Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 41 num. 1 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Live animal and carcass characteristics of South African indigenous goats</b>]]> Eighty-nine intact male, castrates and female South African indigenous goats in three age groups (0, 2 - 6 and 8 permanent incisors) and two pre-slaughter conditioning groups; namely, the non-conditioned which were slaughtered within three months of purchase and the pre-slaughter conditioned, which were slaughtered 6 - 10 months after purchase or birth were used. The effect of sex, age and pre-slaughter conditioning on live animal, carcass dimensions and carcass composition were evaluated. The goats were large with live weight, carcass weight and carcass dimensions in the range of the large breeds of southern Africa. They had a high lean and low fat content. Intact males were suited for high chevon yield because they were heavy, had a high lean and low fat content, and losses during dressing and chilling were reduced by improved nutrition. Goats between 2 - 6 teeth yielded heavy carcasses that were comparable to goats in the 8-teeth group, and had proportionately more lean and less carcass fat. The hind limb was ideal for high lean and low fat, high value cuts but the dorsal trunk was bony and yielded less lean. Pre-slaughter conditioning improved the overall size of the goats and reduced the losses during slaughter and chilling. It also improved the lean/bone and lean and fat/bone indices. <![CDATA[<b>Effects of ractopamine and gender on protein turnover in skeletal muscle of implanted steers and heifers</b>]]> Effects of the β-agonist, ractopamine-HCl (ractopamine), on skeletal muscle protein turnover were evaluated in 16 steers (512 kg) and 16 heifers (473 kg). Treatments were arranged in a 2 × 2 factorial design and included gender (steer vs. heifer) and ractopamine (0 or 200 mg/d). Steers were implanted with 120 mg trenbolone acetate and 24 mg estradiol-17β, heifers with 140 mg trenbolone acetate and 14 mg estradiol-17β. Cattle were fed a diet based on steam-flaked maize. Muscle biopsy samples were collected fromm. longissimus and m. biceps femoris on day 0 (prior to ractopamine feeding) and after 14 and 28 d of ractopamine feeding. In vitro protein synthesis rates in m. longissimus tended to be greater for steers than for heifers, but no effect of gender was observed in m. biceps femoris. Gender did not affect in vitro protein degradation rates for either muscle. Ractopamine significantly decreased rates of in vitro protein degradation in m. longissimus, but rates in m. biceps femoris were not affected by ractopamine. Ractopamine did not affect in vitro protein synthesis rates. In general, there were no striking differences between steers and heifers in response to ractopamine, indicating that its effectiveness should be similar between genders. <![CDATA[<b>Effect of supplemental fat in low energy diets on some blood parameters and carcass characteristics of broiler chicks</b>]]> This experiment evaluated the effects of two fat sources on performance, some blood parameters and carcass characteristics of broiler chicks. One hundred and eighty day-old broiler chicks were randomly assigned to five dietary treatments (three replicates of 12 birds per treatment). The experiment was performed as a completely random design (CRD) and birds were fed isoenergetic and isonitrogenous diets containing no fat (control), 20 and 40 g soyabean oil, 20 and 40 g beef tallow/kg feed from 11 -42 d of age. Food intake and body weight gain both increased significantly with supplemental level of both fat sources, the rate in food intake being higher with soyabean oil than with beef tallow. Feed conversion ratio decreased significantly with both sources in the period 29 " 42 d. Serum triglyceride and very low density lipoprotein (VLDL) contents were unaffected by dietary oil inclusion but cholesterol, high-(HDL) and low (LDL) density lipoprotein contents increased significantly with oil level. Serum glucose (GLU) content decreased significantly with increasing oil inclusion. In all cases the blood parameters responded significantly differently to the two supplemental fat sources with the rate of reduction in GLU, cholesterol and LDL, and the rate of increase in TG, HDL and VLDL being greater with soyabean oil than with beef tallow. Liver and abdominal fat percentages increased significantly with supplemental fat inclusion. The results indicate that supplementation of broiler diets with up to 40 g soyabean oil/kg feed significantly improved the performance and reduced serum cholesterol, LDL and abdominal fat in comparison with chicks receiving diets containing beef tallow. <![CDATA[<b>Do broiler chicks possess enough growth potential to compensate long-term feed and water depravation during the neonatal period?</b>]]> Broiler performance to the end of the rearing period may be negatively influenced by delayed access to feed and water immediately after hatch. This study was conducted with 320 Ross 308 broiler chicks, to evaluate the influence of delayed access to feed and water during the neonatal period (0, 16, 32 and 48 h) on performance and gastrointestinal (GIT) growth. The experiment was conducted as a complete randomized design (four replicate, each with 20 chicks). The results showed that extending post-hatch deprivation of feed and water had a significant negative impact on bird performance. Broilers deprived for 48 h had lower body weights, average daily gains and feed intakes compared to the control and to a lesser extent to the other treatments. Average daily gain, daily feed intake and feed conversion ratio were mostly significantly affected by feed and water deprivation regimens during the first week of the rearing period. At marketing age, the negative impact of severe feed and water deprivation on the birds' performance was substantially decreased, though birds with a 48 h delayed access to feed and water had lower average daily gains and feed intakes compared to the control. Birds mortality rate (%) was not affected by feed and water deprivation during the neonatal period. The results also indicated that the relative weights of the jejunum, ileum and liver of birds getting access to feed and water only at 48 h after arrival were significantly lower when compared to the other groups. The broiler carcass characteristics, abdominal fat percentage at 42 days of age, and gastrointestinal measurements at 21 and 42 days of age were not influenced by the different treatments. In conclusion, the results of this experiment confirmed that immediate access to feed and water after placement will ensure the optimal performance of broiler chicks at market age, and that broiler chicks do not have enough potential to fully compensate for growth retardation caused by long-term deprivation of feed and water during the neonatal period. <![CDATA[<b>Expression profiling analyses of porcine <i>MuRF1 </i>gene and its association with muscle production traits</b>]]> Muscle specific RING finger protein-1 (MuRF1) is a member of the muscle specific RING finger protein family, and it is specifically expressed in cardiac and skeletal muscle tissues and is involved in myocyte differentiation, development and morphogenesis. In this study the complete open reading frame (ORF) of the porcine MuRF1 gene consisting of 354 amino acids was obtained and it shared 93% and 90% identity with those of the human and mice, respectively. Using the INRA radiation hybrid panel (IMpRH) technique, the MuRF1 gene was assigned to SSC6q21-26, closely linked to microsatellite markers SW1823 and SW709. The tissue distribution patterns revealed that MuRF1 mRNA was exclusively expressed in cardiac and skeletal muscle tissues. Real-time quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) results displayed that MuRF1 mRNA was up-regulated in Landrace pigs during the prenatal skeletal muscle development stages. A synonymous T/C single nucleotide polymorphism (SNP) was identified in MuRF1 exon 3 and then a Hin6I PCR -RFLP was developed for SNP genotyping in two pig populations. Association of the genotypes with growth and carcass traits showed that different genotypes of MuRF1 were genetically significantly associated with average daily gain from birth to 90 kg and loin muscle area in one experimental population. The study suggested that the porcine MuRF1 gene might affect muscle growth and development, and could be a potential candidate gene for muscle production traits in the pig. <![CDATA[<b>Parameter estimates for reproductive output and product quality traits of ostrich females within breeding seasons</b>]]> Data involving monthly records of egg production (EP), chick production (CP), hatchability (H), mean egg weight (MEW) and mean day-old chick weight (MCW) were analysed using REML procedures. All traits were treated as hen traits. Egg production of young birds increased to reach a peak of approximately 4 to 5 eggs per month relatively late in the breeding season (September to December). Older hens reached a higher peak of 6 to 9 eggs per month earlier in the breeding season (August to September). There was a secondary peak in older birds from November to December. All birds except 2-year olds exhibited evidence of a slump of production during October. Chick production, MEW, MCW and H followed similar trends. The random effects of direct additive genetic, permanent environment (PE), temporary environment (TE " unique hen-year combinations) and service sire (SS) were estimated from the data. Heritability estimates of the direct additive genetic effect (h²a) of the hen were 0.04 for EP, 0.05 for CP, 0.44 for MEW, 0.67 for MCW and 0.02 for H. The estimates of permanent environment (c²pe) as a ratio of phenotypic variance for the four traits (MCW did not exhibit a significant c²pe effect) were 0.08, 0.08, 0.09 and 0.11, respectively. The effect of service sire as a ratio (c²ss) was significant but relatively low for all traits, ranging from 0.04 for MEW and MCW to 0.06 for CP. Monthly EP and CP were highly correlated at all levels, ranging from 0.74 for the TE correlation to unity (1.00) for the genetic correlation. Egg production was favourably correlated with H at a genetic level (0.98). The genetic correlations of EP and CP with MEW and MCW were variable and in some cases antagonistic as is often found in poultry. The genetic correlations of H with MEW and MCW were positive (0.52 and 0.47, respectively). As expected, the genetic correlation of MEW and MCW was very high at 0.94. The results indicate that selection for improved reproduction (reproductive output and product quality traits) in ostriches is possible. Selection is unlikely to be complicated by unfavourable correlations with H, MEW and MCW.