Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 40 num. 1 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Broiler performance and bone strength minimally affected by either a simulated dusk or night-interruption photoperiod</b>]]> Two genotypes of male broilers were given 12 h of daily illumination; as a conventional photoperiod, with the final hour at reduced illuminance to simulate dusk, or with 1 h of the light given during the middle of the night. The lighting modifications had no significant effect on any performance variable or on tibial breaking strength. Feed intake was unaffected by the lighting treatments during either the 1-h dusk period or the night, but was inexplicably stimulated in the both experimental groups during the main photoperiod. <![CDATA[<b>The effect of oestradiol-17</b><b>β</b> <b>on the motility, viability and the acrosomal status of bull sperm</b>]]> The aim of this study was to test the effect of oestradiol-17β (E2) on the motility, viability and the acrosomal status of bull sperm in vitro. Pooled semen from Holstein bulls were incubated in the presence of 2, 4, and 8 µg E2/mL for 24 h. Semen was also incubated in media without E2. During the incubation, the number of motile, viable sperm and the number of sperm possessing lost/damaged acrosomes, cytoplasmic droplets and coiled tails were counted at 0, 4, 18 and 24 h of incubation. Addition of 2 µg E2/mL at 18 h of incubation increased the total motility over the control. The number of forward progressing sperm was increased by the supplementation of 2 and 8 µg E2/mL over the control group at the 4 h incubation. Lower doses of E2 (2 and 4 µg/mL) did not affect viability of sperm, but a high dose of E2 (8 µg/mL) caused reductions in viability at 4 and 24 h of incubation. The number of sperm cells with lost acrosomes was significantly high in control group at 24 h of incubation. The number of sperm cells possessing proximal and distal cytoplasmic droplets and the number of sperm cells bearing coiled tails were not altered by any of the treatments. A small dose of E2 (2 µg/mL) had a beneficial effect on the motility and acrosome integrity of bull sperm in vitro. Higher dose of E2 (8 µg/mL) had a detrimental effect on viability. <![CDATA[<b><i>Saccharomyces cerevisiae</i></b><b> cell wall products</b>: <b>the effects on gut morphology and performance of broiler chickens</b>]]> The aim of this study was to determine the effect of Bio-Mos® (Alltech Inc.), with or without the addition of a soluble mannan (MRF) (Alltech Inc.) on gastrointestinal health and performance of broiler chickens. A trial was conducted using seven different dietary treatments. It consisted of a negative control, 2 levels of Bio-Mos® (2 g/kg and 4 g/kg), 2 levels of MRF (0.1 g/kg and 0.2 g/kg) and 2 treatments combining the cell wall preparations (2 g/kg Bio-Mos® + 0.1 g/kg MRF and 4 g/kg Bio-Mos® + 0.2 g/kg MRF). Day-old male broiler chicks were randomly allocated to the seven treatments and the trial extended over a 15 day period, upon which two chicks from each replicate were sacrificed and ileum samples taken. Results showed that the cell wall preparations had a numerically positive, but statistically non significant effect on feed conversion ratios. Histology results revealed significantly greater goblet cell densities and sizes for chicks receiving cell wall preparations than those of the control treatment chicks, while villi width and height measurements indicated no differences between treatments. From the results of this study it appears as if yeast cell wall preparations can contribute to the gastrointestinal health and performance of broiler chickens by affecting mucus secreting goblet cells in a favourable manner. <![CDATA[<b>Potential use of high-temperature and low-temperature steam treatment, sodium hydroxide and an enzyme mixture for improving the nutritional value of sugarcane pith</b>]]> The effectiveness of different treatment methods to improve the nutritional value of the sugarcane by-products (pith or bagasse) has been evaluated. The treatment methods included a high-pressure steam treatment (HPST; 19 bar, 3 min), treating the products with sodium hydroxide, sulphuric acid plus an enzyme mixture, or low-temperature steam treatment (LTST) under different conditions. Gas production (GP), two-step in vitro digestibility (IVD) and in situ degradability (ISD) techniques were used to monitor the effectiveness of the treatments. HPST resulted in a significant increased in the total soluble sugar (TSS) content of unsteamed pith (USP), 20 vs. 123.75 mg/100 mL. Except for the enzyme treatment, the other treatments led to a significant improvement in the nutritional value of sugarcane by-products, as measured by the IVD method. LTST resulted in an increase in potential GP (B) at higher temperature, reaction time and amount of acid. The highest potential GP (110.92 mL/300 mg DM) was achieved under the conditions, 134 ºC, 18 g acid/kg DM, 120 min, and the lowest (72.4 mL/300 mg DM) under the conditions, 121 ºC, no acid, 40 min. In situ dry matter degradability (ISDMD) was unaffected by LTST. Dry matter digestibility results indicated that the optimal treatments for treating pith were HPST and NaOH, but that enzymes were ineffective. Furthermore, considering treatment cost (creating high-pressure are more expensive than low temperature treatments), potential environmental health problems and the relative improvement in the nutritional value of pith achieved by the LTST + acid method, compared to the HPST method (as measured using GP), these results suggested that the methods based on the use of LTST and acid (especially under harsher conditions), have the best potential to improve the nutritive value of sugarcane by-products. <![CDATA[<b>Polymorphism of the VEGF gene and its association with growth traits in four goat breeds</b>]]> The vascular endothelial growth factor (VEGF) is a regulator of angiogenesis which is an important physiological adaptation to increased metabolic demand. Thus, mutations of this gene may exert a significant influence on animal growth. We screened the exons of the caprine VEGF gene using PCR-SSCP and DNA sequencing methods in 459 individuals from four goat breeds to identify sequence variations that may have an effect on protein structure and function, and might be related to different phenotypes of growth traits. Two single nucleotide polymorphisms (SNPs) (GU014696:g.49 G>C and GU014696:g.270G>A) were identified in the P3 locus of the caprine VEGF gene. Significant associations were observed between the genotypes of the P3 locus and body length, body height and chest circumference. Individuals with genotype P3-B had a significantly longer body length and higher body height than individuals containing genotype P3-AB. Thus, animals of genotype P3-AB should be culled in a selection programme for fast growth. It is suggested that P3-B could be used as a molecular marker in marker-assisted selection (MAS). <![CDATA[<b>Influence of body weight, age and management system on reproduction of South African Angora goat does</b>]]> The effect of doe age, body weight and different management systems, as practiced in various Angora goat studs, on reproductive performance of does was investigated. The data used were collected from 2000 to 2004 on 12 Angora goat studs kept under different management systems. The data set analysed for this study contained data of 6271 does, each with a varying number of kidding opportunities. This amounted to 14644 doe records where each record included body weight before mating, body weight at scanning (ultrasound scanning for pregnancy diagnosis) and all reproductive performance data. There was a wide range pertaining to reproductive performance among the various studs. Apart from a high kid mortality rate, which is regarded by breeders as the most important factor contributing to low weaning percentages, nearly 20% of the does did not conceive or lost their foetuses before birth. Body weight of does before mating ranged from 13.0 kg to 59.6 kg (average = 34.6 kg) among animals, while body weight at scanning ranged from 18.0 kg to 67.0 kg (average = 38.6 kg). All reproductive parameters recorded had a typical inverted U-shaped relationship with age of dam, where the 2- and 3-year-old does and does older than 9 years of age fared significantly worse than the 4- to 9-year-old does. Management system had a significant influence on reproductive performance of does in the different studs. Higher reproductive rates were recorded under those management systems where additional or supplementary feeding at various stages of the reproductive cycle were supplied. Body weights before mating and at scanning had significant positive relationships with reproduction. For every kilogram increase in body weight before mating, 0.0237 and 0.0218 more kids will be born and weaned, respectively. Body weights before mating of young does that were kept on pastures until 18 months of age were higher than those of maiden does in the other management systems, resulting in higher reproductive rates. Number of kids scanned, born and weaned per maiden doe at first kidding increased with an increase in body weight at first mating. From the results it is evident that body weight, age of the doe and management system all have a significant effect on the reproduction of Angora goats. <![CDATA[<b>Factors affecting pre-weaning kid mortality in South African Angora goats</b>]]> The data used for this study were collected in 12 different Angora goat studs from 2000 to 2004. Data collected on 17534 kids born alive in the different studs were included in the analyses. Average pre-weaning mortality rate was 11.5% and ranged from 8.6% to 16.5% (of the 17534 kids born alive, 2018 kids died between birth and weaning at four months of age). Mortality rate in male kids was higher than that recorded for female kids (11.9% vs. 11.1%). When comparing the management systems followed from mating up until weaning in the different studs with the corresponding pre-weaning mortality rates, it is obvious that there was no discernible trend. Of the 2018 deaths recorded, the probable cause for only 601 (29.8%) deaths was known. The most important problems were predators, small, unthrifty kids who needed help with suckling, does having little or no milk and does abandoning their kids. When combining the latter three causes with udder problems (3.5%), 35.7% of pre-weaning mortalities was due to these causes. Birth weight and sex of the kid had a significant influence on pre-weaning mortality rate. Single-born kids had the lowest mortality rate (10%), followed by twin-born (13%) and triplet-born (22%) kids. Despite large differences in mortality rate recorded between sires within flocks, a heritability of 0.04 ± 0.01 was estimated for pre-weaning mortality rate. This low overall heritability could be attributed to the fact that causes of mortality differed considerably among kids and many of these causes may have no genetic background. <![CDATA[<b>The effect of embryo donor age and parity on the superovulatory response in Boer goat does</b>]]> This study was conducted to evaluate the effect of the age and parity of the embryo donor on the superovulatory response and embryo recovery rate in Boer goat does. The oestrous cycles of seven maiden does (young, 1 - 2 years) and nine multiparous does (adult, 3 - 4 years) were synchronised using controlled internal drug release dispensers (CIDR's) for a period of 17 days, and superovulated with pFSH during the natural breeding season. The superovulation treatment was administered as a total dose of 200 mg pFSH/doe given i.m. in seven dosages (at 12 h intervals) - starting 48 h prior to CIDR removal. Does were observed for oestrous behaviour three times daily, at 8 h intervals following CIDR withdrawal. Cervical inseminations (0.01 mL fresh undiluted semen) were performed 36 h and 48 h following CIDR removal and the embryos surgically flushed six days following the second artificial insemination. All does showed overt signs of oestrus. The time interval from CIDR removal to the onset of oestrus in the adult multiparous does (24.0 ± 4.0 h) was significantly shorter than that recorded in the younger does (32.0 ± 4.6 h). The age and parity of the embryo donors did not have any effect on the duration of the induced oestrous period. The mean number of CL's, structures and embryos recovered were significantly higher in the adult multiparous does (19.8 ± 4.8, 21.3 ± 3.9 and 20.9 ± 4.5, respectively), compared to the young maiden does (13.7 ± 3.8, 11.7 ± 5.0 and 11.7 ± 5.0, respectively). The fertilisation rate, the mean number of unfertilised ova and degenerate embryos recorded did not differ between the young and adult multiparous does. The mean number of transferable embryos in the adult does (15.8 ± 6.4) was, however, significantly higher than in the young does (9.5 ± 3.7). The longer response time taken to the onset of oestrus had no influence on the fertilisation rate in young does. Although the young does recorded an acceptable fertilisation rate, the number of transferable embryos was, however, lower due to the lower total number of embryos produced by the young donor does and this may favour the use of older multiparous does as embryo donors in a multiple ovulation and embryo transfer programme. <![CDATA[<b>Determination and comparison of digestion kinetics of two fibre sources in geese (<i>Anseris</i>)</b>]]> The aim of this study was to determine and compare the digestion kinetics of two fibre sources (lucerne, maize stalk) in different segments of the digestive tract of geese. Sixty Jilin nongan white geese were divided into two groups and fed with a lucerne or maize stalk diet. After 30 days of feeding, all of the geese were fed with Co-EDTA as the marker of liquid digesta, and n-alkane was used as an internal marker. At 1.0 h, 2.0 h, 3.0 h, 4.0 h and 5.0 h after Co-EDTA was fed, five geese per treatment per time period were sacrificed by cervical dislocation. Content of the glandular stomach, gizzard, duodenum, jejunum, ileum, caecum and rectum were collected for the evaluation of the parameters of digestion kinetics. The results showed that digestion kinetics of fibre in geese fed with a lucerne diet is consistent with that of a maize stalk diet. Within the digestive tract, digesta flow was the highest in the jejunum, and the slowest in the gizzard. Mean retention time of the digesta was the longest in the gizzard and duodenum. The digestibility of NDF, ADF and HC was the highest in duodenum, gizzard and duodenum and caecum respectively. Collectively, these findings suggest that the gizzard and duodenum might play important roles in the digestion of crude fibre in geese.