Scielo RSS <![CDATA[South African Journal of Animal Science]]> http://www.scielo.org.za/rss.php?pid=0375-158920150002&lang=pt vol. 45 num. 2 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Genetic prediction models and heritability estimates for functional longevity in dairy cattle</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892015000200001&lng=pt&nrm=iso&tlng=pt 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>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892015000200002&lng=pt&nrm=iso&tlng=pt 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>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892015000200003&lng=pt&nrm=iso&tlng=pt 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>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892015000200004&lng=pt&nrm=iso&tlng=pt 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>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892015000200005&lng=pt&nrm=iso&tlng=pt 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>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0375-15892015000200006&lng=pt&nrm=iso&tlng=pt 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.