Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 48 num. 3 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b><b>Importance and implications of antibiotic resistance development in livestock and</b><b> wildlife farming in South Africa: A Review</b></b>]]> Antibiotic resistance (ABR) is regarded as one of today's major global health challenges. The development of ABR in nature is a complex phenomenon with many influencing factors, of which the farming industry is labelled a significant contributor. The transfer of ABR to humans, which usually occurs via the food chain, is of concern for human health. A food source that is increasing in popularity is game meat, which is farmed widely in South Africa. The natural environment, including wildlife, is not isolated from the rest of the farm, and thus could be a source of ABR or possibly a transfer vector. It is therefore important to assess the ABR situation in wildlife species and the factors that influence its emergence and transfer. Elements that play a part in the development of ABR in game species include certain harvesting and slaughtering and other farming practices and closer contact with humans and other farm animals. Additionally, natural transfer vectors include wind, water, manure, crops and animals. Worryingly, there is lack of knowledge of this situation owing to inadequate monitoring, documentation and control of antibiotics in the farming industry. The objective of this review was to gain better understanding of this situation, which would aid in the development of surveillance systems and methods to prevent or hinder the development of ABR in wildlife species. <![CDATA[<b>Pre- and postpartum effects of starch and fat in dairy cows: A review</b>]]> This review discusses the effects of starch and fat before and after calving on metabolism, energy balance (EB), milk production, and reproduction in dairy cows. The shift in dairy cows from a pregnant non-lactating state to a non-pregnant lactating state induces physiological changes, which affect the metabolic and endocrinal axes to redirect body energy stores towards the mammary gland for milk production. Overfeeding high starch and fat levels during the dry period after calving may result in cows failing to adapt to the negative energy balance (NEB) because of major liver and rumen dysfunction. Alternatively, keeping dry cows on high-forage/low-energy diets adjusts dry matter intake (DMI) to optimize the rumen function and decrease the severity of the NEB during transition. These periparturient biological improvements in dairy cows showed real benefits such as fewer postpartum health complications (e.g. milk fever, ketosis, mastitis, metritis), decreased body condition loss and improved reproductive axis in the subsequent lactation. Adding dietary starch and/or fat to diets of dairy cows following parturition increased milk yield. In addition, milk protein of dairy cows increased with glucogenic diets, but decreased with lipogenic diets. Inversely, milk fat usually increases after feeding lipogenic diets, but it decreases when feeding glucogenic diets to dairy cows. Glucogenic and lipogenic nutrients can affect the cow's metabolism and its EB status positively, as is evidenced by plasma non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHB), glucose, amino acids, insulin, insulin-like growth factor-I (IGF-I), growth hormone (GH), gonadotropin hormones, and progesterone (P4) levels. These metabolites (NEFA, BHB, glucose, amino acids) and hormones (insulin, IGF-I, GH, P4) have been shown to affect folliculogenesis, ovulation, conception, and pregnancy success. Feeding a starch-based diet to dairy cows can lead to acidosis and increase glucose and insulin levels, while decreasing NEFA and BHB levels. Furthermore, an insulinogenic diet favours an early resumption of ovarian activity, but has adverse effects on the quality of oocytes. In contrast, keeping dairy cows on a fat-based diet elevates NEFA and BHB levels and decreases glucose and insulin levels. Additionally, a lipogenic diet increases the plasma P4 levels and improves the quality of oocytes. These evidences suggest that reproductive performances in dairy cows can be enhanced by feeding an insulinogenic diet until the resumption of the ovarian cycle then switching to a lipogenic diet from mating period onwards. Since long-term field studies on fertility are limited and the reproduction process in dairy cows is multi-factorial, further research is needed on the pre- and postpartum effects of starch and/or fat as well as their combinations on reproduction axis and thus to draw conclusions on reproductive performances. <![CDATA[<b><b>Effect of herbal choline and rumen-protected methionine on lamb performance and</b><b> blood metabolites</b></b>]]> Twenty-four lambs (Pelibuey x East Friesian), weighing 22.7 ± 3.2 kg, were fed a basal diet of corn silage, oat hay, alfalfa hay, and concentrate (60% forage and 40% concentrate). Treatments consisted of oral doses of rumen-protected methionine (RPM) (0 and 1.5 g/day) and herbal choline (biocholine) (0 and 4 g/day) in a completely random block design with factorial arrangement of treatments, where lambs were blocked by sex. The experiment was conducted for 60 days, and measurements of live weight and dry matter intake were obtained. No effects of the treatments were observed on performance variables (lamb growth, consumption and feed conversion). Non-esterified fatty acids (NEFA) were increased by biocholine and unaffected by methionine (Met). Biocholine increased glucose and cholesterol, whereas methionine increased triglycerides, albumin and plasma protein. The dietary supplementation with biocholine and RPM did not improve lambs' growth; however, biocholine and Met showed a lipotropic effect by mobilizing NEFA and stimulating glucose and cholesterol synthesis. <![CDATA[<b><b>The effect of peanut pod on performance, small intestine pH and ileum bacteria</b><b> population in broiler chickens</b></b>]]> This experiment was designed to assess the hypothesis that feeding broilers with peanut pod as an insoluble fibre source will result in improved gut digestive capacity growth performance. The experimental diets consisted of a control diet and three diets containing 25, 50, or 75 g peanut pod /kg. The dietary peanut pod, especially at the 50 g/kg level decreased feed intake of the experimental groups. In grower phase, the best weight gain was recorded in the broiler chickens fed the diet containing 75 g peanut pod /kg. All the peanut pod containing diets decreased grower phase feed conversion ratio compared to the control group. In the finisher phase, the growth rate and feed conversion ratio were not affected by the experimental diets. The gizzard weight and gastrointestinal length was increased in the chickens fed 75 g peanut pod /kg, and these groups showed the lowest pH for gizzard content. In the ileum, the birds fed 25 g peanut pod /kg had a higher Lactobacillus population than the 75 g peanut pod /kg group; and the birds fed 25 g peanut pod had lower Escherichia coli (E. coli) population, compared to the control group. The positive effects of dietary insoluble fibre on the growth performance of broilers in this study were probably a result of favourable changes in the bacteria populations and also an increase in digestive capacity of gastrointestinal. <![CDATA[<b>Chemical composition of <i>Lablab purpureus </i>and <i>Vigna unguiculata </i>and their subsequent effects on methane production in Xhosa lop-eared goats</b>]]> The objective of this study was to evaluate the nutritive value and anti-nutrient contents of Lablab purpureus (Lablab) and Vigna unguiculata (cowpea) and their effects on methane production in goats. Legume forages were grown and harvested at three stages of growth of pre-anthesis, anthesis, and post anthesis. Samples were collected at each stage and examined for proximate composition, total phenolics, condensed tannins, and saponins using standard methods. Hay was harvested at the anthesis stage and used in a growth study to evaluate the effects of forage legumes on methane production. Eighteen one-year-old goats, nine males and nine females, were used in the feeding trial. The goats were subjected to three treatment diets with six goats in each treatment, representing both sexes equally, for 60 days in a complete randomized design. Methane was measured with a laser methane detector (LMD). Cowpea showed higher ash (13.11%), acid detergent fibre (ADF) (38.42%), and crude protein (CP) (20.23%) than Lablab, which had values of 11.45 %, 36.17%, and 19%, for ash, ADF, and CP, respectively. Lablab had significantly higher fat content (2.41%), neutral detergent fibre (NDF) (49.27%), and hemicellulose (13.07%) than cowpea (2.1%, 46.91%, and 8.48%, respectively). The tannin, phenolic, and saponin content were influenced significantly by forage species and stage of growth. The diet and sex of the animal affected enteric methane production significantly. Forage legumes met animal requirements for fat, ADF, NDF, and CP. The energy and tannin levels of forage legumes were shown to reduce enteric methane production in goats. <![CDATA[<b>Effects of sex and stocking density on the performance of broiler chickens in a subtropical environment</b>]]> The current study investigated the effects of sex and stocking density and their interaction on growth performance and carcass characteristics of broiler chickens in a semi-arid sub-tropical environment. A total of 1008 day-old Cobb Avian48 chicks, namely 462 males and 546 females, were reared at final stocking densities of 30, 35, and 40 kg bodyweight per square metre (BW/m²) corresponding to 44, 51 and 59, and 52, 61 and 69 chicks per pen for males and females, respectively, during a 42-day production period. The experiment was a 2 χ 3 factorial completely randomized design, with each sex-stocking density combination being replicated three times. After the initial weighing, the birds were weighed individually [grams (g)] each week until the 42nd day. At day 42, four birds from each pen were randomly sampled and slaughtered, and carcass characteristics were measured after 48 hours, and expressed as percentages of bodyweight. Growth performance and carcass characteristic parameters were subjected to analysis of variance using the general linear model procedures of Minitab statistical software version 17. Treatment means were compared using Tukey's test (at α = 0.05). Males gained more weight and were significantly heavier at slaughter age (2649 ± 43.1 g) than females (2270 ± 43.1 g). There was a progressive reduction in feed intake with increasing stocking density, but neither sex nor stocking density influenced feed conversion ratio and mortality rate. Sex significantly affected dressing percentage and carcass parts percentages, namely breast, neck, shank, heart and abdominal fat and thigh, liver and gizzard. On the other hand, stocking density significantly influenced dressing percentage and carcass parts percentages such as breast, thigh, drumstick, neck, shank, liver and gizzard. There was a significant sex x stocking density interaction effect on percentages of thigh and liver. It is therefore suggested that for efficient 42-day production cycles of broilers in the subtropics, Cobb Avian48 males reared at the stocking density of 40 kg BW/m² could be considered the best option. <![CDATA[<b><b>A novel flush technique to simulate natural dispersal of spermatozoa in the female reproductive tract and expedite motility assessment of fresh ejaculated</b><b> Merino <i>(Ovis aries) </i>sperm</b></b>]]> Motility is an important criterion in the assessment and quantification of the quality of ejaculated and epididymal sperm samples. Ovine sperm spermatozoa are particularly susceptible to cryodamage, and shortening the interval from collection to cryostorage may potentially minimize the negative effects of cryopreservation, thereby improving the post-thaw viability of ram spermatozoa. The use of the swim-up technique (SUT) in quantifying spermatozoa motility is well documented, especially for the isolation of highly motile spermatozoa for assisted reproductive purposes. However, this technique is time consuming and involves a swim-up period of 10 minutes before the motility of a sample is recorded by using computerassisted sperm analysis (CASA) software such as the Sperm Class Analyser® (SCA®). The novel flush technique (FT) allows for capturing of sperm motility tracks via the SCA® system shortly after semen collection, that is, within a minute. This study compared fresh ejaculated sperm motility traits by using the SUT and FT. Motility evaluations were performed using 45 semen samples obtained from 15 adult Merino rams (Ovis aries) at weekly intervals. Motility recordings were captured at 100 frames per second, using a calibrated 20 μπι deep Leja slide. The percentage total motile spermatozoa of samples subjected to the FT was 89.2%, which was significantly higher than that recorded by the SUT (83.9%). The results also indicated that the wobble (WOB) parameter showed significantly higher values when using the FT, and parameters curvilinear velocity (VCL) and amplitude of the lateral head displacement (ALH) indicated significantly higher values when using the SUT. Establishing the ideal spermatozoa concentration and analysis of sperm subpopulation motility characteristics would assist in the optimization of the FT, and its use in CASA motility analysis of ovine spermatozoa. Standardization of CASA analysis of ovine semen samples, which would enable the selection of quality spermatozoa samples for use in field insemination (fresh samples) or in vitro fertilization programs, and laparoscopic AI cryopreserved samples warrants further investigation. <![CDATA[<b>Analysis of carcass characteristics and fat deposition of Merino, South African Mutton Merino and Dorper lambs housed in a feedlot</b>]]> The objective of this study was to determine the effect of time spent in a feedlot on the size of the various fat depots and the distribution of the main tissues (muscle, bone, and fat) of three common South African sheep breeds. Lambs were supplied with a balanced diet (16% protein, 10 MJ ME/kg feed) ad libitum and had free access to water. Lambs from each breed were divided into six groups, which were slaughtered at 21-day intervals until a production period of 105 days had been reached. During carcass dressing, visceral and renal fat was removed and expressed as a percentage of carcass weight. The subcutaneous fat (SCF) depth was measured on the longissimus lumborum at the 13th rib position using an electronic calliper. The proportion of muscle, bone and fat was determined by dissecting a three-rib cut made on the prime rib between the 9th and 11th ribs. The percentage of visceral and renal fat increased throughout the production period for all breeds. The percentage of renal fat was up to 2.9% higher than the percentage visceral fat in both SAMM production groups. Dorper lambs tended to have high SCF levels (5.6 mm fat after 42 days) due to the early maturing nature of the breed. They reached a maximum fat depth of 20.4 mm fat after 105 days. The SAMM lambs tended to deposit SCF at a slower rate and the late maturing Merino breed was found to be much leaner, and did not reach the high fat levels of the SAMM or Dorper lambs. The percentage of muscle and bone in all carcasses decreased with an increase in the number of days in the feedlot, while the percentage of carcass fat increased during this period. The increase in late maturing adipose tissue in all breeds as they become older is amplified by the restricted movement in the feedlot and high energy diet that the lambs receive. <![CDATA[<b>Effects of replacing soybean meal with alternative sources of protein on nutrient digestibility and energy value of sheep diets</b>]]> The study determined the potential of eight locally produced protein sources to replace soybean meal (SBM) in the diet of sheep. Three in vivo digestibility trials were conducted using a Latin square (3x3, 4x4 and 4x4) experimental design with castrated Chios rams. The authors estimated nutrient digestibility coefficients and energy value of diets with soybean meal (control), lupin seeds (LS), rapeseed meal (RSM), sunflower meal (SFM), fababean seeds (FBS), vetch seeds (VS), pea seeds (PS), flaxseeds (FS), and chickpea seeds (CS). The results showed that the SBM, RSM, and PS diets had similar nutrient digestibility and energy value. The SFM diet had lower organic matter (OM) digestibility than the SBM diet. The FS and SFM diets had similar crude protein (CP) digestibility to the SBM diet. Additionally, FS, VS, and SBM diets had similar energy value. Furthermore, SBM, SFM, VS and FS diets had similar dry matter (DM), neutral detergent fibre (NDF), hemicelluloses, and cellulose digestibility coefficients. The SBM, LS, FBS, and CS diets had similar DM, OM, NDF, hemicelluloses, and cellulose digestibility coefficients. Additionally, SBM, LS, and CS diets had similar energy value. This study reveals that diets with RSM, PS, FS, and LS, compared with diets with SBM, did not have adverse effects on nutrient digestibility and energy value. These results tend to support the idea that some locally available protein sources seem to have the potential to replace SBM in sheep diets. <![CDATA[<b><b>Chemical composition, organic matter digestibility and energy content of apple pomace silage and its combination with corn plant, sugar beet pulp and pumpkin</b><b> pulp</b></b>]]> The objective of this research was to investigate and compare the quality of apple pomace silage ensiled with corn plant, sugar beet pulp, and pumpkin pulp for nutrient compositions. Fresh samples of apple pomace, corn plant, sugar beet pulp, pumpkin pulp, and their combinations were fermented in glass jars. The treatment groups included i) 100% apple pomace as control, ii) 100% corn plants, iii) 100% sugar beet pulp, iv) 100% pumpkin pulp, v) 50% apple pomace and 50% sugar beet pulp, vi) 50% apple pomace and 50% pumpkin pulp, and vii) 50% apple pomace and 50% whole corn plant. The silage pH was different among treatment groups, ranging from 3.60 to 4.15, being lowest with a combination of apple pomace and pumpkin pulp, and highest with sugar beet pulp. Dry matter (DM) and crude protein (CP) contents of the silages were also different among groups, with corn silage being the highest for both values, namely 29.17% for DM and 9.92% of DM for CP. Although acid detergent fibre (ADF) and crude cellulose (CC) values differed among silages (ADF and CC contents varied between 24.47 and 38.55% of DM and 21.58-28.98% of DM among silages, respectively), neutral detergent fibre (NDF) contents remained similar. In vitro organic matter digestibility of sugar beet pulp silage (74.41% of DM) was highest among all silages, whilst corn silage (55.35% of DM) had the lowest digestibility. Sugar beet pulp silage had the highest metabolizable energy (ME) (2.67 Mcal/kg DM) and net energy lactation (NEL) (1.61 Mcal/kg DM) values among all silages. The results of the current study suggested that nutritive values of the apple pomace silage were comparable with the silages from the other plant sources. In summary, apple pomace silage is a promising feed. <![CDATA[<b><b>Effects of diets containing hemp seeds or hemp cake on fatty acid composition and</b><b> oxidative stability of sheep milk</b></b>]]> High levels of polyunsaturated fatty acids (PUFAs) are desirable in milk for its nutritional quality, but make it vulnerable to oxidation. The aim of this trial was to assess the effects of dietary intake of hemp (seeds or cake) on milk production, fatty acid (FA) profile, and oxidative stability when sheep diet included a source rich in PUFAs. The control diet (C), which was composed of hay-based rations and completed with mixed concentrate, was compared with two experimental diets that were designed to provide the same amount of fat via hemp seed (180 g/d) (HS diet) or hempseed cake (480 g/d) (HC diet). The hemp was determined to have significantly increased the yields of milk, energy-corrected milk (ECM), fat corrected milk (FCM) (6.5%), protein corrected milk (PCM) (5.8%) and milk fat. The hemp generated a greater proportion of n-3 FA, notably α-linolenic acid (ALA), which increased by 49-66%. The addition of hemp also led to an increase in C18:1 t11 (vaccenic acid (VA)) and conjugated linoleic acids (CLA), particularly isomer c9,t11 CLA (rumenic acid (RA)). The HC group showed a greater content of milk ALA and VA and tended to show a greater content of c9,t11 CLA than the HS group. The atherogenic index (AI), thrombogenic index (TI), n-6/n-3 FA ratio and hypocholesterolemic/Hypercholesterolemic (h/H) ratio suggest that hemp could be useful in improving milk quality. The results obtained in this study suggest that the inclusion of hempseed cake appears to be more effective in ameliorating these indices than hemp seed. The author determined the concentration of fat-soluble antioxidant (tocopherol and retinol) by high performance liquid chromatography (HPLC), and assessed the total antioxidant capacity (TAC) by measuring the ABTS (2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid) scavenging capacity and degree of oxidative degradation of lipids -using the classical test based on the concentration of malondialdehyde (MDA). The TAC was higher in the milk of the HS and HC groups compared with C, being in direct correlation with the higher concentration of α -tocopherol of milk and lower concentration of MDA, the extent of the change being greatest for the animals fed the HS diet. Therefore, hemp seeds and hempseed cake appear to be ideal supplements for improving the FA profile and health lipid indices and preventing lipid oxidation in raw milk. <![CDATA[<b><b><i>Orelha de Elefante Mexicans (Opuntia stricta </i>[Haw.] Haw.) spineless cactus as an</b><b> option in crossbred dairy cattle diet</b></b>]]> A new genotype of spineless cactus is being used in the diets of dairy cattle that are raised in semi-arid regions. However, little is known about its nutritional value. This study aimed to evaluate the effects of replacing Miúda (Nopalea cochenillifera Salm Dyck) with Orelha de Elefante Mexicana (Opuntia stricta [Haw.] Haw.) spineless cactus, on nutrient intake and digestibility, milk yield and composition, feeding behaviour, microbial protein synthesis, nitrogen balance, and ruminal and blood parameters of dairy cows. Ten Girolando cows, 500 ± 51.6 kg bodyweight, were distributed in a double Latin square design 5 x 5. The treatments consisted of replacement levels of Miúda (MIU) by Orelha de Elefante Mexicana (OEM) at 0, 25, 50, 75, and 100%. The intake and digestibility of dry matter (DM) (14.38-12.95 kg d-1, 716.3-658.9 g d-1), organic matter (OM) (13.01-11.43 kg d-1, 747.8-704.8 g d-1), crude protein (CP) (2.02-1.61 kg d-1, 863.8845.2 g d-1) and total digestible nutrients (TDN) (9.38-7.92 kg d-1) decreased linearly with the increase in replacement. Despite the decrease in intake and digestibility, the supply of nutrients was sufficient to maintain a milk yield of 12.5 kg d-1. The average daily weight gain decreased linearly with the increase in replacement, while protein microbial efficiency (g microbial CP kg-1 TDN intake; 91.24 to 127.44 g kg-1) increased linearly. Thus, OEM could replace 100% MIU in diets with 48% of spineless cactus, for crossbred lactating cows with 12.5 kg d-1 milk yield. Therefore, OEM is a viable new option for producing milk in smallholder livestock systems in semi-arid regions. <![CDATA[<b><i>In vitro </i>ruminal fermentation and fatty acid production by various oil seeds</b>]]> Rumen simulating techniques (Rusitec) were used to determine the impact of diets containing milled oilseeds on the fermentation parameters and amount of fatty acids (FA) in the effluent. High-forage diets containing no oilseeds (control diet (CD)) or 10% oilseed meal from rapeseed (RS), sunflower seed (SS), or flaxseed (FS) were used on a dry matter (DM) basis. No differences in DM digestibility were observed between the diets. Inclusion of SS and FS significantly reduced the pH values of the ruminal fluid, and a significant decline in the ammonia nitrogen (NH3-N) (mg/d) production in effluent was observed in the vessels with SS. Generally, oilseeds in these diets significantly reduced the amount of total fermentation gases (L/d); however, only a tendency toward methane (CH4, %) decrease was detected. The addition of oilseeds also significantly diminished the amount of total volatile fatty acids (VFA) produced (mmol/d). Significant reductions in the amounts of saturated FA in the vessels with RS and FS were observed compared with the CD and a significantly higher amount of monounsaturated fatty acids (MUFA) was noted in the vessels with RS. An increased amount of polyunsaturated fatty acids (PUFA), compared with the CD, was statistically significant only in the vessels with FS.