Microbial use of recycled urea is dependent on the level and frequency of degradable intake protein supplementation

Protein supplementation increases utilization (intake and digestion) of low-quality forage and ultimately animal performance. Despite its effectiveness, protein supplementation is often expensive. One strategy to reduce the cost of supplementation is to supplement less frequently than daily, generally every other day or every third day. By reducing the frequency of supplementation, the cost of delivering the supplement is reduced. Reducing the frequency of supplementation is an effective strategy for reducing cost, and it only minimally impacts animal performance, with less frequent supplementation resulting in slightly greater losses of body condition score and body weight during the winter supplementation period. Urea recycling, the transfer of urea from the animal\u27s body to the gastrointestinal tract, has been suggested as a mechanism that allows infrequently supplemented cattle to perform similarly to cattle supplemented daily. However, little data is available to substantiate this claim, and such data would be useful in helping nutritionists better understand nitrogen metabolism in infrequently supplemented ruminants. Our objective was determine the role of urea recycling in meeting ruminal nitrogen requirements in infrequently supplemented cattle fed low-quality forage

Microbial use of recycled urea is dependent on the level and frequency of degradable intake protein supplementation

Protein supplementation increases utilization (intake and digestion) of low-quality forage and ultimately animal performance. Despite its effectiveness, protein supplementation is often expensive. One strategy to reduce the cost of supplementation is to supplement less frequently than daily, generally every other day or every third day. By reducing the frequency of supplementation, the cost of delivering the supplement is reduced. Reducing the frequency of supplementation is an effective strategy for reducing cost, and it only minimally impacts animal performance, with less frequent supplementation resulting in slightly greater losses of body condition score and body weight during the winter supplementation period. Urea recycling, the transfer of urea from the animal’s body to the gastrointestinal tract, has been suggested as a mechanism that allows infrequently supplemented cattle to perform similarly to cattle supplemented daily. However, little data is available to substantiate this claim, and such data would be useful in helping nutritionists better understand nitrogen metabolism in infrequently supplemented ruminants. Our objective was determine the role of urea recycling in meeting ruminal nitrogen requirements in infrequently supplemented cattle fed low-quality forage

Relative value of ruminally degradable and undegradable protein on the utilization of low-quality prairie hay by steers

An experiment was performed to investigate the impact of providing six levels of ruminally degradable protein (RDP; protein that is available to ruminal microbes) in combination with two levels of ruminally undegradable protein (RUP; protein that is not available to the ruminal microbes, but can be digested directly by cattle) on the intake and digestion of low-quality prairie hay. Twelve steers were provided unlimited access to low-quality prairie hay (5.3% crude protein and 71.7% neutral detergent fiber) throughout the trial. To simulate dietary RUP, casein was infused abomasally once daily at either 0 or 0.087% of body weight. To simulate dietary RDP, casein was infused ruminally once daily at 0, 0.029, 0.058, 0.087, 0.116, or 0.145% of body weight. As provision of RDP increased, forage intake and fiber digestion increased. Supplementing with RUP alone increased forage intake but not fiber digestion, although the intake response was not as large as providing the same amount of RDP. In conclusion, RUP is less efficient than RDP in stimulating forage intake and digestion

Supplementation with undegradable intake protein increases utilization of low-quality forage and microbial use of recycled urea

Low-quality forage utilization (intake and digestion) is improved by protein supplementation. Typically, the recommendation is to select supplements that are high in degradable intake protein because this fraction of the protein directly addresses the ruminal nitrogen deficiency that exists when low-quality forages are fed. However, the low cost of byproducts (e.g., distiller’s grains) that are high in undegradable intake protein makes them an attractive source of supplemental protein even though the response per unit of supplemental protein is less for undegradable protein than for degradable protein. One of the primary barriers to utilizing highly undegradable protein sources as supplements is the lack of information regarding their ability to provide nitrogen to ruminal microbes and, ultimately, their effectiveness as protein supplements to cattle fed low-quality forage. Because the protein is not ruminally degraded, the use of undegradable protein supplements to meet ruminal nitrogen requirements depends on the ability to recycle nitrogen to the rumen in the form of urea. Subsequently, the urea is utilized as a nitrogen source by ruminal microbes. Our objective was to measure how much nitrogen is recycled as urea and how much recycled nitrogen is used to meet microbial growth requirements when increasing amounts of undegradable intake protein were provided to steers consuming prairie hay. This data will be useful in developing supplementation strategies for cattle consuming low-quality forage

Supplementation with degradable intake protein increases low-quality forage utilization and microbial use of recycled urea

A common production practice throughout the United States is to supplement protein to cattle consuming low-quality forage (forage with a crude protein content of less than 7%) in order to improve animal performance (i.e., maintain body condition score and body weight) during the winter. Protein supplementation increases forage utilization (intake and digestion) and cow performance by supplying ruminal microbes with protein that is essential for microbial growth. Increased microbial activity in turn provides sources of both protein and energy to the cow. In addition to the protein that is fed and degraded in the rumen, ruminants have the ability to recycle urea—the same compound found in fertilizer and cattle feed—to the rumen, where microbes can use the urea to fulfill a portion of their nitrogen requirement. Although nutritionists know that recycling occurs, we have inadequate data to describe this process and, subsequently, the contribution from recycled urea is not adequately included in our present cattle feeding systems. Previous research at Kansas State University has clearly demonstrated that the greatest response to supplemental protein occurs when the supplemental protein is highly degraded within the rumen, as the degradable fraction of protein is directly available to ruminal microbes. The current project’s objective was to measure how much recycled urea is used to meet the microbial nitrogen requirement when increasing amounts of degradable intake protein were provided to steers consuming low-quality forage. Researchers hoped to generate data useful in refining supplementation recommendations for cattle consuming low-quality forage

Determining the influence of different levels of urea supplementation when beef cows grazing winter pasture are supplemented at different frequencies during the prepartum period

One hundred sixty spring-calving Hereford × Angus cows grazing low-quality, tallgrass-prairie range during the winter of 2000-2001 were supplemented before calving either daily or three times weekly. The supplement contained 40% CP with 0, 15, 30, or 45% of the supplemental degradable intake protein from urea. Supplement was fed at 4 lbs/head daily to cows receiving supplement daily. Cows receiving supplement three times weekly were fed the same amount of weekly supplement, but split equally among their supplementation events. After calving, all cows received a supplement without urea on a daily basis. In general, prepartum supplements that contained more urea prompted greater body weight loss; however, the effect of increasing urea was most noticeable when supplements were fed only three times weekly. When averaged across supplementation frequencies, increasing the level of supplemental urea tended (P=0.15) to decrease pregnancy rate in beef cows that had received urea supplementation before calving

Timed-insemination of beef heifers using Cosynch with or without MGA

Our purpose was to determine if feeding melengesterol acetate (MGA) for 1 week in combination with gonadotropin-releasing hormone (GnRH) and prostaglandin-F2" (PGF) would better synchronize heifers for timed artificial insemination. Sixty-nine yearling beef heifers received an injection of GnRH 7 days before receiving an injection of PGF. Half of the heifers were fed MGA between the GnRH and PGF injections (Cosynch+MGA), whereas the remaining heifers were not (Cosynch). All heifers were given a second GnRH injection 2 days after PGF and inseminated at that time. Pregnancy rate for the Cosynch group (43%) was greater (P<0.05) than that for the Cosynch+MGA group (15%). This experiment suggests that short-term feeding (7 days) of MGA in concert with a Cosynch protocol was detrimental to fertility in beef heifers

Effect of source of carbohydrate and degradable intake protein in supplements on low-quality forage utilization by steers

Twelve ruminally fistulated steers were used in an experiment to study the impact of the source of carbohydrate (CHO) and degradable intake protein (DIP) in supplements on low-quality forage utilization. Treatments consisted of two different CHO types (fed at 0.16% of initial BW) each offered with an equal amount of DIP (0.087% of initial BW) but with six different proportions of non-protein nitrogen (NPN) and true protein as sources of DIP. The CHO types were starch and dextrose (a simple sugar). The different proportions of the two sources of N contributing to the DIP were 100:0, 80:20, 60:40, 40:60, 20:80 and 0:100 % of supplemental N as casein (true protein source) vs urea (NPN source), respectively. Interactions were not evident for the traits presented. Forage OM, total OM, and total digestible OM intake increased in response to an increase in the proportion of supplemental true protein. Although CHO type did not affect intake, digestibility of OM and NDF was greater when the simple sugar rather than starch served as the CHO source

Effects of frequency of supplementation on the intake and digestion of low-quality forage by beef steers

A 43% CP (dry basis) supplement was fed to 16 ruminally fistulated steers on 2, 3, 5, or 7 days a week. Supplement was offered at .36% BW (dry basis) daily for steers that received supplement every day. For other treatments, the same amount of supplement was split equally among supplementation events. Forage intake and digestibility increased with increasing supplementation frequency. However, the difference in forage intake tended (cubic, P=.07) to be most prominent for the two extremes; the 3- and 5-days-a-week treatments tended to be similar. Forage intake for steers supplemented on 2 days a week decreased on the days when they were supplemented. Although forage utilization may improve with increasing frequency of supplementation, the impact on performance is likely to be small unless differences in frequency of supplementation are extreme

Effects of frequency of supplementation on performance of beef cows grazing winter pasture

One hundred twenty spring-calving Hereford × Angus cows grazing low-quality tallgrass-prairie forage during the winter of 1998 were fed a 43% crude protein supplement 2, 3, 5, or 7 days a week. Supplement was fed at 4 lb/head daily to cows supplemented daily. The other cows still received 28 lb per week but divided equally among feedings. Cumulative performance (measured by changes in body condition score and body weight) was slightly better with increased supplementation frequency. However, the magnitude of differences in body condition and body weight changes, even for the most extreme treatment comparisons, were relatively small