Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 39 num. 4 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Genetic parameters for ostrich incubation traits in South Africa</b>]]> Data obtained from a pair-mated ostrich flock located at Oudtshoorn, South Africa, were used to estimate genetic parameters for egg weight (EWT), weight of day-old chicks (CWT), water loss to 21 (WL21) and 35 (WL35) days of incubation, and pipping time (PT) for between 13 806 and 19 913 artificially incubated ostrich eggs during the 2003 - 2006 production years. Data were initially analysed as single traits using ASREML. Covariance components and ratios were subsequently derived from two-trait analyses. Single-trait estimates of heritability (h²) were 0.46 ± 0.08 for EWT, 0.34 ± 0.07 for CWT, 0.34 ± 0.07 for WL21, 0.27 ± 0.06 for WL35 and 0.16 ± 0.04 for pipping time. Estimates of maternal genetic effects (m²) were 0.23 ± 0.12 for EWT and 0.29 ± 0.10 for CWT. A maternal permanent environmental effect amounted to 0.25 ± 0.10 for EWT, 0.12 ± 0.09 for CWT, 0.25 ± 0.04 for WL21 and 0.30 ± 0.04 for WL35. Genetic correlations with EWT amounted to -0.21 ± 0.13 for WL21 and to -0.12 ± 0.14 for WL35. Corresponding correlations with CWT were -0.43 ± 0.07 and -0.54 ± 0.11. Parameters indicate that it should be possible to alter evaporative water loss of ostrich eggs by genetic selection. A feasible selection strategy, however, needs to be devised as it is challenging to effect genetic change in a trait with an intermediate optimum. <![CDATA[<b>Non-linear model analysis of categorical traits related to female reproduction efficiency in beef cattle</b>]]> The utilization of non-linear threshold models and linear animal models to estimate variance components for categorical reproductive traits in beef cattle was investigated. Three traits, retention (RET), stayability (STAY) and calf tempo (CT) were defined. The data set consisted of 36 880 Afrikaner beef cattle measurements recorded over a period of 10 years. After editing, the records of 7 746 females from 473 sires were available for the genetic parameter estimation for RET. The corresponding number of records for STAY and CT were 3 018 (243 sires) and 7 653 (465 sires), respectively. Using GFCAT, sire variances for RET, STAY and CT were estimated as 0.202, 0.072 and 0.114, respectively. With error variances pre-set to one, the heritability estimates on the underlying scale were calculated as 0.67, 0.27 and 0.41 for RET, STAY and CT, respectively. From the three traits analyzed in this study CT probably reflects the true fertility of the bull's female progeny best. <![CDATA[<b>Developmental differences in carcass, meat quality and muscle fibre characteristics between the Landrace and a Chinese native pig</b>]]> This experiment was conducted to compare carcass and meat quality traits, and muscle fibre characteristics in the longissimus muscle of the Landrace [an European pig breed] and the Lantang [a Chinese native pig breed] at the ages of 60, 90 and 150 days. The characteristics of muscle fibres were determined by real-time reverse transcription polymerase chain reaction (RT-PCR) and histological methods (ATPase and succinodehydrogenase, SDH). A significant age difference was observed in loin eye area (LEA), backfat thickness (BF), pH45 min , pH24 h , drip loss, moisture, ash, number percentages of αR and αW fibres, muscle fibre cross-sectional area and mRNA expression of myosin heavy chain (MyHC)-slow and MyHC-IIb. The Lantang showed a higher intramuscular fat (IMF) content and BF than the Landrace, while the Landrace exhibited a higher LEA and ash content than the Lantang. Both breeds exhibited similar developments in muscle fibre composition, and there were small differences in muscle fibre composition and muscle fibre cross-sectional area. However, Landrace pigs showed a significantly higher mRNA relative expression of MyHC-IIb. These results suggested that age was an important factor in the variation of carcass, meat quality traits and characteristics of muscle fibres. The main differences between the breeds at the same age were LEA, BF, IMF and ash contents, and fast glycolytic MyHC-IIb in the mRNA level. <![CDATA[<b>Dietary vitamin E (</b><b>α</b><b>-tocopheryl acetate) and organic selenium supplementation</b>: <b>performance and antioxidant status of broilers fed n-3 PUFA-enriched feeds</b>]]> The experiment was conducted to study the effects of organic selenium (Se-enriched yeast) and vitamin E (α-tocopheryl acetate) supplementation, alone or together, on the performance and antioxidant status of broilers fed diets enriched in n-3 PUFAs using fish oil. Day-old Hubbard-JV strain broiler chicks allocated to one of the following treatments: (1) a commercial basal diet containing 0.15 mg inorganic Se /kg as sodium selenite and 50 mg α-tocopheryl acetate (α-TA)/kg feed acted as the control; (2) VE200: Control diet supplemented with 200 mg α-TA/kg feed; (3) OrgSe0.15: Control with inorganic Se replaced with 0.15 mg organic Se/kg; (4) OrgSe0.30: Control with inorganic Se replaced with 0.30 mg organic Se/kg feed; (5) VE200+OrgSe0.15, (6) VE200+OrgSe0.30. Body weight (BW) and body weight gain (BWG) to 42 d were significantly improved with vitamin E or organic Se at 0.30 mg/kg (but not at 0.15 mg/kg) when supplemented individually, but not in combination, except that VE200+OrgSe0.15 improved 28 and 35-d body weights significantly compared with the control. Feed intake (FI), feed conversion ratio (FCR), mortality, carcass characteristics and relative organ weights, except for the spleen, were unaffected by any of the supplementation treatments. The significant positive effect of VE200 on BWG was observed after 21 d. Relative spleen weight was significantly higher in broilers fed VE200 compared to the other treatments. The antioxidative effects of organic Se and vitamin E, alone or together, were not evident in diets enriched in n-3 PUFAs using 1.5% fish oil. <![CDATA[<b>The effect of porcine somatotropin (pST) and gender on production parameters and tissue yield of pigs slaughtered at 135 kg live weight</b>]]> Eighteen F1 crossbred (commercial-type terminal crosses) pigs (boars, barrows and gilts) with an initial weight of 27.2 ± 2 kg were used to investigate the effect of porcine somatotropin (pST) administered for six weeks prior to slaughter on production parameters and tissue yield in the South African scenario. Pigs were grown to 135 kg live weight, which is heavier than the average weight at slaughter in South Africa of 80 - 100 kg. Porcine somatotropin had no significant effect on average daily gain or feed intake. However, pST administration caused a significant increase in feed conversion ratio (kg feed/kg gain) of treated boars, indicating that boars converted their feed less efficiently when treated with pST. This contradicts most of the findings in the literature. The effect of pST on the different carcass cuts was not significant, except for the percentage loin back, which was higher for pST-treated animals and percentage middle back of boars and barrows, which was slightly higher. No significant pST effects were found for live weight, carcass weight, % bone, % fat or % lean meat, but a significant increase in percentage skin was found. <![CDATA[<b>Sex of calf and age of dam adjustment factors for birth and weaning weight in Tswana and Composite beef cattle breeds in Botswana</b>]]> Records on 2 257 Composite and 5 923 Tswana calves born between the period of 1988 and 2006 in Botswana were used to calculate additive correction factors for the effects of sex of calf and age of dam on birth weight and weaning weight. The mature age group in both breeds for the two growth characteristics was 5 - 12 year old dams. Male calves were heavier than their female contemporaries throughout the pre-weaning growth period. The sex of calf adjustments for birth and weaning weights were 2.75 and 8.21 kg in the Tswana while the corresponding values for the Composite were 2.84 and 10.11 kg. Both birth and weaning weights increased with advancing age of dam, reaching a peak in mature dams and declined when dams reached an old age. Age of dam adjustment factors for birth weight in the 3, 4 and 13+ year age groups were, respectively, 1.74, 0.96 and 1.87 kg in the Tswana. Corresponding values for the Composite were 2.28, 0.94 and 2.06 kg, respectively. Age of dam adjustment factors for WW were respectively 10.36 and 5.46 kg for age groups 3 - 4 and 13+ years in the Tswana. Adjustment factors for weaning weight in the Composite breed were 13.84, 3.20 and 9.58 kg for age groups 3, 4 and 13+ years, respectively. These results indicate that adjustment factors for birth and weaning weights should be considered separately for sex of calf and age of dam in these breeds, and also, that these adjustments need to be applied within the breed from which they were derived. <![CDATA[<b>Body weight, scrotal circumference and testosterone concentration in young Boer goat males born during the dry or rainy seasons</b>]]> The aim of this study was to compare testosterone concentration, body weight, scrotal circumference and age to penis detachment from days 30 to 240 in young Boer goat males (n = 22) born during the dry (n = 11) and the rainy (n = 11) seasons. In the dry season the parameters varied as follows: body weight from 3.7 ± 1.1 to 34.0 ± 4.7 kg, scrotal circumference from 7.9 ± 0.8 to 25.7 ± 2 cm, and testosterone concentration from 259.4 ± 172.4 to 4613.4 ± 2892 pc/mL. In the rainy season parameters varied as follows: body weight from 9.7 ± 2.3 to 28.1 ± 6.9 kg, scrotal circumference from 9.5 ± 1.5 to 22.0 ± 3.0 cm and testosterone from 521.9 ± 311.3 to 3417.9 ± 2021.8 pc/mL. At three months of age, 70% of animals born during the rainy season presented with penis detachment, compared to 67.6% of animals born during the dry season at five months of age. Penis detachment occurred in all males at four and seven months for animals born in the rainy and dry seasons, respectively. There was a positive correlation between testosterone concentration and body weight in the dry (r = 0.30) and rainy (r = 0.43) seasons, between testosterone and scrotal circumference in the dry (r = 0.42) and rainy (r = 0.52) seasons, and between body weight and scrotal circumference in the dry (r = 0.93) and rainy (r = 0.88) seasons. The animals born during the rainy season showed earlier development in all the evaluated parameters than animals born during the dry season. It was found that scrotal circumference is directly correlated to body weight and testosterone concentration. <![CDATA[<b>Mortality determination and gender identification of conceptuses in pregnancies of Santa Ines ovine by ultrasound</b>]]> The aim of this study was to monitor early gestation in Santa Ines ewes by ultrasound in order to determine embryo and foetal loss, and to identify foetal sex. Ewes (n = 132) were submitted to controlled natural mating. For the purpose of pregnancy diagnosis and embryo monitoring we used transrectal ultrasound with a linear transducer (6.0 and 8.0 MHz). Pregnancy was diagnosed on day 30. On day 35 ultrasound examination was performed to determine embryo viability or loss. On days 40, 50 and 60 ultrasound examination was used to monitor foetal loss and to determine foetal sex, through identification of the genital tubercle or any external genital structure. Out of 118 pregnant ewes, 76 (64.4%) presented single pregnancy and 42 (35.6%) multiple pregnancy. Embryonic deaths occurred in 10.0% of the 160 monitored embryos: 5.6% (9/160) occurred during the embryonic phase and 4.4% (7/160) during the foetal phase, with no significant difference between them. Embryo loss was significantly lower in single pregnancies (3.9%, 3/76) compared to multiple pregnancies (15.5%, 13/84). Sexing accuracy on day 40 was significantly lower than on day 60. There was no difference between days 40 and 50, and between days 50 and 60. This study on Santa Ines sheep shows that ultrasound is a highly effective method for diagnosis of early pregnancy, determination of embryo and foetal loss, as well as foetal sexing after day 50 of pregnancy. <![CDATA[<b>Feed efficiency and carcass and meat quality characteristics of bulls finished on diets containing varied proportions of wheat straw and wet sugar beet pulp</b>]]> Fifteen young Holstein Friesian bulls (18 mo of age) were divided into three groups of five. All groups were fed a diet consisting of 60% concentrate and 40% roughage. The control (C) group received a mixture of dry meadow hay, dry lucerne and wheat straw as roughage. The second and third treatment groups were fed a similar mixture of roughage partially substituting wheat straw with wet sugar beet pulp (SBP) at levels of 4% and 8% on a dry matter (DM) basis, respectively. Dry matter intake and feed efficiency ratio (kg DM intake/kg weight gain) of the C group were significantly higher than those of the 4% SBP and 8% SBP groups. Slaughter and carcass traits indicated that there were no significant differences between dietary treatments. The inclusion of 8% SBP significantly improved panel ratings for tenderness, juiciness, beef flavour intensity and general acceptance, as well as number of chews before swallowing and the Warner Bratzler Shear value. Proximate analysis of the meat did not demonstrate differences between meat from the bulls fed C and the SBP diets. It was concluded that wheat straw could be replaced by 8% SBP in the finishing diet for young Holstein Friesian bulls in order to improve feed efficiency and sensory quality characteristics of their meat. <![CDATA[<b>Genetic parameter estimates for tick resistance in Bonsmara cattle</b>]]> The objectives of the study were to estimate genetic parameters for tick resistance and to evaluate the effect of the level of tick infestation on the estimates of genetic parameters for South African Bonsmara cattle. Field data of repeated tick count records (n = 11 280) on 1 176 animals were collected between 1993 and 2005 by 10 breeders participating in the National Beef Recording and Improvement Scheme. The distribution of tick count records were normalized using a Box-Cox transformation. Data were divided into seven sub-data sets based on the mean tick count per contemporary group, to facilitate the investigation of the effect of level of tick infestation on the derived genetic parameters. A repeatability animal model including the fixed effects of contemporary group and age of animal at tick counting and random effects of the direct additive genetic, permanent environmental and residual effects was used to estimate genetic parameters using REML procedures. The additive genetic variance for tick count ranged from 0.01 to 0.08. The animal permanent environmental variance ranged from 0.00 to 0.03. Phenotypic variance decreased with increasing mean tick count level while additive genetic variance increased with mean tick count level. The heritability also increased with mean tick count level until a mean tick count level of >30. The highest heritability estimate obtained in the current study was 0.17 for data with mean tick count level >25. These results suggest that sufficient genetic variation for tick count exists in the Bonsmara cattle. Genetic selection for tick resistance is feasible even though genetic progress may be slow. <![CDATA[<b>Fatty acid and cholesterol content, chemical composition and sensory evaluation of horsemeat</b>]]> This study aimed to determine the fatty acid and chemical composition and cholesterol concentration of horsemeat, and to evaluate its taste acceptability by the Brazilian population. Horsemeat samples (M. longissimus dorsi) were obtained from a Paraná State slaughterhouse. The chemical composition revealed a low lipid (2.9%) and high protein content (22.5%). The concentrations of the nutritionally important fatty acids, arachidonic acid (AA, 20:4n-6) and eicosapentaenoic acid (EPA, 20:5n-3), were 2.97% and 0.43%, respectively. The polyunsaturated fatty acid/saturated fatty acid (PUFA/SFA) ratio was 0.97, which is within the recommended range. The cholesterol concentration of 40.5 mg/100 g is lower than that of other meat such as chicken, beef, mutton and pork. The sensory evaluation revealed excellent acceptability. <![CDATA[<b>Identification of gene variation within porcine <i>PRDM16</i> gene and its association with fat and loin muscle area</b>]]> The PR domain containing the 16 (PRDM16) gene, also known as the MDS1/EVI1-like gene (MEL1), may act as a bidirectional switch between brown fat and skeletal muscle in mice. The molecular characteristics and possible biological function of porcine PRDM16 gene have been less reported. In this study, the mRNA expression profile, linkage mapping and association analyses of the PRDM16 gene were carried out in the pig. The PRDM16 mRNA was expressed widely in various tissues including fat and the longissimus dorsi muscle. One SNP c.-3284+171C>T in intron 14 was identified and that made the PRDM16 gene being assigned between SWR1130 and SW122 on SSC6. The different genotypes of c.-3284+171C>T were significantly associated with backfat and loin muscle area in the ISU Berkshire × Yorkshire pig resource family, but such associations were not verified in another pig population. The discovery of additional mutations and association studies are warranted before the PRDM16 gene can be recommended for marker assisted selection in the pig. <![CDATA[<b>Effect of <i>Megasphaera elsdenii</i> NCIMB 41125 drenching on health and performance of steers fed high and low roughage diets in the feedlot</b>]]> Lactate utilising bacteria (LUB) assist in reducing the risk of ruminal lactate acidosis when high concentrate diets are fed to feedlot cattle. Ruminal lactate acidosis can lead to lower animal performance and morbidity. Preliminary studies suggested that the strain, Megasphaera elsdenii (M.e.) NCIMB 41125, is a particularly potent LUB. The potential of M.e.NCIMB 41125 to improve the health and performance of feedlot cattle was investigated. Four hundred and forty eight Bonsmara steers (ca. 240 kg) were used in a 100-day feeding trial. Half the steers received at processing 200 mL M.e.NCIMB 41125 per os (LY) and the other half no LUB (LN). The diets in each of these treatments were divided into a low roughage (2%) (RL) and high roughage (8%) (RH) diet. The effects of LY vs. LN, RL vs. RH as main effects and their respective interactions (LYRL, LYRH, LNRL & LNRH) were compared in terms of morbidity, feedlot performance and carcass characteristics. The steers were weighed at two week intervals, feed was offered daily and the orts were removed weekly from each pen. The faecal consistency score and incidence of morbidity were recorded. At slaughter, carcass data were collected and the health status of the liver and rumen epithelium was assessed. Steers dosed with M.e.NCIMB 41125 had a 5.6% better average daily gain (ADG) during weeks 3 - 5 (2.09 kg/day vs. 1.98 kg/day for LY and LN, respectively). Feed conversion ratio (FCR, Weeks 1 - 13) was better for the steers fed the RL than the RH treatment (4.72 kg/kg vs. 4.99 kg/kg for RL and RH, respectively). Steers on the LNRH treatment during weeks 3 - 5 used more feed per kg gain than steers on the other treatments (5.39 kg/kg for LNRH vs. 4.74 kg/kg and 4.72 kg/kg for LYRL and LNRL, respectively). More steers (21) on the LNRL treatment were treated for morbidity than on the other treatments (8, 7 and 5 for LYRL, LYRH and LNRH, respectively). In general, animal performance was not improved by dosing with M.e.NCIMB 41125, but since ADG was improved in the immediate post-adaptation phase (weeks 3 - 5) and morbidity levels were lower on the low roughage diet, dosing of steers on low roughage, lactate acidosis-prone, diets with M.e.NCIMB 41125 should prove useful. <![CDATA[<b>Effect of niacin supplementation on performance and blood parameters of Holstein cows</b>]]> In this experiment the response to niacin supplementation was evaluated. Twelve multiparous Holstein cows were used in a replicated 4 × 4 Latin square statistical model in four 24 d periods as replicates. At the onset all the cows were in early lactation with days in milk (DIM) at 60.1 ± 16.1 and an average milk yield of 31.4 ± 5.44 L/d. The treatments were: N0 - control (no niacin supplement); N1 - control + 12 g niacin/d; N2 - control + 14 g niacin/d and N3 - control + 16 g niacin/d. Means were compared with the Duncan's least range test. Milk yield, fat-corrected milk (FCM, 3.5%) and total solids percentage (TS) were significantly higher in the N2 compared to the other treatments. There were no significant differences between treatments in milk fat and milk lactose percentages, but milk fat yield was significantly higher and milk fat percentage numerically higher in the N2 than in the other treatments. Milk protein yield and percentage were highest in N2, but milk protein percentage was not significantly different between the N2 and N1 treatments. Milk solids non-fat (SNF) percentage was the highest for N2. Evaluation of blood plasma parameters showed that 14 g niacin (N2) supplementation resulted in a significantly higher glucose concentration and the lowest ß-hydroxybutyrate (BHBA) and nonesterified fatty acids (NEFA) concentrations as compared to the other treatments. This study suggested that the optimal level of niacin supplementation was 14 g niacin/cow/d. <![CDATA[<b>Lack of polymorphism in the oocyte derived growth factor (GDF9) gene in the Shal breed of sheep</b>]]> The families of TGF-β proteins are the most important growth factors in the ovary for growth and differentiation of early ovarian follicles. Three related oocyte-derived members of the transforming growth factor-β superfamily, namely GDF9, BMP15 and BMPR-IB have been shown to be essential for follicular growth and ovulation. The aim of the present study was to detect the incidence of mutation in exon two of GDF9 as a major gene in the Shal sheep breed. Blood samples were collected from 239 sheep and genomic DNA was extracted using the modified salting-out method. The quantity and quality of extracted DNA was examined using spectrophotometery and gel electrophoresis, respectively. A fragment with the size of 139 bp from exon two of GDF9 gene (FecG H) was amplified using polymerase chain reaction (PCR) with a pair of specific primers. The amplified PCR products were digested with DdeI restriction enzyme. In the presence of mutations at this locus, the DdeI enzyme cannot recognize the restriction site. However, in the absence of mutations, the enzyme recognizes one restriction site and divides the amplified fragment into two fragments of 31 and 108 bp. In the present study only the wild type alleles were detected and all the samples showed the AA genotype. The analysis of polymorphism for GDF9 (FecG H) loci in Shal sheep indicates that the genetic factor responsible for twinning or multiple lambing rates is not related to reported mutated alleles at the GDF9 major gene in this breed. Therefore, we should attempt to detect other SNP for the GDF9 gene and/or other loci responsible for twining rate in this breed.