Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 44 num. 4 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>The adaption of the South Africa sheep industry to new trends in animal breeding and genetics: A review</b>]]> The history of sheep breeding research in South Africa can be divided roughly into four eras, namely the research and development phase, the commencement of recording and evaluation, the expansion of recording schemes, and, most recently, the adaptation of schemes to international benchmarks. The most recent era has presented scientists with the greatest challenges, namely the inclusion of genomic breeding values in routine sheep recording and of disease-resistance traits during routine evaluation. The establishment of reference populations for the major South African sheep breeds to estimate genomic breeding values is an immediate challenge. This process may be facilitated by a number of genetic resource flocks that are phenotyped for traits that are not routinely recorded in the national evaluation. A limited number of these animals are also genotyped. There is strong evidence that resistance of sheep to external and internal parasites is heritable, and may be improved by purposeful selection. Efforts should be concentrated on the inclusion of disease resistance traits in national analyses where appropriate. However, seen against the background that South African investment in research is appreciably less than in developed countries, lack of funding and high-capacity manpower may impede rapid progress. There thus seem to be many challenges for future generations of sheep breeding scientists. <![CDATA[<b>Effect of feeding soybean, linseed oil and different forms of tocopherol on the redox and immune profiles of turkey hens</b>]]> The aim of the study was to analyse whether, and to what extent, the use of RRR-d-a-tocopherol in diets containing oil rich in linoleic or linolenic acid (soybean or linseed oil, respectively) would make it possible to halve the dosage of this antioxidant with respect to a-tocopherol without negatively affecting the redox and immune status of turkey hens. The experiment was carried out on 480 turkey hens, type BIG 6, which were divided into four groups. Birds in Group I (control) received soybean oil and synthetic dl-alpha-tocopherol acetate in their feed mixture. Group II received soybean oil and natural RRR-d-alpha-tocopherol. Birds in Group III received linseed oil and synthetic tocopherol, whereas those in Group IV had linseed oil and natural tocopherol. At the end of the ninth, eleventh and fifteenth weeks of life, blood was sampled from their brachial veins for analyses. Haematological, immunological and pro- and antioxidative parameters were measured. The application of linseed oil had a minor effect on the immune and antioxidative systems of the turkey hens. The study showed that the addition of the natural form of RRR-d-alpha-tocopherol with soybean and linseed oils stimulated the mechanisms of the antioxidative defence system more effectively than dl-alpha-tocopherol acetate addition with these oils. It may be possible to use the natural form of tocopherol in diets rich in linoleic and linolenic acid (soybean/linseed oil) without detrimental effect on redox and immune status of turkey hens. However, the commonly used tocopherol acetate, despite the higher dosage, is cheaper. Thus, from an economic point of view, the use of linseed oil with the synthetic form of vitamin E is worth recommending. <![CDATA[<b>Crossbreeding to increase beef production: Additive and non-additive effects on fitness traits</b>]]> Fitness is of paramount importance to efficient and profitable beef production. Thus, the objective of this study was to estimate genetic components of fitness traits measured in Afrikaner (A), Brahman (B), Charolais (C), Hereford (H) and Simmentaler (S). For this study, the fitness traits recorded were percentage of cows exposed that were subsequently certified pregnant (PR), percentage of certified pregnant cows that subsequently calved (CR), percentage of calves born that survived to weaning (SV) and the percentage of cows exposed that ultimately weaned a calf (WR). Data were mean performance of straightbred, F1 cross, backcross and three-breed cross females. All crossbred females were of at least 25% A heritage. Breed group means were equated with their genetic expectations assuming recombination effects were nil and the heterosis effects were proportional to the expected heterozygosity in the crosses relative to the purebreds. With the exception of B-sired females from CA cross dams, the genetic model fit the breed group means with a high degree of fidelity. Breed-specific genetic effects tended not to individually exceed the magnitude of their standard errors. However, when the breed-specific genetic effects were combined to predict breed group means, the fitness of crossbred females, on average, exceeded that of their straightbred contemporaries. No particular advantage was noted for adding Brahman to the breed composition of crossbred females with at least 25% Afrikaner heritage. In summary, these data are viewed as being supportive of the use of breed resources in organized crossbreeding systems, such as two- and three-breed rotations that maintain at least 25% Afrikaner germplasm in the breeding females. <![CDATA[<b>The effects of an organic rearing system and dietary supplementation of an essential oil mixture on performance and meat yield of slow-growing broilers in two seasons</b>]]> In this study, performance and carcass characteristics of slow-growing broiler chicks, reared in organic or conventional systems, and fed a diet with an essential oil mixture (EOM, 48 mg/kg diet), were evaluated in the autumn and spring seasons. The rearing system affected several performance indices, including body weight, feed intake and feed conversion ratio (FCR), but not mortality, within a high statistical significance at 42 and 81 days of age. However, this was observed only from 1 to 42 days in the spring trial. Dietary administration with EOM worsened the FCR at 42 and at 81 days of age in the autumn trial, but not in spring. Organically reared slow-growing chickens consumed less feed mixture per unit of body weight gain, but attained a higher final weight compared with those kept indoors. However, the effect was more pronounced in autumn, which displayed cooler temperatures and robust plant cover availability (i.e. lucerne and trifolium). The carcass yield and cut-up carcass yield were not affected by the rearing system, but EOM diet supplementation increased breast yield only in the spring. The results suggest that autumn conditions promote efficient organic chicken production in the subtropical climatic zone. The amount of herbage consumed represented up to 10% and 3% of the birds' daily protein and ether extract requirements, respectively. Supplementing the diet with a mixture of plant essential oils did not support the hypothesis that phytogenic compounds may favourably affect gut function and poultry performance. <![CDATA[<b>Effect of oxygen supplementation in a hatchery at high altitude and growth performance of broilers reared at low altitude</b>]]> The objective of this study was to investigate the effect of oxygen supplementation on broiler eggs in a hatchery at high altitude on the growth performance and ascites syndrome of broilers reared at low altitude. The treatment groups were low altitude with no oxygen supplemented in the hatchery (LA-NOX); high altitude with oxygen supplementation in the hatchery (HA-OX); and high altitude with no oxygen supplemented in the hatchery (HA-NOX) group. Growth performance, heart weight, the concentrations of the hormones, T3,T4 T3/T4, and and plasma concentrations of haematocrit, haemoglobin, glucose and parameters of ascites syndrome during the growing period were investigated. A total of 243 one-day-old broilers were used for this study. During the growing period, excluding days 7, 28 and 35, oxygen supplementation at high altitude did not affect the live weight of broilers compared with the HA-OX and HA-NOX groups. The cumulative feed consumption was determined to be lower in the LA-NOX group and the same in the HA-OX and HA-NOX groups on the 42nd day. Between 21 and 42 days old, the LA-NOX group had a better feed conversion ratio (FCR) than the HA-OX and HA-NOX groups. Chick weight (CW), yolk sac weight (YSW) and chick heart weight (CHW) were higher in the LA-NOX group than in the HA-OX and HA-NOX groups. At 42 days old, there were no differences between the groups in heart weight, right ventricle weight (RV), left ventricle and septum (LV+Sept.), total ventricle (TV) weight and the RV : TV ratio. The plasma T3 level was lower in the LA-NOX group than in the HA-OX and HA-NOX groups and T4 levels were higher in the HA-OX than in the others at 42 days old. The hypoxic conditions that occurred during the embryonic stage - which altered endogenous functions of prenatal chicks and affected several blood parameters, and oxygen supplementation at high altitude - improved chick quality. However, it did not improve subsequent FCR and feed consumption performance of chickens when they were reared at low altitude. <![CDATA[<b>Effects of organic acid supplementation on antioxidant capacity and immune responses of broilers challenged orally with <i>Salmonella enterica </i>subsp. <i>enterica </i>Typhimurium</b>]]> Four commercial organic acids and a reference antibiotic, Neoxyval, were administered to commercial broilers to evaluate the efficacy of these products during pre- and post-challenge with Salmonella enterica subsp. enterica Typhimurium (S. Typhimurium) on selected indicators of their antioxidant status and immune responses in serum. Two hundred and eight broilers received one of the following seven treatments: positive control group (CTL+); negative control (CTL-); antibiotic Neoxyval, (NEOX); Gallimix (GALI); FormaXOL (FORMA); Fysal (FYS); and Selko-pH in drinking water (SELK). The chicks in treatments T2 to T7 were challenged with (3 x10(9) cfu/mL) of S. Typhimurium on day 16. Each treatment consisted of 10 cage replicates with four birds per cage for a starter (0 - 14 days of age) and a finisher (15 - 42 days of age) period. The results revealed that the total antioxidant capacity (TAC) value was highest when birds were supplemented with organic acids, with the highest value for FORMA (0.70 mM), which was not different from those of the FYS (0.67 mM), SELK (0.66 mM) and GALI (0.64 mM) treatments. Birds receiving treatment, CTL-, produced the highest H2O2 value (75.9 μΜ), while, FYS, FORMA and SELK lowered H2O2 concentration significantly (51.1, 53.8 and 55.0 μM, respectively). Anti-Salmonella titre was significantly improved by dietary organic acid supplementation. The highest Salmonella titre was recorded for birds that received FORMA (1.54) as compared with all other treatments. Week of sampling showed a significant effect on Salmonella and Newcastle disease titres. In summary, the tested organic acids, especially FORMA, had a positive influence on TAC and Salmonella titres and reduced the H2O2concentration in serum.