Protein Supplementation of Low-Quality Forage: Effects of Amount and Frequency of Protein Supplementation on Ruminant Performance and Nutrient Utilization

            Production of beef cattle is consistently the number two agriculture commodity in Oregon.  Consequently, raising cattle is the largest generator of livestock value in Oregon and is dominated by commercial cow/calf production with over 500,000 producing females located in the state.  Most cattle spend their entire lives, except for the final 4 to 6 months in the feedlot, grazing standing forage or consuming hay.  Forage quality is usually sufficient to support normal levels of production early in the growing season; however, as forages mature they increase in fiber content, decrease in crude protein (CP), and decrease in digestibility.  As a result, many cattle in Oregon and the western United States consume low-quality forage (< 6% CP) from late summer through winter and require some form of supplementation to maintain desired levels of performance.

            Protein supplementation of low-quality forage has been shown to increase cow weight gain and body condition score (BCS), forage intake and digestibility, and can improve reproductive performance.  However, winter supplementation can be very expensive.  Winter feed costs in the intermountain west often total $150 to 250 per cow per year.  In addition to actual supplement costs, winter supplementation includes other expenses such as the labor, time, and equipment associated with supplement delivery.  In contrast to other areas of North America, winter feed costs represent an economic disadvantage and could substantially threaten the economic future of the beef industry in this region.

            Decreasing the frequency of protein supplementation is one management practice that can decrease labor and time costs by greater than 80% compared with daily supplementation.  Ruminants have the ability to recycle excess absorbed nitrogen back to the rumen; therefore, recycling of absorbed nitrogen may support ruminal fermentation between times of supplementation.  Consequently, past research has shown that protein supplements can be fed at infrequent intervals and still maintain acceptable levels of performance; however, data is limited comparing the effects of altering the amount of protein provided at infrequent intervals on forage intake and digestibility, animal performance, and efficiency of N use.

            It is possible that ruminants consuming low-quality forage may be able to adapt to infrequent supplementation of CP by increasing their ability to recycle nitrogen, thereby improving efficiency of CP use.  We hypothesize that as the supplementation interval increases ruminants will become more efficient in their use of supplemental CP.  As a result, we should be able to provide LESS total CP and maintain performance comparable to more frequent supplementation of MORE total CP.  This will not only save time and labor, but will decrease the amount and cost of supplement provided to beef cows consuming low-quality forage, and therefore increase economic returns of Oregon’s beef producers.

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