FUNDING CYCLE 2015 – 2017 TITLE : Impacts of Stocking Density on Welfare and Productivity of Replacement Beef

Stocking density is one example of management that may impact welfare and reproductive efficiency of beef females in Oregon cows-calf systems. In spring-calving herds, replacement heifers are weaned late in the fall and exposed to their first breeding season the following spring/summer. Therefore, these heifers are often developed in drylot systems during the winter/early spring to facilitate management and supply of feed and water. However, data from our research station indicates that in years when heifers are developed in drylots (stocking density of 150 ft2/heifer), they have greater growth rate (1.65 vs. 1.25 lbs/day) but reduced puberty attainment (15% vs. 50% of pubertal heifers by the beginning of their first breeding season) compared to years when heifers are maintained on a pasture (stocking density of 10,000 ft2/heifer). It is important to know that heifers are maintained on pastures previously harvested for hay and with no forage available for grazing. Hence, nutritional management of heifers developed in drylot or pasture during the winter/early spring in our research station is similar across years. These outcomes suggest that developing beef heifers in confined areas is detrimental to their reproductive development and future performance, although research with heifers concurrently reared in different stocking densities is warranted. Given that rearing cattle in confined areas is known to stimulate stress reactions, while acute and chronic stress directly impairs reproductive function in beef cattle, we hypothesized that elevated stocking density (less area available per animal) impairs reproductive development and welfare of beef heifers.