Feed Processing Affects Palatability of Ventenata-Infested Grass Hay

Ventenata (Ventenata dubia) is an invasive grass species that infested rangelands in the inland Northwest, causing significant economic damage through declines in forage production. Despite its nutritional similarity to other forages such as cheatgrass in terms of crude protein content and NDF digestibility, its palatability for livestock is poor. The objective of this study was to investigate the role of texture and surface-bound microbes in determining palatability of ventanata-infested hay. Thirty-five weaned Charolais calves were separated into five treatments according to a taste-preference study that lasted for seven days. Each animal had access to two feed bunks: one with a reference diet (mixed grass hay), and one with a treatment diet. The five treatments were: Control – Mixed grass hay used as the reference diet (CTRL); ventenata-infested hay (VENT); autoclaved mixed grass hay (AUTO-M); autoclaved ventenata-infested hay (AUTO-V); and pelleted ventenata-infested hay (PELT). Preference between mixed-grass hay and ventenata-infested hay was calculated such that: 0% preference implies a total preference against the treatment diet; 50% preference implies an equal preference between mixed grass hay and ventenata-infested hay; and 100% preference implies a total preference for the treatment diet. Body weight gain was measured at the start and end of the experiment. Daily, intake of the reference diet and treatment diet were measured and % preference was calculated. Among the five treatments, there was no difference in body weight gain during the 7 days on treatment. The CTRL treatment showed no difference from 50% preference, indicating that our feed preference test worked. Calves on the VENT treatment had a preference of 19%, highlighting the poor palatability of ventenata-infested hay. While autoclaving ventenata-infested hay made no difference to palatability, the PELT treatment increased preference to 50%, completely erasing the negative palatability of the ventenata-infested hay. Together, these results show the poor palatability of ventenata-infested hay may be due to texture of the hay, and ventenata’s palatability can be improved through feed processing.