Rarely have I recommended planting winter pasture, specifically small grains, for mature cattle because of the inefficiencies associated with grazing a high-quality, high-input crop with animals that are physiologically mature and metabolically adequately conditioned. The forage quality of most small grains and other cool-season annual grasses is most efficiently utilized by growing and under-conditioned livestock. Couple this with the annual input costs of small grain establishment, and it is difficult for mature cattle to create a positive return on investment. However, in limit-grazing situations when managed properly, winter pasture can be used by mature cattle very efficiently but as a protein supplement. Thus, the objective of this study is to develop guidelines for limit-grazing small grain pasture with mature cattle.
In order to properly manage a mature cattle limit-grazing scenario, there are several variables that need to be known or determined.
These variables are the livestock requirements based on average body weight and physiological condition of the cattle, forage quality of hay or reserve forage and forage quality of the winter pasture that is to be limit-grazed. Livestock specialists can determine cattle requirements based on NRC guidelines, but forage quality data has to be sampled and analyzed. Hay can be analyzed well ahead of the anticipated feeding period. For most accurate results, winter pasture should be sampled and tested about two weeks prior to the anticipated feeding period and then periodically throughout the feeding period to monitor for any changes in quality.
In January of 2001, I reported the results from this project using mature cattle, specifically fistulated steers averaging 1,657 pounds at the initiation of each study, over two winters. In February and March 2003, we performed a similar study with fistulated replacement heifers, averaging 904 pounds over the two months, which were bred later in the spring. A subsequent study will be conducted with these bred heifers this winter while they are in the last trimester of pregnancy.
Table 1 represents the forage conditions for each trial. There was some pasture variability between years due to growing conditions, fertility applications and pasture maturity at the onset of the study (winter 03). It is interesting to note that forage production per acre inch (lb. DM/ac. in.) is relatively similar, and that the cattle in each trial consistently grazed a higher-quality diet than what was sampled in the pasture.
In tables 2 and 3, results on crude protein intake and total forage intake are tabulated for each grazing interval for both mature steers and replacement heifers. There are some noted differences in the tables. The larger steers consumed more volume than the smaller heifers over the 45-minute duration, but intake as a percentage of body weight was higher for the heifers. Also, crude protein intake was less for the heifers, probably due to the lower forage quality. Therefore, it is important to know the quality of forage to be limit-grazed because it directly affects crude protein intake.
The most important information needed to be communicated is the relative cost of supplementation comparing limit-grazing winter pasture with supplemental feed alternatives. Table 4 illustrates these comparisons using data from the trials and assigning feed costs for each supplement. Cost per day of supplement for each alternative is indicated under the daily feed requirement. As illustrated, if winter pasture is limit-grazed properly by mature cattle, it can be a cost-efficient protein supplement for those with appropriate resources and skills.