South African Journal of Animal Science

**Yeast culture (Saccharomyces cerevisiae) and its active metabolites affect the cecal microbiome of broilers**

Yeast cultures (YCs) are defined as promising feed additives that maintain the health of birds and improve growth performance by modulating gut microbiota. YCs contain effective metabolites such as glycine, fructose, inositol, galactose, and sucrose. This study investigated the effects of YCs and their effective metabolites on carcass traits and cecal microflora in broilers. A total of 280 one-day-old mixed-sex Arbor Acres broilers were randomly allocated to seven groups. The basal diet (control DZ) was supplemented with various proportions of glycine, fructose, inositol, galactose, and sucrose (Groups A, B, and C), 24-hour grown Saccharomyces cerevisiae cultures (Group D) (YC), and a commercial yeast culture product (SZ) at concentrations of 0.1% and 1% (Groups E and F). Bodyweight of broilers was correlated positively with proportions of Proteobacteria in Group C and Lactobacillus and Roseburia in Group B (P <0.05). Broilers fed diets supplemented with YC or its active metabolites had the highest proportions of bacteria involved in nucleotide metabolism, and amino acid and carbohydrate metabolism. These results suggested that the dietary addition of YC could alter the proliferation of beneficial bacteria in broilers.

Response of sheep fed urea-treated corncob and supplemented with cassava leaf meal

The objective of this study was to evaluate the effects of feeding untreated or urea-treated ground corncob and supplementing with cassava leaf meal (CLM) in a total mixed ration on growth, feed intake, nutrient digestibility, nitrogen (N) utilization and rumen fermentation of sheep. Five diet treatments with five replications consisted of untreated corncob + concentrate (CC); urea-treated corncob + concentrate (UCC); and CC and UCC supplemented with CLM and designated as CC+CLM and UCC+CLM, respectively. A diet formulated with a mixture of elephant grass and concentrate was used as control (EG). There were no significant differences in dry matter intake (DMI) between treatments. The average DMI was 4.17% bodyweight. Average daily gain (ADG) of sheep fed the treatment diets was between 146.3 and 176.2 g/h/day, and was higher than EG (89.1 g/head/day). Thus, the treatments improved feed conversion ratio (FCR). Nitrogen retention was lowest for EG and highest for UCC and UCC+CLM. The addition of CLM had no effect on growth, feed intake, nutrient digestibility, nitrogen utilization and rumen fermentation characteristics. It was concluded that corncob could be used as a replacement for elephant grass in postweaning diets for sheep.

**Oxidative stress and effects of dill (Anethum graveolens dhi) powder on the performance and health status of broilers**

Effects of dill powder (Anethum graveolens dhi) on performance and biochemical traits, immune response, blood cells and microbial population of cecum broilers after stress induced with dexamethasone were investigated. Two hundred and forty broilers were arrayed in completely randomized design with six experimental groups, five replications and eight broilers per replication. The experimental groups consisted of G1: control diet without additives, G2: control diet supplemented with 1.5% dill powder, G3: control diet supplemented with 1.5% dill powder under dexamethasone stress, G4: control diet supplemented with 3% dill powder, G5: control diet supplemented with 3% dill powder under dexamethasone stress, and G6: control diet under dexamethasone stress. After 31, 33, 38 and, 40 days, 2 mg/kg bodyweight (BW) dexamethasone was injected in right chest muscle in groups 3, 5, 6, and samples were taken after 35 and 42 days. Use of 3% dill powder reduced cecum microbial population significantly. Under dexamethasone oxidative stress conditions dill powder improved biochemical traits and the number of white blood cells significantly. Without stress induced by dexamethasone injection, use of 3% dill powder improved internal organs, increased the length of the digestive tract, improved weight gain, reduced FCR and improved antibody titers to Newcastle disease (ND) and avian influenza (AI) viruses. All levels of dill powder prevented negative impacts of dexamethasone on functional and biochemical traits. Thus, 3% dill powder has beneficial effects on performance, immune response, blood cell and microbial population, and could be used as a growth promoter and to prevent oxidative stress.

**Effects of traditional tenderization treatments on Transversus abdominis muscles obtained from Holstein carcasses**

The aim of this study was to evaluate the effects of traditional tenderization treatments on Transversus abdominis (TrA) muscles (inside skirts) of Holstein carcasses. The muscles were collected from carcasses of 12 healthy 18- to 22-month-old Holstein steers that had been subjected to similar care and nutrition programmes. A replicated 4 x 4 Latin square design was used to compare the effects of the treatments of blade tenderization, enzymatic tenderization, marination and control. Blade tenderization and enzymatic tenderization had statistically similar colour values to the control, whereas marination had negative effects on the colour of raw and cooked samples. Blade tenderization had the lowest mean Warner-Bratzler shear force value (37.88 N), whereas enzymatic tenderization had the second lowest value (42.87 N). In sensory evaluation, significant differences were observed when the samples cooked to an internal temperature of 82 °C. A simple ranking test indicated that the most preferred sample was obtained with the blade tenderization. Also, blade tenderization and then enzymatic tenderization had the highest scores for tenderness in sensory evaluation. Although Holstein cattle are known for superior milk production and may not be a suitable breed for high-quality meat production, the results indicated that blade tenderization and enzymatic tenderization could be used to improve the tenderness of TrA steaks from Holstein carcasses and use them better.

Optimization of response to selection using genomic selection in indigenous chicken breeding programmes

This study tested the hypothesis that the use of pooled genetic and phenotypic parameters and genomic selection would optimize selection response in indigenous chicken breeding programmes. This premise was tested with deterministic simulation in three breeding schemes based on the sources of information used to estimate breeding values. These schemes used a conventional breeding scheme with non-pooled parameters (CSN), pooled parameters (CSP), and genomic information in a genomic selection scheme (GSS). A one-tier closed nucleus breeding programme was considered with a mating ratio of 1 to 5 for males to females, Four traits were used in the breeding goal, namely live weight at twelve weeks (LW), egg number for twelve weeks (EN), age at first egg (AFE), and antibody response (Ab). The genetic gain for CSN was 1.5 times higher than that of CSP. The rate of inbreeding for CSN was 19% lower than in CSP. The accuracy of selection followed the same trend with CSN producing 9% higher accuracy of selection than CSP. The GSS scheme resulted in an additional 59.3% genetic gain and 30% accuracy compared with CSP. The GSS scheme also had a reduced rate of inbreeding by 46% compared with CSP. When compared with CSN, GSS produced 38.7% greater genetic gain, a 27% lower rate of inbreeding and 21.0% higher accuracy of selection. Use of pooled parameter estimates and genomic information optimized response to selection, whereas non-pooled inputs overestimated and underestimated rates of genetic gain and inbreeding.

Performance and intestinal histology of sheep fed detoxified castor bean meal in sugarcane silage

This study evaluated histological changes in the digestive organs and kidneys of sheep fed sugarcane silage augmented with detoxified castor bean meal (CBM). Forty Santa Inês sheep (initial weight 20 ± 0.3 kg) were adapted to the experimental regime for 14 days, after which data were collected for 60 days. The treatments consisted of S0: sugarcane silage (SC); S5: SC augmented with 5% CBM; S10: SC augmented with 10% CBM; S15: SC augmented with 15% CBM; and S20: SC augmented with 20% CBM. After 74 days of confinement, the animals were slaughtered, and then fragments of the liver, rumen, intestine, and kidney were collected for histomorphometric analyses. The intake of dry matter and the average weight gain increased linearly with the level of CBM (P <0.05), as did the rumen absorption area, the height of the papillae and the width of the papillae. The thickness of the keratinized portion of the epithelium was not influenced, Thus, no effect was detected of the anti-nutritional factor of CBM on this organ. In the intestine, CBM increased the height of the villi and the number of goblet cells. However, S20 caused some kidney damage and decreased hepatic glycogen stock, but not sufficiently to reduce performance. Thus, augmentation of sugarcane with CBM, up to 20%, is viable in feeding sheep.

Effects of supplemental bee pollen on performance, meat quality, serum constituents and immunity system in growing quails

This study focused on the effects of adding various levels of bee pollen to diets for Japanese quail (Coturnix coturnix Japonica). The response variables that were examined included their performance, carcass characteristics, meat colour, immune system, and some serum constituents. A total of 160 one-day-old quail chicks were used. These chicks were randomly assigned to four treatments, each consisting of 40 chicks. These groups were further divided into four replicates of ten birds. The treatments consisted of diets to which 0.0, 2.5, 5.0, and 10 g/kg bee pollen were added. The feeding period lasted 42 days. The performance and serum biochemistry of the growing quails were not affected by the addition of bee pollen to the diet. The addition of 5 g/kg bee pollen increased the follicle weight and the L* value of the breast, and decreased the a* value of the thigh. It also improved the serum immunoglobulin A (IgA) content. Thus, the addition of 5 g/kg bee pollen to the diet of growing quails was effective in improving follicle development, meat quality and immune system.

Spineless cactus-based diets associated with various nitrogen sources in sheep diets

This study evaluated the effects of various nitrogen (N) sources augmenting spineless cactus-based diets on intake, digestibility, rumen kinetics and N balance in sheep. Eight rumen-fistulated sheep with an average initial bodyweight of 62 ± 6.83 kg were allotted to one of two 4 x 4 Latin squares. The diets consisted of spineless cactus (Nopalea cochenillifera), Tifton hay, corn grain, vegetable oil and a mineral mixture augmented with either soybean meal (SBM), cottonseed meal (CSM), whole cottonseed (WCS) or urea (U) to provide additional nitrogen. Dry matter (DM), crude protein (CP), and neutral detergent fibre (NDF) intakes were similar (P >0.05) for sheep fed the diets with SBM, CSM, and WCS. The digestibility coefficients of DM and CP were similar (P >0.05) for SM, CM, and U diets. The rate of DM disappearance from the rumen did not differ (P >0.05) between treatments. However, the rumen ammonia, pH and N balance was higher (P <0.05) for sheep fed the WCS and U diets. The N absorbed and N retained did not differ (P >0.05) between the diets. Soybean meal and CSM are similar in their effects and can be used for sheep in diets based on spineless cactus. Whole cottonseed and U are interesting sources of N but should be used with caution owing to their effects on digestibility and nutrient intake in sheep.

Gene-set enrichment analysis of selective sweeps reveals phenotypic traits in Nguni cattle

Adaptation of animals to different environments is typically associated with structural and functional genomic variations. High throughput SNP genotyping and next-generation sequencing (NGS) have made it possible to study positive selection footprints and adaptation traits. Nguni is a small frame-size breed, mostly horned, and well known for being adapted to diverse South African environmental conditions. This study used previously identified selective sweeps to perform functional analysis of genes related to phenotypic characteristics in Nguni. Two hundred and sixty-four candidate selective sweeps were used for gene-set enrichment analysis in molecular functional categories (KEGG pathways) using the database for annotation, visualization, and integrated discovery (DAVID). In total, 107 genes were identified across all the chromosomes with 74 genes associated with eight phenotype queries, including fat content, milk production, walking ability, heat tolerance, meat production, reproduction, and bone and muscle development. Gene CRHR2was associated with meat quality (juiciness and flavour). The IRAK3 gene was associated with decreased body size, feed intake and fatness in cattle, and CARD15 with disease resistance. Gene annotation using phenotype queries identified four genes (SPI, YWHAZ, RGS4, and RGS5) that were associated with myometrial relaxation in cattle. Genes such as NOD2 and IL21R were associated with inflammatory bowel diseases in cattle, whereas CPLS gene was associated with fat content. These genes are important to the phenotypic and adaptive characteristics present in South African Nguni cattle and hold potential for selection for traits of economic importance.

Interaction of protein supplementation and ecotype on growth performance and carcass traits of Nguni goats

Nguni goats are thought not to respond to dietary protein supplementation. The objective of the study was to determine the interaction of protein supplementation and ecotype on growth performance and carcass traits of Nongoma, Msinga and Cedara Nguni goat ecotypes. Thirty-six five-month-old castrated males were randomly allotted to a 3 χ 3 factorial design experiment and provided 0, 150 and 300 g protein concentrate per day. There was an interaction of ecotype and protein supplementation on average daily gain (ADG). The ADG of the Nongoma and Cedara goats increased with protein supplementation, but the Msinga ecotype was not affected by the treatments. Goats of the Cedara ecotype weighed 34.4 kg when provided 300 g of supplement, whereas the Nongoma ecotype weighed 26.5 kg at slaughter when unsupplemented. The dressing percentage did not differ with the level of protein supplementation or ecotype. From the fifth quarter, the skin was affected by ecotype, gut fill by protein supplementation and the weight of the head by both factors. The Cedara ecotype had a heavier fifth quarter at 300 g supplementation. There was no interaction of protein supplementation and ecotype on dissectible fat. Intestine and visceral fats were affected by protein supplementation, whereas stomach fat was affected by ecotype.

Estimates of variance components for feedlot traits of the Simmentaler breed in South Africa

Breeding of beef cattle is changing, with more emphasis on efficiency of production. Feed cost is the highest expense, and reducing it has the potential to increase profitability. Common measures of efficiency are ratio traits such as feed conversion (feed consumed/weight gain) and feed efficiency (weight gain / feed consumed). Feed conversion ratio is commonly used in South Africa in an attempt to improve feed efficiency. These ratio traits are associated with growth rate. Selection for them would result in higher growth as a correlated response and might also increase the mature size of the cows and their maintenance cost. Thus, alternative efficiency traits such as residual feed intake and residual daily gain have been proposed. In this study, variance components, and genetic parameters for feedlot traits for the South African Simmentaler breed were estimated, with emphasis on the efficiency traits. The focus was to evaluate the use of residual feed intake as an alternative trait. The results indicate non-significant correlations between residual feed intake and body weight and growth traits, implying that residual feed intake should have little effect on the other traits. This is in contrast to the moderate to strong correlations of feed conversion ratio with the same traits. The study demonstrates that considerable genetic variation exists for residual feed intake, which can be exploited. Selection for residual feed intake can reduce the carbon footprint of beef due to the associated lower methane emissions.