Effect of diet and muscle type on meat quality characteristics of Tanzania Shorthorn Zebu

M B Muchakilla, L Asimwe, A E Kimambo, L A Mtenga and G H Laswai

Department of Animal Science and Production, Sokoine University of Agriculture,
P.O. Box 3004, Morogoro, Tanzania
lovinceasimwe@yahoo.com

Abstract

Effects of dietary treatments and muscles type on meat quality characteristics of Tanzania Shorthorn zebu (TSZ) cattle were assessed using twenty five steers fed on five different feedlot diets for 90 days and five steers from traditional grazing system as a control treatment. The animals were slaughtered and three muscles namely Semitendinosus (ST), Infraspinatus (IS) and Glacilis (GL) were separated from the silver side, shoulder blade and top side meat joints. The muscles were assessed for meat quality attributes using Warner-Bratzler Shear force (WBSF) instrument and panelists.

Meat from grazing animals had highest WBSF value (52.3 + 0.77N) compared to meat from animals from the feedlot (44.8+ 0.77N). The ST muscle had higher WBSF value (47.7+ 0.50N) than GL muscle (45.5+ 0.55N) and IS muscle (45.0+ 0.50N). For sensory attributes, the meat from grazing animals was least preferred. The ST and GL muscles were ranked more tender than IS muscles. It is concluded that concentrate supplementation improves meat quality of TSZ cattle but the effect varies  with muscle type.

Keywords: beef muscle, concentrate diets, meat cuts, sensory panel scoring

Introduction

Tanzania Shorthorn Zebu (TSZ) cattle are widely distributed in Tanzania and produce 54% of the total meat consumed in the country (MLFD 2012). These cattle are mostly produced from an extensive grazing system which relies on rangeland forages without any supplementation resulting in poor quality beef. Low nutrient concentration in the feeds and delay in slaughtering animals can be the major factors that affects poor quality beef production from tropical cattle breeds. Many livestock keepers slaughter very old animals which yield tough meat because neither finishing strategies before slaughter nor meat processing after slaughter is done. There is also an increasing tendency to import meat in Tanzania to meet the demand of quality beef in the niche markets. This imported meat could however be produced from these local indigenous TSZ cattle using the locally available feed resources (Mwilawa 2012). The modification of ration composition and level of feeding can alter muscle characteristics at slaughter which can then affect the sensorial attributes of the meat (Geay et al 2001). Agro-processing by-products including cereal milling by products, oil-seed cakes and molasses have high nutritive values and could be used as alternative feeds to maize grain in Tanzania (Nandonde 2008) in feeding cattle under feed lotting system. Several studies have shown that supplementation using these agro–processing by-products have improved body weight gain of grazing cattle (Mawona 2010) and alter carcass cut yields and carcass composition (Zakaria 2010) but eating quality attributes of such meat have not been reported with TSZ cattle. Diet is a more important factor than breed in affecting sensory quality of meat and grain (concentrates) fed cattle generally rank higher than grass (forage) fed cattle for the major meat attributes of flavour (Shepherd 2013; Duckett et al 2013) and tenderness (Medeiros et al 1987 Xiong et al 1996).

There is little information on meat cut yields and sensory characteristics of Tanzanian indigenous breed of cattle raised on natural pastures with or without concentrate supplementation. Thus, the aim of the paper is to report on effects of diet and muscle type on meat quality characteristics of Tanzania shorthorn zebu.

Materials and methods

Experimental design and treatments

This was part of research conducted at Kongwa national ranch in Dodoma to assess the possibility of replacing maize grain with agro-processing by-products (Asimwe et al 2014). In brief, 45 TSZ steers were randomly allocated to five experimental diets which were compounded to contain molasses or maize grain with rice or maize by-products in a complete randomized design (CRD) in a 90 day feeding trial. In addition, 5 steers which were grazing in the ranch were added and used as control for the current study.

Slaughter procedure

Twenty five (25) steers out of 45 steers finished on the different five agro-processing by-products diets were used for this study. Five steers from each of the five dietary treatments plus five from grazing were selected at random and transported to Dodoma abattoir for slaughter. After slaughter, bleeding, removal of hides and evisceration was done and the carcass of each steer was split longitudinally into two halves using electrical saw. The carcasses were kept at room temperature for 10 hrs before they were moved to the cold room set at 0 ^oC.

Meat joints

Three carcass joints namely shoulder blade, topside and silverside were removed from the right side half carcasses 48 h post mortem (PM) using the FAO (1991) guideline. Separation of the forequarter and hindquarter from the carcass side was done by a cut along the 10^th rib at right angles to the vertebral column through the ventral portion of the flank, retaining ten (10) ribs in forequarter and three (3) ribs in the hindquarter. Shoulder blade was prepared from the forequarter by following a natural seam between the rib and scapular. Topside that is situated caudal to the femur and attached to the aitchbone was removed by following the natural ridge between the thick flank and silverside. Silverside that is situated lateral/caudal to the fermur and attached to the aitchbone was removed by following the natural ridges between the thick flank and topside. The different joints were weighed using an electronic balance and the weights were recorded and expressed as a percentage of weights of the right half carcass.

Removal of muscles

Three muscles were anatomically dissected from the three primal cuts and weighed. Glacilis (GL) muscle was removed from the topside along the natural seam, Semitendinosus(ST) muscle was prepared from the outside of silver side by following the natural seam between the gluteobiceps muscle and Semitendinosus muscle while Infraspinatus (IS) muscles were obtained from the shoulder blade. Three pieces of meat were obtained from each muscles type, weighed to obtain initial weight (W1), vacuum packed and frozen before they were used for assessment of meat quality that is assessment of thaw loss, cooking loss, tenderness, sensory evaluation and chemical composition.

Thawing loss, cooking loss and shear force

Muscle samples for determination of thawing loss, cooking loss and shear force were prepared. The pre-weighed samples were removed from the freezer thawed at 4°C overnight. The bag was opened and muscles were then blotted dry with filter paper and weighed again (W2) and thawing loss (%) was calculated as [(W_{1 -} W₂) / W₁] × 100. The samples were then packed into a water-tight plastic bag and boiled in a thermostatically controlled water bath set at 75 °C for 1 hrs. After boiling, the samples were cooled for 2 hrs in cold running water, blotted dry with dry towel and weighed (W₃) for determination of cooking loss (%) as [(W_{2 –} W₃) / W₂] × 100. Warner-Bratzler shear force (WBSF) values were determined using a Zwick/Roell 22.5 (Germany) equipped with a Warner Bratzler (WB).

Sensory evaluation of meat quality

Sensory evaluation was conducted in the laboratory at the Department of Animal Science and Production of Sokoine University of Agriculture. The frozen steaks were thawed at 4 ºC overnight in vacuum bags before cooking. Samples were cooked at 75 ºC for 1 h in a circulating water bath. After cooking each steak was trimmed of any external connective tissue, and cut into equal pieces of approximately 2x2x2 cm. The pieces were stored in warm pans at 60 °C and served to panelists while warm. Twenty consumer panelists consisting of Departmental staff members and postgraduate students were used to evaluate the meat. The identification of samples during sensory evaluation did not allow panelists to relate them to experimental treatments. The panelists were asked to evaluate the intensity of aroma, tenderness, juiciness, texture and overall acceptability respectively using eight -point scales ranging from 1 to 8 where:1= extremely weak , extremely tough, extremely dry, extremely abundant, dislike extremely and 8= extremely intense, extremely tender, extremely juicy, none, as described by Muchenje (2007).

Chemical analysis of meat samples

The proximate composition of the meat samples was determined according to the AOAC method (AOAC 2000). Moisture content was determined by drying the samples overnight at 105⁰C. The crude protein (CP) content was determined by the Kjeldahl method and the crude lipid content was determined by the Soxhlet method. The ash content was determined by ashing the samples for 6 hours at 550 ºC.

Statistical Analysis

Data were analyzed by the Mixed Procedure of SAS (2000) considering a 6 x 3 factorial designs with six dietary treatments and three muscles types as main effects. Individual animal was used as the experimental unit in the model; therefore, residual error was used to test the main effects and interaction effects. Least square means were calculated for all measured variables; the LSD test was used to determine significant differences (P<0.05).

Results and discussion

Meat cuts and muscle yield

The yield of silverside was higher in animals fed MMMO than those fed RPMM and the Control (Table 1).. The animals fed HFMO diet had higher weight of topside than other treatments. The yield of shoulder blade was highest in animal fed HFMO. Semitendinosus and Infraspinatus muscles from animals fed HFMO diet were heavier than those from other dietary treatments. Infraspinatus and Glacilis muscles from the animals in the control group weighed less  than those from other diets while Glacilis muscle was heavier in animals fed RPMM than those on other treatments. These results indicate that feedlot fattening using agro-processing by products improves the yield of meat cuts. This is in agreement with research reviewed by Zakaria (2010). They concluded that steers given concentrates had higher growth rate and heavier carcasses and primal cuts than steers raised on pasture.

Thaw loss, cooking loss and WBSF value

The WBSF value on meat from for the grazing animals (Control) was higher than for those fed concentrates (Table 2). Animals fed on diet HFMM produced meat with lowest WBSF value. The Semitendinosus muscle had higher mean WBSF value than Infraspinatus and Glacilis muscles. Muscle tenderness has been a targeted area for research because of its importance to consumer’s perception of beef palatability (Morgan et al 1991). The observed difference in shear force values between diets were expected because animals react differently on different diets and produce meat with different tenderness. The results on WBSF from the present study were lower than those reported by Bowling et al (1977) (84N for steers fed forage diet and 56N for steers fed grain diet) but similar with values reported by Shackelford et al (1997), Muchenje (2007) and Kennedy et al (2010).  As shown by Dannenberger et al (2006), and in the current study, animals fed concentrate diets produce meat with lower shear force and hence meat that is more tender.  This is because high energy diets usually give rise to lower concentration of connective tissues per unit weight of muscle bundle (Andersen et al 2005). Low concentration of connective tissue is associated with meat tenderness (Maltin et al 2003). Diets with low energy content such as grass or natural grazing give rise to muscles with higher shear force value when compared to high energy diets. The observed high WBSF value from grazing animals without supplementation (Control) agrees with other studies (Andersen et al 2005; Mwilawa et al 2010).

 Infraspinatus and Glacilis muscles had lower WBSF value than Semitendinosus muscle. In grading muscles according to their tenderness, the present results are in agreement with those of Calkins and Sullivan (2007).  Infraspinatus muscle has lower concentration of connective tissue because of fewer activities associated with the position of the muscle in the body. Semitendinosus and Glacilis muscles are mostly used for locomotion, hence are more active and carry the heavy load of the body and hence are tougher than Infraspinatus muscle.

Effect of diet on eating quality attributes (sensory evaluation)

With exception of aroma, all animals from the control group (grazing only) had lower scores for meat quality attributes than the other treatments (Table 3). There were no differences in aroma, juiciness, texture and overall acceptance between the three selected muscles. However, type of muscle had effects on tenderness score, where Infraspinatus muscle scored higher, followed by Semitendinosus muscles and finally Glacilis. The overall mean acceptability score in the present study shows that concentrates based diets produced meat that was moderately more acceptable than meat from a grass diet. The present results are comparable with those reported by Young and Kauffman (1978). 

Concentrate-fed steers had less detectable amount of connective tissue than the natural pasture fed steers. The greater amount of connective tissue may have been related to the age of the steers at slaughter as reported by Bidner et al (1986) and Short et al (1999) who reported that connective tissue content and flavour intensity score increased with increased time on feed. Infraspinatus was the highly rated muscle in tenderness followed by Glacilis and Semitendinosus. These findings agree with those of Shackelford et al (1995) who found that Infraspinatus muscles are rated more tender than others. There was strong agreement between tenderness determined by WBSF analysis and that determined by trained sensory panel in the present study, and as noted by Bowling et al (1977) and Schroeder et al (1980).

Chemical composition

Muscles from the control group had highest moisture content and lowest fat and crude protein content than other treatments(Table 4). Protein content was higher in animals fed diet HFMO. Infraspinatus muscle had higher moisture content and lower ether extract and protein in comparison to Glacilis and Semitendinosus muscles.  In general, the chemical composition values obtained in the present study were within commonly reported values of 74 - 77% moisture, 21 - 24% protein and 1.2 -1.9% ash, although the fat levels were lower than the 4 - 10% fat values, as reported by Tornberg (2005), Anwer et al (2013) and Costa et al (2012).

Conclusion

• Meat from TSZ cattle fed diets based on agro-processing by-products was more tender with more acceptable sensory scores than meat from grazing animals.

Acknowledgements

This research was funded by BTC (Belgium Technical Cooperation) as well as the ENRECA- IGMAFU project funded by DANIDA. The steers were slaughted at Dodoma abttoir and meat samples were analysed in the Department of Animal Science and Production, Sokoine University of Agriculture.

References

Andersen H J, Oksbjerg N, Young J F and Thekildsen M 2005 Feeding and meat quality - a future approach. Meat Science 70: 543-554.

Anwer M, Khan M I, Pasha I, Tariq M R and Sohaib M 2013 Quality assessment of meat in relation to colour and muscle fiber types. Pakistan Journal of Food Science 23(2), 80-86

AOAC 2000 Official Methods of Analysis, 17th ed. Association of Official Analytical Chemists, Arlihton, VA.

Asimwe L, Kimambo A E, Laswai G H, Mtenga L A, Weisbjerg M R, Madsen J, Mushi D E 2014 Growth performance and carcass characteristics of Tanzania Shorthorn Zebu cattle finished on molasses or maize grain with rice or maize by-products. Unpublished manuscript

Bidner T D, Schupp A R, Mohamad A B, Rumore N C, Montgomery R E, Bagley C P and Macmillan K W 1986 Acceptability of beef from Angus-Hereford or Angus- Hereford-Brahman steers finished on all-forage or a high energy diet. Journal of Animal Science 63: 381-387.

Bowling R A, Smith G C, Carpenter Z L, Dutson T R and Oliver W M 1977 Comparison of forage-finished and grain-finished beef carcasses. Journal of Animal Science 45: 209.

Calkins C R and Hodgen J M 2007 A fresh look at meat flavour. Meat science 77:63-80.

Costa R S, Henry F C, Ferreira K S, Do Valle F R A F and Quirino C R 2012 Characterization of rigor mortis of longissimus dorsi and triceps brachii muscles of male cattle carcasses. African Journal of Biotechnology 11 (32), 8127- 8132.

Dannenberger D, Nuernberg K, Nuernberg G, and Ender K 2006 Carcass and meat quality of pasture vs concentrate fed German Simmental and German Holstein bulls. Archiv Tierzuchit Dummerstorf 49 (4), 315-328.

Duckett S K, Neel J P S, Lewis R M, Fontenot J P and Clapham W M 2013 Meat quality effects of forage species or concentrate finishing on animal performance, carcass and meat quality. Journal of Animal Science 91:1454-1467.

FAO (Food and Agriculture Organization of United Nation) 1991 Guideline for slaughtering, meat cutting and further processing www.fao.org/docrep/004/t0279e/T0279E00.htm

Geay Y, Bauchart D, Hocqette J, Culioli J 2001 Effect of nutritional factors on biochemical, structural and metabolic characteristics of muscles in ruminants, consequences on dietetic value and sensorial qualities of meat. Reproduction Nutrition Development 41:1–26.

Kennedy P C, Dawson L E R, Moss B W, Fearon A and Kilpatrick D J 2010 Instrumental meat quality and fatty acid composition of lean muscle from beef steers offered grass silage alone or in combination with legume/cereal based whole crop silage at two concentrate levels. Queens University, Belfast, United Kingdom.

Maltin C, Balcerzak D, Tilley R, Delday M 2003 Determinants of meat quality: tenderness. Proceedings of the Nutrition Society 62(2): 337-347.

Mawona F 2010 Feedlot performance under different practices in Mwanza region. Dissertation for Award of Msc Degree at Sokoine University of Agriculture, Morogoro, Tanzania, 132pp.

Medeiros L C, Field R A, Memkhaus D J and Russell W C 1987 Evaluation of range-grazed and concentrate fed beef by trained sensory panel, a household panel and a laboratory test market group. Journal of Sensory Study 2259.

MLDF 2012 Ministry of livestock development and fisheries. Budget speech 2012/13 Retrieved from http://www.mifugouvuvi.go.tz/

Morgan J B, Savell J W, Hale D S, Miller R K, Griffin D B, Cross H R and Shackelford S D 1991 National beef tenderness survey. Journal of Animal Science 69: 3274–3283.

Muchenje V 2007 Growth performance, carcass characteristics and meat quality of Nguni, Bonsmara and Angus steers raised on natural pasture. PhD Thesis submitted Fort Hare Alice University of Republic of South Africa, 184 pp.

Mwilawa A J T, Kimambo A E, Mtenga L A, Madsen J, Hvelplund T, Weisbjerg M R, Christensen M, Laswai G H and Mgheni D M 2010 Carcass and meat quality characteristics of indigenous cattle in Tanzania. In Proceedings of the 5th Research week and International Conference held on 22 ^nd – 24^th September 2010 at Egerton University, Kenya.

Mwilawa A J T 2012 Effects of different diets on weight gain, carcass and meat quality characteristics of two indigenous cattle in Tanzania. PhD Thesis submitted to the Sokoine University of Agriculture, Morogoro, Tanzania, 341 pp.

Nandonde S W 2008 Assessment of the Availability of Major Resources for Production of Quality Beef in Tanzania. MSc. Dissertation. Sokoine University of Agriculture Morogoro, Tanzania. 126pp.

SAS (2000) SAS User’s Guide: Statistics (Version 6 Ed.). SAS Inst. Inc., Cary, NC, USA.

Schroeder J W, Cramer D A, Bowling R A and Cook C W 1980 Palatability, shelf life, and chemical differences between forage- and grain-finished beef. Journal of Animal Science 50: 852-859.

Shackelford S D Wheeler T L and Koohmaraie M 1997 Tenderness Classification of Beef: I. Evaluation of Beef Longissimus shear force at 1 or 2 days post-mortem as a predictor of aged beef tenderness. Journal of Animal Science 75: 2417– 2422.

Shepherd L M K 2013 The effects of method of forage-finishing and cattle breed on growth performance, carcass characteristics, meat quality, and fatty acid composition. MSc. Dissertation. Sokoine University of Guelph Ontario, Canada. 140pp.

Short R E, Grings E E, Mac Neil M D, Heitschmidt R K, Williams C B and Bennett G L 1999 Effects of sire growth potential, growing-finishing strategy and time on feed on performance, composition and efficiency of steers. Journal of Animal Science 77: 2406-2417.

Tornberg E 2005 Effects of heat on meat proteins- implications on structure and quality of meat products. Meat Sci. 70: 493-508

Xiong Y L W G, Moody S P, Blanchard G Liu and W R Burris 1996 Postmortem Proteolytic and Organoleptic Changes in Hot-Boned Muscle from Grass- and Grain-Fed and Zeranol-Implanted Cattle. Food Research International. 29(1):27-34.

Young A W and Kauffman R G 1978 Evaluation of beef from steers fed grain, corn silage or haylage-corn silage diets. Journal of Animal Science 46: 41.

Zakaria A 2010 Effect of nutrition and breed on body measurements and meat cuts yields. Dissertation for award of MSc. Degree at the Sokoine University of Agriculture, Morogoro

Received 14 May 2014; Accepted 22 September 2014; Published 3 October 2014

Go to top