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Grazing studies were carried out over a 5-year period using pregnant cows, yearling calves and 2-year-old heifers to investigate the influence of diet on intake, methane (CH4) emissions and retention of nitrogen (N). Monoculture legume (birdsfoot trefoil, BFT and cicer milkvetch, CMV) or grass (meadow bromegrass, MBG) pastures were rotationally stocked, and during year 4 and year 5, treatments were contrasted with total mixed rations (TMR) fed in confinement. The sulfur hexafluoride (SF6) method was used to continuously measure enteric CH4 emissions. Intake was greater on legume pastures and on TMR than on grass pastures, and enteric CH4 emissions per unit of intake were lower on legumes compared with grass pastures. Legume pastures had elevated non-fiber carbohydrate (NFC) concentrations (400 g kg−1 dry matter; DM) typical of perennial legumes cultivated in the Mountain West. A N balance calculated in 2017–2018 demonstrated that N retention was greater for TMR and legume than grass pastures. Enteric CH4 emissions of grazing cow herds account for the majority of greenhouse gas (GHG) emissions from beef production and can be significantly reduced by using highly digestible forage legumes. The N retention of legumes can potentially enhance the efficiency of N use, thereby increasing the sustainability of grasslands.

Fall- or spring-born steers grazed monoculture irrigated birdsfoot trefoil (BFT; Lotus corniculatus L.) or cicer milkvetch (CMV; Astragalus cicer L.) pastures for approximately 12 weeks for 3 years and were compared with steers on concentrate diets. In the 3rd year, an irrigated meadow bromegrass (MBG; Bromus biebersteinii Roem. and Schult.) pasture treatment was added for further comparison. Steer average daily gain (ADG) was 1.31, 0.94, 0.83 and 0.69 kg d−1 on concentrate, ‘Norcen’ BFT, ‘Oberhaunstadter’ BFT, and ‘Monarch’ CMV diets, respectively; ADG on grass pastures was 0.43 kg d−1. The ADG on the concentrate diet was greater than ADG on legume or grass pastures, ADG was greater on BFT than CMV in every year (p < 0.03), and ADG on BFT was greater than ADG on grass (p < 0.03). The rate constant of gas production of an in vitro rumen fermentation demonstrated a slower rate of microbial digestion for CMV than for BFT. The elevated ADG on BFT pastures may be due to greater non-fiber carbohydrate (NFC) concentration and reduced neutral detergent fiber (NDF) concentration combined with condensed tannins that protect proteins in the rumen but do not impede protein digestion in the abomasum and intestines.

This study aimed to determine the influence of finishing diet on beef appearance and lipid oxidation of three beef muscles. A total of 18 Angus steers were selected from three diet treatments: grass-finished (USUGrass), legume-finished (USUBFT), and grain-finished (USUGrain). After processing, longissimus thoracis (LT), triceps brachii (TB), and gluteus medius (GM) steaks were evaluated over a 7-d display period. A muscle × diet interaction was observed for instrumental lightness (L*) and redness (a*) (P ≤ 0.001). Within each combination, USUGrass was considered darker with lower (P < 0.05) L* compared with USUGrain. For USUBFT, L* was similar to USUGrain for the TB and LT, while the L* of USUBFT and USUGrain GM differed (P < 0.05). In terms of redness, LT a* values were elevated (P < 0.05) in USUGrass compared with USUBFT and USUGrain. For GM steaks, a* of USUBFT and USUGrass were each greater (P < 0.05) than USUGrain. Surface a* of TB steaks were greatest (P < 0.05) for USUGrass followed by USUBFT, and with USUGrain, being lowest (P < 0.05). An overall increase in L* was observed throughout display dependent on diet (P = 0.013). During display, USUGrain steaks had the greatest (P < 0.05) L* followed by USUBFT and USUGrass. Additionally, a day × muscle interaction was observed for a* (P = 0.009). Initially, TB steaks had the greatest (P < 0.05) a* values. However, at day 3, a* values were similar (P > 0.05) among muscles. Visual color scores were in agreement with loss of redness (a*) during display, dependent on diet and muscle type (P < 0.001). Similarly, a day × diet × muscle interaction was observed for visual discoloration (P < 0.001). Day and diet interacted to influence thiobarbituric acid reactive substances (TBARS) (P < 0.001). Initial values did not differ (P > 0.05) between USUGrain and USUBFT; however, USUGrass had lower initial (P < 0.05) TBARS than both USUGrain and USUBFT. At days 3 and 7, TBARS were greatest (P < 0.05) in USUGrain steaks, followed by USUBFT, which was greater (P < 0.05) than USUGrass. A diet × muscle interaction was observed for 10 volatile compounds originating from lipid degradation (P ≤ 0.013). These compounds were less (P < 0.05) abundant in USUGrass compared to TB or GM of USUGrain. This study determined grass-finished beef to have a darker more red color and less lipid oxidation in multiple muscles. Possible mechanisms for this may include an increase in endogenous antioxidants in grass-finished beef.

Abstract This study aimed to determine the influence of finishing diet on beef appearance and lipid oxidation of three beef muscles. A total of 18 Angus steers were selected from three diet treatments: grass-finished (USUGrass), legume-finished (USUBFT), and grain-finished (USUGrain). After processing, longissimus thoracis (LT), triceps brachii (TB), and gluteus medius (GM) steaks were evaluated over a 7-d display period. A muscle × diet interaction was observed for instrumental lightness (L*) and redness (a*) (P ≤ 0.001). Within each combination, USUGrass was considered darker with lower (P < 0.05) L* compared with USUGrain. For USUBFT, L* was similar to USUGrain for the TB and LT, while the L* of USUBFT and USUGrain GM differed (P < 0.05). In terms of redness, LT a* values were elevated (P < 0.05) in USUGrass compared with USUBFT and USUGrain. For GM steaks, a* of USUBFT and USUGrass were each greater (P < 0.05) than USUGrain. Surface a* of TB steaks were greatest (P < 0.05) for USUGrass followed by USUBFT, and with USUGrain, being lowest (P < 0.05). An overall increase in L* was observed throughout display dependent on diet (P = 0.013). During display, USUGrain steaks had the greatest (P < 0.05) L* followed by USUBFT and USUGrass. Additionally, a day × muscle interaction was observed for a* (P = 0.009). Initially, TB steaks had the greatest (P < 0.05) a* values. However, at day 3, a* values were similar (P > 0.05) among muscles. Visual color scores were in agreement with loss of redness (a*) during display, dependent on diet and muscle type (P < 0.001). Similarly, a day × diet × muscle interaction was observed for visual discoloration (P < 0.001). Day and diet interacted to influence thiobarbituric acid reactive substances (TBARS) (P < 0.001). Initial values did not differ (P > 0.05) between USUGrain and USUBFT; however, USUGrass had lower initial (P < 0.05) TBARS than both USUGrain and USUBFT. At days 3 and 7, TBARS were greatest (P < 0.05) in USUGrain steaks, followed by USUBFT, which was greater (P < 0.05) than USUGrass. A diet × muscle interaction was observed for 10 volatile compounds originating from lipid degradation (P ≤ 0.013). These compounds were less (P < 0.05) abundant in USUGrass compared to TB or GM of USUGrain. This study determined grass-finished beef to have a darker more red color and less lipid oxidation in multiple muscles. Possible mechanisms for this may include an increase in endogenous antioxidants in grass-finished beef.

This thesis project explored the use of perennial legumes, including the non-bloating birdsfoot trefoil (BFT; Lotus corniculatus L.) for beef production. In 2011 and 2012, cattle averaged approximately 300 kg at the beginning of the grazing season, and approximately 450 kg in 2013. Average daily gain on pastures ranged from a low of 0.63 kg d-1 on cicer milkvetch (CMV; Astragalus cicer L.) in 2011 and 2013 to a high of 1.03 kg d-1 on Norcen BFT in 2013. Feedlot gains ranged from 1.14 to 1.57 kg d-1. Blood plasma fatty acids did not differ when feeding treatments were imposed, but at the end of each grazing season saturated and omega-6 fatty acids were elevated in feedlot-fed cattle compared with pasture-fed cattle, while trans-vaccenic acid (TVA) and omega-3 fatty acids were elevated in pasture-fed cattle. The ratio of omega-6 to omega-3 fatty acids was always higher in feedlot-fed cattle at the end of the grazing season, but in 2013, when all cattle were nearing slaughter weight, the omega-6 to omega-3 ratio was 50% higher for feedlot-fed than for BFT-fed cattle and double that of grass-fed cattle. Digestive (enteric) methane (CH4) production of beef cows was lower when cattle grazed BFT and CMV pastures (167 and 159 g CH4 per cow per d, respectively) compared to cows on meadow bromegrass (MB; Bromus riparus Rehmann) (355 g CH4 per cow per d). Meadow bromegrass has more fiber than legume forages, which will increase the proportion of acetate to propionate created by microbial digestion in the rumen, increasing the production and release of CH4. Perennial legume forages fix nitrogen, eliminating the need for chemical nitrogen fertilizer, and tannin-containing legumes can be grazed without risk of bloat. These forages will play an important role in developing more environmentally and economically sustainable agricultural production systems.