Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 40 num. 3 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Relationship between production characteristics and breeding potential of 25-month old extensively managed Bonsmara bulls</b>]]> The aim of the study was to determine if the breeding potential of 25-month old Bonsmara beef bulls could be predicted from production characteristics. Forty-one Bonsmara bulls were included in an on-farm performance test (also known as the Phase D growth test) for a period of 180 days. At an average age of 24.7 months the bulls were subjected to a libido test and overall breeding soundness evaluation (OBE). The bulls were categorised into independent breeding potential categories according to the scores they obtained for the measured reproductive traits. The categories included sperm morphology and motility. One-way ANOVA revealed that none of the production traits measured had a significant effect on the different breeding potential categories. A positive correlation (r = 0.33) was recorded between pre-weaning growth rate and percentage morphologically normal sperm, while a negative correlation (r = -0.36) was recorded between total acrosomal- and flagellar sperm defects and pre-weaning growth. A positive correlation was demonstrated between sperm motility and pre-weaning growth (r = 0.36), and a consequent negative correlation (r = -0.38) between the percentage aberrant sperm movement and pre-weaning growth. The correlation between the percentage morphologically normal sperm and percentage progressively moving sperm was r = 0.50, while the correlation between percentage morphologically normal sperm and aberrant and immotile sperm was r = 0.48 for both variables. The number of total defects correlated highly significantly with flagellar and acrosomal defects (r = 0.72 and r = 0.93, respectively) and correlated poorly with the total number of nuclear defects (r = 0.32). These results suggest that total sperm defects were mainly due to acrosomal and flagellar defects, rather than nuclear defects and as the percentage morphologically normal sperm decreased, the motility also decreased. High growth rates before weaning may have a positive effect, while high growth rates after weaning may have a negative effect on the breeding potential of a bull. None of the measured reproductive and production traits had a significant effect on libido score and thus, cannot be used to predict the libido of young extensively maintained bulls. <![CDATA[<b>Performance and carcass characteristics of Japanese quail as affected by sex or mannan oligosaccharides and calcium propionate</b>]]> The effect of sex and the supplementation of the prebiotic, mannan oligosaccharides (MOS), the acidifier, calcium propionate (CPr) or their combination in the feed of Japanese quail (Coturnix japonica) on their performance and carcass quality was examined in this experimentation. Three hundred, 1-day old Japanese quail were divided into four groups with three replicates each. One group that served as control received the basal diet. The three experimental diets consisted of the basal diet to which either 6 g CPr/kg, 2 g MOS/kg or both 2 g MOS/kg and 6 g CPr/kg was added. The body weight, feed consumption, feed conversion ratio (kg feed/kg weight gain) and mortality were examined at weekly intervals. At the end of the 42-day feeding period the birds were slaughtered, the carcasses were processed and the carcass weight, carcass dressing percentage and carcass part percentages were calculated. Also, the breast meat composition and its fatty acid profile were analyzed. Results showed that the female quail had a higher body and carcass weight and liver to live weight percentage, whereas they had lower carcass dressing percentage than males. The dietary addition of MOS increased body and carcass weight, whereas it decreased liver to live weight percentage and crude fat content of the breast meat. The dietary addition of CPr lowered carcass dressing percentage and ash content of the breast meat. Interactions between the two examined supplements were observed in feed consumption, feed conversion ratio and carcass weight. An interaction between MOS and sex was observed on carcass weight. It was concluded that MOS and calcium propionate can be used effectively in Japanese quail diets. <![CDATA[<b>Interactive effect of dietary protein level and zilpaterol hydrochloride on feedlot performance and meat quality of steers</b>]]> Bonsmara type steers were used to determine the effect of dietary zilpaterol hydrochloride (ZH) in combination with different dietary crude protein (CP) levels (100, 120 and 140 g CP/kg) on growth performance and meat quality. Treatment groups (T) consisted of 12 steers each. T1 - 100 g CP/kg + 0.15 mg ZH/kg live weight (LW); T2 - 120 g CP/kg + 0.15 mg ZH/kg LW; T3 - 140 g CP/kg + 0.15 mg ZH/kg LW and T4 - 120 g CP/kg + 0 mg/kg LW. Steers received the diets from an initial LW of 278 kg and fed to a target mass of 390 kg. After a seven day ZH withdrawal period the steers were slaughtered and carcasses electrically stimulated. Samples from m. longissimus thoracis, m. semitendinosus and m. triceps brachii were kept in airtight polyethylene bags and matured for ten days at 4 ºC. Zilpaterol treatment increased the average daily gain (ADG) non-significantly (NS) by 9.6%. Zilpaterol treatment improved feed conversion ratio (FCR) by 20% (NS). T2 showed a significant 39.4% improvement in FCR in comparison with T4. Warner-Bratzler shear force (WBSF) of m. semitendinosus and m. biceps brachii samples differed between ZH treated groups. Cooking loss (CL) for m. longissimus thoracis was lower for T2 in comparison with T1, T3 and T4. ZH treatment for 35 days, electrical stimulation and a maturation period of 10 days generally left the WBSF and CL unaffected while the FCR in combination with 120 g CP/kg improved significantly. <![CDATA[<b>Variation in nutrient composition and structure of high-moisture maize dried at different temperatures</b>]]> Maize cobs with grains were harvested at a relatively high moisture content (23%) from the field in northern New South Wales, Australia. The cobs were divided into four categories and dried in the sun or artificially in a forced draft oven at 80, 90 or 100 ºC for 24 h. The samples were subjected to proximate and detailed nutrient analyses. In vitro nutrient digestibility and ultra structure of samples were also assessed. Proximate analysis of maize revealed that dry matter (DM, 980 g/kg) and ash (1.32 g/kg) content were highest in the 100 ºC samples, but crude protein (98.4 g/kg), ether extract (45.0 g/kg) and phytate-P (1.8 g/kg) content were the highest in the sundried samples. Gross energy was little affected by heat treatment but the metabolizable energy value increased with rising temperature. The concentrations of most of the amino acids but not lysine were increased in samples dried at 80, 90 and 100 ºC in comparison to sun drying. Total starch, resistant starch (RS) and amylose content were slightly increased by artificial drying while amylopectin was reduced under the same conditions. Starch content (691 g/kg) was highest at 80 ºC while RS (363 g/kg) and amylose (304 g/k) were lowest in the same batch. The mineral concentration of samples decreased with increasing temperature except copper, which was slightly increased. The soluble non-starch polysaccharide (NSP) content was increased while the insoluble NSP decreased with increasing temperature. The morphological structure of maize observed under a scanning electron microscope showed some shrinkage of starch granules as a consequence of artificial drying temperature. In vitro digestibility of DM was improved as a result of artificial drying of high moisture maize but starch digestibility was reduced. It may be inferred that the nutritive value of maize grain varies with drying temperature and drying process. These differences may explain changes in nutritive value of the grain when fed to chickens. <![CDATA[<b>Characteristic of slaughter value and meat quality of three synthetic pig lines</b>]]> The aim of the study was to evaluate the quality of meat in different lines of pigs with consideration of the intramuscular fat level of the longissimus muscle. The research was conducted on 60 pigs from three pig lines, P76, Redone and Galia, (20 gilts in each group), slaughtered at ca. 105 kg live weight. The percentage meat in the carcass and hot carcass weight were estimated. Samples were taken from the longissimus muscle. The pH value after 1, 3 and 24 h post mortem, natural drip loss, cooking yield and parameters of meat colour were measured. Furthermore, fat level and glycolytic potential (GP) of the muscle were determined. Intramuscular fat level was determined chemically, and marbling on the basis of sensory evaluation according to a Japanese photographic standard. The results showed significant differences between lines in slaughter value of carcasses and for pH3, pH24, GP, colour parameters and marbling of raw meat. The P76 line was characterised as the most meaty line with satisfactory meat quality. The Redone line was characterised by meat with the highest intramuscular fat content and marbling. <![CDATA[<b>Effects of ratios of non-fibre carbohydrates to rumen degradable protein in diets of Holstein cows: 1. Feed intake, digestibility and milk production</b>]]> To evaluate the effect of different ratios of non-fibre carbohydrates (NFC) to rumen degradable protein (RDP) on lactation responses, digestion and dry matter intake (DMI), nine multiparous mid-lactation Holstein cows, averaging 171 ± 17 days in milk and 24.1 ± 3.3 kg of milk/d were assigned to a 3 × 3 Latin square design. The total mixed rations (TMR) included 45% forage on a dry matter (DM) basis and 55% concentrates. The RDP (g/kg of DM) and NFC : RDP ratios of diets were respectively: 1) 98 and 4.10 (LRDP), 2) 108 and 3.71 (MRDP), 3) 118 and 3.34 (HRDP). Ratios were achieved through altering the RDP content of the diets while the NFC was held constant at 401 g/kg of DM. Urea was supplemented as a source of RDP to decrease the ratio. DMI and organic matter intake (OMI) were affected by treatment and tended to decrease linearly from LRDP to HRDP. Crude protein intake (CPI) increased linearly as the amount of RDP in the diets increased. Apparent organic matter digestion in the total tract decreased significantly in the HRDP diet. Percentage of protein and solid non-fat (SNF) and concentration of milk urea-nitrogen (MUN) in milk increased linearly when cows were fed diets with the higher amounts of RDP. Results showed that low producing cows are less likely to respond to altering NFC : RDP ratios than high producing cows, but digestibility in the MRDP treatment was higher and RDP level equal to 108 (g/kg of DM). A NFC : RDP ratio equal to 3.71 was useful and recommendable for mid-lactation dairy cow. <![CDATA[<b>Effects of ratios of non-fibre carbohydrates to rumen degradable protein in diets of Holstein cows</b>: <b>2. Rumen and plasma parameters and nitrogen metabolism</b>]]> Nine multiparous mid-lactation Holstein cows, averaging 171 ± 17 days in milk and producing 24.1 ± 3.3 kg of milk/d were assigned to a replicated 3 × 3 Latin square design to study the effects of altering the non-fibre carbohydrates (NFC) to rumen degradable protein (RDP) ratios on rumen and plasma parameters and nitrogen (N) metabolism. Diets were based on a barley concentrate and 45 forage to 55 concentrate ratio. Rumen degradable protein (g/kg) and NFC : RDP ratios averaged 98 and 4.10; 108 and 3.71 and 118 and 3.34 for the LRDP, MRDP and HRDP treatment diets, respectively (dry matter (DM) basis). Ratios were achieved through altering the RDP content of the diets while NFC was held constant at 401 g/kg DM. Urea was supplemented as a source of RDP to decrease the ratio. The effect of treatments on NH3-N concentration in rumen fluid and plasma urea nitrogen (PUN) was significant and increased linearly. Nitrogen intake, absorbed N and urinary N increased linearly between LRDP to HRDP. As a proportion of N intake, faecal N tended to decrease linearly from the LRDP diet to the HRDP diet, i.e. as dietary RDP increased. As a proportion of N apparently absorbed, milk N tended to decrease linearly from LRDP to HRDP as dietary the NFC: RDP ratio decreased. Results showed that indicators of the metabolic efficiency of N were more affected than milk yield, confirming that low producing cows are less likely to respond to altering NFC : RDP ratios. Hence, balancing rations to further improve the N utilization efficiency may be of a higher priority. <![CDATA[<b>Chemical characteristics of red hartebeest (<i>Alcelaphus buselaphus caama</i>) meat</b>]]> The aim of this study was to determine the effect of region (Qua-Qua, Maria Moroka, Sandveld and Tussen die Riviere) and gender on carcass characteristics and chemical composition of meat from the red hartebeest. The parameters measured on 29 red hartebeest included body weight, carcass weight, dressing percentage, proximate composition, fatty acid, cholesterol, amino acid and mineral content. The average carcass weight of males (79.3 kg) was significantly higher than that of females (56.0 kg); however, there was no difference in dressing percentages. The animals obtained from the Qua-Qua region had the highest lipid content (1.3 g/100 g meat sample) compared to hartebeest sampled in other regions. Differences in concentrations of individual fatty acids, amino acids and minerals were minor and of no practical value. The ratio of polyunsaturated to saturated fatty acids (0.78) is above the recommended 0.7 and therefore has positive implications for human health. These nutrient values determined in meat from red hartebeest could be incorporated into human food composition tables. These results will also be of value to the South African game meat exporters who may wish to market their products in terms of their nutritional value in order to compete with meat from domestic livestock or international venison products. In such cases, it is required by law (both locally and internationally) to provide adequate nutritional labelling. <![CDATA[<b>Effects of whey and molasses as silage additives on potato hash silage quality and growth performance of lambs</b>]]> The aim of the study was to determine the effect of whey or molasses on the fermentation quality when added to potato hash silage. In addition, lamb performance, digestibility and feed intake of diets containing potato hash silage were compared with a diet containing maize silage (MSd). Potato hash silage (treated with no additive, or whey, or molasses) and MS were produced in 210 L drums for 90 days and the fermentation quality of the silages was determined thereafter. Diets were formulated and fed ad libitum to 32 South African Dorper lambs (23.5 ± 0.873 kg live weight) for 63 days. A digestibility study was conducted during the last week of the study. The untreated potato hash silage (UPHS) was poorly fermented as indicated by higher concentrations of butyric acid, ammonia-N and pH compared to the other silages. Higher dry matter intake (DMI) and daily weight gains (218 and 250 g/d) were obtained with MSd and molasses treated potato hash silage diet (MPHSd) compared to the other diets. Nutrient digestibility was lower in the UPHS diet compared to the other dietary treatments. It was concluded that the fermentation quality of potato hash was improved with the addition of whey and molasses. Furthermore, growth performance was higher with the MSd and MPHSd than of the other treatments, suggesting that MPHSd can safely replace MSd in a lamb diet at a dietary inclusion level of 20% without any adverse effect on animal performance. <![CDATA[<b>Effects of glycine and glutamic acid supplementation to low protein diets on performance, thyroid function and fat deposition in chickens</b>]]> Consumption of low crude protein (CP) diets causes elevation in fat accumulation in chickens, and this effect is independent of dietary essential amino acid levels. Thyroid hormones, because of their metabolic regulatory characteristics, might be an effective factor in lipogenesis. Therefore, a study was conducted to investigate the influence of low CP diets on hormonal function of the thyroid. Two hundred and sixteen male broiler chicks, 10 - 25 days of age, were fed experimental diets that contained 230, 210, 190 and 170 g CP/kg with adequate amounts of total and digestible essential amino acids at or above NRC (1994) recommendations. Two other diets were the same as the 190 and 170 g CP/kg diets but contained additional glycine and glutamic acid. Reduction in CP below 190 g/kg led to a decline in body weight and feed intake and an increase in fat deposition in body, as would be expected. Plasma T4 concentration decreased significantly in the birds on the 170 g CP/kg diet and supplementation of glycine and glutamic acid had no effect on hormonal levels of the thyroid despite the reduction in whole-body and abdominal cavity fat deposition. Plasma T3 concentration was not affected. Therefore, it is concluded that a reduction in circulatory levels of T4 that occurs in broiler chicks fed diets containing below 190 g CP/kg though with adequate essential amino acids, may be an effective method of increasing fat deposition. <![CDATA[<b>Effects of cladode age on biomass yield and nutritional value of intensively produced spineless cactus for ruminants</b>]]> A randomized complete block design with five replications was used to assess biomass yield, in vitro dry matter digestibility (IVDMD) and nutritional value of spineless cactus (Opuntia ficus-indica) produced under drip irrigation and fertilization. Cladodes were harvested from an established plantation at 30, 37, 45, 60, 75 and 90 d of growth. Weight per cladode increased linearly and length increased quadratically with maturity. Biomass yield (t/ha), gross energy (GE), dry matter (DM), crude protein (CP), neutral detergent fibre and acid detergent fibre increased quadratically with maturity. Thus, the curve became asymptotic at 60 d of growth (28.9 ± 2.1 cm). As growth progressed, concentration of CP and nitrates decreased, and that of fibre increased. In vitro solubility, potential digestibility and digestibility rate of DM decreased linearly with increased maturity of the cladodes. However, there was a quadratic effect of maturity on total digestibility of DM. Thus, the curve became asymptote at 75 d. The optimal yield of nutrients, nutritional value and IVDMD of cladodes were recorded between 60 and 75 d of age when they were 29 to 31 cm in length. <![CDATA[<b>Frozen rumen fluid as microbial inoculum in the two-stage <i>in vitro</i> digestibility assay of ruminant feeds</b>]]> This study was carried out to investigate the possibility of using frozen rumen fluid (RF) as an inoculum source in the determination the in vitro dry matter digestibility (IVDMD) of ruminant feeds. In the first experiment six roughages (barley straw, wheat straw, lentil straw, wheat silage, maize silage and lucerne hay) and six different compound feeds (two dairy cattle, two beef cattle, one ram lamb and one lamb finishing compound feeds) were chosen as test material. Two different types of cryoprotectants (5% glycerol vs. 5% dimethyl sulfoxide, DMSO) and two types of freezing methods (liquid nitrogen vs. deep freezing) were used to preserve the RF. Fresh RF was used as the control. In response to the results of the first experiment, a second experiment was conducted to establish if microbial digestibility could be improved by extending the duration of incubation of the roughages from 48 to 60, 72 or 96 h. When using the RF inoculum treated with 5% DMSO and frozen in liquid nitrogen, the IVDMD of the compound feeds were similar to those of the control. However, when the 5% DMSO treated inoculum was frozen in the deep freezer, some of the compound feeds had similar IVDMD values to the control but not all. Lower IVDMD values were recorded when glycerol was used as a cryoprotectant. In the case of the roughages the use of both freezing methods and cryoprotectants resulted in lower IVDMD values compared to the control. In the second experiment the increasing of the duration of incubation of roughages from 48 to 72 h improved their IVDMD to values similar to that of the control. This suggested that the length of the incubation of roughages should be 72 h instead of 48 h when using inocula treated with 5% DMSO as a cryoprotectant and frozen in a deep freezer. However, further research is required before frozen RF can be recommended as source of inoculum. <![CDATA[<b>Effects of dietary boron on performance, egg production, egg quality and some bone parameters in layer hens</b>]]> In this study dietary boron at different doses (0, 25, 50, 100 and 200 mg/kg feed) was supplemented to layers from 4 to 64 weeks of age. There was no significant difference between treatments with respect of mortality, egg production, egg weight, egg mass and cracked eggs. Significant increases were observed in body weight as age rose. Body weight was not affected by dietary boron supplementation at 16 and 40 weeks of age. At 64 weeks of age boron additions of 50, 100 and 200 mg/kg to the diet resulted in significant lower body weights than that of the control group. Egg quality parameters; albumen height and Haugh units, were improved when 25 or 50 mg boron/kg diet was supplemented above the other treatments. Shape index, shell thickness, shell breaking strength were not affected by treatments, though 25 mg boron/kg diet tended to increase shell breaking strength. Tibia bone strength and phosphorus content in the tibia and femur were not affected by boron supplementation. Boron supplementation at 25 and 50 mg/kg significantly increased femur bone strength, and ash and calcium content of the tibia and femur bones. Concentration of boron in bone increased with the increase in dietary boron. <![CDATA[<b>CuZnSOD gene expression and its relationship with anti-oxidative capacity and pork quality</b>]]> The antioxidant enzyme, copper zinc superoxide dismutase (CuZnSOD) plays an important role in protecting tissues from damage by reactive oxygen species (ROS) reactions. The objective of this investigation was to determine the CuZnSOD mRNA level as an indicator of CuZnSOD activity and the effect it has on meat quality in three important pig breeds in China, the Laiwu Black (LW), Lulai Black (LL) and Large Yorkshire (LY). Thirty six castrated boars (114 kg; LW, n = 12; LL, n = 12 and LY, n = 12) were used in this study. Samples were taken from the longissimus dorsi muscle, backfat and liver. Results showed that there was a significant breed × tissue interaction; and the maximum mRNA level of the CuZnSOD gene was recorded in the LW and the minimum in the LY. The proportion of gene expression was positively correlated with the anti-oxidative capacity in muscle. The expression of the CuZnSOD gene was positively correlated with meat colour and tenderness; and negatively correlated with marbling score, drip loss, cooking loss and intramuscular fat. The higher the level of CuZnSOD mRNA expression, the better was the quality of the pork. This implies that the difference in CuZnSOD mRNA expression in breeds was involved in the mechanisms of meat quality that related to superoxide dismutase (SOD) activity and anti-oxidant capacity of the muscle.