Scielo RSS <![CDATA[South African Journal of Animal Science]]> http://www.scielo.org.za/rss.php?pid=0375-158920110003&lang=en vol. 41 num. 3 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Quality related principles of the South African beef classification system in relation to grading and classification systems of the world</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300001&lng=en&nrm=iso&tlng=en ABSTRACT This paper addresses the principles related to different grading and classification systems of the world with specific focus on beef quality related outcomes. The paper uses the definitions that classification is a set of descriptive terms describing features of the carcass that are useful as guidelines to those involved in the production, trading and consumption of carcasses, whereas grading is the placing of different values on carcasses for pricing purposes, depending on the market and requirements of traders and consumers. The literature shows that the criteria used in grading systems rank carcasses fairly accurately according to expected eating experience of the loin muscles, but not of higher connective tissue cuts of the hind and forequarter. Criteria used in classification systems give limited descriptions of the quality related characteristics of the carcass. Only the Meat Standards Australia (MSA) cuts based grading system of Australia seeks to define or predict consumer satisfaction with a cooked meal for each cut of the carcass. Its success is based on a palatability assured critical control point (PACCP) approach to satisfy the consumer. However, MSA requires high technical skills, a well organised infrastructure and proper traceability, high level of integrity from different role players and could be very costly, involving high additional personnel cost. The South African classification system should probably focus on distinguishing between young feedlot and somewhat more mature pasture animals with different criteria within each subcategory to describe the variation in product quality. Correct pre-slaughter and slaughter management (stress, weight, chilling rate, electrical stimulation, post mortem aging) could improve consistency within the age group. <![CDATA[<b>Effect of dietary protein on the allometric relationships between some carcass portions and body protein in three broiler strains</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300002&lng=en&nrm=iso&tlng=en ABSTRACT This paper reports the allometric relationships between some of the physical parts and body protein weight of three commercial broiler strains reared, sexes separate, on four dietary protein levels to six weeks of age. Birds were sampled at day old and then weekly from each of the treatments to determine the weights of the physical parts and the chemical composition of each of 582 birds. Allometric regressions were compared between strains, sexes and dietary protein levels using linear regression with groups. Whereas these regressions were similar over strains and sexes, some interactions were evident between factors, and differences occurred when broilers were fed differing dietary protein levels. These differences may be explained on the basis that lipid is deposited to different extents in each of the parts in response to dietary protein, although this was not tested. The allometric regressions presented are an attempt to provide information that would enable the prediction of the weights of breast meat, thigh, drum and wing at different stages of growth of broilers whose genotype and feed composition are adequately described. <![CDATA[<b>Maintenance requirements for methionine and cysteine, and threonine for poultry</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300003&lng=en&nrm=iso&tlng=en This study aimed to estimate the methionine & cystine (M&C), and threonine (THR) requirements for maintenance of adult roosters differing in liveweight and body composition, and to estimate the concentrations of M&C and threonine in 'ideal' protein for maintenance. Five metabolism trials were conducted using 42 mature Bovans White (in trials 1 and 3) and 42 Cobb (in trials 2 and 4) roosters. In the first two trials, designed to measure the M&C requirements for maintenance, the M&C content in the diets ranged from 0 to 138 mg/kg d (687 mg/BPm0.73/d) for the Bovans White, and from 0 to 64 mg/kg d (346 mg/BPm0.73/d) for the Cobb strain, respectively (where BPm is mature body protein weight). In trials 3 and 4 in which the THR requirement for maintenance was measured, the THR levels ranged from 0 to 127 mg/kg d (624 mg/BPm0.73.u/d) and from 0 to 106 mg/kg d (584 mg/BPm0.73.u/d) for the two strains, respectively. Excreta were collected in trays, weighed, homogenized, dried and ground and the nitrogen contents of excreta and diets were then determined. The M&C requirement for maintenance was estimated as 19 mg/kg empty body weight (EBW)/d, 26 mg/kg EBW0.75/d or 87 mg/BPm0.73/d. The maintenance requirement for THR was estimated as 17 mg/kg EBW/d, 22 mg/kg EBW0.75/d or 76 mg/BPm0.73/d. The concentration of M&C in 'ideal' protein for maintenance was estimated as 11, and THR, 9.4 g/kg body protein. <![CDATA[<b>Effects of breed on milk fatty acid profile in dairy ewes, with particular reference to <i>cis</i>-9, <i>trans</i>-11 conjugated linoleic acid</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300004&lng=en&nrm=iso&tlng=en The objective of this study was to determine and compare the fatty acid profile of milk fat, with particular reference to cis-9, trans-11 conjugated linoleic acid (CLA), in two indigenous Romanian sheep breeds (Spanca and Turcana), irrespective of the effects of diet and season. The ewes (n = 25 for each breed) received the same feed (total mixed rations) and were maintained under identical conditions. Four samples were collected from each individual ewe to determine fatty acids (FA), as methyl esters, using gas chromatography. The fatty acid groups, namely saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) acids were examined together with individual acids. Differences have been obtained between the two local breeds for the majority of FA. Fat in the milk of Turcana ewes has a healthier fatty acid profile than that of Spanca breed which has a lower concentration of SFA (60.9 vs. 73.3%) and higher concentrations of MUFA (31.0 vs. 21.0%) and PUFA (8.06 vs. 5.61%, respectively). Compared with the Spanca breed, fat in the milk of Turcana ewes had higher concentrations of trans-11 C18:1, C18:1 n9c, and cis-9 trans-11 CLA (2.67 vs. 1.01%, respectively). Δ9-desaturase activity is breed specific; vaccenic acid (trans-11 C18:1) desaturation and its conversion into cis-9, trans-11 CLA were more intense in the Turcana breed ewes. In conclusion, breed has a strong effect on the FA composition of ewe milk fat, and on cis-9, trans-11 CLA, in particular. The results obtained, support the sustainable use of animal genetic resources to improve the milk fat quality of ewes. <![CDATA[<b>Polymorphism of the porcine <i>CGA</i> gene and its association with growth and carcass traits</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300005&lng=en&nrm=iso&tlng=en Glycoprotein hormones in the pituitary gland affect a myriad of biological processes such as development, growth, metabolic control and gametogenesis. The quantitative trait loci (QTL) near their common glycoprotein alpha(A) subunit gene (CGA) have been reported inconsistently. The aim of this study was to dissect potential genetic factors for these unstable results and validate the association or linkage relationship of CGA gene with growth and carcass traits. By resequencing all the exons and part of the introns of the porcine CGA gene, 22 polymorphisms in total were identified in this study. Five single nucleotide polymorphism (SNP) markers were chosen and evaluated in six pure-bred pig breeds (n = 228). Breed-specific haplotypes were found and a map of the porcine CGA polymorphisms' evolution history was inferred. A resource family (n = 365) with different genetic backgrounds from those used in other papers was used to perform an association study. The resource family was created based on crosses of Pietrain and Jinhua pigs (Central China type pigs). Results indicated that a low correlation between haplotype blocks may abolish each other's effects. Moreover, a significant association of SNP C-925T with growth rate and back-fat thickness in this study confirmed the existence of previously reported QTL. SNP C-925T and SNP A+15599G could be useful linkage markers and SNP C-925T may also be a candidate causative SNP for the corresponding traits. Further investigation for variants within of the CGA promoter region and their association with growth rate and back-fat traits is suggested. <![CDATA[<b>Genetic parameter estimates for live animal ultrasound measures of carcass traits in South African Angus cattle</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300006&lng=en&nrm=iso&tlng=en Genetic parameters were estimated for body weight at scanning (SCW) and live animal ultrasound measures of rump fat thickness (P8FT), rib fat thickness (RBFT), rib eye-muscle area (REA) and intramuscular fat percentage (IMF) for South African Angus beef cattle. A multiple-trait animal model was used to estimate genetic parameters using the Residual Maximum Likelihood procedure (REML). Ultrasound data was used on 1 122 animals that participated in the South African National Beef Cattle Improvement Scheme. The fixed effects that were significant included contemporary group, sex and age of the animal at scanning. Random effects considered were the direct additive genetic effect and the residual. Heritability estimates were 0.38 ± 0.08, 0.34 ± 0.06, 0.33 ± 0.05, 0.32 ± 0.06 and 0.38 ± 0.06 for SCW, P8FT, RBFT, REA and IMF respectively. Genetic correlation between SCW and REA was high (0.79 ± 0.07). Genetic correlations with SCW were 0.24 ± 0.14 for P8FT, 0.25 ± 0.12 for RBFT and 0.29 ± 0.11 for IMF. Measures of body fat were genetically highly correlated with one another, with correlations ranging from 0.71 to 0.99. The magnitude of heritability estimates obtained in the current study indicates that genetic improvement for ultrasound indicators of carcass traits should be effective. However, the indirect selection of carcass traits using ultrasound data, should consider the antagonistic genetic relationship between subcutaneous and intramuscular fat. <![CDATA[<b>Parentage verification of South African Angora goats, using microsatellite markers</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300007&lng=en&nrm=iso&tlng=en ABSTRACT South African Angora goats are farmed under extensive production systems in relatively large herds. As a result, breeders make use of group and flock-mating systems that limit accurate parentage recording and selection efficiency. In this study the aim was to refine a panel of microsatellite markers suitable for parentage verification in South African Angora goats. The markers were first evaluated based on the number of alleles, allele frequency, PIC, H E, H O and individual exclusion probability, and secondly as part of a panel. Eighteen markers were tested in 192 South African Angora goats representing different family structures with known and unknown parent information. The final set of microsatellite markers, with the strongest exclusion and the least number of microsatellite markers, consisted of 14 microsatellite markers namely BM1258, BM1329, BM1818, BM7160, CSRD247, HSC, INRA63, INRABERN192, MCM527, OarFCB48, SRCRSP5, SRCRSP8, SRCRSP9 and SRCRSP24. This panel had a combined first-parent exclusion probability of 99.7% and it was possible to perform parental identification in a test family. <![CDATA[<b>Effects of partial replacement of barley with sugar beet pulp on pre- and post-partum performance of Zel ewes</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300008&lng=en&nrm=iso&tlng=en Sixteen Zel ewes (BW = 37 ± 3.10 kg) were used in a completely randomized design to determine the effects of partial replacement of barley grain with beet pulp (BP), during late pregnancy and early lactation, on litter weight, lamb's daily gain, milk yield and milk composition. Dietary treatments were initiated approximately three weeks prior to expected lambing dates, and continued for three weeks post-partum. Treatments consisted of 1) a basal diet + 330 g/kg of barley grain (BBG), and 2) a basal diet + 195 g/kg of barley + 135 g/kg BP (BBP). The basal diet contained 444, 117, 101 and 8 g/kg of wheat straw, wheat bran, canola meal and mineral-vitamin mix supplement, respectively. Both diets were offered as a total mixed ration twice daily. Partial replacement of BP increased feed intake. Diets did not affect milk compositions but feeding BBP increased milk yield (1084 vs. 737 g/d), litter weight (3453 vs. 2735 g) and lambs' daily gain (218 vs. 156 g/d). The lambs' live weight at 14 d (5992 vs. 4749 g) and 21 d (7553 vs. 5854 g) was affected by maternal nutrition and a higher BBP. The results of this study indicate that late gestation and early lactation ewes can be supplemented with BP without detrimental effects on milk production or milk composition, and feeding ewes with BP during this period resulted in increased litter weight and growth of lambs. <![CDATA[<b>Influence of incubation management on pipping position, hatching ability and survival of ostrich chicks</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300009&lng=en&nrm=iso&tlng=en Despite numerous studies, the effect of artificial incubation on the hatchability and survival of near-term ostrich chicks is still not well understood. Records from 13 975 eggs with embryos of 35 days and older, artificially incubated between 2006 and 2008, were analysed to determine the potential effect of pipping position upon the hatchability, and the subsequent survival of ostrich chicks. A total of 864 near-term chicks (6.9%) failed to pip. Chicks that pipped in the correct position had a higher probability of surviving hatching than those pipping in the incorrect position. Genotype did not affect the proportion of chicks pipping in the correct position, or the survival of hatching ostrich chicks pipping in either the correct or incorrect positions. Although female age had a significant effect on the proportion of chicks pipping, the survival of hatchlings was independent of female age. Chicks hatching during winter were more likely to pip than chicks hatching in spring, whereas chicks hatching in summer were more likely to pip in the correct position. In winter the proportion of chicks pipping in incorrect positions were significantly higher than in either summer or autumn. The survival rate of chicks hatching during winter was generally higher than those hatching in the other seasons. The transfer of eggs between setters during incubation, had a negative influence on the ability of ostrich chicks pipping in the correct position. Incubated ostrich eggs with intermediate levels of water loss, i.e. between 9.0 and 18.9% of fresh-egg weight, were more likely to pip in the correct position overall than those with higher or lower levels of water loss. Chicks from eggs stored for intermediate periods, i.e. 3, 4 and 6 days prior to being set, were more likely to pip than chicks from those eggs set directly after collection without storage. Storage time also affected pipping position, with chicks from eggs stored for five days being more likely to pip in the correct position than chicks from those eggs set directly after collection. These results emphasize the need for ostrich incubation facilities to avoid the transfer of eggs between setters during artificial incubation, strive to achieve an optimal level of water loss, and apply a protocol of not setting eggs immediately after collection to maximize the hatchability of chicks pipping in the correct position and post-hatching survival. <![CDATA[<b>Effect of breed on performance and carcass characteristics of Mexican hair sheep</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300010&lng=en&nrm=iso&tlng=en To determine the effect of breed on growth performance and carcass characteristics in Mexican hair sheep, 48 lambs (average 38.9 ± 1.56 kg body weight, BW) were used in a completely randomized experimental design. The breed types assessed were 16 Pelibuey (PB), 16 Pelibuey x Katahdin (PB-KT) crossbred and 16 Pelibuey x Dorper (PB-DP) crossbred lambs. The lambs were fed a maize grain-based diet (88% concentrate and 12% forage) containing 155 g CP and 12.13 MJ ME/kg DM. The growth performance trial lasted 45 days. The average daily gain was significantly higher for the PB breed than for the PB-KT and PB-DP cross-breds. Feed intake in the PB and PB-KT was significantly higher than in the PB-DP. The feed conversion ratio was lower for the PB than for PB-KT and PB-DP lambs. Hot carcass dressing and leg perimeters were significantly lower for the PB than for the PB-DP lambs, and similar to that of the PB-KT lambs. The lowest dorsal fat values were measured in the PB breed, compared with both the PB-KT and PB-DP cross-breds. Mesenteric fat (as % of BW) in the PB was significantly higher than in PB-KT and PB-DP lambs. Empty rumen and small intestine weights (as % of BW) in the PB lambs were significantly higher than in the PB-DP lambs, but their large intestine was significantly smaller than in the other two breeds. It was concluded that the PB lambs have a better growth performance and carcass characteristics than the PB-DM lambs, but similar to that of the PB-KT lambs. <![CDATA[<b>Physical impact of sheep grazing on arid Karoo subshrub/grass rangeland, South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300011&lng=en&nrm=iso&tlng=en ABSTRACT Grazing levels and rotational schemes need to be tailored to each individual farm or pasture, and more studies are needed on the resilience of rangelands and on separating the effects of grazing and climate. The direct short-term impact of three rates of stocking (4, 8 and 16 Small Stock Units-SSU/ha) was quantified in terms of composition and cover of arid Nama Karoo vegetation (subshrub/grass). Mature Merino wethers grazed in one hectare plots during May in 1995 and 1996 (the plots were not subjected to grazing at any other time). The basal cover of the Karoo bushes (shrubs) showed a decrease at the highest stocking rate only, with the species Phymaspermum parvifolium the most sensitive to intensive grazing. An increase in stocking rate caused a significant decrease in both canopy cover and canopy-spread cover. The canopy cover of palatable Karoo bushes such as Felicia muricata, Salsola calluna and Walafrida geniculata decreased most. Light stocking (4 SSU/ha) was apparently the least detrimental to the vegetation composition and cover. Regardless of stocking rate, an 11-month resting period was possibly sufficient for all the vegetation parameters concerned to be fully restored after grazing took place. The rangeland rapidly reacted to rainfall as the ephemeral cover increased temporarily. The higher the stocking rate was, the greater the increase in ephemerals occurring. The ecological sustainability of the Nama Karoo ecosystem, utilised by high stocking densities, is questioned. <![CDATA[<b>Effects of oxidised oil and vitamin E on performance and some blood traits of heat-stressed male broilers</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300012&lng=en&nrm=iso&tlng=en The present study was conducted so that the possible effects of thermally-oxidised dietary oil and vitamin E supplementation could be determined on the performance, lipid peroxidation, antioxidant defence system and some blood and meat quality traits of broilers. Broilers were fed grower diets containing fresh or oxidised oil, supplemented with and without vitamin E (200 mg/kg) from four to six weeks of age. Neither oxidised dietary oil nor vitamin E supplementation had any adverse effect on weight gain, feed consumption or feed conversion ratio. However, the broilers that received oxidised oil had lower levels of plasma cholesterol and triglyceride compared to the control. The glucose level was neither influenced by oxidised oil nor by vitamin E supplementation. The plasma malondialdehyde level increased slightly in broilers fed oxidised oil, indicating increased lipid peroxidation. Higher glutathione peroxidise (GSH-Px) activity observed in the broilers fed oxidised oil suggests greater oxidative stress. Vitamin E supplementation partly depressed GSH-Px activity in broilers fed oxidised oil. This depression in enzyme activity might be the result of homeostatic compensation. The uric acid concentration was not affected by oxidised oil and vitamin E supplementation. Feeding oxidised oil did not cause a marked discolouration in breast meat. Vitamin E supplementation had some beneficial effects on colour measurements. <![CDATA[<b>Comparison of analyses to predict ruminal fibre degradability and indigestible fibre in temperate grass silages</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300013&lng=en&nrm=iso&tlng=en ABSTRACT The objective of this study was to compare the ruminal degradability of neutral detergent fibre (NDF) and indigestible NDF (INDF) between silages (n = 24) that originated from three different temperate grass species, i.e. Dactylis glomerata L., Festuca arundinacea L. and hybrid, Felina - Lolium multiflorum L. × Festuca arundinacea S. The data is used to create prediction equations for the effective degradability of NDF (ED NDF), assuming ruminal solid outflow rates of 0.02 (low), 0.05 (medium) and 0.08/h (high), and INDF. The highest values for the potentially degradable fraction of NDF (b), ED NDF2, ED NDF5 and ED NDF8 (874, 560, 366 and 272 g/kg NDF, respectively) and the lowest for INDF (73.1 g/kg DM) were found for F. arundinacea. These parameters were significantly different from the hybrid Felina, which presented the lowest rate of NDF degradation (c), ED NDF5 and ED NDF8 (0.033/h, 341 and 250 g/kg NDF, respectively). The highest for c (0.038/h) and INDF (86.9 g/kg DM) and the lowest for b (847 g/kg NDF) were detected for D. glomerata. The combination of acid detergent fibre (ADF) and acid detergent lignin (ADL) (R² = 0.844) were identified by a backward, stepwise, multiple regression analysis as the most accurate to predict INDF. Crude protein, ADF and NDF were found as the most suitable combination for predicting ED NDF2 (R² = 0.715), ED NDF5 (R² = 0.669) and ED NDF8 (R² = 0.648). Calculated equations found practical application in laboratory analyses to evaluate the nutritional quality of feeds for ruminants. <![CDATA[<b>Feeding of whole cottonseed on performance, carcass characteristics and intestinal morphology of Zandi lambs</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892011000300014&lng=en&nrm=iso&tlng=en The present study was conducted to determine the effect of including different levels of whole cottonseed (WCS) in the finishing diet of lambs on their dry matter intake (DMI), live weight gain, feed conversion ratio (FCR, kg feed/kg gain), carcass characteristics and small intestinal morphology. Twenty Zandi male lambs (29.8 ± 1.6 kg body weight) were assigned to one of four diets in a completely randomized experimental design. The experimental diets contained 0%, 4%, 8% and 16% WCS on a dry matter (DM) basis. The diets were prepared as total mixed rations and fed to the lambs ad libitum. The lambs were slaughtered on day 90 and carcass data was collected. The DMI and average daily gain (ADG) were significantly greater for lambs fed the 8% WCS diet compared with the other treatments. The FCR was significantly lower in the diets containing WCS compared to the control, viz. 6.11, 5.6, 5.46 and 5.68, for treatments 0, 4, 8 and 16% of WCS, respectively. However, the positive effects of including 8% cottonseed in the diet were significant in hot carcass weight, dressing percentage, liver, fat tail, intestinal fat and spleen compared with the control group. Furthermore, villous morphology and depth of crypt gland were affected by both diet and sampling site. No negative effects were observed in the organs and carcasses of the lambs that received different diets. The results indicate that the inclusion of 8% WCS in lamb diets could have a positive effect on most of the traits, but increasing the WCS inclusion up to 16% in the diet may have negative effects on lamb performance.