The rapid decline in China’s swine herd due to African swine fever has caused volatility in U.S. domestic prices, Goldman Sachs analyst Adam Samuelson told clients last week in a research report. China’s total swine inventory will be down 13 percent to 374 million head by the end of this year, according to a USDA report.

“With the Chinese pork industry representing roughly 20% of global protein production, the potential...