Subsequent Carcass Merit of Feedlot Cattle May Be Improved by Limit Feeding a High-Energy Diet During the Backgrounding Phase

Objective: Determine and analyze the impact of limit feeding a high-energy diet in the backgrounding phase, primarily based on dry-rolled corn and Sweet Bran (Cargill Animal Nutrition, Blair, NE), on animal performance in the finishing phase and carcass merit. Study Description: This project was a continuation of the performance backgrounding study previously conducted at the Kansas State University Beef Stocker Unit. All cattle were shipped to Pratt Feeders (Pratt, KS) on August 26–27, 2019, and were fed in four separate feed groups (approximately 100 head/ pen) according to standard operating practices at the feed yard. Original backgrounding treatment integrity was maintained. Cattle were processed at National Beef (Dodge City, KS) on January 14 and February 4, 2020, and carcass data were obtained. The Bottom Line: Limit feeding a high-energy diet to cattle in the backgrounding phase appears to improve muscle deposition, especially in the light-sort cattle during the finishing phase.


Subsequent Carcass Merit of Feedlot Cattle May Be Improved by Limit Feeding a Subsequent Carcass Merit of Feedlot Cattle May Be Improved by Limit Feeding a High-Energy Diet During the Backgrounding Phase High-Energy Diet During the Backgrounding Phase Abstract Abstract
Objective: Objective: Determine and analyze the impact of limit feeding a high-energy diet in the backgrounding phase, primarily based on dry-rolled corn and Sweet Bran (Cargill Animal Nutrition, Blair, NE), on animal performance in the finishing phase and carcass merit.
Study Description: Study Description: This project was a continuation of the performance backgrounding study previously conducted at the Kansas State University Beef Stocker Unit. All cattle were shipped to Pratt Feeders (Pratt, KS) on August 26-27, 2019, and were fed in four separate feed groups (approximately 100 head/ pen) according to standard operating practices at the feed yard. Original backgrounding treatment integrity was maintained. Cattle were processed at National Beef (Dodge City, KS) on January 14 and February 4, 2020, and carcass data were obtained.
The Bottom Line: The Bottom Line: Limit feeding a high-energy diet to cattle in the backgrounding phase appears to improve muscle deposition, especially in the light-sort cattle during the finishing phase. Introduction In a typical feedlot setting, cattle are fed ad libitum in order to maximize energy intake. This has also been the case for many backgrounding operations, where primarily roughages are used. Recent work conducted at the Kansas State University Beef Stocker Unit demonstrated that limit feeding a high-energy diet based on corn in the backgrounding phase does not negatively impact rate of gain; efficiency of energy intake is improved in growing cattle when compared to those fed a high roughage diet ad libitum. However, what is not known is the extent of limit-feeding's impact on subsequent cattle performance in the feedlot, and ultimately, how carcass merit is affected. Another question raised is whether this strategy causes a greater incidence of liver abscesses. Research is also needed to identify how economically important carcass traits may be affected by the limit feeding strategy prior to finishing.

Experimental Procedures
A total of 418 weaned, crossbred heifers (body weight = 615 ± 53 lb) were purchased at auction markets in Texas and New Mexico, assembled at two different farms approximately 90 miles southwest of Amarillo, TX, then shipped 570 miles to the Kansas State University Beef Stocker Unit, Manhattan, KS, on May 28, 2019. The heifers were used in an 84-day receiving and growing study to evaluate the impact of limit-fed diets containing dry-rolled corn and Sweet Bran (Cargill Animal Nutrition, Blair, NE) compared to high roughage diets fed ad libitum on animal performance. Upon completion of the backgrounding phase, each treatment group was split into a light and heavy sort. All cattle were shipped 188 miles to Pratt Feeders in Pratt, KS, on August 26-27, 2019, for the finishing phase, and original treatment integrity was maintained throughout. Cattle were fed according to Pratt Feeders' standard protocols. Heavysort cattle were sent to National Beef (Dodge City, KS) for processing on January 14, 2020, and light-sort cattle were sent on February 4, 2020. Carcass data were obtained, including liver scores, by a team of researchers from West Texas A&M University.

Results and Discussion
Carcass results and liver scores for each feed group are shown in Table 1. The heavysort, high-energy, limit-fed cattle had the greatest backfat thickness (P < 0.01). Moreover, they scored nearly one-half of a yield grade higher compared to the other feed groups. The light-sort, high roughage, ad libitum cattle had almost 1 in 2 less ribeye area compared to the other feed groups (P < 0.01). In terms of quality grade, the light-sort, high roughage, ad libitum cattle had the most prime carcasses (P < 0.05). Regarding the livers, the light-sort, high-energy, limit-fed cattle had the least amount of edible liver tissue (P < 0.01), whereas the heavy-sort, high-energy, limit-fed group had the most edible liver tissue (P < 0.01). Both the light and heavy-sort, high-energy, limit-fed cattle trended toward greater incidence of major abscesses, or the A+ score, according to Elanco's liver scoring system (P < 0.11). Despite this, effects of limit feeding a highenergy diet during the backgrounding phase on the promotion of liver abscesses were not apparent.

Implications
Cattle previously receiving a high-energy, limit-fed diet in the backgrounding phase appeared to have greater backfat deposition and higher overall yield grade scores, along with greater muscle deposition, particularly in the light-sort cattle. The effects of limit feeding the high-energy diet on liver abscesses were not apparent.
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