Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 45 num. 2 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Genetic prediction models and heritability estimates for functional longevity in dairy cattle</b>]]> Longevity is a major component of the breeding objective for dairy cattle in many countries because of its high economic value. The trait has been recommended for inclusion in the breeding objective for dairy cattle in South Africa. Linear models, random regression (RR) models, threshold models (TMs) and proportional hazard models (PH) have been used to evaluate longevity. This paper discusses these methodologies and their advantages and disadvantages. Heritability estimates obtained from these models are also reviewed. Linear methodologies can model binary and actual longevity, while RR and TM methodologies model binary survival. PH procedures model the hazard function of a cow at time t derived from survival from first calving to culling, death or censoring. It is difficult to compare methodologies for sire evaluation and ranking across countries because of the variation in the definition of longevity and the choice of model. Sire estimated breeding values (EBVs) are derived differently for the models. Sire EBVs from PH models are expressed as deviations of the culling risk from the mean of the base sires, expected percentage of daughters still alive after a given number of lactations, expected length of productive life in absolute terms or as standard deviation units. In linear, TM and RR modelling, sire EBVs for longevity have been expressed as deviations of survival from the mean estimated with Best Linear Unbiased Prediction (BLUP). Appropriate models should thus be developed to evaluate functional longevity for possible inclusion in the overall breeding objective for South African dairy cattle. <![CDATA[<b>Phenotypic correlations of backfat thickness with meatiness traits, intramuscular fat, <i>longissimus </i>muscle cholesterol and fatty acid composition in pigs</b>]]> The aim of the present study was to determine the phenotypic correlations of backfat thickness with meatiness traits and intramuscular fat, cholesterol and fatty acid composition in the longissimus muscle of pigs. For this study, 60 barrows and 60 gilts (Pietrain χ Duroc boars and Polish Large White crossbred sows) were slaughtered at 100 kg bodyweight. Lean meat percentage (LMP), loin muscle area (LMA), backfat thickness measured at five locations and average backfat thickness (ABF), and intramuscular fat (IMF), cholesterol (CHLM) and fatty acid composition in the longissimus muscle were determined. Phenotypic correlations of individual backfat thickness measured at five locations and ABF with LMP, LMA and polyunsaturated fatty acids (PUFAs), including C18 :2n-6, were negative and moderate to high, while with monounsaturated fatty acids (MUFAs), including C16:1 and C18:1 were positive and very low. Correlations of individual backfat thickness and ABF with saturated fatty acids (SFAs) and C16:0 were positive (0.29 to 0.56), while for C18:0 were low (0.10 to 0.23). Correlations of IMF and CHLM with LMP, LMA and PUFAs, especially C18:2n-6, were negative and high, while with SFAs and MUFAs were positive and moderate to high. Correlation between IMF and CHLM was high (0.74). The results of the present study indicate that increased IMF content results a significant decrease in carcass meatiness (LMP and LMA) and of PUFAs content and an increase in backfat thickness and contents of SFAs, MUFAs and CHLM. <![CDATA[<b>Influence of frozen storage on the fatty acid composition of ostrich meat enriched with linseed and rapeseed</b>]]> The aim of the study was to evaluate the effect of the duration (24 hours, 60 days and 120 days) of frozen storage (-20 °C) on the fatty acid composition of meat from ostriches supplemented with linseed and rapeseed. The study was carried out on muscles of 40 ostriches raised on five dietary groups: control with no supplementation (C), with 4% linseed (L4); 8% linseed (L8); and 5% rapeseed (R5); or 10% rapeseed (R10) in the diet. As the frozen storage period increased, the fatty acid profile of the ostrich meat in all the "enriched" groups changed, especially treatments L4 and L8. There was a decrease in the polyunsaturated fatty acid content (especially from 61 to 120 days of storage) including linolenic, arachidonic and docosahexaenoic acids. However, storage did not influence the fatty acid profile of ostrich meat up to 60 days. These results suggest that freezing is an acceptable method for preserving ostrich meat (up to 60 days), causing only a small decrease in the fatty acids of ostrich meat enriched with n-3 fatty acids. However, further research on prolonged frozen storage is recommended. <![CDATA[<b><i>In vitro </i></b><b>degradation of melamine by ruminal microorganisms</b>]]> An in vitro study was conducted to determine the extent of melamine degradation in rumen liquor. Rumen liquor was collected from two ruminally cannulated Holstein cows on four separate dates, one week apart. Erlenmeyer flasks (250 mL) were prepared for incubation by adding 1000 mg of a dairy feed substrate, 100 mg melamine and 100 mL incubation medium, purged with CO2 and fitted with rubber stoppers equipped with one-way gas release valves. The initial melamine concentration was thus 1000 mg/L. The substrates consisted of 600 mg of a commercial dairy concentrate, 200 mg lucerne hay and 200 mg oat hay. The incubation medium consisted of 19 mL rumen liquor, 77 mL of Van Soest buffer and 4 mL of a reducing solution. The flasks were incubated at 39 °C for 0, 6, 24 or 48 hours (two flasks per time in each of four replicates). The 0 h incubation served as a control treatment to enable the calculation of melamine recovery values. For the control treatment (0 h), fermentation was terminated at the onset of the trial by aerating the rumen liquor and submerging the flasks in 50 mm ice. On termination of the incubation, 100 mL 0.2 M perchloric acid was added to each flask in order to dissolve any undegraded melamine. Melamine concentrations were determined by liquid chromatography-tandem mass spectrometry. Melamine degradation was low after 6 hours and 24 hours of incubation (3.2% and 5.5%, respectively) and increased to 13.6% after 48 h of incubation. It was concluded that melamine has low degradability in rumen liquor. <![CDATA[<b>Assessing nutrient adequacy from the crop contents of free-ranging indigenous chickens in rural villages of the Venda region of South Africa</b>]]> The aim of the study was to evaluate the nutritional status of scavenging chickens by assessing the composition of their crop contents. The study was conducted on 288 free-ranging indigenous chickens from six adjacent rural villages in Venda region of South Africa over three seasons (autumn, winter and spring). The chickens consumed grains, kitchen waste, seeds from the environment, plant materials, worms and insects, and some undistinguishable materials. Household waste accounted for 78.6%, 91.1% and 75.8% and materials of animal origin, including insects and worms, accounted for 7.4%, 10.4% and 16% of the crop content in autumn, winter and spring, respectively. Grains and kitchen waste consumption and macro- and micro-nutrient concentrations varied with season. The crude protein (CP) level of the crop contents of adult chickens in all seasons and the calcium and phosphorus levels in winter corresponded with the requirements of poultry for maintenance and growth, but not egg production. Supplementation of CP to young birds in all seasons and calcium and phosphorus in autumn and spring might be necessary to improve their growth. Concentrations of copper, manganese, zinc and cobalt were above the requirements of poultry, but below their maximum tolerance levels (MTL). Iron concentrations ranged from 2907 mg/kg DM to 6424 mg/kg DM, which are well above MTL, suggesting potential detrimental effects on the birds if the iron in the crop contents is bioavailable. Aluminium concentrations ranged from 2256 mg/kg DM to 4192 mg/kg DM, though aluminium is considered non-toxic. It was concluded that the birds would not suffer from micro-mineral deficiencies, and that a risk of toxicity would depend on the bioavailability of the consumed element. <![CDATA[<b>Fatty acid profile, cholesterol and oxidative status in broiler chicken breast muscle fed different dietary oil sources and calcium levels</b>]]> The aim of the present study was to evaluate the effects of three feeds containing 6% oils: palm oil (PO), soybean oil (SO) and linseed oil (LO); and three calcium levels (NRC recommendation, 1.25% and 1.50%) on the fatty acid profile, lipid oxidation and cholesterol concentrations of broiler breast meat in a 3 χ 3 factorial experiment. A total of 378 one-day-old chicks were randomly assigned to the diets and fed for six weeks. Birds fed diet supplemented with LO, SO and PO had higher proportions of α-linolenic, linoleic and oleic acids, respectively. The LO diet increased the total n-3 fatty acids and decreased the n-6 : n-3 compared with the PO and SO diets. Birds fed the PO diet had higher oxidative stability and cholesterol compared with those fed the SO and LO diets. However, the level of cholesterol in all treatments was within the normal range. The level of calcium and interaction between source of oil and calcium level did not influence lipid oxidation, fatty acid profile and cholesterol level of broiler breast muscle. It can be concluded that dietary LO and SO enhanced n-3 and n-6 polyunsaturated fatty acids, respectively, while dietary PO enhanced the oleic acid and oxidative stability of broiler breast muscle. Thus, this study showed that PO can be used as an alternative oil source in broiler diets with a positive effect on the oxidative stability of chicken meat refrigerated at seven days when compared with vegetable oils that are rich in linoleic and α-linolenic acid. <![CDATA[<b>Changes in certain serum and faeces parameters in weaned piglets as a response to nutritional stress</b>]]> Weaning is associated with several stress factors and their effects on the piglet's body are fairly well known. Thus, changes were estimated in certain serum and faecal parameters after weaning owing to dietary protein level, though essential amino acid (AA) levels were maintained or reduced. Eighteen Topigs piglets were assigned randomly to three homogenous groups. The dietary protein level was reduced by 10% in diets 1 and 2 compared with diet C. Diet 1 had similar levels of essential AA to diet C, while the levels of essential AA in diet 2 were reduced by 10%. Blood samples were collected by jugular venipuncture in the farrowing unit on four occasions: before and after separation from the sow; the day after transfer to the nursery; and seven days after weaning. Faecal excreta were collected daily. No major health problems arose, and total pathogen germs were not different among treatments. Cortisol concentration reached similar values to those from the farrowing unit seven days after weaning. Whatever the diet, vitamin E in plasma decreased significantly in the first seven days post weaning. The reduction of dietary protein, as well as essential AAs, adversely affected the concentration of Cu (by 17.3%) in plasma. Selenium concentration in plasma increased slightly, irrespective of diet. The authors conclude that providing dietary protein at a particular level (diet 1), while maintaining AAs at normal level, limits faecal nitrogenous content without significantly modifying stress indicators (except vitamin E) or faecal composition. <![CDATA[<b>Effect of production system on welfare traits, growth performance and meat quality of ducks</b>]]> The effects of production system on welfare traits, growth performance and meat quality of ducks were explored. A total of 120 newly hatched ducklings were randomly assigned to three groups: i) floor-reared system (FRS); ii) welfare-reared system (WRS) and iii) net-reared system (NRS) (n = 8 ducklings/pen, 5 pens/group). In the FRS, ducks were reared on sawdust bedding that was changed every 2 - 3 days. The WRS was similar to the FRS, the difference being the addition of environmental enrichment devices such as perches, coloured balloons and ribbons. In the NRS, ducks were reared on plastic nets on a bamboo bed, and their droppings were cleaned daily with water. After 35 d, welfare traits, growth performance and meat quality of the ducks were measured. Moving and playing durations of WRS ducks were longer than FRS and NRS ducks. Bathing and feather pecking durations of NRS ducks were longer than FRS and WRS ducks. Duck feather quality was greater and gait defects were reduced in NRS system compared with FRS and WRS systems. Fluctuating asymmetry (FA) was not affected by the production system. Growth performance was not significantly different between FRS and WRS systems. Average daily weight gain of FRS ducks was higher than in NRS ducks. Feed conversion ratio of FRS ducks was lower than in NRS ducks. There was no difference in acidity, conductivity of pectoralis and leg muscle, and drip loss among the production systems. The conclusion was that NRS proved to be the best production system on welfare traits, while WRS and FRS were the best production systems on growth performance. <![CDATA[<b>Ingestive behaviour of grazing ewes given two levels of concentrate</b>]]> This study aimed to evaluate the influence of concentrate supplementation on the ingestive behaviour of grazing ewes. Twelve pregnant pluriparous sheep were used, six of the Santa Inês breed and six of the Morada Nova breed. The supplement was formulated to supply the animals with two feed levels (0.5% and 1.5% of body weight) of nutrition. The experimental design was a randomized 2 x 2 x 2 factorial arrangement (two breeds, two supplementation levels and two feeding shifts, morning and afternoon) with six replicates per treatment, totalling 24 experimental units. Focal sampling was used to record the time spent on the adopted behaviour at 10-minute intervals for 10 continuous hours, with three replications, totalling 180 records per animal. Sampling started at 07:00. Time spent grazing, ruminating and resting did not correlate with the level of concentrate supplementation. It was expected that concentrate supplementation would reflect directly on forage intake owing to the substitution effect, which causes sheep where the supplement supplied a small proportion of net energy requirement, to have a greater grazing intensity. The two breeds differed in the time spent ruminating or lying, with the Santa Inês sheep spending more time in these activities. Greater intensity of grazing and ruminating occurred in the morning, which is directly related to the climatic conditions of the region. Time of day is a factor that imposes limitations on the feeding behaviour patterns of ewes that are supplemented on pasture. <![CDATA[<b>Diallel analysis for bodyweight involving three genotypes of Nigerian indigenous chickens</b>]]> To evaluate heterosis, reciprocal effect, general and specific combining abilities for bodyweight, a diallel crossing experiment was conducted using three genotypes of Nigerian indigenous chickens: normal (N), frizzle (F) and naked-neck (Na). A total of 601 chicks was hatched from all possible matings between the three genotypes. The chicks used in this study were hatched from a foundation stock of 90 chickens comprising 25 hens and 5 cocks for each of the three genotypes. A mating ratio of 1 male : 5 females was employed. Furthermore, data on bodyweight were scrutinized with complete diallel analysis after they had been corrected for significant effects of hatch of birds using least squares constants. The results revealed that bodyweight (BWT) was significantly influenced by genetic groups with the frizzle-naked (FNa) having the best performance at all ages (4 - 20 weeks) except at hatch, with a mean final BWT of 1173 g at 20 weeks old. The next best performing was its reciprocal, the naked-frizzle (NaF), with a mean final BWT of 1162 g. Furthermore, the FNa gave the best estimates for heterosis and specific combining ability, while the F and NNa gave the best estimates for general combining ability and reciprocal effect, respectively. Therefore, the F genotype as sire and the Na as dam provided the most suitable combination for improved BWT. Furthermore, the use of the Na genotype as dam was more suitable owing to the significant reciprocal effect. <![CDATA[<b>First-time characterization of <i>JY-1-</i>like sequence in goats</b>]]> The JY-1 protein is oocyte specific, and is associated with folliculogenesis and early embryo development, and thus influences the chance of pregnancy. It was the first protein of maternal origin to be described for a single ovulating species, namely cattle. JY-1-like sequences corresponding to 3' coding and the untranslated region have been reported in other vertebrate species. This is the first description of the partial JY-1 (exon 3 and 3'UTR) in a livestock species other than cattle and buffalo. The sequence was characterized in a panel of nine Indian goat breeds, which differ in reproductive traits (twinning percentage and age of sexual maturity). Forty three variations were recorded in the analysed region of goats JY-1 compared with cattle. Nucleotide variations in the codifying region of goats correspond to seven amino acid changes that could affect the biological function of the protein and possibly reproductive differences between goats (higher proportion of multiparous animals) and cattle (mainly uniparous). A novel single nucleotide polymorphism (C15329T) has been identified in Indian goats, which was genotyped in 272 animals from six breeds. Further studies to investigate other regions of the gene and its expression in goat female reproductive tissues would clarify the role of JY-1 in farm animal species that are not primarily uniparous. <![CDATA[<b>Potential enhancing effects of a carbohydrase mixture on phytase efficacy in late-phase laying hens fed wheat-based diets</b>]]> A total of 360 65-week-old Lohmann LSL-Lite laying hens were used in a six-week experiment to examine the potential enhancing effects of a commercial carbohydrase preparation on phytase efficacy. Two cultivars of wheat (Marvdasht and Sardari) were used to formulate basal diets containing 2.2 g or 2.9 g non-phytate phosphorus (NPP)/kg levels. A further eight dietary treatments were formulated by supplementing these diets with a commercial source of phytase individually or together with a carbohydrase preparation, resulting in 12 dietary treatments in a 2 χ 2 χ 3 factorial arrangement. The production performance and egg quality traits were not affected by treatments. Birds receiving a diet with Marvdasht cultivar and 2.2 g NPP/kg exhibited the highest serum concentration of thyroxine. The lymphocyte and eosinophil counts increased and the heterophil counts and the ratio of heterophils to lymphocytes decreased in birds receiving phytase supplementation compared with those receiving phytase and carbohydrase simultaneously. According to the results, the supplementation of wheat-based diets with enzymes in the late phase of egg production does not affect productive performance of laying hens. However, enzymes may have special effects on bird health. <![CDATA[<b>Chemical composition and nutritive value of South African sorghum varieties as feed for broiler chickens</b>]]> Sorghum (Sorghum bicolor (L.) Moench) is the fifth most important grain crop after wheat, rice, maize and barley. It is cultivated for food and feed in America, Asia, Australia and Africa. Newly developed sorghum varieties should be evaluated for their suitability as food and feed. The physical characteristics and proximate composition, total phenolic content, mineral content, amino acid profile and digestibility, and true metabolizable energy of four sorghum varieties were studied. The condensed tannin sorghum varieties PAN8625 and NS5511 had higher total phenolic content and antioxidant activity than the non-tannin varieties PAN8816 and PAN8906. Crude protein content diverged narrowly across the varieties, ranging from 81.2 to 95.4 g/kg DM. Starch and gross energy contents also differed, though varieties that were used had similar total and individual mineral contents. The threonine, leucine, phenylalanine, valine, proline and alanine contents of PAN8625 and PAN8906 were higher than those of NS5511 and PAN8816, which had similar contents. Amino acid digestibility and metabolizable energy of the tannin varieties were generally lower than those of the non-tannin ones. These results indicate that chemical and nutrient composition of sorghum varieties should be considered when selecting for broiler chicken feeding.