underperformed.

Ready-to-cook pounds of chicken were up 3.1% year-over-year on a trailing four-week basis on higher heads slaughtered. Egg sets, a 10 to 12-week leading indicator of production, are up 1.8% year-over-year on a trailing four-week basis, while chicks placed are up 0.7% on a trailing four-week basis. Production growth continues to outpace demand, pressuring chicken pricing, particularly breast meat.

Packaged meats trends remain mixed, with weakness in bacon offset by more stable performance across categories such as sausage and sliced lunchmeat. Lower pork costs are providing some relief while elevated beef trim costs continue to pressure margins.