Relationship between population genomic structure and growth profiles of South African goats under different production systems.

Goats play a major role in poor marginalized communities of South Africa for food security and socio-economic purposes. Majority of the goats are raised in villages with poor infrastructure and resources, therefore facing challenges that affect growth performance which leads to low mature weights. Investigating growth profiles will shed light on growth performances and will aid in goat improvement and selection. This study investigated the growth profiles and genomic structure of SA indigenous breeds raised in different production systems to unravel the genetic potential of indigenous goat populations. Live weights and morphological body measurements were collected from a total of 83 kids representing the commercial meat-producing SA Boer (n = 14); the indigenous veld goats (IVG) of NC Skilder (n = 14), Mbuzi (n = 13), and Xhosa lob (n = 14) raised under intensive systems; and nondescript village goat populations (n = 14) raised in intensive and others (n = 14) raised in extensive production systems. The remaining 72 of 83 phenotyped goats were genotyped using the Illumina Caprine SNP50K BeadChip. The SA Boer had a higher weight (28.96 ± 0.30 kg) gain as compared to other populations. The Mbuzi population was the smallest (14.83 ± 0.33 kg), while the village goats raised in Pella Village were relatively smaller (17.55 ± 0.37 kg) than those raised on the research farm (19.55 ± 0.36 kg). The study concluded that both genetics and management systems can lead to improved growth performance in goat production. The outputs of this study can be used to identify suitable breeds and potential genotypes for optimal growth and establish optimal goat management systems suitable for communal farmers for improved productivity.

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.

The changes in springbok (Antidorcas marsupialis) Longissimus thoracis et lumborum and Biceps femoris muscles during the rigour period.

This study describes the changes taking place during rigour in springbok (Antidorcas marsupialis) Longissimus thoracis et lumborum (LTL) and Biceps femoris (BF) muscles. Samples from six male and six female springbok were snap-frozen at 2, 3, 5, 8, 12, 18, 24 and 30h post-mortem (PM) and the pH, calpains I, II and calpastatin activities and cathepsins B, BL and H activities were determined. The temperature was also recorded. Significant third-order interactions were found for the pH and temperature, with the female LTL cooling more rapidly and acidifying slower than the other samples. Female muscles were at risk of developing cold-shortening and all the samples cooled more rapidly than recommended for cattle or sheep. Cathepsin BL activity increased PM, likely due to the degradation of the lysosomes. Calpains I, II and calpastatin activity declined during rigour, indicating that the calpains were activated early PM. Gender and muscle had a significant effect on calpain and cathepsin activity.

Protein kinase activities in ripening mango, Mangifera indica L., fruit tissue. I: Purification and characterization of a calcium-stimulated casein kinase-I.

A Ca(2+)-stimulated protein kinase (PK-I), active with dephosphorylated casein as exogenous substrate, was purified from ripening mango fruit. The purification procedure involved 30-70% ammonium sulphate fractionation and sequential anion exchange-, affinity-, hydrophobic interaction- and gel filtration chromatography. PK-I was purified ca. 40-fold with an overall yield of < 1%. The final specific activity in the presence of 0.1 mM Ca2+ was 55 nmol min-1 mg-1. Analysis of the most highly purified preparations revealed a monomeric enzyme with an M(r) of 30.9 kDa and pI of 5.1. PK-I efficiently phosphorylated casein and phosvitin, but did not phosphorylate histone II-S, histone III-S, protamine sulphate or bovine serum albumin. PK-I activity was stimulated by micromolar concentrations of Ca2+ and was dependent on millimolar Mg2+ concentrations, which could not be substituted with Mn2+. PK-I activity was stimulated by, but was not dependent on Ca2+. Calmodulin and calmodulin inhibitors did not affect PK-I activity, but heparin and cAMP acted as inhibitors. The pH and temperature optima of the enzyme under standard reaction conditions were 6.5 and 35 degrees C, respectively. The kinetic reaction mechanism of PK-I was studied by using casein as substrate. Initial velocity and product inhibition studies with ADP as product inhibitor best fit an ordered bi-bi kinetic mechanism with the Mg(2+)-ATP complex binding first to the enzyme followed by binding of the protein substrate. The K(m)ATP and K(m)casein of PK-I were 9 microM and 0.26 mg ml-1, respectively. The KiADP of PK-I was 9 microM.

Protein kinase activities in ripening mango, Mangifera indica L., fruit tissue. III. Purification and characterisation of a calcium-regulated protein kinase.

A calcium-dependent protein kinase (PK-III), not requiring calmodulin for activity, was purified from extracts of ripening mango fruit tissue. Purification was achieved by ammonium sulfate fractionation and sequential anion exchange-, hydrophobic interaction-, dye ligand affinity- and gel filtration chromatography; which allowed a recovery of 1-5% of the total available kinase activity. The final specific activity in the presence of 1 mM Ca2+ was consistently 9 nmol min-1mg-1. The purified enzyme was a monomer with a Mr of 49000, but was resolved by denaturing electrophoresis into two related protein bands of 49 and 45 kDa. Enzyme activity was activated >30-fold by micromolar amounts of free calcium and was dependent upon millimolar Mg2+ or Mn2+ concentrations. Calmodulin (1 microM) had no effect on PK-III activity but the calmodulin antagonists, calmidazolium and chlorpromazine, inhibited PK-III in a dose-dependent manner over a range of 0 to 100 microM. The results suggest a regulatory domain that is similar to calmodulin. PK-III phosphorylated histone III-S and to a lesser extent casein, but did not phosphorylate histone II-S, phosvitin or protamine sulfate. The enzyme phosphorylated substrate proteins on either serine or threonine but not tyrosine. Some endogenous substrates and the ability to autophosphorylate were revealed by autoradiographic studies. PK-III displayed a broad pH optimum (pH 6.6-9.5), and the optimum reaction temperature with histone III-S as substrate was 35 degreesC. The kinetic reaction mechanism of PK-III was studied by using casein as substrate. The KmATP and Kmcasein of PK-III were determined as 10 microM and 1.0 mg ml-1, respectively.

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 physical and biochemical changes in springbok (Antidorcas marsupialis) Longissimus thoracis et lumborum and Biceps femoris muscle during ageing.

This study aimed to determine the optimum ageing period for vacuum-packed springbok (Antidorcas marsupialis) Longissimus thoracis et lumborum (LTL) and Biceps femoris (BF) muscle stored at 5.4 ± 1.0°C. Portions of muscle from seven male and six female springbok were aged 1, 2, 5, 8, 14 or 21 days. The Warner Bratzler shear force declined most during the first five days post-mortem (PM), while purge and cooking losses increased significantly with ageing. Calpains I and II and calpastatin activity declined significantly up to five days PM, suggesting that they may be responsible for tenderization. Cathepsins B, BL and H activity increased significantly during ageing. The BF muscle had significantly higher pH, lower purge loss, higher cooking loss, higher WBSF and higher calpain and calpastatin activity than the LTL. No significant differences between the genders or muscles were found for the collagen content or collagen solubility. Springbok LTL and BF muscles should not be aged for longer than five days.

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.

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.

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.