Interest in locally produced, grass-fed beef has increased tremendously among the general public, chefs, and agricultural community in Hawaii as a sustainable model for beef production and also to increase the level of food self-sufficiency for the island state. This project was designed to evaluate growth performance, and carcass and meat quality characteristics of pasture-finished cattle in selected ranches of Hawaii, and to evaluate characteristics of pastures on which cattle are finished in collaboration with local ranchers. Results of the project show that a large proportion of Hawaii grass-fed beef is reasonably tender even though large variation exists. Younger slaughter age, not marbling beyond a certain level (probably High Slight) showed an important factor improving the tenderness of grass-fed beef. Results also demonstrated potentials of the incorporation of leucaena (Leucaena leucacephala), a high protein legume tree, into a tropical pastoral rotational grazing system to improve grass-fed beef production.
The “Grass-fed beef” label indicates meat that is produced by feeding forages from start to finish without any grain supplementation (USDA-AMS 2007, Federal Register 72:58631–58637). Many healthful aspects of grass-fed beef have been identified, including lower total fat content and higher content of omega-3 fatty acids, conjugated linoleic acids (CLA), and antioxidants as compared to feedlot-finished beef (Razminowicz et al. 2006, Meat Science 66:567–577; Faucitano et al. 2008, Journal of Animal Science 86:1678–1689). The healthy nutritional profile of grass-fed beef, along with the perception that grass-finishing promotes animal well-being and environmental sustainability, has probably contributed to the recent increase in the demand for grass-fed beef.
Even though beef cattle production is the third largest agricultural commodity in Hawaii, only 20-30% of weaned calves are raised for local slaughter with the majority being shipped to the mainland USA due to greater access to marketing options compared to the high cost of shipping concentrates feed to Hawaiian Islands to support a feed-lot finish sector. However, since year-round maintenance of pasture is possible in some regions of Hawaii due to the subtropical climate, grass-fed beef production may be a viable alternative to shipping out weaned calves. Moreover, grass-fed beef may provide a sustainable production model to improve the level of food self-sufficiency for the island state.
For the development of a sustainable grass-fed beef industry, a consistent supply of high quality of grass-fed beef is a key and important element. However, some studies reported that palatability of grass-fed beef is inconsistent, often leading to consumer dissatisfaction with this product (Van Elswyk and McNeill 2014, Meat Science 96:535–540). Also, the lack of information on the nutritional quality of pastures on which grass-fed beef are produced is a limiting element in developing strategies of improving carcass and meat quality characteristics of grass-fed beef in Hawaii.
The objectives of the proposed project were to evaluate growth performance, carcass and meat quality characteristics of pasture-finished cattle in selected ranches of Hawaii and to evaluate characteristics of pastures on which cattle are finished. The results of the project were disseminated through workshops, presentations at various international, national and local meetings, and extension publications, and other publications.
Meat sample collection
Three hundred fourteen ribeye steak samples from grass-fed cattle were obtained from two slaughterhouses on Hawaii Island (HI, USA) between November 2013 and June 2015. The one-inch bone-in steaks were collected from the 12th rib a few days after slaughter, individually vacuum-packaged, then shipped in a cooler with ice packs to the Human Nutrition, Food and Animal Sciences Department’s meat lab of University of Hawaii at Manoa, USA. Upon arrival at the lab, the packages were removed and the boneless ribeye steaks were trimmed to less than 2 mm of subcutaneous fat and vacuum-packaged again. Vacuum-packaged samples were aged in a refrigerator for 2 weeks from the slaughter date and then were stored at -20oC for later measurement. Approximate animal age (based on dentition), sex, carcass weight, breed type (based on hide color), and level of marbling were evaluated during slaughter mostly by personnel at the slaughterhouses, and some evaluations were done by the research team.
Cooking and Shear Force Measurement
Shear force measurements were carried out periodically when about 70 samples had been collected. Steak samples were thawed overnight in a refrigerator. The thawed, vacuum-packaged steaks were cooked in a water bath at 70oC for one hour, cooled at room temperature for one hour, and chilled overnight in a refrigerator, as described in a protocol by the USDA-ARS Meat Animal Research Center (Wheeler et al. 2005, http://www.ars.usda.gov/SP2UserFiles/Place/30400510/protocols/ShearForceProcedures.pdf). The pouches were unwrapped, and cooled steaks were gently dried with paper towels. For a shear force measurement, 6 core samples (1.3 cm diameter) were taken parallel to the longitudinal orientation of muscle fibers of each of the cooled steaks. The force required to cut the cores was measured by a Warner-Bratzler machine (G-R Manufacturing, Manhattan, KS, USA). The Warner-Bratzler shear force (WBSF) value was the mean of the maximum forces required to shear each set of core samples.
Proximate analysis of ribeye muscle
Selective rib-eye muscles were removed without subcutaneous fat, then ground three times using meat grinder for proximate analysis. Moisture and lipid contents were determined according to AOAC methods (AOAC, 1980). Ash content was determined as the residue after combustion at 600ºC for six hours. Protein concentration was estimated by the difference between the weight of moisture, ash and fat and the total sample weight.
pH measurement of ribeye muscle
Two grams of ribeye muscle samples were homogenized at room temperature in a 10 ml of 5 mM iodoacetate solution containing 150 mM KCl, then the pH of the homogenate was measured using a pH meter.
Forage Sample Collection and Analysis
A total of 62 forage samples including guinea grass (Panicum maximum), kikuyu grass, (Pennisetum clandestinum) and leucaena (Leucaena leucocephala, cv. Wondergraze)) were randomly hand collected at a time right before grazing from pastures of four different ranches plus University of Hawaii research farm (Mealani station) on Hawaii Island in winter (12/18/2014-12/20/2014) and summer (8/17/2015/-8/19/2015). Once samples arrived at the University of Hawaii-Manoa Agricultural Sciences building, the forage samples were oven dried at 65 oC overnight to determine dry-matter (DM). Samples were ground in a 1-mm screen using a Wiley mill to get samples to a uniform particle size and were stored for later proximate analysis.
Nutrient composition of forage samples was determined using near-infrared reflectance spectroscopy (NIR) at a certified commercial laboratory (Dairy One Forage Laboratory, Ithaca, NY). Multiple nutrients were determined by utilization of spectral properties of feeds using the LOCAL calibration software and samples were analyzed for overall nutrient composition.
To examine the WBSF value as affected by age, three age groups were established: Group 1, less than 24 months old; Group 2, 24 to 30 months; and Group 3, greater than 30 months old. The effects of age, sex class, carcass weight, and marbling on shear force value were determined by ANOVA procedure using Prism6 program (Graphpad, San Diego, CA, USA).
The Nutrient profiles of forages were using MIXED procedure of SAS software v9.2 (SAS institute Inc., Cary, NC). Means were compared using Tukey’s method and all differences were considered significant at P<0.05. Guinea grass (GG) and Kikuyu grass (KK) nutrient profiles were compared by type (GG vs KK), season (summer vs winter) and location (Ranch B vs Ranch C vs Ranch D vs Ranch E). Nutrient variables were the dependent variables or the fixed factor. Type, season and ranch were treated as independent variables or random factors. Type × season and type × ranch was also considered to determine if there was an interaction between these factors.
Carcass traits and meat tenderness
Heifers and steers comprised 45.3% and 54.7% of cattle, respectively. Considering that some heifers are typically retained as cow replacements, it is expected that the proportion of heifers for grass-finishing would be lower than that of steers. The majority (64%) of grass-fed cattle were between 24 and 30 months of age with 17% and 19% being below 24 months and over 30 months of age, respectively.
The mean carcass weight was 279.4 kg with 17.8% coefficient of variation, indicating a large variation in carcass size. The mean carcass size was much smaller than the US national mean carcass size of 372 kg (USDA, 2016). The mean marbling value was Low Modest. Several studies (Davis et al. 1981, Journal of Animal Science 53:651–657; Realini et al. 2004, Meat Science 66:567–577; Van Elswyk and McNeill 2014, Meat Science 96:535–540) reported that intramuscular fat content of grass-fed beef is much lower than that of feedlot-finished beef, with a marbling in the Slight to Small range. In this regard, the high marbling score is somewhat unexpected, and further studies are needed to examine underlying factors leading to the high marbling of current grass-fed beef samples.
The mean WBSF value was 4.43 kg, with values ranging from 1.95 to 11.37 kg. The distribution of WBSF values is shown in Fig. 1. Miller et al. (2001, Journal of Animal Sciences 79:3062–3068) reported that 86% of consumers expressed that they had had a satisfying experience when the WBSF value of their steaks was less than 4.3 kg. In 2013, USDA launched a program certifying beef tenderness, under which eligible beef products can carry “USDA Certified Tender” or “USDA Certified Very Tender” labels. The minimum tenderness threshold values (MTTV) to claim “USDA Certified Tender” and “USDA Certified Very Tender” are 4.4 kg and 3.9 kg WBSF value, respectively (American Society for Testing and Materials International 2011). If we apply the MTTV of “USDA Certified Tender” as a standard for tender grass-fed beef in Hawaii, about 60% of Hawaii grass-fed beef appears to fall into this category.
We examined whether WBSF value was associated with animal age, sex, carcass size, or marbling score. Animal age appears to have a significant association with WBSF value (Fig. 2A), with younger animals having lower values than older animals. In our previous study (Kim et al. 2007, FST-27, Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawai‘i, Manoa), it was also observed that steaks from cattle more than 36 months old had significantly higher WBSF values. Steers had significantly greater mean WBSF value, with more variation, than heifers (4.60 vs 4.28, Fig. 2B). In contrast to the current result, our 2007 study showed that steers had a lower WBSF value (4.96 vs 5.52). With regard to the effect of sex on beef tenderness, results of various studies are not consistent (Gracia et al. 1970, Journal of Animal Science 31:42–46; Prost et al. 1975, Journal of Animal Science 41:541–547; Choat et al. 2006, Journal of Animal Science 84:1820–1826; Wulf et al. 1996, Journal of Animal Science 74:2394–2405), suggesting that some factors other than inherent sex-related factors, such as animal age and marbling, come into play together to influence meat tenderness. In the current study, more than 30% of steers were in the age group greater than 30 months, while only 3.5% of heifers were in this age group (data not shown). Also, steers had in general a lower marbling score (data not shown). It is thus speculated that the older age of steers compared to heifers contributed to higher WBSF values of steers. Neither the carcass weight nor the marbling score had a significant association with WBSF value (Fig. 2C and 2D). Similarly, our previous study found no significant correlation between intramuscular fat and WBSF value (Kim et al. 2007, FST-27, Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawai‘i, Manoa).
Variation in meat tenderness was observed among ranches (Fig. 3). Examination of animal age group, sex, carcass size and marbling score separated by ranches did not show that any of those parameters are associated with the variation in shear force among ranches. Future studies, thus, need to examine how the combination of various production factors influence the tenderness of grass-fed beef.
Examination of nutritional profiles of various pastures on which cattle are finished
Guinea grass (GG) and kikuyu grass (KK) are commonly found in tropical pastures for grass-fed beef production in Hawaii. Little is known about their nutrient profiles during different seasons (summer and winter) and at different locations (ranches) on Hawaii Island, and this project examined nutritional profiles of these two main pasture forages. In addition, nutritional profile of leucaena (Leucaena leucocephala cv. Wondergraze), a high protein tree legume, and the incorporation of leucaena in pasture on animal growth performance were examined.
Nutrient composition differed among pasture types (Table 1, 2). As expected, season significantly affected the composition of various nutrients, with generally higher nutritional value during a season with high precipitation as compared to dry season (Table 1). Seasonal differences were found when GG and KK were analyzed together, with forages during high precipitation period yielding higher values for certain nutrients such as crude protein and being more digestible (less aNDF Form), resulting in higher RFV value than during periods of low precipitation.
The crude protein content of leucaena was almost double of KK or GG grasses on a dry matter basis, resulting in almost a two-fold increase in relative feed value (RFV) of leucaena as compared to those of kikuyu or guinea grasses. Acid detergent fiber (ADF) and ash-free neutral detergent fiber (aNDF) of leucaena were both significantly lower than those of GG or KK, indicating that leucaena contains less indigestible fiber than GG and KK. Leucaena incorporation in GG pasture (a mix of 60% guinea and 40% leucaena) significantly improved average daily gain (1.64 vs. 1.18 lb) of cattle from weaning to slaughter, resulting in significantly shortened grazing period (707 vs 532 days) in pasture when cattle were slaughtered at a constant body size, demonstrating the possibility of improving grass-fed beef production by the incorporation of leucaena into a tropical pastoral rotational grazing system.
KK, as compared to GG, tended to have higher crude protein (16.0% vs 13.8%), lower ash content (9.7% vs 13.2%), resulting in higher total digestible energy (57.7% vs 54.7%) and relative feed value (96.1% vs 92.7%). Nutrient composition of both GG and KK were significantly different among ranches. It is not clear whether the difference in pasture nutritional quality among ranches is associated with climate and/or soil conditions of the ranches or due to difference in pasture management of ranches.
Educational & Outreach Activities
- Yong Soo Kim, Glen Fukumoto, Matthew Stevenson, Mark Thorne, and Rajesh Jha. December 2015. Carcass Traits and Tenderness of Hawaii’s Grass-fed Beef. UH-CTAHR, LM-29,
- Yong Soo Kim, Glen Fukumoto, Matthew Stevenson, Mark Thorne, and Rajesh Jha. 2016. Carcass traits and tenderness of grass-fed beef from subtropical pastures in Hawaii. The 16th AAAP Congress Proceedings 1525-1529
- 2013, October 28, The 5th Korea-US International Joint Symposium Interdisciplinary Research for High Quality Beef Production. “Grass-fed beef in Hawaii: a review on carcass and meat quality characteristics”.
- 2013, October 30, Hanwoo Experiment Station, RDA, Korea, “Grass-fed beef in Hawaii: a review on carcass and meat quality characteristics”
- 2015, October 10, 1st International Symposium on Beef Cattle Sciences and Industry Technology Development. October 9 – 11, 2015 Yanji, China. “Improving meat quality characteristics of grass-fed beef in Hawaii”
- 2015, April 10, 2015 Spring CTAHR Student Research Symposium, A presentation entitled ‘Nutrient profile of leucaena and guinea grass and growth performance and carcass quality of beef cattle grazed on these pastures in Hawaii’, was made by Ms. Kayla Butler, a graduate student partly supported by the SARE project.
- 2016, April 8, 2016 Spring CTAHR Student Research Symposium, A presentation entitled ‘Seasonal and locational variation of nutrient profile and in vitro digestion kinetics of guinea grass and kikuyu grass for grass-fed beef production system on Hawaii island’, was made by Ms. Kayla Butler, a graduate student partly supported by the SARE project.
- 2016, August 22-25, Yong Soo Kim, Glen Fukumoto, Matthew Stevenson, Mark Thorne, and Rajesh Jha. Carcass traits and tenderness of grass-fed beef from subtropical pastures in Hawaii. 17th Asian Australian Animal Production Animal Science Congress, Fukuoka, Japan
- A workshop with the title of “A Primer on Local Beef” sponsored by the Hawaii Culinary Education Foundation was presented by Mr. Glen Fukumoto to 22 chefs and industry personnel (April 7, 2014). The workshop also introduced the important role of grass-fed beef in sustainable agriculture in Hawaii.
- A workshop was organized by the SARE project team to disseminate preliminary findings and to discuss issues with grass-fed beef producers in association with grass-fed beef production. The workshop was held on July 25, 2014 at the North Hawaii Education and Research Center, Honokaa, Hawaii County. There were 23 participants in the workshop.
- In a Kauai beef workshop held at March, 2016, results from the SARE project was presented, “Big Island Beef quality Research Update”
- A second workshop was organized by the SARE project team to disseminate our findings and to discuss issues and future directions with project participating ranchers and other grass-fed beef producers in association with grass-fed beef production in Hawaii. The workshop was held on July 8, 2016 at the North Hawaii Education and Research Center, Honokaa, Hawaii County. There were 24 participants in the workshop.
Results of the project shows that a large proportion of Hawaii grass-fed beef is reasonably tender even though a large variation exists. Younger slaughter age appears to be an important factor improving the tenderness of grass-fed beef, while marbling beyond a certain level (probably High Slight) appears not to be a factor influencing grass-fed beef tenderness. Results also demonstrate the potential of incorporating leucaena into a tropical rotational grazing system to improve the grass-fed beef production. The results of this project were disseminated to Hawaii beef producers through various individual meetings and workshops. Through the results of this project, grass-fed beef producers will be able to make informed decisions to develop strategies on profitable and sustainable beef production. The project also provided an opportunity to educate an individual in the area of grass-fed beef production through a master thesis.
Areas needing additional study
Beyond tenderness, a taste panel study is needed to evaluate consumer acceptability or preference for grass-fed beef. The information is essential in developing effective marketing and educational strategies for a sustainable grass-fed beef production.
Leucaena incorporation into a tropical pastoral rotational grazing system has shown its potential to improve the grass-fed beef production. For grass-fed beef producers to adopt the technology, there are questions to be addressed, including impact of leucaena establishment on economic return and soil health parameters, and best management practice of leucaena-grass pasture.