407 Performance, digestion, and passage of whole cottonseed offered either ad libitum or under restriction to beef cows nursing calves.

Abstract In the southeastern United States, whole cottonseed (WCS) is a widely available, nutritious, and cost-effective feed option for beef cattle. According to the NRC (2016), WCS consists of about 52% neutral detergent fiber (NDF), 24% crude protein (CP), and 18% crude fat. Feeding guidelines for WCS in beef cattle diets were originally developed in the 1980s, based on the seed quality at that time. However, recent research has shown that changes in cottonseed varieties have altered its nutritional composition in the Southeast. This study aimed to determine appropriate WCS supplementation levels in beef cow diets, considering these industry shifts. The experiment followed a generalized complete block design with two feeding pens (blocks), each containing eight cow-calf pairs. These pairs were randomly assigned to one of four feeding treatments: a control group receiving only bermudagrass (BMG) hay (CON), BMG supplemented with WCS at 15% of targeted dry matter intake (DMI), BMG supplemented with WCS to reach a crude fat intake of 4% dry matter (FAT), and BMG supplemented with WCS on an ad libitum basis (LIB). Cows in the LIB group consumed the greatest amount of WCS (P < 0.01; 5.60 kg/day), followed by the FAT group (3.41 kg/day) and the DMI group (1.92 kg/day). However, total daily intake was highest in the LIB (13.2 kg/day) and FAT (13.1 kg/day) groups, lowest in the CON group (9.9 kg/day), and intermediate in the DMI (11.5 kg/day) group (P = < 0.0001). There was no effect of treatment on milk production in dams (P = 0.57) or calf body weight (BW) (P = 0.82). These findings suggest that beef cows nursing calves can consume WCS at near ad libitum levels without negative effects, though this may not always align with economic production goals.