Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 43 num. lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Guest editorial</b>]]> <![CDATA[<b>The ethics of meat production and quality - a South African perspective</b>]]> The global livestock industry has recently been inundated with criticisms about the impact of animal production systems on anthropogenic greenhouse gas emissions (GHG), animal welfare, environmental sustainability and human health and well-being. Although it is accepted that the estimate of GHG emissions from animal agriculture has been exaggerated by the FAO's publication "Livestock's Long Shadow", the 18% estimate is a gross exaggeration. Industrialisation in the agricultural sector in some developing countries without "enlightenment" has been associated with environmental problems like among others, land degradation and water pollution. It is estimated that global livestock production will double by 2050 to satisfy demands, which suggests a faster than expected growth compared to any other agricultural sector. Demand for meat, milk and eggs is expected to increase by about 30% in the next 8 years. These trends resulted in calls for stricter environmental and animal welfare legislation. By contrast, there are also growing concerns about the world's ability to provide in the considerably growing protein needs of a rapidly growing human population, especially in developing countries where it is unlikely that the demands will be met. The importance of the latter is emphasized by the UN's focus on 'the right to food as a global goal' and the fact that Rio+20 will also have to be held accountable for the effects of environmental legislation on humans' physical and economic access to food. The purpose of this paper is to focus on some of these conflicting issues and the effects of a shift to intensive production systems on the ethics of meat production, quality and animal welfare in African countries with knowingly limited natural resources. <![CDATA[<b>Estimates of lactation curve parameters for Bonsmara and Nguni cattle using the weigh-suckle-weigh technique</b>]]> ABSTRACT Milk production accounts for about 60% of the variation in weaning weight and is therefore considered an economically important trait in beef production. However, milk production data is not routinely available in beef improvement programmes and therefore weaning weight is used as a proxy for milk production. Despite the importance of milk production in beef cattle, little research has been done to evaluate the milk production potential of South African indigenous beef cattle. The objective of this study was to estimate average lactation curve parameters for the South African Bonsmara and Nguni cattle. Milk yield was estimated using the weigh-suckle-weigh technique. Lactation curves were modelled using a nonlinear form of the incomplete gamma function (Wood function): Yt = at b exp-ct. Estimates of the a, b and c parameters were 4.095 ± 0.808, 0.274 ± 0.063 and 0.005 ± 0.001 for the Bonsmara, respectively. Corresponding estimates for the Nguni were 1.869 ± 1.527, 0.451 ± 0.242 and 0.008 ± 0.003. Peak lactation time was estimated to be 59 days in Bonsmara and 54 days in Nguni. Estimates of peak yields were 10 kg and 7 kg for the Bonsmara and Nguni, respectively. Estimates of daily milk yield obtained in the current study provide useful baseline information for more accurate modelling of South African beef production systems. <![CDATA[<b>Winter and spring variation in daily milk yield and mineral composition of Jersey, Friesian cows and their crosses under a pasture-based dairy system</b>]]> This study was conducted to determine the effects of genotype and season on daily milk yield (DMY) and mineral composition of pasture-based dairy cows. This was done by collecting data from 20 Friesian, 20 Jersey and 20 Friesian × Jersey crossbred cows in the early stage of their 4th parity in winter and spring, respectively. Automated milk meters were used to measure the DMY. Mineral composition was determined by using the Inductively Coupled Plasma Optical Emission Spectrometric (ICP-OES) method. The data collected from milk yield and mineral composition were analysed using the general linear model of SAS. The results showed that milk yield was highest from Friesian cows both in spring and winter seasons while Jersey cows had the lowest yield. Seasonal effects were also observed in mineral concentrations, with winter having higher values for aluminium, boron, copper, iron, magnesium, manganese, zinc and sodium while phosphorus was higher in spring. Crossbred cows yielded higher concentrations of calcium, phosphorus and magnesium. It was therefore concluded that both milk yield and mineral compositions are affected by genotype and season. <![CDATA[<b>The effect of dietary lipid saturation and antioxidant source on the nutrient digestibility of lamb finishing diets</b>]]> The influence of a synthetic or natural antioxidant and lipid saturation on the apparent digestibility of nutrients in a standard lamb finishing diet was investigated. The four dietary treatments consisted of the same basal diet, providing 187 g CP-, 355 g NDF- and 71 g EE per kg DM, but differing in supplemental lipid source (30 g/kg of either saturated beef tallow or unsaturated soybean oil) and type of antioxidant included (125 g/ton of either a synthetic or natural antioxidant). The digestibility study was conducted over a period of 12 days (including a 4-day adaptation to the faecal collection bags). Twenty-eight S.A. Mutton Merino lambs (45.1 ± 3.0 kg) were randomly allocated to the four dietary treatments (n = 7 lambs/treatment). Composite feed, feed refusal and faecal samples of individually penned lambs were collected for chemical analysis. The apparent digestibility coefficients, digestible nutrient and available energy content were calculated accordingly. The DMI of the lambs did not differ significantly between the various experimental diets. The inclusion of unsaturated soybean oil reduced the apparent digestibility of NDF in the diet. The apparent digestibility of NDF seems to be higher when a natural antioxidant was included in the diet. The comparatively negative effects of the unsaturated lipid source and synthetic antioxidant on the apparent digestibility of NDF were associated with a significantly lower digestible NDF content in the experimental diet. Accordingly, soybean oil resulted in a significantly lower ME content in the diet. However, estimating ME from DE with a constant factor of 0.8 probably underestimates the ME content of diets supplemented with lipids rich in unsaturated fatty acids. The latter are known to reduce methane production, and hence, energy losses. <![CDATA[<b>Carcass composition of Namaqua Afrikaner, Dorper and SA Mutton Merino ram lambs reared under extensive conditions</b>]]> This study evaluated the differences in the muscle-fat-bone yield of Namaqua Afrikaner (NA), Dorper (D) and SA Mutton Merino (SAMM) ram lambs. The breeds constituted an indigenous, hardy and late maturing, fat-tailed breed (NA), an early maturing, commercial meat breed (D) and a late maturing commercial dual-purpose breed (SAMM). Lambs were slaughtered at 35 (± 8) days post weaning. Carcasses were cooled for 24 h, separated into retail cuts (leg, loin, rib, and shoulder), weighed and deboned. Meat and fat were separated after deboning and weighed to calculate the muscle-fat-bone yield per cut. Least-square means were computed for the respective breeds, using slaughter age as covariate. Results for percentage meat indicate that, with exception of the rib, retail cuts from the NA breed contained a lower percentage of meat than D and SAMM breeds, particularly in the valuable loin and leg cuts. The shoulder of the NA had a lower percentage meat than that of the D. The percentage fat in retail cuts did not differ between breeds for any of the cuts. In comparison with both D and SAMM, NA contained a higher percentage bone in all cuts. Dorper and SAMM carcasses did not differ in terms of the percentage of bone, fat or muscle for any of the retail cuts. The lower meat yield, particularly in the more expensive loin and leg of the NA, when compared to the commercial meat breed (D) could make the former less preferred for meat production. However, the NA compared more favourably than the dual-purpose SAMM. Differences in carcass composition could be attributed to the fact that the NA is an unimproved and late maturing sheep breed. <![CDATA[<b>Effect of dietary conjugated linoleic acid (CLA) on the metabolism and reproduction of dairy cows</b>]]> Rumen-protected conjugated linoleic acid (CLA) reportedly improves fertility in lactating dairy cows by reducing the postpartum interval to first ovulation and enhancing the circulating insulin-like growth factor-I (IGF-I) levels. The objectives of this study were to evaluate the blood metabolites, hormones, follicular fluid (FF) and liver for the effect of CLA supplementation (50 g top-dressed daily from 15 days pre-partum to 65 days in milk -DIM -). Pre-partum Holstein cows (n = 24) were assigned to two treatments: a Control and CLA group (n = 12 cows/group). Dry matter intake (DMI) and milk production were recorded daily. At 26 DIM, ovulation was synchronized and at 34 DIM, plasma and FF were analysed for paraoxonase 1(PON) levels. Moreover plasma was analysed for IGF binding protein 2 and 3 (IGFBP). From 34 DIM, blood samples and FF from follicles >9 mm were collected and analysed for estradiol, progesterone, IGF-I and lipoproteins. A liver biopsy was performed at 65 DIM and analysed for the expression of IGF-I, growth hormone receptor (GHR), pyruvate carboxylase (PC) and cytosolic phosphoenolpyruvate carboxykinase (PECK). CLA supplemented cows, compared to the control group, recorded a significant lower milk fat production, improved DMI and energy balance and recorded significant increased plasma concentrations of IGF-I, cholesterol, low density lipoprotein (LDL) and IGFBP-3 (interaction treatment x DIM). The concentration of IGF-I, high density lipoprotein (HDL) and LDL tended to be higher in FF than plasma. This study confirms the positive effects of dietary CLA supplementation on the metabolism, by improving the energy intake and reducing the negative energy balance. Moreover, the improvement of plasma IGF-I levels observed in this study, coupled with a better energy balance support previous studies showing a positive effect of CLA supplementation on reproduction. However, CLA did not alter the plasma and the FF concentration of PON, nor the liver gene expression. <![CDATA[<b>Quantifying avoidance-related behaviour and bleeding times of sheep of different ages, sex and breeds slaughtered at a municipal and a commercial abattoirs</b>]]> The effect of abattoir type, age, sheep breed and sex on avoidance-related behaviour and bleeding times at slaughter were determined. Castrates and ewes of different age groups and breeds were used. From the commercial abattoir, 90 castrates and 110 ewes were used while 66 castrates and 19 ewes were obtained from the municipal abattoir. Avoidance-related behaviour and bleeding times differed with abattoir type and age classes. Animals slaughtered at the commercial abattoir were calmer and had shorter bleeding times (61 ± 1.16 s) than those slaughtered at the municipal abattoir which had a mean bleeding time of 74.2 ± 2.11 s. Older animals were calmer and had longer bleeding times (67.5 ± 1.82 s) than the younger animals which had a mean bleeding time of 61.6 ± 2.64 s. Avoidance-related behaviour also differed with breed and the sex of the animals with Merino and Dorper + Merino crosses being the calmer than the pure Dorper breed. About 95% of ewes were calmer than the castrates. It can be concluded that abattoir type, age, breed and sex have an effect on animal behaviour at slaughter. Only abattoir type and sex had an effect on bleeding times. <![CDATA[<b>Physico-chemical shelf-life indicators of meat from broilers given <i>Moringa oleifera</i> leaf meal</b>]]> The objective of the study was to determine the effect of using Moringa oleifera leaf meal (MOLM) as an additive on physico-chemical shelf life indicators of meat from broilers. A total of 432 1-day-old chicks were randomly allocated to four treatments (TRT's). Water and feed was provided ad libitum. The feeding phases were pre-starter (0 to 7 days), starter (8 to 18 days), grower (19 to 28 days) and finisher (29 to 35 days).The four TRT's contained graded levels of the MOLM at 1000 g/ton, 750 g/ton, 500 g/ton and 0 g/ton (control), respectively. The birds were slaughtered at 35 days of age and the breast muscle was sampled for meat pH, colour and drip loss measurements over 7 days. The pH levels in all the TRT's were constant from Day 1 to Day 5, peaking on Day 6, and then declining on Day 7. Using MOLM as an additive had a significant effect on chickens, with TRT1 having the highest lightness (L*) values. The redness (a*) values were the highest in TRT2. Using MOLM as an additive had an effect on yellowness (b*) values. Drip loss was not affected by the dietary treatments. Using MOLM as an additive in broiler feeds produced chicken breast with a light (L*) appearance while shelf life indicators generally remained constant in the first 5-days of storage. <![CDATA[<b>The novel use of "point of care" devices to evaluate transport duration on selected pork quality parameters</b>]]> Point-of-care (POC) devices were used to measure plasma metabolic substrates in pigs subjected to stressful conditions. These were then related to the meat pH, drip loss and carcass temperature. Forty Large White x Landrace pigs (20 females and 20 males) weighing approximately 67 ± 6.5 kg were used in the study. Twenty of the pigs were subjected to a stressful regimen for two hours and the other 20 pigs were transported for 15 minutes from their pens directly to the abattoir. Salivary cortisol, plasma glucose, triglycerides and lactate concentrations were determined before and after transportation to the abattoir and carcass temperature, pH and drip loss were measured after slaughter. There were no differences in the lactate, cortisol, pH and triglycerides measurements from the pigs of different sexes. Female pigs had higher carcass temperature and lower glucose levels than male pigs. Regression analysis showed that back fat and lactate accounted for 99% of variation in the pH24h of pigs transported over a short duration while lactate was responsible for only 16% of the variation in pigs transported over the long duration. The difference in lactate accounted for 78% of variation in the carcass temperature at 45 minutes for pigs transported over the short duration while in the long duration group, the weight was responsible for 81% of the variation. In conclusion, POC devices measured differences in lactate concentrations in pigs transported over different durations and relationships between the lactate and the carcass pH, carcass temperature and drip loss was determined. <![CDATA[<b>Exogenous fibrolytic enzymes to unlock nutrients: Histological investigation of its effects on fibre degradation in ruminants</b>]]> There is a need for a better understanding of the mode-of-action of exogenous fibrolytic enzymes (EFE) used as additives in ruminant feeds. Four forages, treated with EFE, were evaluated in vitro and histologically, in an attempt to determine the effect of EFE on tissue degradation. Weeping love grass, kikuyu leaf material, lucerne and wheat straw stem material were histologically evaluated. Simultaneously, milled samples were incubated in the rumen fluid inoculated media for the determination of in vitro digestibility. The main focus, however, was a quantitative assessment of the degradation of the plant tissue at histological level over a 24 h incubation period. Degradation of cell wall components were quantified using the image analysis software. After 12 h of incubation, cell walls of the metaxylem of kikuyu and weeping love grass leaf material were thinner for the EFE treatment than for the control treatment. Treatment also resulted in a significant thinning effect of the cell walls of kikuyu phloem (12 h) and the adaxial epidermis (24 h). The abaxial epidermis at 12 h was thinner for weeping love grass due to EFE treatment. For stem material, a thinning of the epidermis of EFE treated lucerne was observed. Histological findings were concomitant with higher in vitro digestibilities of EFE treated lucerne and kikuyu. It was concluded that image analysis can be useful to quantify changes in cell wall due to the treatment of forages with EFE. There was a definite, subtle thinning effect of EFE on cell wall thickness of plant material which could be indicative of the mode-of-action of EFE. <![CDATA[<b>The effect of geographical region of birth on the reproductive performance of the Nguni in southern Mozambique</b>]]> The objective of this study was to assess the effect of place of birth on the reproductive performance of two Nguni ecotypes (Nguni and Landim) raised in a sub-tropical environment to enhance strategies for livestock development and restocking programmes within the southern African region. Reproduction data collected between 1994 and 2009 from 301 cows of the Landim (n = 122) and Nguni (n = 179) ecotypes were analysed. Results indicated that ecotype and place of birth had significant effects on age at first calving (AFC) and calving interval (CI). The means for AFC were 1085 and 1003 days, those for CI were 422 and 436 days, while the calving rate (CR) was 90.0% and 85.7% for the Nguni and Landim, respectively. This study demonstrates for the first time a possible genotype by environment interaction between Nguni ecotypes. This might aid future cattle development and restocking programmes in southern Africa, taking into consideration the adaptation of indigenous genotypes and climate change. <![CDATA[<b>Effect of pre-slaughter conditions on physico-chemical characteristics of mutton from three sheep breeds slaughtered at a smallholder rural abattoir</b>]]> The effects of pre-slaughter conditions and breed on physico-chemical characteristics of mutton were determined. The study was conducted at Adelaide Municipal abattoir in the Eastern Cape Province, South Africa. Records were taken from 84 sheep from the South African Mutton Merino, Blackhead Persian and Dorper breeds as identified on arrival at the abattoir. The South African Mutton Merino (SAMM) had the highest values for meat pH at 24 hours (pH24) (5.9 ± 0.64), lightness; L* (34.2 ± 0.97), yellowness; b* (12.2 ± 0.50) and Warner-Braztler shear force WBSF (26.8 ± 1.51). Linear relationships were also observed between pre-slaughter variables and physico-chemical characteristics of mutton. Principal Component Analysis (PCA) showed a large variation being contributed by meat pH24 and L*. It was therefore concluded that, transport time and lairage duration negatively affected the quality of mutton. Furthermore, breed affected the physico-chemical characteristics of meat. <![CDATA[<b>Effects of egg weight on hatchability, chick hatch-weight and subsequent productivity of indigenous Venda chickens in Polokwane, South Africa</b>]]> A study was conducted to determine the effect of egg weight on hatchability, chick hatch-weight, mortality and subsequent productivity of indigenous Venda chickens. Three hundred and sixty indigenous Venda chicken eggs were collected for a period of a week and selection was done based on the weight of the eggs. A complete randomized design was used, with four treatment weights, each with 90 eggs. The four treatment weights were as follows: below 49 g, between 50 and 59 g, between 60 and 69 g, and above 70 g. Egg weight was positively and strongly correlated with egg hatchability (r² = 0.727) and chick hatch-weight (r² = 0.953). Heavier-sized eggs hatched chicks had higher mortality rates. Growth rate and live weight of the chickens were optimized at different egg weig hts of 56 (r² = 0.657) and 60 (r² = 0.870) g, respectively, for chickens aged 1 to 7 weeks, and egg weig hts of 61 g (r² = 0.514) and 60 g (r² = 0.948), respectively, for chickens aged 8 to 13 weeks. It is concluded that indigenous Venda chicken egg weight affects hatchability, hatch-weight, mortality and subsequent productivity of the chickens. It is concluded that production variables were optimized at different egg weights. This means that the selection of eggs for incubation will depend on the parameter in question. <![CDATA[<b>Dietary energy level for optimum productivity and carcass characteristics of indigenous Venda chickens raised in closed confinement</b>]]> A study was conducted to determine dietary energy levels for optimum productivity and carcass characteristics of indigenous Venda chickens raised in closed confinement. Four dietary treatments were considered in the first phase (1 to 7 weeks) on two hundred day-old unsexed indigenous Venda chicks indicated as EVS1, EVS2, EVS3 and EVS4 (11, 12, 13 and 14 MJ ME/kg DM, respectively) and each treatment was replicated five times. In the second phase (8 - 13 weeks), 160 indigenous Venda female chickens, aged eight weeks, were randomly allocated to four dietary treatments and each treatment was replicated five times in a completely randomized design. The diets used in both trials were isonitrogenous but with different energy levels. A quadratic equation was used to determine dietary energy levels for optimum feed intake, growth rate, FCR and ME intake at both the starter and grower phases and the carcass characteristics of the birds at 91 days. Dietary energy levels of 12.91, 12.42, 12.34 and 12.62 MJ ME/kg DM feed supported optimum feed intake, growth rate, FCR and ME intake, respectively, for the starter phase. At the grower phase, dietary energy levels of 12.56, 12.66, 12.62 and 12.71 MJ ME/kg DM feed supported optimum feed intake, growth rate, FCR and ME intake, respectively. Carcass, drumstick, thigh and wing had optimum weights at dietary energy levels of 13.81, 13.23, 13.43 and 13.18 MJ ME/ kg DM, respectively. Thus, dietary energy level for optimization depended on the particular production parameter in question. <![CDATA[<b>The effect of dietary lipid saturation and monensin-Na on the CLA content of lambs' meat</b>]]> A study was conducted to investigate the influence of an ionophore antibiotic and lipid saturation within a standard finishing diet on the conjugated linoleic acid (CLA) content of lambs' meat. Two identical sheep grower diets containing 145 g CP, 282 g NDF and 45 g EE per kg DM were formulated. One diet contained no ionophore antibiotic and the other monensin-Na included at 165 g/ton. These two basal diets were supplemented, according to a 2 x 3 factorial design, with three lipid sources [i.e. 20 g/kg of either beef tallow, sunflower oil or a CLA oil concentrate] differing in saturation level and fatty acid profile. Sixty South African Mutton Merino lambs (31.15 ± 2.83 kg) were randomly allocated to the six treatments. After dietary adaptation of 10 days, the lambs received their respective treatment diets for the remaining period of 51 days. At the end of the study seven lambs (45.11 ± 2.99 kg) were randomly selected per treatment and slaughtered. Muscle and subcutaneous fat tissue from loin chops of each carcass were used for lipid extraction and fatty acid analysis. The supplementation of CLA oil in the diet resulted in a significantly lower vaccenic acid concentration of lamb muscle tissue. In contrast, supplementing sunflower oil increased the linoleic acid concentration of only the subcutaneous fat tissue significantly. Sunflower- and CLA oil supplementation increased the cis-9, trans-11 CLA isomer of both subcutaneous fat and muscle tissues, whereas only the CLA concentrate increased the trans-10, cis-12 isomer of both mentioned tissues significantly. The dietary inclusion of monensin-Na decreased the vaccenic-, linoleic- and CLA (cis-9, trans-11 isomer) concentrations of both lamb subcutaneous fat and muscle tissues significantly. The manipulation of the CLA content of lamb seems to be effective when adding either sunflower oil or a CLA oil concentrate to the finishing diet of lambs. However, this effect is inhibited by the addition of monensin-Na to the same diet. <![CDATA[<b>Milk composition as technique to evaluate the relative bioavailability of a liquid rumen protected methionine source</b>]]> Rumen protected amino acids (RPAA) are increasingly being used in dairy cattle diet formulation to obtain the required concentrations of lysine and methionine in metabolisable protein for optimal milk and milk protein production. The objective of this study was to evaluate the relative bioavailability of a liquid rumen protected lysine prototype using the milk composition technique. Forty mid-lactation Holstein cows were used in a complete randomised block design experiment and allocated to one of four experimental treatments. The treatments were: (1) Methionine deficient (Met-) diet, (2) Met- diet supplemented with Smartamine M (SMM), (3) Met- diet supplemented with liquid rumen protected prototype (LRPMet) and (4) Met- diet supplemented with DL Met (DLMet), a hydroxyl analogue of methionine. After an adaptation phase all four groups received the Met- diet and thereafter switched over to the four treatments. Cows supplemented with SMM had higher milk protein and milk fat % compared to the other treatments and increased milk casein % significantly when compared to the Met-control treatment. The milk protein percentages were 3.06, 3.25, 2.95 and 3.46 and the milk fat percentages 3.84, 3.93, 3.75 and 4.27 for the Met-, LRPMet, DL Met and SMM treatments, respectively. SMM again proved to be the RPAA with a high relative bioavailability, while the LRPMet failed to elicit any milk yield or milk composition response. The milk composition technique proved to be a simple but effective technique to evaluate the bioavailability of rumen protected products or prototypes. <![CDATA[<b>Variability of indigestible NDF in C<sub>3</sub> and C<sub>4</sub> forages and implications on the resulting feed energy values and potential microbial protein synthesis in dairy cattle</b>]]> Estimation of indigestible neutral detergent fibre (iNDF) is necessary for accurate and precise predictions of feed energy values and potential microbial protein from digested NDF in the rumen. Due to lengthy laboratory procedures, iNDF has been estimated using the formula ADLx2.4 (iNDF2.4). The relationship between iNDF and acid detergent lignin (ADL) is more variable, across and within forage species. The purpose of our study was then to assess the variability of iNDF and respective implications on ration fine-tuning for dairy cattle. Sixty forages, including grasses, maize silages and lucerne hays, were fermented in vitro from 0 to 240 hours. Residual NDF of the fermented samples were obtained at 0, 6, 12, 24, 36, 48, 72, 96, 120, 144, 216 and 240 h, with the last value assumed to represent iNDF (iNDF240).This was used to obtain the potentially digestible NDF fraction (pdNDF). Rates of digestion of pdNDF were obtained assuming a first order decay. Simulations with the Cornell Net Carbohydrate and Protein System (CNCPS v 6.1, 2012) were done to evaluate the effects of the different estimated iNDF and NDF rate of digestion (kd) on energy and microbial protein estimations, assuming the requirements of a high-yielding lactating cow and a standard TMR with at least 50% forage. Results were dependent on the amount of forage and respective NDF and ADL. The iNDF240 values resulted between 1% and 136% higher than the iNDF240 values. The reduced pdNDF pool resulted in both lower cell wall linked protein in the rumen and microbial protein of around 5 to 165 g, and, as a consequence, on a total decreased metabolizable protein for milk. Use of iNDF240 showed consistently lower metabolizable energy (ME) between 2 and 10 MJ/day, compared to when using iNDF240. The improved metabolizable protein (MP) and ME values would result in 0.3 to 3.2 kg/d less milk when using iNDF2.4. This research demonstrates how points later in the fermentation curve, even if not biologically relevant for the cow, result in a more accurate and precise estimation of the rate of NDF digestibility. Indigestible NDF estimated at 240 h would give better predictions of rumen parameters in models like the CNCPS and better fine-tuning in dairy cow diets, especially when using high forage and/or NDF rations. <![CDATA[<b>Influence of Kosher (Shechita) and conventional slaughter techniques on shear force, drip and cooking loss of beef</b>]]> The objective of this study was to evaluate the effects of Kosher (Shechita) and conventional slaughter methods on shear force, drip and cooking losses of beef (m. longissimus dorsi samples) from South African feedlot cattle. Results revealed significantly lower shear force values for meat samples from cattle slaughtered by the Kosher method compared to those from cattle slaughtered by the conventional slaughter method. Cooking loss was significantly higher for meat samples from cattle slaughtered in the conventional way compared to those from cattle slaughtered by Kosher method. However, no significant difference was observed for drip loss between slaughter methods. These findings suggest that captive bolt stunning before sticking resulted in higher cooking losses and yielded less tender meat compared to the Kosher slaughter method. <![CDATA[<b>Possible reasons for differences in residual feed intake: An overview</b>]]> Selection for residual feed intake (RFI) as a trait to improve production efficiency was proposed as early as 1963. A low RFI value indicates a more efficient animal and heritability estimates of between 0.28 and 0.58 have been reported for RFI in the literature. It is also reported that a 13.38 g/d reduction in methane emission was associated with a 1 kg/d reduction in the Estimated Breeding Value (EBV) for RFI, with low-RFI steers emitting 25% less methane daily. The difference in methane production in high and low RFI animals cannot be explained by the difference in feed intake alone. Possible reasons could be digestion of feed, protein turnover and overall tissue metabolism (mitochondrial function, body composition, Insulin Growth Factor-I (IGF-I) and cortisol levels), activity, thermoregulation and growth. Low-RFI animals tend to digest feed better than high-RFI animals, and as intake increases there is a tendency for digestion to decrease. The correlation between RFI and dry matter (DM) digestibility has been determined to be r = -0.33. A positive correlation exists between metabolisable energy for maintenance (ME) and RFI, as well as between ME and protein turnover. Thus protein secretion in low-RFI animals are the same as high-RFI animals, but the breakdown of protein in low-RFI animals is less. Clear differences can be observed in heat production, with low-RFI animals producing up to 21% less heat than high-RFI animals. Selection for low-RFI animals may thus reduce the carbon footprint of beef cattle. <![CDATA[<b>Sensory characteristics and tenderness of meat from Ankole bulls: Influence of crossbreeding and feeding system</b>]]> Eating-quality attributes of meat from Ankole cattle and their Friesian and Boran crossbreds finished in different feeding systems were evaluated. Seventy two 8-month-old bulls (24 each of pure Ankole (A), Ankole x Boran (B) and Ankole x Friesian (F) (191 ± 9.6 kg average weight) were allotted to three feeding systems in a completely randomized design with a 3 x 3 factorial treatment, and were slaughtered after 120 days. The longissimus dorsi muscle was excised from the carcasses and divided into five samples for sensory and shear force analysis. Samples aged 2, 7, 14 and 21days were subjected to the Warner Braztler shear force (WBSF) machine for textural tenderness determination. Steaks from Ankole and Friesian crossbreds attained WBSF values below 55N within 7 days of post mortem storage, whereas Boran crossbreds attained a similar level of tenderness at 14 days. Steaks from Ankole and Friesian crossbreds were rated more tender, juicy and acceptable than Boran crossbreds by panelists. Steaks from grazed bulls were rated less tender, juicy and palatable than steaks from supplemented and feedlot finished bulls. It was concluded that when grazed and supplemented or finished in a feedlot and meat aged for 7 days, Ankole bulls produce tender meat of an as high eating-quality as their Ankole x Friesian crossbreds. <![CDATA[<b>Maize silage as a finisher feed for Merino lambs</b>]]> A study was conducted to determine whether silage can be used as an ingredient in the finishing rations of Merino lambs. One of the concerns regarding the use of silage as the main ingredient of a sheep feed is its high moisture and neutral detergent fibre (NDF) content and relatively poor protein value. Forty lambs, in a four-way completely randomized block design, were used in a 60-day finishing study. The diets consisted of a control with no silage and three diets containing, on a dry matter (DM) basis 20%, 50% or 70% maize silage. With the exception of fibre (NDF and acid detergent fibre), all diets were formulated on an iso-nutrient level. Dry matter intake (DMI) decreased as the silage inclusion increased. This resulted in significant differences between the cumulative intake of the low and the high silage diets. The 20% and 50% silage diets resulted in higher dressing percentage than the control and 70% silage diet. It was concluded that silage can be successfully incorporated into sheep diets and that optimal inclusion levels need to be quantified within high specification feedlot diets. <![CDATA[<b>Behaviour response of Namaqua Afrikaner, Dorper and South African Mutton Merino lambs towards humans</b>]]> The response of Namaqua Afrikaner, Dorper and South African Mutton Merino lambs, of approximately four months of age, towards a human being situated between them and their flock mates was studied in an arena test. The objective of the study was to determine whether the unimproved Namaqua Afrikaner, with an arguably shorter history of selection, would react differently to humans in an arena test compared to commercial breeds. A total number of 305 animals, born in 2010 and 2011 and raised under extensive veld conditions, were assessed in a modified arena test when the lambs born in each year were approximately four months old. From the test results it was possible to calculate the following parameters of the behaviour of the sheep: (i) The mean distance from the human operator, (ii) the time a lamb spent in a specific zone situated either close to or far from the human, and (iii) the total number of boundaries crossed, which gives an indication of the total distance travelled by an individual lamb. Other data recorded were the number of bleats and the number of times an animal urinated or defecated. There were no significant sex and birth type differences for any of the behaviour traits. No conclusive breed differences were found for any of the traits describing the behaviour of the lambs, except for the number of bleats. Namaqua Afrikaner lambs bleated significantly (24.0 ± 1.2) more in the three minute testing period than Dorper (8.2 ± 0.9) and South African Mutton Merino lambs (11.9 ± 2.5). Further research is necessary to see if this slight indication of anxiety could be related to other traits such as lamb survival or product quality. <![CDATA[<b>Effect of finishing system on carcass characteristics and composition of Mubende goats and their Boer goat crossbreds</b>]]> A study was conducted to evaluate the influence of feeding systems on carcass characteristics and composition of Mubende goats and their Boer goat crossbreds. A 2 x 3 factorial arrangement was used to randomly allocate 60 castrates, 30 purebred Mubende and 30 Mubende x Boer, aged 9 - 12 months, to three feeding systems: sole grazing (T1), grazing + non-molasses based concentrate (T2) and grazing + a molasses based concentrate (T3). Carcass measurements included carcass weights, carcass length, internal chest width, hind-limb length and maximum hind limb width. Tissue composition was estimated using the 6th rib. Crossbreds had heavier and longer carcasses (23.1 kg) and (65.7 cm) than the Mubende (19.0 kg and 63.2 cm), respectively. Crossbreds also had bigger hind quarters (39.0 cm) and higher blockiness (0.38) indices than Mubende goats, 37.1 cm and 0.29, respectively. Dissectible lean and fat percentages varied in an ascending order of 66%, 72%, 72.6% and 8%, 14% and 16.5% for T1, T2 and T3, respectively. A reverse trend was observed for bone percentages with carcasses from T1 having higher bone percentage (18.1%) than T2 (16.5%) and T3 (16.1%) irrespective of genotype. The study showed that supplementation of grazing goats has a great potential for goat meat production in Uganda. <![CDATA[<b>Effect of dietary fatty acid saturation on egg production at end-of-lay</b>]]> This study was conducted to investigate the effects of dietary fatty acid saturation on production performances of laying hens at end-of-lay. Five isoenergetic (12.6 MJ AME/kg DM) and isonitrogenous (170 g CP/kg DM) diets were formulated using different lipid sources at a constant 30 g/kg inclusion level. The control diet was formulated using a blend (50 : 50) of linseed- and fish oil, while the other treatments consist of pure fish oil (polyunsaturated n-3), sunflower oil (polyunsaturated n-6), high oleic acid (HO) sunflower oil (monounsaturated n-9) and tallow (SFA). Two hundred, individually caged Hy-Line Silver-Brown laying hens (20 weeks of age) were randomly allocated to the five dietary treatments (n = 40 replicates/treatment) and received the experimental diets for 54 weeks from 20 to 74 weeks of age. During weeks 58, 62, 66, 70 and 74 of age (end-of-lay period), all eggs produced were recorded and individually weighed while feed intake, as well as body weights of birds, were determined. Data for the respective collection weeks were pooled to calculate and statistical analyse production parameter means for the end-of-lay period. Average daily feed intake of birds in the polyunsaturated n-3 treatment (97.5 g/b/d) were the lowest while that of the polyunsaturated n-6 treatment (102.4 g/b/d) the highest. Furthermore, despite the significant effect of fatty acid saturation on feed intake, it had no effect on hen-day egg production, egg weight, egg output, feed efficiency or body weight of hens during end-of-lay. Since results of the current study fail to indicate a clear trend regarding dietary fatty acid saturation on feed intake of birds, it could be concluded that the long term exposure to a range of fatty acid saturation levels, has no negative effect on hen performance. <![CDATA[<b>The effect of lipid saturation on nutrient digestibility of layer diets</b>]]> A study was conducted to investigate the effect of dietary lipid saturation on nutrient digestibility of layer diets. Five isoenergetic (12.6 MJ AME/kg DM) and isonitrogenous (170 g CP/kg DM) diets were formulated using different lipid sources at a constant 30 g/kg inclusion level. The control n-3 diet was formulated using a blend (50 : 50) of linseed- and fish oil, while fish oil (polyunsaturated n-3), sunflower oil (polyunsaturated n-6), high oleic acid (HO) sunflower oil (monounsaturated n-9) and tallow (saturated fatty acid) were used as other supplementary lipid sources. The five dietary treatments were randomly allocated to the two hundred (200) individually caged Hy-Line Silver-Brown laying hens (20 weeks of age) (n = 40/treatment). Experimental diets were provided to the birds on an ad libitum basis for a 22 week period (from 20 to 42 weeks of age). At 42 weeks of age, six hens per treatment (n = 6 replicates/treatment), were randomly selected to partake in a digestibility study over a 7 day period using the total collection technique. The polyunsaturated n-6 treatment resulted in the lowest crude protein digestibility, whereas the saturated fatty acid treatment resulted in the lowest fat digestibility. Furthermore, the polyunsaturated n-3 diet resulted in the highest dietary AME (13.29 MJ/kg DM) and AMEn (12.74 MJ/kg DM) content. <![CDATA[<b>Effects of dietary energy content and provision of </b><b>β</b><b>-adrenergic agonist on the production of feedlot lambs</b>]]> Recent increases in mutton lamb prices have resulted in many lamb producers opting to finish more and more lambs on the farms in a feedlot system rather than marketing directly from the field. The aim of this trial was to determine the effect of dietary energy, as well as the inclusion of a β-adrenergic agonist, on the production of feedlot lambs. South African Mutton Merino lambs (108) of different sexes were weaned (± 36.4 kg) at ca. 120 days of age and were randomly divided into six experimental groups (18 lambs per group), which were adapted to each treatment. Lambs were housed in individual pens. The treatments consisted of three diets (diet 1: 11.3 MJ ME/kg food, diet: 2 12.0 MJ ME/kg food and diet 3: 12.7 MJ ME/kg) with either the inclusion or absence of a ß-adrenergic agonist at 8.5 g/ton. The experimental design was a 3 x 2 x 2 factorial design with dietary energy level, the provision of a ß-adrenergic agonist and sex as main factors. No interaction occurred between treatments and data are presented as the effect of dietary energy level and the inclusion of a stimulant on the intake, growth and feed conversion ratio (FCR). Neither the dietary energy content nor the β-adrenergic agonist had an effect on FCR. Neither one of the main factors had a significant effect on feed intake. The sex of the lambs had a significant effect on the average daily gain of the lambs with the ewes growing faster than the rams. <![CDATA[<b>The effect of dietary energy and the inclusion of a ß-adrenergic agonist in the diet on the meat quality of feedlot lambs</b>]]> β-adrenergic agonists are commonly used in livestock production to enhance meat production and decrease the fat content of the body. β-adrenergic agonists normally improve growth performance. Recent increases in meat prices and the change in consumer preference towards leaner meat have resulted in more lamb producers opting to finish leaner mutton/lamb on farms in a feedlot system. The aim of this trial was to determine the effect of dietary energy, as well as the inclusion of a β-antagonist, on the meat quality of feedlot lambs. South African Mutton Merino lambs (108) of different sexes (rams and ewes) were weaned at 120 days of age and were randomly divided into six groups (18 lambs per group). The treatment consisted of three different dietary energy levels (high 12.7 MJ ME/kg feed, medium 12.0 MJ ME/kg feed and low 11.3 MJ ME/kg feed) with either the inclusion of a β-adrenergic agonist (zilpaterol hydrochloride) at 8.4 g/ton or not. Data were analysed according to a 3 (dietary energy) x 2 (inclusion of a stimulant) x 2 (sex) factorial analysis. No interaction occurred between treatments and the data were presented as the effect of dietary energy level, the inclusion of a stimulant and sex on proximate components, fat thickness and the tenderness of the meat. The factors ß-adrenergic agonists and dietary energy level had no effect on the proximate components, fat thickness or the tenderness of the meat. The ewe lambs' 9-11th rib-cut had a significantly higher fat content than the ram lambs (27.9% vs. 23.1%, respectively). Meat from ram lambs was less tender (63.60N) compared to that from ewe lambs (57.82N). Neither the inclusion of the β-adrenergic agonist (59.8N vs. 61.9N) nor the dietary energy level (59.3N vs. 63.5N vs. 59.3N) had an effect on the tenderness of meat from lambs in this study.