Interpretive Summary: The influence of age and environmental conditions on supplement intake and behavior of winter grazing beef cattle on mixed-grass rangelands
Presented at the 2018 WSASAS Annual Meeting
By: Lindsay Tretter
Sam Wyffels from Montana State University
During the winter in the western U.S., harvested forages are used to meet nutrient requirements for grazing livestock, but the cost of these resources is increasing. Dormant season grazing can meet the animals forage requirement, however, it is common to become deficient in protein. Therefore, a protein supplement should be provided to meet nutrient requirements and allow grazing for as long as possible.
The goal of this study was to meet nutrient requirements while optimizing intake of stockpiled forage. However, intake levels can vary among individual animals,
The study was conducted at Thackeray Ranch on a 329 hectare mixed grass pasture from November to January of 2016-17 and 2017-18. Three hundred Angus and Angus-Simmental crosses were utilized (275 in the first year and 301 in the second). All cows were blocked by age and offered a free choice supplementation from a self-fed trailer system. Supplementation intake was targeted at .0.91 kg/cow/day. Individual animal id’s were read as they approached the feed bunk.
Environmental impacts on intake were measured using an HOBO weather station that was attached to the feed trailer. Daily weather data was collected and paired with the individual animals’ intake.
Results from the study showed that in year 1 the younger animals (ages 1 to 3) consumed a greater amount of supplement, however, a linear decrease in intake was reported as they aged. While year two was similar, a lower decrease in intake was reported as age increased. In both years, the cattle ate more than the targeted amount of supplement. The presenter explained that the difference in intake between year one and two was most likely due to year one being much colder, explaining the increased intake levels. In addition, year two also had a larger range in temperature. The difference between the first and second year could be explained by year 1 being colder than year 2.
Using the data found in this study, it will be possible to have more strategic supplementing techniques. It was suggested that older cattle decrease intake during cold temperatures, which is a behavioral response of experience versus a naïve animal and plan to test this in the near future.