Growth performance, hematology, and meat quality characteristics of Mutton Merino lambs fed canola-based diets.

A 56-day feeding trial was carried out to evaluate the effect of feeding canola meal (CM) on growth performance, hematology, and meat quality parameters of lambs. Twenty lambs with an average body weight of 23 ± 2.64 kg were randomly assigned to five dietary treatments and fed in individual cages for 56 days. The soya bean meal (SBM) in the control ration was replaced with canola meal at 0 (CM0), 25 (CM25), 50 (CM50), 75 (CM75), and 100 % (CM100) inclusion levels. Average daily weight gain (ADWG) and average daily feed intake (ADFI) were significantly higher in the CM25 and CM50, respectively. Feed conversion ratio (FCR) (3.09-3.41) and slaughter weight (SLW) (33.2-34.7 kg) were, however, similar among the treatment groups. Diet had no effect on carcass length (78.7-83.7 cm) and ultimate meat pH (pHu) (5.70-5.81). Nevertheless, hot carcass weight (HCW) (16.5-18.7 kg) and cold carcass weight (CCW) (16.2-18.2 kg) were higher (P < 0.05) in the CM0 and CM50 treatment groups. The shear force measurements (1.67-2.17 kg) differed (P < 0.05) across treatments. There was no dietary effect on the lightness (L*) (33.5-35.8), redness (a*) (11.35-12.7), and yellowness (b*) (13.4-14.8) of meat. In conclusion, CM can completely replace SBM in lamb diets without any negative effects on growth performance, general health, and meat quality of Mutton Merino lambs.

A South African beef quality survey.

In this study a survey of various meat quality characteristics of beef loin cuts was conducted in the City of Tshwane Metropolitan Municipality (Gauteng Province of South Africa) to determine the variation and consistency of beef quality of products purchased over time. Four hundred and twenty beef loin samples were collected on 20 occasions over 308 days from 13 outlets of 2 supplier types (butcher and supermarket). Packaging type, label information and price were considered for the evaluation of meat tenderness, colour, cooking loss, tissue composition and steak thickness. The results demonstrate that large variation in characteristics relevant to consumers' choice and satisfaction among and within different products sold as porterhouse steak in South Africa. In particular, muscle tenderness varied (P < 0.0001) across the 20 products and also showed significant inconsistency over the 20 purchasing events for certain products.

The comparison of three ß-agonists for growth performance, carcass characteristics and meat quality of feedlot cattle.

Forty-eight Bonsmara steers were assigned to three treatment groups and one control group consisting of 12 animals each. The control (C) received no ß-agonist, while the three treatment groups received zilpaterol (6ppm) (Z), ractopamine (30ppm) (R) or clenbuterol (2ppm) (Cl) for the last thirty days on feed. Growth performance (final 30 days), USDA quality and yield grades and meat quality (shear force, chemical, histological and biochemical) were compared for the three ß-agonist and control groups. Animals responded negatively to Cl treatment during initial stages of supplementation, which was evident in lower feed consumption and initial growth rates. For carcass growth and yield, Cl had greater and more efficient growth rates, higher dressed out yields (proportional), lower USDA yield grades, and reduced marbling compared with C (P<0.05). For meat quality measurements, the M. longissimus (LL) and M. semitendinosus (ST) were sampled. Cl had the greatest effect (P<0.05) on WBSF, especially on the LL, followed by Z. Variation in tenderness and ageing effects corresponded with variation in calpastatin activity and myofibrillar fragmentation between treatment groups. While zilpaterol and ractopamine are currently the only products registered for cattle in different countries, it seems that zilpaterol has an advantage in carcass growth efficiency and yield without showing any adaptation problems for animals such as experienced by the more aggressive ß-agonist clenbuterol.

Evaluation of biochemical parameters and genetic markers for association with meat tenderness in South African feedlot cattle.

A large proportion of South African feedlot cattle are crossbreds of Brahman (BrX, Bos indicus), and Simmental (SiX, Bos taurus). A sample of 20 grain fed bulls from each of these crossbreeds was used to compare meat quality with that of the small frame indigenous Nguni (NgX, Sanga) by evaluating a variety of biochemical and genetic parameters previously shown to be associated with meat tenderness. Shear force values were generally high (5.6kg average at 14days post mortem), with SiX animals higher than BrX or NgX (P=0.051) despite higher calpastatin:calpain ratio in BrX (P<0.05). Calpain activity and cold shortening were both correlated with tenderness for all classes. The sample size was too small to accurately estimate genotypic effects of previously published markers in the CAST and CAPN1 genes, but the allele frequencies suggest that only modest progress would be possible in these South African crossbreds using these markers.

Do indigenous Southern African cattle breeds have the right genetics for commercial production of quality meat?

The establishment of cattle breeds which are now indigenous to Africa is believed by historians to be very closely associated with man, his development, migration and specific behaviour from 6000 years BC. Today these breeds compete with exotic breeds in a commercial system driven by global economical principles. Results from various trials are discussed to verify if these breeds can adhere to these principles and compete in the South African beef market to produce quality beef economically. Variation in frame size among indigenous breeds will determine their suitability as feedlot cattle depending on the price and feed margins driving profit in this industry sector. Meat quality analyses indicate small or no differences between indigenous and exotic European/British breeds but with potentially superior quality compared to Bos indicus breeds.

Meat quality of Nguni, Bonsmara and Aberdeen Angus steers raised on natural pasture in the Eastern Cape, South Africa.

The current study compared meat quality of Nguni, Bonsmara and Angus steers raised on natural pasture. Fifteen seven-month-old weaners of each breed were kept at the University of Fort Hare Farm for 12 months till slaughter. Monthly weights of the steers were recorded. Carcasses were electrically stimulated. The m. longissimus thoracis et lumborum was sampled for the measurement of meat colour, pH, drip loss, sarcomere length, myofibrillar fragmentation length and Warner Bratzler (WB) shear force. The Nguni had the highest (P<0.05) average daily gain. Bonsmara and Angus steers had higher (P<0.05) carcass weight and dressing percentage than the Nguni steers. Meat quality characteristics were similar among all the breeds except that Nguni meat was darker (L(∗)) (P<0.05) than meat from the other two breeds. The respective L(∗) values for Nguni, Bonsmara and Angus steers were 36.5, 38.6 and 39.9. There were significant (P<0.05) correlations among some meat quality traits. There were significant (P<0.05) correlations between WB values of meat aged for 2 and 21 days in Nguni and Bonsmara, but not in Angus. Meat quality from Nguni compares favourably with that from established breeds, when raised on natural pasture.

Should electrical stimulation be applied when cold shortening is not a risk?

This experiment was designed to show whether delayed high voltage stimulation (ES) is more beneficial than no stimulation (NS) to secure tenderness under circumstances where rigor conditions are difficult to control due to variations in carcass size, fatness and/or chilling capacity. Ten Charolais carcasses were split during slaughter, the left sides were stimulated at 45min post-mortem for 45s, and the right sides were left unstimulated. The carcass sides were then chilled at a medium chilling rate. Sarcomere length measurements confirm that there was neither cold nor heat shortening in the M. longissimus (LD). LD from ES sides aged for 2 days was more tender than non-stimulated LD (NES), although prolonged ageing eroded the advantage of ES to a non-significant advantage after 14 days. Initial tenderness differences coincided with lower 24h calpain activity, suggesting an early onset of proteolysis and ageing (tenderisation). In contrast to conventional early ES, delayed ES, appears to be beneficial for the early development of tenderness without too much interference with enzyme. Myofibril fragment length (MFL) was a good indicator of the development of tenderness during prolonged ageing but not for the early post-mortem variation in tenderness. No colour (L*, a*, b*) differences, occurred due to stimulation treatment, while drip loss was slightly higher at 24h post-mortem for ES meat.

The effects of spray-chilling on carcass mass loss and surface associated bacteriology.

The effect of spray-chilling on carcass mass loss and bacteriology was tested in this trial. The spray-chill treatment consisted of intermittent spraying of carcasses for either 60 or 120 s every 15 min, for 10, 14 or 17 h. The 17 h/120 s spray-chill treatment gave the highest and 10 h/60 s the lowest moisture savings after 18 h of chilling. Due to insufficient drying time between the end of spraying (17 h) and the end of chilling (18 h) the carcass sides of the 17 h/60 s and 120 s treatments appeared pale and wet; this was not the case with the other treatments. Regarding microbial analyses, the results indicated that, except for the 17 h/20 s spray-chill treatment, the mean total and Enterobacteriaceae counts of the spray-chill treatments were similar to their respective control groups (conventionally chilled). The mean total and Enterobacteriaceae counts of the 17 h/20 s spray-chill treatments increased, while those of the controls decreased.

Characterisation of indigenous African cattle breeds in relation to meat quality traits.

Meat quality characteristics of two Sanga (indigenous) breeds (Afrikaner and Nguni), one indigenous composite breed (Bonsmara), one foreign composite breed (Santa Gertrudis) and two continental breeds (Brown Swiss and Pinzgauer) were compared. Means were adjusted for mean overall subcutaneous fat level (4.7%). Meat tenderness was then related to certain muscle characteristics. Shear force measurements indicated that Santa Gertrudis (SG) meat was significantly less tender than that of the two continental breeds and the three indigenous breeds (P<0.05). Pairwise linear correlations showed that differences found in background toughness (connective tissue) among breeds did not have a significant effect on tenderness. However, higher myofibrillar fragmentation indices, as well as lower white muscle fibre percentages for the three indigenous breeds, especially the two Sanga breeds, proved their potential to produce meat of comparable tenderness to that of continental breeds under specific slaughter and post-slaughter conditions.

Meat quality of designated South African indigenous goat and sheep breeds.

Carcass composition, proximate meat composition, fatty acid composition and sensory characteristics of two breeds of goats, Indigenous (n=12) and Boer goats (n=12), and two breeds of sheep, Damara (n=12) and Dorper (n=12), on extensive pasture-grazing, were analysed. The right side of each carcass was processed into wholesale cuts and dissected into subcutaneous fat, meat and bone. Meat and fat were minced together and sampled for proximate analysis as well as fatty acid profiles. The remaining minced meat was formed into meat patties, which were cooked for descriptive sensory evaluation of aroma, tenderness, juiciness and flavour characteristics by a trained panel. Goat and sheep breeds had different meat qualities. The composition and properties of subcutaneous and intramuscular fat contributed to the differences in meat quality observed within and between the species studied. Goats had proportionally smaller carcasses. Sheep yielded more dissectable fat and lean and less bone as a percentage of carcass weight than goat breeds, although the proportional lean content per cut of Boer goats was comparable to that of sheep. The percentage of bone was highest for Indigenous goats. Concentrations of saturated fatty acids were higher in goats compared to sheep. Sheep patties were more tender, juicy, greasy and less chewy compared to goat patties. The species related goaty and muttony flavour were clearly distinguishable. It is recommended that goats should be valued as a different species compared to sheep.

Effect of South African beef production systems on post-mortem muscle energy status and meat quality.

Post-slaughter muscle energy metabolism meat colour of South African production systems were compared; steers (n=182) of Nguni, Simmental Brahman crossbreds were reared on pasture until A-, AB-, or B-age, in feedlot until A-AB-age. After exsanguination carcasses were electrically stimulated (400 V for 15 s). M. longissimus dorsi muscle energy samples were taken at 1, 2, 4 and 20 h. Post-mortem samples for meat quality studies were taken at 1, 7 and 14 days post-mortem. Production systems affected muscle glycogen, glucose, glucose-6-P, lactic acid, ATP, creatine-P glycolytic potential (P<0.05), with the muscles of feedlot carcasses having a faster glycolysis rate than pasture carcasses. Energy metabolites correlated (0.40.5) water holding capacity, drip loss, and Warner Bratzler shear force. Muscle energy only affected muscle contraction of the A-age-pasture system (shortest sarcomere length of 1.66 µm vs 1.75 µm highest WBS of 6 kg vs 5 kg 7 days post-mortem).

Effect of dietary beta-agonist treatment, vitamin D3 supplementation and electrical stimulation of carcasses on colour and drip loss of steaks from feedlot steers.

In this study, 20 young steers received no beta-agonist (C) and 100 animals all received zilpaterol hydrochloride (Z), with 1 group receiving Z while the other 4 groups receiving Z and vitamin D(3) at the following levels (IU/animal/day) and durations before slaughter: 7million for 3days (3D7M) or 6days (6D7M), 7million for 6days with 7days no supplementation (6D7M7N) and 1million for 9days (9D1M). Left carcass sides were electrically stimulated (ES) and right sides not (NES). Samples were analysed fresh or vacuum-aged for 14days post mortem. Parameters included drip loss and instrumental colour measurements. In general, zilpaterol showed increased drip loss, lighter meat, and reduced redness. Vitamin D(3) supplementation could not consistently overcome these negative effects. All vitamin D(3) treatments reduced drip loss of stimulated aged steaks.

Effect of age and cut on cooking loss, juiciness and flavour of South African beef.

The juiciness and flavour characteristics of 15 aged primal beef cuts of electrically stimulated carcasses, from three different age groups, were assessed (n=61). Cooking losses were determined and proximate analyses (moisture, fat, nitrogen and ash) were performed. Tender cuts were cooked by a dry heat method, and less tender cuts were cooked by moist heat methods. A trained panel (n=10) evaluated sensory quality characteristics including initial and sustained juiciness, aroma and flavour. Flavour intensity was the biggest discriminant between the three age groups and declined with an increase in age. Initial impression of juiciness decreased with increased age of the animal and cooking losses increased nonlinearly with age, irrespective of the muscle. In contrast sustained juiciness increased with increased age. Cuts cooked according to a dry heat cooking method were reported juicier (both initial and sustained) than those cooked by moist heat methods.

Effect of age and cut on tenderness of South African beef.

The tenderness characteristics of 15 primal cuts of beef of three different age groups were assessed, and the most reliable cut to predict carcass tenderness was determined. Fifteen wholesale cuts from each age group, representing the full variation in fatness, were aged, cooked and underwent sensory evaluation, shear force resistance and proximate analysis. Collagen content and solubility was determined. Percentage fat was used as a covariant during statistical analyses. Tenderness, residue and collagen solubility of all cuts decreased significantly with animal age. Collagen solubility was the largest discriminant between the three age groups, while animal age had no significant effect on collagen content. Tenderness of primal cuts from the same carcass varied considerably, with collagen content and shear force resistance as the largest discriminants between the cuts. Cuts most representative of total carcass tenderness were M. vastus lateralis, M. semimembranosus, M. gluteobiceps, M. semitendinosus and M. triceps brachii caput longum.

Variation in meat quality characteristics between Sanga (Bos taurus africanus) and Sanga-derived cattle breeds and between Sanga and Brahman (Bos indicus).

Cattle breeds indigenous to Africa (Sanga) compare favourably to Bos indicus breeds with regard to adaptation to harsh environments. This study compared the meat quality of three Sanga breeds (Nguni, Tuli and Drakensberger), a Sanga-related breed (Bonsmara) and a B. indicus breed (Brahman) and supported these results with biochemical and histological measurements on the M. longissimus lumborum. Twelve young grain-fed steers of each breed were slaughtered and carcasses were electrically stimulated. All Sanga (and related) breeds, with the exception of the Tuli, had lower Warner-Bratzler shear force (SF) values at 2 and 21 days post mortem compared with the BR (P < 0.05). Measurements related to the calcium-dependent protease system and myofibrillar fragmentation explained the bulk of the variation among breeds, whereas variation in fibre type, sarcomere length and connective tissue properties gave less convincing support. With the exception of the Tuli, Sanga and Sanga-related breeds produced more tender (according to SF) meat than BR, mainly due to favourable calpain-to-calpastatin ratios. Small differences in colour, drip loss and cooking properties were found among breeds (P < 0.05).

The effects of a beta-agonist treatment, vitamin D3 supplementation and electrical stimulation on meat quality of feedlot steers.

In this study, 20 young steers received no beta-agonist (C), 100 animals all received zilpaterol hydrochloride (Z), with 1 group only receiving Z while the other 4 groups received zilpaterol and vitamin D3 at the following levels (IU/animal/day) and durations before slaughter: 7 million for 3 days (3D7M); 7 million for 6 days (6D7M); 7 million for 6 days with 7 days no supplementation (6D7M7N) and 1 million for 9 days (9D1M). Left carcass sides were electrically stimulated (ES) and the right side not stimulated (NES). Samples were aged for 3 or 14 days post mortem. Parameters included Warner-Bratzler shear force (WBSF), myofibril filament length, sarcomere length and calpastatin and calpain enzyme activity. Both ES and prolonged aging reduced WBSF (P<0.001). 6D7M, 6D7M7N and Z remained significantly tougher than C (P<0.001), while 3D7M and 9D1M improved WBSF under NES conditions. ES is more effective to alleviate beta-agonist induced toughness than high vitamin D3 supplements.

Effects of duration of zilpaterol hydrochloride supplementation on growth performance, carcass traits and meat quality of grain-fed cull cows.

Several studies have shown that feeding of an energy-dense diet over short periods to cull cows could be profitable in terms of increased saleable yield and improved carcass conditions. Although the application of growth promoters, such as anabolic implants and beta agonists, in finishing of cull cows have been recorded, there is no conclusive evidence as to the timing and duration of beta agonists in cull cow production. In this study, 288 cull cows with four or more permanent incisors and varying weights and body conditions were divided into four treatment groups so that variation in age, weight and body condition were equally distributed among groups. One group received concentrate feed without any beta agonist (C), whereas the other three groups also received concentrate feed with zilpaterol hydrochloride (6 p.p.m.) for 20 (Z20), 30 (Z30) or 40 (Z40) days, respectively, followed by a 2-day withdrawal. Animals were adapted for 10 days on a grain-based diet and fed an additional 40 days before slaughter. Growth rate and efficiency (live and carcass), trimmed meat yield and meat tenderness (Warner Bratzler shear force and sensory) of the aged (10 days) m. longissimus thoracis (LT) and m. semitendinosus (ST) were recorded. In general, Z cows had higher carcass gains and efficiency of gain than C cows (P < 0.05). In addition, Z carcasses showed higher proportional trimmed meat yields than C carcasses (P < 0.05). No significant differences in tenderness measurements were recorded for LT or ST. In general, supplementation of zilpaterol for 30 days showed better growth performance and higher trimmed meat yield than 20 and 40 days supplementation.

Meat quality of Nguni steers supplemented with Acacia karroo leaf-meal.

The objective of the study was to determine the meat quality of Nguni steers supplemented with Acacia karroo leaf-meal. Thirty 19-month old steers were randomly assigned to A. karroo leaf-meal (AK), sunflower cake (SF) and a control (CN) diets. Steers on the AK and SF diets were given an additional 150 g of protein per day for 60 days. The steers were slaughtered at 21 months and the m.longissimus thoracis et lumborum was sampled for meat quality measurements. Steers that received SF diet had lighter-coloured (L*) (P<0.05) meat than those on AK and CN diets. The highest redness (a*) (17.3+/-0.29) values were recorded in steers supplemented with AK compared to those that received SF and CN diets. Diet had no effect on pH, drip loss, water holding capacity, sarcomere length, muscle bundle areas, myofibrillar fragment length, Warner-Bratzler shear force and cholesterol values. Steers supplemented with AK (22.4+/-0.08%) and SF (22.5+/-0.08%) had higher (P<0.05) meat protein content than those on the CN (20.2+/-0.08%) diet. Highest muscle fibre area (3472.6+/-119.51 microm(2)), fat content (1.2+/-0.11%) and cooking loss (25.2+/-0.73%) of meat aged for 2 days were recorded in steers given the SF diet compared to those on the AK and CN diets. Supplementing Nguni cattle with A. karroo leaf-meal produced beef of comparable quality to natural pasture alone but with a fresher appearance and higher protein content.

The efficiency of electrical stimulation to counteract the negative effects of ß-agonists on meat tenderness of feedlot cattle.

Beta agonists used as growth enhancers are known to affect the aging potential of beef muscle negatively. On the other hand, procedures like electrical stimulation could accelerate rigor and the aging process. In this study, 20 out of 40 young steers received no beta agonist (C), the remaining twenty steers received a beta agonist (zilpaterol hydrochloride) (Z) for the 30 days prior to slaughter followed by 4 days withdrawal. After slaughter carcasses were split, the left side electrically stimulated (ES) and the right side not stimulated (NES). Samples were aged for 3 or 14 days post mortem. Parameters included Warner Bratzler shear force (WBSF), myofibril filament length (MFL), sarcomere length and calpastatin and calpain enzyme activity. Zilpaterol resulted in increased (P<0.001) WBSF mainly due to an increased (P<0.001) calpastatin activity. ES improved tenderness (P<0.001) in general by early onset of rigor triggering the activity of calpains. ES also reduced the calpastatin activity (P<0.001), which partially countered the effect of high calpastatin activity on the aging potential of Z loins. ES can therefore be implemented to improve meat tenderness in zilpaterol supplemented steers, although steers without zilpaterol will still have an advantage in final tenderness.

Relationship between pre-slaughter stress responsiveness and beef quality in three cattle breeds.

The relationship between stress responsiveness and beef quality of 40 Nguni, 30 Bonsmara and 30 Angus steers was determined. The L(∗) values, pHu, cooking loss (CL) and Warner-Bratzler shear force (WBSF) were determined. Catecholamine levels were determined from urine samples collected at slaughter. Bonsmara steers had the highest (P<0.05) levels of catecholamines with respective epinephrine, norepinephrine and dopamine concentrations of 10.8, 9.7 and 14.8nmol/mmol. Nguni steers had the lowest (P<0.05) levels of catecholamines, with respective catecholamine concentrations of 5.1, 4.3 and 4.0nmol/mmol. In the Nguni steers, there were significant (P<0.05) correlations between catecholamines and L(∗) and between dopamine and tenderness in meat aged for two days (WBSF2). In the Bonsmara, dopamine was correlated (P<0.05) pHu, WBSF2 and CL. No significant correlations were found in the Angus. Therefore the relationship between stress responsiveness and certain beef quality traits may not be similar in different breeds.