Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 38 num. 3 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Male broiler performance and nocturnal feeding under constant 8-h or 16-h photoperiods, and various increasing lighting regimens</b>]]> This paper describes the responses of two genotypes of male broilers to constant 8- and 16-h photoperiods, and to an abrupt transfer from 8 to 16 h at 10, 15 or 20 d. Body weight, feed intake, and feed conversion efficiency were not significantly different at any stage during the 35 d study. Mortality and the incidence of Sudden Death Syndrome were similar for all lighting groups at 35 d. When these data were pooled with previously reported data for female broilers, growth and feed conversion efficiency post 21 d and through to depletion for constant 8-h and birds transferred from 8 to 16 h at 20 d were significantly superior to constant 16-h birds. Constant 8-h birds ate about half their feed during the dark period, whilst 16-h birds consumed no more than 10%. Birds which had been started on 8 h and transferred to 16 h at 10, 15 or 20 d reduced their rate of nocturnal feeding when changed to the longer photoperiod, however, they still consumed more feed in the 8-h dark period than birds that had always been given 16 h illumination. Cobb and Ross genotypes responded similarly to all lighting treatments. <![CDATA[<b>Genetic parameter estimates for growth traits of Large white pigs in Kenya</b>]]> Variance components and genetic parameter were estimated for piglet growth traits of Large White (LW) pigs managed under intensive production systems in Kenya. Data were on piglet performance of LW pigs born between 1982 to 1996. Growth performance traits of the piglets that were considered, were body weight (BW, in kg) at birth (BW0), three weeks (BW3), eight weeks at weaning (BW8), 12 weeks ( BW12), 24 weeks (BW24) and 36 weeks (BW36); and average daily gain (g/day) from birth to eight weeks (DG08) and from weaning to 24 weeks (DG8-24). Variance components and genetic parameters were estimated using univariate and multivariate animal models. Direct heritability estimates from univariate analyses were 0.38, 0.24, 0.47, 0.39, 0.36 and 0.26 for BW0, BW3, BW8, BW12, BW24 and BW36, respectively. Maternal heritabilities were 0.42, 0.25 0.15 and 0.18 for BW0, BW3, BW8 and DG0.8, respectively. Genetic correlations among growth traits were positive and ranged from 0.45 to 0.98 while phenotypic correlations ranged from 0.54 to 0.95. Early piglet growth was highly heritable and under the influence of maternal effects. Selection programmes for genetic improvement of early growth performance should be based on models that account for direct and maternal genetic and litter effects. <![CDATA[<b>Growth and carcass characteristics of male dairy calves on a yeast culture-supplemented diet</b>]]> This experiment was carried out to study the effect of the inclusion of a yeast culture in the diet of feeder dairy calves on their growth and carcass characteristics. Thirty male Friesian calves were randomly allocated to two groups of 15 each (treatment and control). The calves were fed a total mixed ration for a period of 294 days and then slaughtered to obtain carcass measurements. The yeast culture was added to the diet of the treatment group at a level of 20 kg yeast culture/ton of feed. The addition of the yeast culture did not affect final weight, average gain or average daily gain, but reduced total and daily dry matter intakes. Feed conversion ratio was not affected by treatment. Yeast culture supplementation had no effect on fasting weight or cold carcass weight, dressing percentage nor on non-carcass components. Differences in back-fat thickness and in the weight and percentage of carcass cuts were not significant between treatments. Similarly, carcass characteristics and quality measures did not show any significant differences between treatments. In this experiment the inclusion of a yeast culture in the finishing off diet of dairy calves had no effect on their growth rate, feed conversion ratio, carcass characteristics or meat quality. <![CDATA[<b>Effects <i>of post mortem</i> temperature on rigor tension, shortening and pH in ostrich muscle</b>]]> Fully developed rigor mortis in muscle is characterised by maximum loss of extensibility. The course of post mortem changes in ostrich muscle was studied by following isometric tension, shortening and change in pH during the first 24 h post mortem within muscle strips from the muscularis gastrocnemius, pars interna at constant temperatures of 7 °C and 37 °C. Maximum shortening was significantly higher at 37 °C (33.4 ± 3.57%) than at 7 °C (10.7 ± 2.63%). The rate of rigor development was temperature dependent, reaching a maximum tension at 4.08 ± 3.89 h post mortem in muscle strips at 37 °C; while at 7 °C maximum tension was reached at 10.5 ± 6.47 h post mortem. It was concluded that the completion of rigor occurred at the point of minimum pH. <![CDATA[<b>Genetic variation of indigenous chicken breeds in China and a Recessive White breed using AFLP fingerprinting</b>]]> Amplified fragment length polymorphism (AFLP) using six marker combinations were applied to detect genetic variation and phylo genetic relationships among 12 indigenous Chinese chicken breeds and a Recessive White chicken breed introduced from France. The DNA was pooled for each group. Polymorphic bands, breed-specific bands and genetic similarity coefficients of 13 chicken breeds were derived from the AFLP data. A total of 280 polymorphic bands was generated from which nine specific bands were observed for the Shouguang and the Dongxiang Dark chicken. One specific band was observed in the pooled DNA of the Jiuyuan Dark chicken, the Xingyi Bantam chicken and the Recessive White chicken. The genetic similarity coefficients among the 12 indigenous Chinese chicken breeds varied between 0.635 - 0.860, and 0.188 - 0.360 between the Recessive White and the indigenous Chinese chicken breeds. The UPGMA based tree yielded two clusters for the 13 chicken breeds, with the Recessive White chickens forming a distinct cluster. In summary, the genetic similarity coefficients and the UPGMA tree of the 13 chicken breeds were consistent with their breeding history and geographical distribution. These results provide useful data with regard to the genetic diversity, genetic relationships and identification of chicken breeds in China. <![CDATA[<b>Broilers <i>(Gallus gallus)</i> are less stressed if they can smell a mother odorant</b>]]> Performance, physiological and behavioural parameters of two groups of domestic chickens were compared. Chickens were raised in classical commercial conditions in buildings housing 12000 birds. One group acted as a control, while the environment of the other was perfused with MHUSA (Mother Hens' Uropygial Secretion Analogue), a synthetic analogue of a mother-hen odorant secretion which has shown its potential in reducing stress-related reactions in chickens. At the end of the rearing period the animals treated, appeared less stressed, as determined by a range of behavioural and physiological parameters. Even if there was no treatment effect on live weight, the carcasses of MHUSA treated animals were heavier and showed less scarring from fights. The influence of MHUSA was proven when it was removed from the atmosphere. Sex and age appeared to have an importance with regard to the action of MHUSA on the number of suffocated animals. There were no differences between the two groups in a variant of the tonic immobility test. Thus this semiochemical appears to have a positive effect on broiler welfare. <![CDATA[<b>Effects of ovariectomy and anabolic steroid implantation on the somatotrophic axis in feedlot heifers</b>]]> A 2 x 2 factorial experimental design was used to evaluate effects of ovariectomy and implantation (200 mg trenbolone acetate and 28 mg estradiol benzoate; Synovex-Plus) on the performance, serum urea nitrogen, serum insulin like growth factor -1 (IGF-1), and mRNA expression of hepatic IGF-1, growth hormone (GH) receptor and estrogen receptor-a as well as pituitary GH, estrogen receptor-a and GH releasing hormone receptor in feedlot heifers. Thirty-two British x Continental heifers were randomly assigned to either an ovariectomized (OVX) or intact group and then to either a control group or a Synovex-Plus implant group. Heifers were fed a 900 g/kg concentrate steam-flaked maize based diet for 42 d. Liver biopsies were taken before OVX for baseline expression of IGF-1, GH receptor and hepatic estrogen receptor-a, which did not differ between treatment groups. Blood and body weight (BW) were taken on d 0, 28, and 42 and one heifer/pen was slaughtered on d 42 for liver and pituitary tissue samples. Initial and final BW did not differ due to OVX or implant. No gender x treatment interaction was observed for average daily gain (ADG) or final BW. Neither OVX nor implant affected ADG for the final 14 d of the feeding period, but 28 and 42 d ADG were greater in implanted than in control heifers. No 2- or 3-way interactions with day were observed for serum urea nitrogen. Serum urea nitrogen was greater in control heifers than in implanted heifers, but gender had no effect. Both implant and OVX increased serum IGF-1 and a gender x treatment interaction was observed. Neither gender nor implant treatment affected hepatic estrogen receptor-a, hepatic IGF-1, hepatic GH receptor, GH releasing hormone receptor, GH, or pituitary estrogen receptor-a. Data indicate that implanting heifers with Synovex-plus increases serum IGF-1, but the reason for this increase cannot be explained by mRNA expression of key somatotropic genes in the present study. <![CDATA[<b>Effects of different raising systems on colour and quality characteristics of Turkish pekin duck meats</b>]]> The current trial was conducted to determine the influence of different raising systems on the meat quality properties of male Turkish Pekin ducks. Ninety male ducklings were randomly allocated to three experimental groups: an animal-fish integrated farming group (IG), a non-animal-fish integrated farming group (NIG) and a poultry house group (PHG). All ducklings were fed a starter diet from weeks 2 to 6 and a finisher diet from weeks 6 to 10. Feed and water were offered ad libitum. At the end of the trial all ducks were slaughtered and the carcasses were stored at 3 °C for 24 hours, after which L*, a* and b* values of the carcass skins were measured. After standard dissection of carcasses, pectoralis muscles were obtained on which pH, colour (L*, a*, b*, C and H), total aerobic mesophilic, total aerobic psychrotrophic, lactic acid bacteria, Micrococcus/Staphylococcus, yeast-mould and Enterobacteriaceae counts were determined. The different raising systems of the ducks had significant effects on the pH, total aerobic mesophilic, Enterobacteriaceae, and L* and b* values of the pectoralis muscle. The lowest pH, total aerobic mesophilic and Enterobacteriaceae counts were found in the PHG group. The lowest L* values for the pectoralis muscle were found in the IG group while the highest a* value was recorded in the IG group. Significant differences in skin colour were observed between the experimental groups. For all production groups, all microbial counts were found to be within acceptable ranges. However, pH, total aerobic mesophilic and Enterobacteriaceae results were found to be lower in the PHG group than in the other groups. Different raising systems were thus found to affect the meat and skin colour of ducks, which may influence the preference of consumers. <![CDATA[<b>Procedures for estimation of genetic persistency indices for milk production for the South African dairy industry</b>]]> Procedures have been developed for calculation of a Persistency Index for South African dairy breeds. This index is based on the Canadian Persistency Index, which is simple and easy to understand. Data used in this study were test-day records of the first three lactations, as included in the National Dairy Genetic Evaluations of South Africa, of the Ayrshire, Guernsey, Holstein and Jersey breeds. Interpolation, using the Wilmink curve, was done on these test-day records to calculate 60-day and 280-day yields for each cow and lactation. Variance components have been estimated for these yields to be used in breeding value estimations, using bivariate evaluations and a repeatability model. To obtain independence of persistency from total milk yield, 305-day milk yield estimated breeding values were included as covariates in the genetic model for estimation of breeding values for 60- and 280-day yields. The Persistency Index will be released for sires with progeny following each national dairy genetic evaluation, allowing the South African dairy industry to select for changes in persistency in future. <![CDATA[<b>Effects of genotype and egg weight on hatchability traits and hatching weight in Japanese quail</b>]]> The effects of genotype and egg weight on hatching weight, fertility, hatchability of fertile eggs and incubated eggs were investigated in Japanese quail. The birds were obtained at an age of 20 weeks from four genetic lines selected for 11 generations for either a high (HL) or a low body weight (LL) at five weeks of age, a randomly bred control line (C) and a layer line (L) selected for egg production over 120 days. Eggs were allocated according to their weight to <10.0 g, 10.1 - 11.0 g, 11.1 - 12.0 g, 12.1 - 13.0 g and &gt;13.1 g groups. There was a significant difference between groups in terms of hatching weight, fertility, hatchability of fertile eggs and hatchability of incubated eggs. The highest hatching weights were recorded in the &gt;13.1 g egg weight group. Genotype affected egg weight significantly, with the highest egg weights recorded in the HL genotype and lowest in the LL genotype. There was a significant positive phenotypic correlation (r = 0.72) between egg weight and hatching weight, and hatching weight increased with an increase in egg weight. <![CDATA[<b>Effects of implant programs on performance, carcass characteristics, and lipogenic gene expression in Holstein steers</b>]]> Nineteen Holstein steers were randomly assigned to one of four treatments; no implant (CON); 36 mg zeranol (Ralgro) on d 0 and 20 mg estradiol benzoate plus 200 mg progesterone (Synovex S) on d 84 and 169 (RSS); Ralgro on d 0, Synovex S on d 84, and 28 mg estradiol benzoate plus 200 mg trenbolone acetate (Synovex-Plus) on d 168 (RSP); or Ralgro on d 0, and Synovex-Plus on d 84 and 168 (RPP). Subcutaneous adipose biopsies were collected before implanting (d -14) and on d 97, 182 and at slaughter for measurement of mRNA concentrations of fatty acid synthetase (FAS) and acetyl CoA carboxylase (ACC). Implanted steers had greater average daily gain, dry matter intake, final body weight, hot carcass weight and longissimus muscle area than controls. No differences were observed in feed conversion ratio (FCR), dressing percentage, 12th rib backfat, kidney pelvic and heart fat, marbling score, yield grade or Warner-Bratzler shear force values. Treatment did not affect serum metabolite concentration. Real Time PCR analysis of subcutaneous adipose mRNA concentrations indicated implants decreased ACC and FAS expression on d 97. ACC expression was increased significantly for RPP compared to RSP on d 182 and increased for the average of RSP and RPP compared to RSS on d 259, whereas FAS expression was not affected on d 182 or 259. Results suggest that lipogenic gene expression is affected by anabolic implants, particularly early in the feeding period and may partially explain how implants affect carcass characteristics, albeit a limited number of steers were used. <![CDATA[<b>Acceptability of chevon from kids, yearling goats and mature does of indigenous South African goats</b>: <b>A case study</b>]]> Consumer sensory evaluations of oven-roasted goat and sheep m. longissimus dorsi samples were conducted in two series to determine the acceptability of chevon from indigenous South African goats to consumers. Chevon samples were from goat carcasses of known description. In series I, castrate and female goats and female sheep, all with 2 - 6 permanent incisors, were compared. Castrate males were significantly heavier and yielded heavier carcasses than the female goats. Nonetheless, the two groups did not differ significantly in carcass and meat characteristics. Cooking losses from mutton samples were significantly higher than losses from chevon from female goats only. In series II, male kids (milk teethed), old does (8 permanent teeth) and sheep (2 - 6 permanent teeth) were compared. Does were heavier at slaughter, but the mean carcass weight did not differ significantly from that of the kids. There were no significant differences between the does and kids in carcass tissue composition and sarcomere lengths. The pHu of does was significantly higher than that of kids. Cooking losses from mutton and chevon samples in series II did not differ significantly. Amongst the consumer characteristics, level of education was the most important determinant of consumer acceptance of the sensory attributes and intended frequency of consumption in both series. Population group was a significant factor in the judgement of the more diverse meats of series II only. Sensory evaluations indicate that all meat types were highly acceptable to the consumers who on average were willing to eat any of the meats at least once a week. The study indicated that chevon from indigenous South African goats is acceptable to consumers and may be as acceptable as mutton, provided that the meat is from goats of about two years of age or younger. <![CDATA[<b>Effects of L-carnitine in layer diets containing different fat sources and energy levels on hen performance and egg quality</b>]]> The study was conducted to determine the effects of feeding diets containing two levels of metabolisable energy (normal or low) and three sources of fat (palm-, sunflower- or fish-oil) with or without L-carnitine (0 or 500 mg/kg diet) on the performance and egg quality parameters of Brown egg-type laying hens. The hens receiving the low energy diet had significantly higher body weights and feed intakes (FI) than the birds on the normal energy diet, but their feed conversion ratio (FCR) was poorer. L-carnitine in the diet containing sunflower oil (SO) increased FI significantly, resulting in a poorer FCR. However, the FI and FCR were higher when the fish oil (FO) was added to diets without L-carnitine compared to the other diets. The palm oil (PO) supplemented diet without L-carnitine significantly decreased the specific gravity of the eggs. L-carnitine inclusion into the diet containing PO significantly increased the Haugh unit and albumen index of the eggs, while the inclusion of FO in the low energy diet increased the Haugh unit and albumen index significantly. However, when PO was included these parameters decreased significantly. The addition of L-carnitine to the normal energy diet reduced the pH of the egg yolk, while it increased egg yolk pH when added to the low energy diet. The inclusion of FO in the low energy diet resulted in a significant increase in yolk pH. Albumen pH was significantly decreased by dietary L-carnitine supplementation, but increased when the diet low in energy contained FO, as well as the normal energy diet containing SO. The inclusion of FO to both the normal and low energy diets, except the low energy diet with L-carnitine, improved the breaking strength of the eggshells. Similarly, SO and PO inclusion to low energy diets with L-carnitine increased eggshell breaking strength. The supplementation of PO and L-carnitine to the diet enhanced the Haugh unit and albumen index. Palm oil and the normal energy diet decreased egg yolk indices.