Winnebago Industries Inc. today reported lower earnings in the quarter ended Nov. 28 but a big improvement in its gross margin compared with the year-ago period. The Forest City-based manufacturer reported fiscal first-quarter net income of $8.6 million, or 32 cents per share, versus $9.9 million, or 37 cents per share, in the year-ago quarter. The company’s first quarter gross margin increased 90 basis points due in part to improved motorized product mix, a greater contribution from towables and lower workers’ compensation expense. The improvement was partly offset by continued labor-related manufacturing inefficiencies and unfavorable trends in warranty expense. Gross margin is the percent of total sales revenue that the company retains after incurring the direct costs associated with producing the goods sold. Year over year, motor home retail registrations increased 3 percent in the fiscal 2016 first quarter.