The Effects of Different Zilpaterol Hydrochloride Feed Supplements and Extended Aging Periods on the Meat Quality of Feedlot Bulls

This study researched the effects of two commercially available zilpaterol hydrochloride (ZH) β-adrenergic agonists, denoted as ZH-A and ZH-B, on the meat quality characteristics of typical South African feedlot bulls (taurine × indicus composites), over extended aging periods of up to 120 days. The effects of ZH were studied to address concerns about the possible adverse effects of ZH on beef quality following extended aging, which typically occurs during the exportation of beef by boat. The completely randomized control study consisted of 3 homogenous experimental groups, with 3 replicates per treatment and 50 bulls per replicate = 450 animals. Treatments were a negative control (CT) with no ZH supplementation added to the basal diet or a basal diet supplemented with either zilpaterol hydrochloride A (ZH-A) or zilpaterol hydrochloride B (ZH-B), both at 105 g ZH/ton, fed from the first day of the finishing period (D0) for 30 days. Subsamples were collected from 38 random carcasses from each treatment for proximate analysis and meat quality analysis using Longissimus dorsi samples. ZH supplementation decreased meat tenderness (Warner-Bratzler shear force values (WBSF)) of bulls fed ZH-A or ZH-B, compared to those fed the CT diet (p < 0.05; η2 = 0.24). The WBSF values of both ZH treatments were about 0.5-0.8 kg higher during the aging periods compared to the CT, but ZH did not affect post-mortem meat aging or meat quality characteristics differently compared to the CT. Post-mortem aging per se influenced all meat quality characteristics investigated (p < 0.001; η2 > 0.30), showing improvements in WBSF, a decrease in meat colour and an increase in drip and cooking losses. L*-values increased from 3 to 56 days of aging and then decreased to day 120 (p < 0.001; η2 = 032). Chroma values decreased from day 3 to day 120 (p < 0.001; η2 = 0.50). Hue° decreased from day 3 to day 7 and stabilized until day 120 (p < 0.001; η2 = 0.40). Moisture and cooking loss (CL) increased to 56 days and then decreased to 120 days.

Liver moisture content in animals and possible causes of variations in hepatic dry matter content

The concentration of trace elements in the liver is used as an indicator of the mineral nutritional status of an animal, as a benchmark of environmental mineral exposure, to follow the metabolism of an element in the body and for various other purposes. Concentrations are expressed on a wet (fresh) liver basis or on a dry liver basis. From a literature search and evidence from an analytical laboratory, large variations (varying from < 20% to > 40%) have been recorded on the percentage of moisture in the livers of ruminants. Such variations potentially compromise the interpretation of results on mineral concentrations in livers, and preclude robust comparisons between studies. Among the factors that can affect the moisture content of livers are: inconsistencies in sampling and preparation of liver samples; exposure to toxic substances; ill-health of the animal; fat content of the liver; and age of the animal. It was estimated that the mean dry matter (DM) content of the livers of healthy ungulates containing less than 1% liver fat is between 27.5% and 28.5%, and on a fat-free basis 25-26% DM. For routine analyses of liver samples it is suggested that to limit variations owing to differences in liver moisture content, liver mineral concentrations should be expressed on a DM basis, and for in-depth scientific studies on mineral metabolism on a dry, fat-free basis. However, if mineral concentrations are expressed on a wet basis, it is advisable to supply the liver DM content as well.

Color Attributes and Glycolytic Energy Metabolites of Meat From Light and Heavy Bovine Feedlot Carcasses Stimulated With Low-Voltage Electricity

This study investigates the influence of timing and duration of low-voltage electrical stimulation (ES) as well as carcass weight, which are important factors affecting muscle glycolysis and meat color attributes. Longissimus samples from 147 cattle, representative of typical South African feedlot cattle, were assigned to 10 treatment groups according to the combination of carcass weight (small or heavy), time of ES (early [7 min] or late [45 min] postmortem), and duration of ES (30 or 60 s). Early ES and longer ES duration (60 s) produced the highest (P &lt; 0.05) meat lightness (L*). The combination of early ES and heavier carcasses produced the highest (P &lt; 0.05) chroma (C*) 2 d postmortem (butchery period). These results were corroborated by the energy metabolites, such that early stimulation produced the highest amount (P &lt; 0.05) of muscle lactate, glucose, and glucose-6-phosphate, as well as the lowest glycogen, creatine phosphate, and adenosine triphosphate early postmortem. This shows that the application of low-voltage ES on heavier carcass is advantageous in terms of meat color, but the advantages diminish as ageing progressed from 2 to 14 d postmortem.

Scrotal tick damage as a cause of infertility in communal bulls in Moretele, South Africa

Calving rate in communal cattle influences both food security and socio-economics in rural households. A previous study indicated that scrotal damage caused by ticks could affect the fertility of communal bulls and reduce the annual calving rate. The objectives of the study were to investigate the annual calving rate in communal herds by counting calves during herd visits, perform breeding soundness examinations on bulls and identify adult ticks attached to their genitalia. This prospective longitudinal survey was based on participatory rural appraisal. Calving rates were estimated in cows (n = 2398) from 100 randomly selected communal herds in Moretele over 12 months in 2013, during routine visits by animal health technicians. Randomly selected bulls (n = 50) from these herds were tested for Brucella abortus, Trichomonas foetus and Campylobacter fetus subspecies venerealis. The calving rate was 35.86% (0.359). The mean scrotal circumference was 37.63 ± 3.42 cm. Total sperm motility was 78.73 ± 35.73%; progressive sperm motility was 27.39 ± 15.81% and non-progressive sperm motility was 51.34 ± 19.92%. Thirty-five of the 38 bulls examined for breeding soundness exhibited severe scrotal and preputial lesions caused by the adult ticks Amblyomma hebraeum and Hyalomma rufipes. Tick control methods used included spraying (n = 20), pour-on (n = 11), no control (n = 1) and various (n = 18). It was concluded that in Moretele genital tick damage had a more serious impact on the fertility of communal bulls than contagious diseases. Targeted acaricidal spot treatment of the genitalia of communal bulls to prevent infestation is recommended, as tick control strategies used by farmers appeared to be inadequate.

Epidemiological and partial budget analysis for treatment of subclinical Staphylococcus aureus intramammary infections considering microbiological and cytological scenarios

An innovative method was investigated to aid in the elimination of Staphylococcus aureus (S. aureus) intramammary infections (IMI) from dairy herds. A stochastic model explore the economic benefit of three-day or eight-day treatment of subclinical IMI in all S. aureus infected cows or in only those with a somatic cell count (SCC) exceeding 200,000 cells/ml. An epidemiological model was developed to run parallel to the economic model that would predict the S. aureus IMI likely to persist, develop new infections and clinical mastitis. In the economic model a first algorithm was used to consider the low prevalence (LP) scenario and made use of S. aureus prevalence information provided by retrospective analysis of microbiological and cytological results in South Africa (2008-2012). The data used considered Staphylococcus aureus prevalence from [1.495; 1.595]_95% to [6.72; 6.95]_95% for SCC≤200,000 and SCC>200,000 cells/ml respectively. A second algorithm considered the high prevalence (HP) scenario to evaluate a simulated situation with a 5[U1] [R12] to 25% prevalence. Scenarios of low or high transmission ratio (TR) were included in the model according to the hygiene management on the farm. Probabilities and costs were calculated over 255days. The economic models predicted average cost indices for low S. aureus IMI and low TR to vary from -3179 ZAR (South African Rands) when subclinical cases with SCC higher than 200,000 cell/ml were treated for eight days, to -3663 ZAR when all subclinical S. aureus IMI were treated for three days. With a HP and high TR of S. aureus the average cost indices changed from -18,042 ZAR when none to -5433 ZAR per 255days when all S. aureus IMI were treated for eight days. The epidemiological model in this study predicted substantial benefit of treatment mainly in high TR scenarios. New IMI decreased up to77% in the three-day and up to 91% in the eight-day treatment scenarios. In the HP scenarios, persistent IMI were reduced by 94%. The number of clinical cases predicted with no treatment for subclinical infections was higher than the total number of clinical and subclinical cases in scenarios where cows were treated three or eight days. Initial prudent treatment of subclinical IMI resulted in less overall treatments and less new, persistent and clinical cases. Combined results of economic and epidemiological models indicated that the option that cost the least did not always have the best epidemiological outcome. Models may assist in optimising and balancing decisions relating to financial and IMI.

Validity of somatic cell count as indicator of pathogen-specific intramammary infections

The objective of this study was to determine whether somatic cell count (SCC) was an effective test, with a sensitivity exceeding 85%, to determine species-specific bacterial infections. In addition, the relation between the SCC and various udder pathogen groups was investigated. SCC thresholds of greater than 200 000 cells/mL were used in quarter and greater than 150 000 cells/mL in composite milk samples. A retrospective study was conducted on a data set for 89 635 quarter and 345 467 composite cow milk samples. Eleven SCC threshold values were used to evaluate the diagnostic efficacy for the following bacteria: Gram-positive major pathogens: Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae and Streptococcus uberis; Gram-negative major pathogens: Escherichia coli, Klebsiella pneumonia and Serratia spp.; minor pathogens: coagulase-negative staphylococci, Micrococcus spp., Staphylococcus pseudintermedius, Streptococcus pyogenes, Enterococcus faecalis, Enterococcus canis, Trueperella pyogenes and other Enterobacteriaceae. Sensitivity and specificity were calculated taking the effect of clustering into account with quarter milk samples. Most samples yielding major Gram-positive pathogens (88.9% in quarter and 79.9% in composite samples) and minor pathogens (61.4% in quarter and 51.7% in composite samples) had SCC greater than 200 000 cells/mL. Sensitivity of the SCC test to detect major pathogens at an SCC threshold of greater than 200 000 cells/mL in quarter samples and greater than 150 000 cells/mL in composite milk samples was 88.2% and 84.2%, respectively, but specificity was low (57.7% and 52.8%, respectively).

Somatic cell count thresholds in composite and quarter milk samples as indicator of bovine intramammary infection status

The objective of the study was to establish an operational somatic cell count (SCC) threshold to predict the presence of intramammary infection (IMI) in composite milk samples and compare findings with those in quarter milk samples. South African dairy producers now preferred composite milk samples for herd udder health analysis because of increasing cow numbers, convenience of sampling and lower cost. A retrospective study was conducted on 345 461 composite and 89 638 quarter milk samples from South African herds. Variance estimates for the proportion of quarter samples testing positive were adjusted to account for the lack of their independence within individual cows. The IMI at SCC thresholds of 150 000 cells/mL and 200 000 cells/mL differed only by 3.26% in composite milk samples. Youden’s index indicated the optimum SCC thresholds for composite and quarter milk samples as 150 000 cells/mL and 200 000 cells/mL, respectively. At 150 000 cells/mL, sensitivity (95% confidence intervals [CI]) in composite milk samples was 65.3% (64.0%, 66.6%) and specificity was 66.8% (65.7%, 67.9%); and in quarter milk samples, sensitivity at 200 000 cells/mL was 70.8% (69.5%, 72.0%) and specificity was 63.6% (62.4%, 64.8%). The likelihood of infection for udders and quarters, respectively, was 1.034 and 1.327 at an SCC threshold of 150 000 cells/mL and 0.864 cells/mL and 1.177 cells/mL at 200 000 cells/mL. The area under the curve of the receiver operating characteristics graph was 0.7084 and 0.7277 for composite and quarter samples, respectively, indicating that the SCC test could be considered as a good indicator of IMI in both sample types.

A pathogen-specific approach towards udder health management in dairy herds: Using culture and somatic cell counts from routine herd investigations

A dedicated udder health diagnostic programme was developed and used over a 15-year period in South Africa to analyse milk samples based on microbiological and cytological patterns within various groups and for individual cows and udder quarters in dairy herds. These pathogen-specific analyses are utilised for pro-active improvement and management of udder health in South African commercial dairy herds. The programme acts as a monitoring tool and identifies management areas at risk and individual cows with udder disease and uses both quarter and composite milk samples. Intra-mammary infection (IMI) is a dynamic situation and depending on the time a milk sample is taken, false-negative results may be obtained. A new IMI and an infection that is curing may both have low somatic cell counts (SCCs), masking the true bacterial status. SCC in individual infected udder quarters may differ greatly depending on the causative bacterial species, its pathogenicity, the host immune status and the environmental factors involved. A pathogen-specific udder health approach was followed with repeated herd tests to take account of these udder health dynamics. The results of the herd IMI investigation are applied in practice to assist veterinarians, udder health consultants and managers to make informed and specific detailed decisions at both a herd and on an individual cow basis regarding udder health.

Influence of electrical stimulation on carcass and meat quality of Kosher and conventionally slaughtered cattle

In a previous study regarding the effects of Kosher and conventional slaughter techniques on carcass and meat quality of cattle, it was speculated that electrical stimulation may have affected some of the meat qualities. Therefore, the objective of this study was to investigate the effects of electrical stimulation (ES) and non-electrical stimulation (NES) on key carcass and meat quality attributes of cattle slaughtered by Kosher vs. conventional slaughter methods. Carcass pH and temperature profiles over a 24 h post mortem (pm) period, meat shear force and water holding capacity were investigated in feedlot type cattle of comparable weights and breed types. Results showed that the combined effects of slaughter methods did not influence the meat quality attributes, but there were differences within the slaughter groups. The effect of ES on carcass pH lasted longer within the conventionally slaughtered group (12 h), than in the Kosher slaughter group (6 h). Muscle samples from the ES groups for both slaughter methods were more tender. Electrical stimulation also had a significant effect on the cooking loss from Kosher meat, while there was no significant difference in meat from the conventional slaughter methods. The results show that ES influences certain meat and carcass quality attributes of cattle, based on the way cattle were slaughtered.Keywords: Carcass pH, cooking loss, drip loss, electrical stimulation, shear force, slaughter technique

A new application of pelvis area data as culling tool to aid in the management of dystocia in heifers

Although fetomaternal disproportion is the major cause of dystocia in heifers, pelvis area (PA) is not recommended as a culling tool due to its relatively low importance and genetic correlation with calf birth weight (BWT), the most important factor associated with dystocia. The objective of this observational study of 484 limited bred yearling beef heifers was to compare the effects of different methods of adjustment of PA data for culling to select against dystocia. Multivariable analyses were used to determine predictors of PA, calf BWT, and dystocia. Hypothetical culling rates of 10 and 20% were then applied after ranking heifers by each of the following: unadjusted PA, PA adjusted to 365 d of age by subtracting 0.27 cm(2) per day of age difference between each heifer's age and 365 d (APA), PA:prebreeding BW ratio (PA:BW), PA adjusted to the median BW of the group using the regression coefficient of PA on BW within age group (BWPA), and PA similarly adjusted to the median lean BW (LBWPA). Dam parity, sire, prebreeding age, prebreeding BW, and prebreeding BCS were associated with PA whereas dam parity, sire, own BWT, PA, AI bull, and calf gender were associated with calf BWT (P < 0.05). Dam parity, calf BWT, and either BWPA or LBWPA were the only independent predictors of dystocia (P < 0.05). Adjusting PA to BW or lean BW (LBW) improved the sensitivity and specificity to predict dystocia. After hypothetical culling by PA, retained heifers were heavier and had a higher calving rate and calves tended to be heavier at birth compared to culled heifers, but dystocia rates were not different. Culling by APA resulted in similar effects, except that dystocia rate tended to be lower in retained heifers. Culling by PA:BW resulted in lower dystocia rate in retained than in culled heifers, but retained heifers had lower prebreeding BW than culls. Culling by BWPA and LBWPA resulted in lower proportions with dystocia and a tendency towards higher calving rates in the retained heifers, without affecting the prebreeding BW or calf BWT. It is concluded that pelvimetry is a useful culling tool to aid in the management of dystocia in yearling heifers and that adjustment of PA to median BW or LBW within age group improves its accuracy and avoids the undesirable side effects.

A perspective on the impact of reproductive technologies on food production in Africa

Africa for the largest part is still regarded as part of the developing world and has a history of political instability, natural disasters, floods and droughts that all had an effect on the development of livestock production systems and the potential application of biotechnologies. It is expected that the human population in sub Saharan Africa will experience a growth of 1.2 % per year over the next 30 years. There is therefore pressure to increase sustainable productivity of livestock. Reproductive technologies such as Artificial Insemination in Africa were driven primarily by the need to control or prevent venereal diseases like Trichomoniases and Campylobacter fetus in cattle. Reproductive biotechnology had a limited impact in Africa due to several factors including a lack of infrastructure and animal recording systems, clear breeding objectives and continuously changing production systems and markets. Africa has a large variety of genetic resources adapted to the diverse environment and production systems and biotechnology should be applied within this context for an increase in food production.

Interactions between negative energy balance, metabolic diseases, uterine health and immune response in transition dairy cows

The biological cycles of milk production and reproduction determine dairying profitability thus making management decisions dynamic and time-dependent. Diseases also negatively impact on net earnings of a dairy enterprise. Transition cows in particular face the challenge of negative energy balance (NEB) and/or disproportional energy metabolism (fatty liver, ketosis, subacute, acute ruminal acidosis); disturbed mineral utilization (milk fever, sub-clinical hypocalcemia); and perturbed immune function (retained placenta, metritis, mastitis). Consequently NEB and reduced dry matter intake are aggravated. The combined effects of all these challenges are reduced fertility and milk production resulting in diminishing profits. Risk factors such as NEB, inflammation and impairment of the immune response are highly cause-and-effect related. Thus, managing cows during the transition period should be geared toward reducing NEB or feeding specially formulated diets to improve immunity. Given that all cows experience a reduced feed intake and body condition, infection and inflammation of the uterus after calving, there is a need for further research on the immunology of transition dairy cows. Integrative approaches at the molecular, cellular and animal level may unravel the complex interactions between disturbed metabolism and immune function that predispose cows to periparturient diseases.

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 (0.4<r<0.9) with meat colour (CIE, L*a*b*), (0.3<r>0.5) 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 energy and protein levels on fatty acid composition of intramuscular fat in double-muscled Belgian Blue bulls

Seventy six Belgian Blue (BB) bulls, with double-muscled conformation, were randomly allocated to six dietary treatments in a 2 × 3 factorial experiment. The treatments included low (N(L)=127 g CP/kg DM), medium (N(M)=153 g CP/kg DM) and high (N(H)=172 g CP/kg DM) levels of dietary protein in combination with low (E(L)=7.38 MJ ME/kg DM) and high (E(H)=8.03 MJ ME/kg DM) levels of dietary energy. Fatty acid composition was determined on total lipid samples of the M. longissimus thoracis of all animals and on the separated triacylglycerol and polar lipid fatty acid fractions of the medium-protein group. Dietary energy and protein levels influenced the carcass characteristics of BB bulls but the effects were small. Carcass fat cover score, carcass fat content and intramuscular fat content were slightly but significantly higher in the animals on the high versus the low energy diets. The overall intramuscular fat content was very low (<1%) and the overall polyunsaturated:saturated fatty acid ratio (0.39) high compared to normal figures for beef. The high versus the low dietary energy level increased the monounsaturated (P<0.001) and decreased the polyunsaturated (P<0.001) fatty acid proportion with no change in the saturated fatty acid proportion. This may have been due in part to the addition of beef tallow to increase the energy level of the diet. Concomitant shifts in the individual fatty acids included increased proportions of C14:0 (P<0.001), C16:0 (P<0.03), C16:1 (P<0.01), C18:1 (P<0.001) and decreased proportions of C18:2 (P<0.001) and C20:4 (P<0.001). Increasing dietary protein levels had inconsistent effects on the fatty acid profiles. The proportion of polar lipid fatty acids in the total fatty acids was 0.34 and 0.25 for the E(L) and E(H) group, respectively, in the Nm treatment group. Changes in fatty acid proportions of the triacylglycerol fatty acid fraction were similar to those seen in the total lipid fatty acids when related to dietary energy level, but no significant changes in the polar lipid fatty acid proportions were observed. Significant linear relationships were found between measures of carcass and muscle fatness and fatty acid proportions. With increasing muscle total fatty acid content, saturated and monounsaturated fatty acid proportions increased (r=0.38 and r=0.55, respectively, P<0.01) and the polyunsaturated fatty acid proportion decreased (r=-0.73, P<0.01). The diet had some effects but the relatively unsaturated intramuscular fatty acid composition was mainly related to the low total fat content of the BB animals.

Viability of cattle sperm under different storage conditions in Cameroon

A study was carried out to evaluate the viability of extended cattle semen, without freezing, under different storage conditions. The semen was collected from Holstein Friesian bulls using artificial vaginas. The semen was extended and stored in a 3-by-4 factorial design (storage system × ice change). The storage media were ice boxes, buckets, and refrigerator. The ice in these media was either replaced daily, on the first and third day, first day only, or no ice at all after the semen collection. Results showed an overwhelming evidence of the effect of storage medium and ice change on sperm viability (P<0.0001). Individual motility before processing was highest in the refrigerator with averages of 44.5%, 39.5% in ice boxes, and 10% in buckets during the 8-day experiment. There was no significant difference (P>0.05) in progressive motility after processing in the refrigerator (34%) and in ice boxes (33%) but significantly higher (P<0.01) to the 10% obtained in buckets. It was shown that spermatozoa in the ice box retained 45% individual motility up to the sixth day after semen was collected on the condition that the ice was changed on the third day. Progressive motility after processing in the ice box was 40% up to the sixth day with the ice changed on the third day while the spermatozoa were well preserved up to the fourth day in the same medium if the ice put on the first day was not changed. This study shows that, if farmers plan to inseminate cows within the first day after semen collection, they can use buckets with ice for the transportation of the extended semen ampoules from the artificial insemination center. Otherwise, the semen needs to be kept in ice boxes and the ice changed on the third day after collection and this semen could be used within a week.

Impact of management interventions on smallholder dairy farms of the Western Highlands of Cameroon

A study was carried out to evaluate the impact of interventions to solve constraints in smallholder dairy farms of the Western Highlands of Cameroon. The interventions consisted of improved breeding through introduction of artificial insemination, better feed supplementation, farmers training in milk processing and better veterinary services. Results show that there was a decrease in average monthly expenditures of 18% relative to the month before interventions started. Much of the expenditures were related to feed (38% of all costs). There was an overall increase in farm income. Close to 2/3 of the income were derived from milk products from home processed milk and culled animals. Only 7% income came from milk sold to the processing plant. The partial budget shows that before interventions, farmers lost $4.5/cow/month but gained $38/cow/month because of the interventions. The return was 2.32 and included opportunity income for milk home consumed and shared. When this opportunity income was ignored, the return stood at 1.93. The positive impact of interventions led to poverty alleviation and some farmers acquired more cows. A spill over effect is that more crop farmers are willing to be engaged at least partially in dairy farming. It will be good if many more farmers could benefit from these interventions.

Prevalence of Brucella abortus antibodies in serum of Holstein cattle in Cameroon

Holstein cattle of a small scale dairy production systems were screened for Brucella abortus antibodies in 21 villages in Cameroon by ELISA. Results show a general seroprevalence of 8.4% in Holstein cattle. Of the 192 cows tested, 14 were infected giving a within-sex seroprevalence of 7.3% while 6/74 bulls were infected with a seroprevalence of 8%. There was no evidence (P=0.11) of differences in seroprevalence between age groups although animals above one year and below three years accounted for nearly half of the infected animals. 64% of infected animals were found in three locations (P=0.015): Kutaba (32%), Bamendankwe (16%) and Finge (16%). A specific control programme should be organized at these locations. Measures should be taken to ensure the eradication of the disease within the population and sound control measures adopted to avoid a further spread of the disease to larger cattle populations. Infected animals should be slaughtered systematically. All farmers should be advised to boil milk before consumption. Vaccination against Brucella abortus should be instituted and use of artificial insemination propagated. In order to ensure a productive and healthy population of Holstein cows within the dairy production scheme, regular Brucella testing should be instituted.

The animal fat paradox and meat quality

The purpose of this paper is to address some of the paradoxical issues and perceptions regarding animal fats and the related effects on meat quality and consumer perceptions. Meat scientists have been studying carcass characteristics for many years and although the factors that influence the accumulation, distribution and composition of carcass fat in livestock have been extensively researched, the role, value and perceptions of animal fats in meat quality differ significantly in importance between producers, abattoirs, butchers, retailers and consumers. Fat and long-chain fatty acids, whether in adipose tissue or muscle, contribute to important aspects of meat quality and are central to the nutritional and sensory values of meat. In this review the nutritional value of fat, as well as the importance of fat in terms of carcass and meat quality will be highlighted. The 'quality' of meat depends greatly on the socio-demographic backgrounds of the consumer. The aim is to focus on the global importance of fat in the carcass to the producer, processor and consumer. There is currently no clear cut definition for fat quality because the acceptability and perceived quality of fat varies significantly in terms of quantity, colour, consistency and chemical composition in different species of livestock around the world. The association between animal fats and human health is critical and recommendations by health professionals range from excluding fats altogether to a moderate consumption of fats due to their essential role in the body. Recently the emphasis has shifted away from fat quantity to fat quality. Despite these recommendations and years of bad publicity in terms of the adverse affects of animal fats in human health, the livestock industry seems reluctant to shift its focus to fat quality rather than quantity. This approach may adversely affect future meat consumption by consumers who are becoming increasingly critical about the food they eat.

Effects of 12 hour calf withdrawal on conception rate and calf performance of Bos indicus cattle under extensive conditions

Fifty-two multiparous Brahman type cows with reproductive tract scoring (RTS) >/=4 at 45 days post-partum were randomly assigned to two groups of 26 cows each separated into an ad libitum suckling group (C) and treatment group (T). Calves in the T group were separated for 12 h during the night from 45 days post-partum to the onset of the breeding season. Body condition score (BCS) and body weight (BW) were recorded 45 days post-partum, at the start of the breeding season, and at pregnancy diagnosis. Calves were weighed at calving and weaning. Weaning weights were corrected to 205 days. BW and BCS at the onset of the breeding season were similar (p > 0.05) between the experimental groups. Calving to breeding intervals were 93 +/- 18 d and 99 +/- 22 d for T and C groups, respectively. Calving to conception intervals differed significantly between the groups (111 +/- 10 d for T and 133 +/- 19 d for C) and a similar result was obtained for the breeding to conception intervals (18 +/- 15 d for T and 31 +/- 19 d for C). Conception rates were 80% for the T group and 59% for the C group, which correlated better with BW than BCS at the onset of the breeding season. Weaning weights differed (p < 0.05) between C and T groups. From 45 days post-partum to the onset of the breeding season, cows in the T group experienced a positive energy balance (3%) while those in the C group had a negative energy balance (-0.1%). It was concluded that 12 h calf separation at night increases the conception rates and improves the calf weaning weights of Bos indicus beef cattle under extensive production systems in sub-tropical conditions.

Economic opportunity survey of small scale dairy farms of the north west province of Cameroon

An Economic Opportunity Survey was conducted on dairy farms in the North West Province of Cameroon. Results showed that median (range) number of cows in milk per farm was zero point six (0-4) and six (3-12) in the zero grazing and transhumance systems, respectively. Medians (range) of three (0-24) and four (3-10) litres of milk were sold per farm per day, corresponding to 30% and 60% of milk produced. 24% and 13% of total cattle per herd were milking cows in the zero grazing and transhumance systems respectively. Median milk production per cow on one day was two (0-25) and two (1-3) litres. Median calf production interval was 14.5 (12-25) and. 21.5 (14-29) months. More milk produced per day represented the best economic opportunity in both systems while reduced age at first calving and longer lactation length were the next in both. Wastage of milk through spoilage from poor hygiene and lack of cooling was a major problem. Holstein cows, which were in the zero grazing system, had unexpectedly short lactations. Constraints identified led to the setting up of interventions of training and advice for farmers and of better nutrition.

Electrocardiographic surrogates of structural myocardial alterations in the Dorper sheep heart

In this study we evaluated the validity of well-known human electrocardiographic markers of myocardial pathology in Dorper sheep. These markers include: the duration of the QRS complex of premature ventricular complexes (PVCs), the presence of notching of the QRS complex of PVCs and change of the ST-segment of PVCs. It was shown that these three electrocardiographic phenomena correlate with myocardial pathology in the hearts of Dorper sheep. We also describe a new electrocardiographic indicator of myocardial pathology, namely an increase in the frequency of cardiac memory T waves as a new electrocardiographic surrogate for myocardial pathology in the hearts of Dorper sheep.

Ventricular dyssynchrony as a cause of structural disease in the heart of Dorper sheep

Ventricular dyssynchrony is a disturbance of the normal, organized electromechanical coupling of the two ventricles. This condition has many causes, such as left bundle branch block, ventricular preexcitation, right ventricular pacing and right ventricular premature ventricular complexes (PVCs). Ventricular dyssynchrony has many adverse haemodynamic effects on the left ventricle and we wanted to know whether these adverse haemodynamic effects might have any structural consequences on the left ventricles of such hearts. Six healthy Dorper wethers were subjected to numerous right ventricular PVCs to induce ventricular dyssynchrony in order to determine whether any structural consequences will occur in the left ventricles of these hearts. Myocarditis in the musculature of the left ventricles of all six these hearts was seen.

An economic analysis of communal goat production

The economic impact of different extension messages used was calculated using enterprise budgeting (gross margin analysis). Input data were gleaned from the literature, from participatory appraisals, as well as a field study, spanning 12 months, of small-scale communal goat farming systems in Jericho in the Odi District of North West Province. The number of offspring weaned per annum, as a proportion of does owned, was selected as the desired output for analysis. This study has shown that small-scale communal goat farmers are not adopting or implementing extension messages to improve production capacity. In South Africa the majority of goats are slaughtered in the informal sector. If the informal sector is to be persuaded to market goats commercially through formal channels, then knowledge of the economics of goat farming on communal lands should be provided. The economic aspects of extension messages are probably an important factor in determining acceptance and sustainability yet appear to be seldom investigated. The probable reason for lack of adoption of standard extension messages, which promote improved nutrition, parasite control, vaccination and treatment of goats, was economic. In other words, the so-called 'poor management practices' used by communal farmers appeared to be economically more profitable than the 'good management practices' suggested to increase production. The price of communal goats was not related to their mass. A higher level of inputs would probably have resulted in a heavier kid, however it was established that this would not have influenced the price received as a majority of the goats were slaughtered for ritual purposes where age, colour and sex were more important to the purchaser than body mass. It is standard practice in commercial farming systems to evaluate the economic benefits of all management practices before they are implemented. Production animal veterinarians use veterinary economics to compare different scenarios to control diseases or select management practices in commercial herds. It is suggested that the inputs and outputs of small-scale farming systems should be carefully analysed and that veterinary economics should also be used to evaluate the probable impact of extension messages formulated by veterinarians and animal health technicians.

The heart remembers: observations of cardiac memory in the Dorper sheep heart

Memory is a property common to a diverse range of tissues. Cardiac memory has been demonstrated in the human, dog, rat and rabbit. This is a peculiar phenomenon, reflected in the T wave of the electrocardiogram. The heart is able to remember periods of alterations in the sequence of ventricular activation and once there is a return to a normal sequence of ventricular activation the T waves may manifest memory. Cardiac memory is noted when the T wave during normal ventricular activation retains the vector of the previous abnormal QRS complex, caused by a period of altered ventricular activation. Possible mechanisms of memory in the heart are alterations of the transient outward potassium current (I10) in ventricular myocytes and new protein synthesis inside myocytes. These two mechanisms operate in short- and long-term cardiac memory respectively. Currently, it is unknown whether memory may have adverse structural consequences in the heart. We were able to demonstrate memory in the hearts of Dorper wethers and this is the first report of cardiac memory in Dorper sheep.

Ventriculo-atrial conduction in the ovine heart, caused by premature ventricular complexes

In humans, and certain animals, the atrioventricular conduction system is capable of bidirectional conduction. Depolarization impulses, originating in the ventricle itself, may thus be conducted in a retrograde direction towards the atria. Two common causes for this phenomenon of ventriculo-atrial (retrograde) conduction are premature ventricular complexes and ventricular pacing. The surface electrocardiogram can be used for the detection of such retrogradely conducted beats. The purpose of this study was to investigate the possibility of ventriculo-atrial conduction in Dorper sheep. Premature ventricular complexes in eight healthy Dorper wethers were induced and it was possible to document retrogradely conducted beats on the surface electrocardiogram in all of them. It is concluded that the Dorper sheep heart is capable of ventriculo-atrial conduction.

Copper, manganese, cobalt and selenium concentrations in liver samples from African buffalo (Syncerus caffer) in the Kruger National Park

Animals may act as bio-indicators for the pollution of soil, air and water. In order to monitor changes over time, a baseline status should be established for a particular species in a particular area. The concentration of minerals in soil is a poor indicator of mineral uptake by plants and thus their availability to animals. The chemical composition of body tissue, particularly the liver, is a better reflection of the dietary status of domestic and wild animals. Normal values for copper, manganese and cobalt in the liver have been established for cattle but not for African buffalo. As part of the bovine tuberculosis (BTB) monitoring programme in the Kruger National Park (KNP) in South Africa, 660 buffalo were culled. Livers (n = 311) were randomly sampled in buffered formalin for mineral analysis. The highest concentrations of copper were measured in the northern and central parts of the KNP, which is downwind of mining and refining activities. Manganese, cobalt and selenium levels in liver samples indicated neither excess nor deficiency; however, there were some significant area, age and gender differences. The results will be useful as a baseline reference when monitoring variations in the level and extent of mineral pollution on natural pastures close to mines and refineries.