Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 42 num. 2 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Animal factors affecting fatty acid composition of cow milk fat</b>: <b>a review</b>]]> The review summarizes literature dealing with the effects of animal factors (breed, cow individuality, parity and stage of lactation) on fatty acid (FA) composition of milk fat. Genetic parameters affecting the composition of the FAs in milk are reviewed and the possibilities for altering milk fat composition are discussed. Cow individuality and the stage of lactation appear to be the main animal factors affecting milk fat composition. Breed and parity affect the variability in FA composition to a limited extent. Some of these factors can be used effectively to alter milk fat composition. Polymorphism of the enzymes, stearoyl-CoA desaturase (SCD) and acyl-CoA-diacylglycerol acyltransferase (DGAT) can explain to some extent the variability among cows. The great individual differences, probably given by varying SCD activities, may be used in breeding programmes, supported by the heritability estimates determined for individual FAs. Effective results can also be achieved through the combined effect of several factors. For instance, the level of conjugated linoleic acid could be increased not only by feed factors, but also through thorough knowledge of rumen biohydrogenation or by cow selection using information on SCD and DGAT polymorphism. The animal factors that are discussed are closely related to milk yield, particularly fat content. Both parameters can change FA composition. Thus, it is necessary in breeding programmes to take these relationships into consideration, along with known genetic correlations. <![CDATA[<b>Fatty acid profile and cholesterol content of m</b>: <b>longissimus of free-range and conventionally reared mangalitsa pigs</b>]]> This study investigated the effects of different feeding systems (free-range versus conventional rearing) on carcass characteristics, chemical composition, fatty acid profile and cholesterol content of the musculus longissimus lumborum et thoracis (MLLT) of Mangalitsa pigs. Depending on the rearing system employed and live weight observed, we found statistically significant differences in the weight of the warm and cold Mangalitsa carcasses. Furthermore, we observed that conventionally reared Mangalitsa pigs weighed more. Measurements showed that the free-range-fed pigs had a lower total backfat thickness in comparison with the group reared in the conventional system, but that these differences were not significant. Outdoor rearing of the pigs led to higher protein, ash and water contents, and to a decrease in total fat content and pH values of the MLLT. The choice of rearing system did not significantly affect the cholesterol content. The fat of the free-range pigs had a higher concentration of n-3 and n-6 polyunsaturated fatty acids (PUFA), while the n-6/n-3 PUFA ratio was significantly lower than in conventionally reared pigs. The proportion of PUFA/SFA (saturated fatty acids) was not significantly different, whereas the proportion of monounsaturated fatty acids (MUFA/SFA) was significantly lower in the free-range group. It is concluded that the rearing system affects the carcass properties and chemical characteristics of Mangalitsa meat; it does so in particular by improving the fatty acid composition in free-range pigs. <![CDATA[<b>Pedigree analysis of an ostrich breeding flock</b>]]> Pedigree records, maintained from 1978 to 2005 at the Oudtshoorn Research Farm, South Africa, of 40 074 birds of a pair-breeding ostrich flock were used to estimate the effective number of founders (f e), the effective number of ancestors (/0), the effective population size and the effective genome equivalents (fg) under random mating, to assess the genetic variability present in the population. The average level of completeness of the pedigrees was high (99.3%) in the first generation, and the average level of inbreeding (F), calculated from the pedigrees, was 0.51%. The reference population was defined as the 39 784 birds hatched from 1990 to 2005. The estimated measures of variability were f g = 47.3, f e = 59 and f a = 58, with an fjfa ratio of 1.02. The numbers of ancestors responsible for 100%, 50% and 20% of the genes in the reference population were 254, 21 and 6, respectively. The largest individual contribution to the population hatched from 1990 to 2005 was from a male that was responsible for 4.85% of the genetic variability. The generation interval for the four selection pathways - calculated as the average age of parents when offspring that were kept for reproduction were born - were sire to son (7.74 ± 4.92), sire to daughter (7.77 ± 5.13), dam to son (7.50 ± 4.29) and dam to daughter (7.90 ± 4.92). The average generation interval of the reference population was 7.72 ± 4.79 years. The linear regressions of mean annual individual rate of inbreeding on year of birth for the two distinct periods 1995-2002 and 2003-2005 were 0.08% and -0.07% per year, respectively. The estimate of effective population size (Ne), computed via the increase in the individual rate of inbreeding, was 112.7. Estimates of Ne using the alternative methods of tracing the numbers of generations were 73.6, 177.4 and 95.3 for complete, maximum and equivalent complete generations. The results of this study indicated that the population under study was at an acceptable level of genetic variability. <![CDATA[<b>Foster parenting, human imprinting and conventional handling affects survival and early weight of ostrich chicks</b>]]> The effects of human imprinting and foster parenting by adult ostriches on the survival and growth performance of ostrich chicks were compared to conventional chick-rearing practices in two separate experiments. In the first experiment, the growth rate and survival of chicks imprinted onto humans were compared with those of chicks reared by adult foster parents (n = 100 for both groups). Survival is expressed as proportions, while weights were measured in kg. Treatment did not affect chick survival to 3 weeks (0.90 for imprinted chicks vs. 0.89 for foster chicks), or from 4 to 12 weeks (0.86 vs. 0.83, respectively). Chick weight was not significantly different between groups at 4 weeks, but at older ages, those chicks reared by foster parents consistently outperformed imprinted chicks (means ± SEs being 12.8 ± 0.4 vs. 8.2 ± 0.4 kg at 9 weeks, 37.1 ± 0.8 vs. 19.9 ± 0.80 kg at 18 weeks and 46.2 ± 1.1 vs. 28.6 ± 1.2 kg at 22 weeks). In the second experiment, the treatments consisted of a human-imprinted group of chicks and a group subjected to conventional rearing methods (as customary on the research farm). Chick survival to four weeks was significantly higher for imprinted chicks than for conventionally reared chicks (0.97 vs. 0.84), although chick weight was independent of treatment at 4 weeks (6.27 ± 0.16 kg for the imprinted group vs. 6.18 ± 0.17 kg for the conventional group) and at 15 weeks (respectively 16.5 ± 0.68 vs. 15.2 ± 0.70 kg). Overall, chicks reared by foster parents were heavier than human-imprinted chicks, while early survival of imprinted chicks was better than that of chicks reared by conventional handling. Imprinting thus affected survival of ostrich chicks relative to conventional rearing practices. Because most ostrich chicks are reared with conventional methods, the present study indicates that improvements can be made by adopting alternative approaches. Further studies are needed to ascertain how foster parenting and imprinting may be utilized to optimize chick performance, including the long-term consequences of these practices. <![CDATA[<b>Effects of a novel carbohydrate fraction on broiler performance and intestinal function</b>]]> This study was performed to determine the effects of a natural yeast-based feed ingredient (natural carbohydrate fraction (NCF) isolated from a specific strain of yeast) on broiler chickens, and to examine its mode of action. The trial was set up as a complete randomized design with three treatments and eight replicates (38 Ross 308 chickens per pen). Two levels of NCF, 0.2 g/kg and 0.4 g/kg, were compared to a negative control. The NCF addition increased body weight during the initial period, but this benefit was lost towards the end of the trial. Feed conversion ratio was improved significantly with 0.4 g NCF/kg (1.79 compared with 1.83 in control group). Mortality was numerically lower in the groups receiving NCF. Significant effects on caecal bacterial population were not found. Intestine length and weight were not affected by treatments, while some changes in intestine histology were found. The area described as the 'cup' of mucus-producing cells, representing the quantity of stored mucins, was significantly larger in chickens receiving NCF. Relative weights of the spleen and bursa of Fabricius did not change significantly compared with the control. The NCF can improve performance and affects mucus-producing cells. Full elucidation of the mechanisms of action requires further research. <![CDATA[<b>Effect of in ovo injection with L-arginine on productive and physiological traits of Japanese quail</b>]]> This study evaluated the influence of administering different levels of L-arginine into eggs of 0-day-old Japanese quail embryos. On day 0 of incubation, 480 eggs (120 for each treatment group) were injected with 0% arginine (C group), 1% arginine (T1), 2% arginine (T2) or 3% arginine (T3). After hatching, 336 quail chicks (84 chicks produced from each in ovo injection treatment) were placed in an experimental quail house and allocated to four treatment groups of three replicates, with 16 quail chicks for each replicate. Traits involved in this study were hatchability rate, initial body weight (7 days of age), final body weight (42 days old), feed intake, weight gain, feed conversion ratio and blood serum glucose, protein, cholesterol, total lipids, triglycerides, calcium and phosphorus concentrations, and proportional weights of the carcass, breast, legs, backbone, wings, neck, abdominal fat, liver, heart and gizzard. Results revealed that in ovo injection with different levels of L-arginine on day 0 of incubation resulted in significant increases in the hatchability rate, initial body weight, final body weight, feed conversion ratio, and blood serum glucose, protein, total protein, calcium and phosphorus concentrations, as well as the proportional weights of the carcass, breast, legs, liver, heart and gizzard. However, there was no significant difference in feed intake between treatment groups. Significant decreases were recorded in blood serum cholesterol, total lipids and triglyceride concentrations, and proportional weights of the backbone, wings and abdominal fat. In conclusion, the inoculation of different levels of L-arginine into eggs of 0-day-old quail embryos, especially at the levels of 2% and 3% arginine, resulted in a significant improvement in the productive and physiological performance of the quail. Hence in ovo injection with L-arginine could be used as a tool for enhancing the hatchability rate and productive performance of quail hatched from the egg. <![CDATA[<b>Genetic analysis of body weight in South African Angora kids and young goats</b>]]> The data used for this study consisted of 27 485 kid records, the progeny of 599 sires and 10 077 dams, and were collected on the 2000- to 2009-born kids of 11 Angora goat studs. Variance and covariance components and ratios pertaining to direct additive genetic variation, maternal additive genetic variation, maternal permanent environmental variation, and the relationship between direct and maternal effects for birth weight (BW; kg), weaning weight (WW; kg) and body weight at 8, 12 and 16 months (W8, W12 and W16; kg) were estimated with the ASReml program. Direct additive heritability estimates of 0.22, 0.20, 0.12, 0.34 and 0.58 were obtained for BW, WW, W8, W12 and W16, respectively. Maternal heritabilities were 0.10, 0.09, 0.03 and 0.06 for BW, WW, W8 and W12, respectively, while maternal environmental effects of 0.13, 0.11, 0.06 and 0.04 were estimated for the latter traits, respectively. An unfavourable correlation of -0.38 was obtained between direct and maternal genetic effects for BW. Low to medium positive direct genetic correlations were estimated between birth weight and body weights recorded at a later stage in life. High positive direct genetic correlations were estimated among WW, W8, W12 and W16. The maternal genetic correlations obtained between birth weight and the other body weights were medium to high. Phenotypic correlations among the traits ranged from low to high. Genetic trends of body weight at different ages indicate that although not many breeders use objective measurement as a selection tool, body weight increased slightly in the 11 studs over the 10-year study period. Since reproduction and body weight should be included in a selection programme for Angora goats, the relationship between the direct and maternal additive effects should be clarified. The importance of a sufficiently structured and related pedigree, especially on the part of the dams and maternal grand dams, has been highlighted in this study. As this is one of the constraints of this data set, data collection in the Angora goat industry should continue until a suitably structured data set has been built up that could be used to estimate multi-trait breeding values for the industry. <![CDATA[<b>Genetic variation within and among three ostrich breeds, estimated by using microsatellite markers</b>]]> Genetic diversity within and among three ostrich populations was investigated to corroborate whether these populations can be classified genetically as three different breeds. The DNA of South African Black (SAB, n = 30), Zimbabwean Blue (ZB, n = 32) and Kenyan Redneck (KR, n = 17) birds was assessed for genetic differences using 19 microsatellite loci. The number of alleles, as well as observed and expected heterozygosity of alleles, was determined. Genetic differentiation was measured using the F-statistic (FST) and Nei's genetic distance. Significant differences were observed among the three breeds. The SAB and ZB (F ST = 0.10 and Nei = 0.49) were genetically more similar, whereas the genetic distance between the KR and ZB breeds was the greatest (F ST= 0.13 and Nei = 0.61). The SAB strain exhibited the greatest observed heterozygosity (Ho = 0.72) within its population while the ZB and the KR exhibited lower levels of heterozygosity (Ho = 0.68). Based on these results, it was suggested that crossbreeding between these breeds would lead to heterosis in commercial ostrich enterprises. <![CDATA[<b>Effect of forage sources and <i>Saccharomyces cerevisiae</i> (Sc 47) on ruminal fermentation parameters</b>]]> Diet composition has been suggested as a factor that influences the variability of responses when Saccharomyces cerevisiae (SC) is fed to ruminant animals. Diets based on lucerne hay (462 g/kg DM) and maize silage (488 g/kg DM) were fed to determine the effects of 0 or 5 g SC 47 (8x10(9) cfu/g) on ruminal digestion, fermentation and protozoa population. Ruminal pH, acetate, propionate, degradation rate and effective degradability were significantly affected by the forage sources. The addition of SC caused an increase in degradability of forage neutral detergent fibre (NDF), and tended to enhance degradability of total diet organic matter (OM), and the concentration of propionate and result in a decrease in protozoa numbers at 3 h post feeding. Ruminal crude protein degradation, ammonia-N concentration, acetate : propionate ratio and pH were not elicited by the addition of SC. Although the ruminal environment was significantly affected by the forage sources, no interaction between SC and forage sources occurred for ruminal digestion parameters: pH, ammonia-N and protozoa populations. However, compared with the maize silage, the SC increased the initial degradability (3 h after feeding) of forage NDF (4.6% vs. 1.7%), total diet OM (3.1% vs. 1.0%) and crude protein (CP) (5.5% vs. 0.1%) to higher proportions for lucerne hay. Moreover, acetate concentration was increased on the diet based on maize silage and decreased on the diet based on lucerne hay with supplementation of SC. Although ruminal environments were considerably altered by the forage sources, the SC exhibited a transitory effect (3 h post feeding) without overall improvement on ruminal digestion and fermentation; nevertheless, this observation was more pronounced for lucerne-based diet. <![CDATA[<b>Withdrawal or reduction of the dietary vitamin premix on bone parameters of broiler chickens in two rearing systems</b>]]> This study was conducted to compare the withdrawal or reduction of the vitamin premix (VP) from broiler diets at between days 29 and 42 of age on the characteristics of leg bones of the broilers in a battery cage (Trial 1) and a floor (Trial 2) rearing system. Seven experimental diets were formulated, based on wheat and barley, and consisted of four replicates per treatment. The metatarsus bone was used for measuring biomechanical bone characteristics, and alkaline phosphatase (ALP) activity and calcium concentrations blood serum to assess vitamin D3 status. The results of the first trial showed that there were no significant differences in body weight, strength of metatarsus bone and contents of ash, Ca and P in the toe with reduction or withdrawal of the vitamin premix from the diets during days 29 - 35. However, after 36 - 42 days there were significant differences for these parameters between the treatment without the vitamin premix (T1) and the other treatments. At 29 - 35 days and 36 - 42 days there were significant differences for ALP activity between T1 and the other treatments. The results of Trial 2 showed that the reduction in the vitamin premix and withdrawal at d 29 did not impair body weight, bone parameters and blood concentrations during the final growth period of the broilers. Finally, the results of the present study indicate that in the battery cage system it is possible to reduce the level of the dietary vitamin premix during the finisher period, but withdrawal can negatively affect body weight and bone parameters of broiler chickens, while in the floor system it is possible to withdrawal VP from broilers' finisher diets. <![CDATA[<b>Effects of different penning conditions, feeding regimens and season on growth and carcass attributes of boars of a selected genetic line</b>]]> The study tested the performance of intact male pigs from a selected genetic line subjected to differing feeding regimens and penning conditions. The trial was a 2 x 3 x 2 x 3 factorial design, consisting of winter and summer periods, three sire lines, two diets and three feeding regimens. The pigs were intact males grown over three phases, starter (25 to 50 kg); grower (51 to 80 kg) and finisher (81 to 105 kg).The pigs were randomly allocated to three feeding regimens, a controlled single feeding, ad libitum single feeding and ad libitum group feeding, with six animals per ad libitum group. This resulted in 96 pigs in six treatments with six replicates. The diets were high (HF) and low (LF) nutrient dense feeds, where the LF was 95% of the HF. Season affected growth; the winter animals had a significantly greater growth response, end-mass and average daily gain (ADG). The HF diet resulted in significant improved ADG, feed conversion ratio and protein deposition rate, especially during summer. However, end-mass, ADG and average protein deposition rates of controlled-fed pigs were significantly lower compared to the ad libitum group and single-fed animals. The hypothesis was affirmed that high-performing intact male pigs are sensitive to and affected by feeding regimens and penning conditions that will affect their production. <![CDATA[<b>Effect of water treatment of sorghum on the performance of broiler chicks</b>]]> The present study was conducted to observe the efficacy of water treatment on sorghum grain and to determine its optimum inclusion in broiler diets. Sorghum grain was treated with water and dried. Seven isoenergetic and isonitrogenous diets were prepared, using raw and treated sorghum, and designated diets A, B, C, D, E, F and G. Diet A, containing 0% sorghum, was kept as control. In diets B, C and D, raw sorghum was used at levels of 10%, 20% and 30%, respectively, while in diets E, F and G, treated sorghum was used at the same levels. Two hundred and ten day-old chicks were randomly divided into 21 experimental units of 10 chicks each. These experimental units were randomly allocated to seven treatments. It was observed that water treatment reduced the tannin contents of sorghum. Birds fed diets A, E and F showed the best weight gains, and diet G showed a better weight gain than diets B, C and D. The best feed efficiency was observed in chicks fed diets with treated sorghum compared with those fed raw sorghum. There was no significant effect of treated or raw sorghum on the weight of the internal organs. The study revealed that tannin contents in sorghum grain can be reduced with water treatment and that this treated sorghum can be used in broilers' diet up to the level of 20% to obtain efficient broiler production. <![CDATA[<b><i>Megasphaera elsdenii</i></b><b> on the performance of steers adapting to a high-concentrate diet, using three or five transition diets</b>]]> Megasphaera elsdenii (M.e.) NCIMB 41125 is a robust lactate utilizing strain of M.e. that is effective in minimizing the risk of ruminal acidosis in feedlot cattle. When dosed orally, cattle adapt smoothly to increasing concentrates in the diet, the incidence of digestive disturbances, morbidity and mortality is reduced, and carcass yield improves. One could therefore expect that the smooth transition should benefit overall performance. Dosing with the organism also provides the opportunity of a reduction in the time necessary for adaptation, rendering a further decrease in the cost of feeding. These two objectives were tested with 80 yearling crossbred steers blocked by weight before allotment to the respective treatments. The trial design was a randomized 2 χ 2 factorial of two drench treatments (M. e. vs. placebo) and two adaptation periods (17 vs. 8 days). In the M.e. treatment, 40 steers were dosed orally on day 1 of the trial with 200 mL inoculum containing 10(11) cells. In the placebo treatment, the other 40 steers were dosed orally with only the 200 mL inoculum. In the 17-day transition period, five diets (5-transition) were used, which increased progressively in concentrate percentage, whereas in the 8-day transition period only three of the five diets were fed (3-transition). The steers were fed individually for 63 days before being transferred to group pens and fed until day 95, when they were slaughtered. Dry matter intake was not affected by dose or transition treatment. Body weight at 28 days and 63 days did not differ between dose and transition treatments; neither did ADG and FCR. Hot carcass weight was higher in M.e. steers than in placebo steers. None of the parameters differed significantly between the 5-transition and the 3 -transition treatments. It was concluded that dosing with M.e. NCIMB 41125 should provide a small benefit to performance of feedlot cattle, with a further benefit in cost savings as dosing with the organism should allow a shorter adaptation period.