Supplementation Strategies for Growing and Finishing Beef Cattle on Tall Fescue Pastures in the Southeast

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Date
2024-03-15
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Virginia Tech
Abstract

While the Southeastern U.S. does not produce cereal grains at the same output as Midwestern states, a relatively temperate climate and consistent rainfall allow for abundant forage production. Tall fescue dominated pastures in this region provide a high-quality forage source to support consistent cattle growth and production. Furthermore, the nearly year-round grazing potential serves as a cost-effective feed source. Leveraging forage resources is imperative for the U.S. beef industry to maintain consistent production of a quality human protein source at a consumer-friendly price, but energy content in purely forage diets is lacking to produce comparable growth and carcass performance to concentrate-based diets. Therefore, the objectives of this dissertation are to examine supplementation strategies for growing and finishing cattle in fescue-based systems in the Southeast to optimize value for cattle producers. The first experiment investigated whether steer performance and grazing behavior was affected by supplement feeding time and delivery method in a forage-based backgrounding program. Traditionally, producers choosing to supplement backgrounding cattle with grain or coproduct feeds do so in a single meal event in the early morning. It has been hypothesized that these morning feedings could disrupt the natural diurnal grazing pattern of cattle to negatively affect forage utilization and overall cost of gain. Additionally, while self-feeder systems using supplements containing intake limiters give producers an option to reduce feeding labor compared to daily hand-fed supplementation, alternate methods of supplement delivery also have the potential to influence grazing behavior and cost of gain within backgrounding programs. This experiment used backgrounding steers supplemented daily at 0930 (AM), steers supplemented daily at 1330 (PM), and steers provided supplement through a self-feeder (SELF) to provide cattle performance and economic data directly relevant to regional producers. Combined 2-yr results show that while AM, PM, and SELF cattle all exhibited altered grazing routines, treatments did not result in differences (P ≥ 0.18) in final body weight (BW), average daily gain (ADG), ultrasound 12th rib fat thickness (uFT), or overall forage mass disappearance. Dry matter intake (DMI) in the SELF treatment exceeded the target despite inclusion of intake limiters, resulting in increased (P < 0.01) supplement DMI, a tendency (P = 0.07) towards decreased G:F, and substantially greater (P < 0.01) cost of gain in SELF relative to the hand-fed treatments. Results support that producers have flexibility in scheduling daily supplementation routines without compromising steer performance in pasture-based backgrounding programs. Furthermore, producers should consider the tradeoff between labor efficiency and ration cost when considering utilizing self-feeders containing intake limiters. The second experiment investigated the effects of frame size and supplementation containing a rumen protected fat (RPF) on growth performance and carcass characteristics of pasture finished cattle. Market dynamics continue to favor cattle that produce heavier carcasses, which discounts smaller framed feeder calves at sale barns. At the same time, Virginia is flush with cow-calf production, high quality tall fescue pastures, and access to population dense areas with markets that incentivize pasture-finished beef through price premiums. Together, this provides an alternative marketing channel for smaller framed calves through pasture-finished beef markets, but questions remain on how to optimally produce this specialty beef. Supplemental feeds can increase cattle production on pasture, and RPF offer a feeding strategy to increase energy intake without negatively effecting ruminal fiber digestion. There is limited work investigating the application of RPF within beef cattle systems and carcass traits, and it is unclear if RPF has been utilized specifically within pasture finishing systems. Therefore, this experiment examined growth performance, carcass characteristics, and organoleptic qualities of beef from small-framed (SM) and medium-framed (MED) cattle on novel endophyte-infected fescue pasture finishing systems either offered no supplement (NON) or daily supplementation (SUP) containing RPF. Pasture treatments were compared relative to a grain-fed feedlot control (F) to show these cattle had the genetic merit to meet expectations of the U.S. fed-beef system. Results from this 2-yr experiment indicate that frame size had little impact on growth performance, with SM and MED cattle having similar (P ≥ 0.37) final BW, ADG, and forage DMI in this pasture finishing system. However, MED cattle produced more valuable carcasses compared to SM cattle as evident by greater (P ≤ 0.04) mean HCW, 12th rib fat thickness, and marbling score. Samples of M. longissimus thoracis from MED cattle also had greater (P ≤ 0.02) concentrations of 14:0, 16:0, 18:0, 18:1, and 18:2 fatty acids compared to samples from SM cattle. While NON cattle produced carcasses with a lower (P = 0.01) yield grade than SUP cattle, overall, SUP cattle were more productive by both live and carcass metrics. The SUP treatment produced greater (P ≤ 0.04) final BW, ADG, 12th rib fat thickness, HCW, marbling score, dressing percentage, and concentrations of 14:0, 16:0, 18:0, 18:1, and 18:2 fatty acids. Similarity (P = 0.55) in objective measures of meat tenderness between F and pasture treatments emphasizes the importance of harvesting cattle before 2 years of age to prevent declines in meat tenderness associated with advancement of connective tissue. There tended (P = 0.05) to be a frame by supplement interaction for marbling score driven by lower values in SM-NON in relation to other pasture treatments. Tendencies towards frame by supplement interactions for Warner-Bratzler shear force (P = 0.08) and total energy (P = 0.06) were also driven by increased values in SM-NON relative to other pasture treatments. Taken together, a lack fat deposition in SM-NON cattle appears to have a negative impact on beef tenderness relative to pasture treatments. Overall results of this experiment support low levels of supplementation in pasture-finishing systems to improve carcass value, and that medium framed cattle are more flexible in profit margins compared to smaller framed counterparts. Collectively, these investigations support that tall fescue grazing systems in the Southeast can serve as a nutritional foundation to beef cattle growing and finishing enterprises. Data from these experiments can be directly applied to help producers match cattle type to feed resources when supplementing a pasture-based system to optimize resource management and overall profitability.

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Keywords
carcass, rumen, tall fescue
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