Forage‐Based Beef Finishing Systems: A Review

The objective of this paper is to review alternative methods of increasing the use of forage in beef finishing systems. Most finishing systems based on an all‐forage diet have not been particularly successful. Without grain finishing, the final product can have an inconsistent quality grade and a grassy flavor. The greatest sensory difference between forage‐fed and grain‐fed steers appears to be the flavor of the fat. Diterpenoids seem to be the off‐flavor's source. These are derived from the action of ruminal microorganisms as they break down chlorophyll. Phyt‐2‐ene has been identified as the most discriminating compound for off‐flavor. It was also found to be the strongest indicator that a steer had been forage‐finished. As time on grain lengthened, the levels of ‐ tetradecalactone and ‐hexadecalactone increased, indicating their correlation with desirable flavor characteristics of grain‐finished beef. Other investigators have correlated the off‐flavor to C 18:3 unsaturated fatty acids. The two methods that show the most promise and increase the use of forage in beef finishing systems are (i) supplemental feeding of cattle on pastures to reduce length of time required for feedlot finishing and (ii) finishing cattle in a pasture with supplemented energy. Efforts to reduce feedlot time have lessened the total concentrate fed and have been economically successful. When finishing cattle in a pasture with supplemental energy, those studies that limited grain intake the last 60 to 80 d before slaughter had mixed results. However, when proper forage management was used in order to ensure adequate supply of high quality forage, carcasses with acceptable quality were produced. Researchers who provided limited supplementation or energy for at least 112 d and fed free choice grain the last 60 to 80 d before slaughter reported that USDA Choice beef was produced. However, USDA quality grade is not necessarily an adequate means to determine the effectiveness of a pasture‐based finishing system. Researchers have to determine when meat flavor changes from “grass” to “grain” and the possibility of achieving this transfer on pasture with energy supplementation. Research Question Cattle are typically finished in a confinement feedlot. Lately, these feedlots have come under close scrutiny. Two of the major concerns are: (i) animal waste with its potential impact on water quality and (ii) economic implications of feeding large amounts of grain to fatten cattle. To respond to these concerns, there is a growing interest in using more pasture in the finishing phase of cattle production. Three of the major reasons for this interest are: (i) an increasing pressure to use practices that are environmentally friendly, (ii) a search for alternative methods of finishing that are profitable, and (iii) a desire to reduce the amount of grain fed to livestock. The beef industry needs to seriously consider all alternative production systems for finishing beef. This study reviews methods of increasing the use of forage when finishing beef, while maintaining the flavor, juiciness, and tenderness required for consumer satisfaction. Literature Summary Researchers have investigated several alternatives to conventional feedlot finishing in an effort to increase forage use in finishing systems. All‐forage systems have not been particularly successful due to poor quality grades and a grassy flavor in the meat. On the other hand, some reports indicate that beef produced from all‐forage systems was similar to grain‐fed beef. The type and quality of forages that were fed may have caused some of the disparity in these reports. Few studies have compared the effect of forage species in pastures to the ability of pasture to produce finishing weight gain. The literature suggests that the grassy flavor in beef comes from chemical derivatives developed in the breakdown of chlorophyll. In some studies grain was fed to cattle on pasture followed by a shorter time in the feedlot. In certain cases this practice reduced finishing time, but the addition of grain to the diet decreased the efficiency of pasture use and the amount of grain fed was still high. Feeding high fiber by‐product feeds as an energy source could make the system more successful, but some confinement feeding might still be required. Grain‐on‐pasture finishing systems appear to offer an acceptable alternative that has to be investigated further. Grain‐on‐pasture offers the advantage of nutrient recycling, which leads to reduced fertilizer needs for pastures. Only a few reports in the literature address the significant nutrient return to the soil by cattle being fed on pasture. Reports indicate that soil nutrient levels increase from cattle excreta deposited during a controlled rotational grazing system. No reports were found that monitored changes in the soil nutrient levels on pasture for the purpose of detecting detrimental buildup of soil nutrients. The majority of the energy supplementation on pasture could be provided by high fiber by‐product energy sources to reduce the negative associative effects of feeding grain with forages. It appears that acceptable quality grade of beef can be achieved with a short 70‐d finishing phase. The problem is that quality of beef grade will not indicate the acceptability of the final product of the grain‐on‐pasture system because it is not necessarily related to tenderness and flavor. Researchers have to determine when the flavor of the final product differs from the preferred grain finished flavor, and whether feeding grain on pasture will dilute the grassy flavor. Identifying these difference would point out the length of the required grain‐feeding period, the amount of grain needed in the daily ration, and subsequent acceptability of the finished product. Study Description The Current Research Information Service, the National Agricultural Library Alternative Farming Systems Information Center, the Sustainable Farming Agriculture Network Data Base, and the Agricultural Online Access, were searched in preparation for this literature review. Applied Questions What are the most effective supplemental levels for finishing cattle on management‐intensive pastures? How does pasture affect the flavor of beef from cattle finished on pasture? Will supplemental grain feeding on pasture increase the accumulation of soil nutrients above levels observed in unsupplemented pastures? How should animal waste in pasture‐finished beef systems be managed, compared with feedlot systems? How can high quality, consumer acceptable beef be produced from pasture‐based finishing systems? Can flavor acceptability of beef from pasture‐based finishing systems be consistently achieved? In this review, no reports that adequately addressed these questions were identified. Therefore, research on these topics is needed.