South African Journal of Animal Science

Should the South African red meat classification system be revised or maintained? A review

The objective of this review was to determine whether the current South African red meat classification system still needs to be revised and changed or maintained. It also gives insight into the most significant challenges related to meat quality evaluation in this system. Red Meat Research and Development South Africa (RMRD SA) was requested to lead an investigation into the relevance of the current South African red meat classification system. A final decision was made to maintain the system as it was in 2016. Nonetheless, it is still unclear whether consumers buy meat according to the standards set by the system, since it is mostly understood and practised efficiently by middlemen, especially abattoir operators. The general perception that this system is not quality based, but descriptive, has resulted in seeming non-transparency among some red meat industry stakeholders. Although the red meat industry is emphasizing that a quality assurance system remains too expensive to be implemented in South Africa and that the current system should be sustained, there is still room for revising it. All predictions in this review indicate that the present system cannot satisfy all the needs of the current consumer. The system seems to be inclined towards meat traders, since it is value based and may not reflect the expectations and needs of consumers in terms of meat quality. This paper therefore concluded that the South African red meat classification system still needs to be revised and more research should be done for it to become more effective.

Association between postpartum blood levels of glucose and urea and fertility of cross-bred dairy cows in Sudan

This study aimed to find correlations between blood glucose and urea levels and the duration of postpartum period (PPP), number of services per conception (S/C), open period (OP), conception rate (CR) to first service, and the overall CR in 80 multiparous cross-bred dairy cows. The two metabolites were measured 1, 4, 7, 10, and 13 weeks postpartum. The CR to first service and overall CR were 13.8% and 42.8%, respectively. Based on S/C, three groups were identified: Group 1 (G-1) (n = 11) consisting of cows that conceived from first service; G-2 (n = 46) representing cows that needed two inseminations to conceive; and G-3 (n = 23) consisting of repeat breeders (RB). G-1 represented 13.8%, with PPP and OP shorter than cows in G-2 and in G-3, and had blood glucose levels 17.5% and 27.9% higher than levels in G-2 and in G-3, respectively. Until the 7th week postpartum, blood levels of urea were higher in G-1 and lower in G-3. However, in the 10th and 13th weeks postpartum, results were reversed. The PPP, S/C, and OP were negatively correlated with blood glucose over the study period and with blood urea at the first seven weeks postpartum. However, these traits were positively correlated with blood urea measured at 10 and 13 weeks postpartum. It can be concluded that, from this study, maintaining high blood glucose until the 13th week postpartum, high blood urea during the first 7 weeks postpartum, and low blood urea during the 10th and 13th weeks postpartum were associated with good fertility in dairy cows.

Sesame meal as the first protein source in piglet starter diets and advantages of a phytase: a digestive study

Soybean meal (SBM) is the protein source that is used most in feeding piglets, but its high price has prompted a search for alternatives. One option is sesame meal (SM), a by-product of sesame oil. This study evaluated the effects of SM and phytase on the intestinal morphology, total trypsin activity (TTA) and specific trypsin activity (STA), apparent ileal digestibility (AID) of amino acids (AAs), and apparent total tract digestibility (ATTD) of phosphorus (P), calcium (Ca), and energy (E) in weaned piglets. Twenty piglets weaned at 17 days old were placed in metabolic cages in a temperature-controlled room. When the piglets were 21 days old, cannulas were fitted at the terminal ileum. From the fourth day after surgery, piglets received the experimental treatments for nine days, namely an SM or SBM diet, each with or without phytase. The protein source or phytase did not affect villus height, crypt depth, or TTA. However, phytase increased STA. The AID of dry matter (DM), E, crude protein (CP), and AA was similar among treatments, except for arginine, which was more digestible in the SM diets (85.8) than in the SBM ones (81.6). The ATTD of DM and E was higher in the SM than in the SBM diets. Phytase increased the ATTD of Ca (22.7 %) and P (27.9 %). The findings showed that SM can be used as a protein source for piglets and that its consumption increases arginine intake. The addition of phytase to the diet increases the ATTD of P and Ca.

Influence of ß-galacto-oligosaccharide on growth performance and components of intestinal barrier in broilers during heat stress

This study aimed to investigate the influence of ß-galacto-oligosaccharides (ß-GOS) on growth performance, organ development and intestinal microarchitecture of broilers during heat stress. Day-old chicks (n = 125) were divided into five groups. The control or thermoneutral zone group (TNZ) was raised under standard management until the 35th day. Four groups were exposed to cyclic heat stress (35 °C 8 h/d) from the 22nd to the 35th day. The TNZ and heat stress control (HSCT) groups were fed a corn-based diet and HS + 0.1% ß-GOS; HS + 0.2% ß-GOS; and HS + 0.5% ß-GOS were fed a corn-based diet supplemented with ß-GOS (0.1%, 0.2%, and 0.5%), respectively. Exposure to heat stress reduced feed consumption, feed efficiency and the relative weight of the liver, bursa of Fabricius, and small intestine, compared with the TNZ group. Morphometric evaluation of the small intestine revealed reduced villus surface area, villus height to crypt depth ratio (VH : CD) and intraepithelial lymphocytes (IELs) in all segments, and reduced acidic goblet cells (AGCs) in the ileum of the HSCT group compared with the TNZ group. Compared with the HSCT group, dietary ß-GOS (0.2% and 0.5%) improved the feed efficiency and relative weight of the small intestine. Furthermore, dietary ß-GOS (0.1%) increased villus surface area in the duodenum and IEL count in the small intestine compared with the HSCT group. Dietary ß-GOS 0.5% increased villi surface area (VSA) in the jejunum and ileum, whereas the IEL count in the small intestine and acidic goblet cells (AGCs) in the jejunum and ileum were reduced compared with the HSCT group. In conclusion, dietary supplementation of ß-GOS (0.2% and 0.5%) improved the growth performance and intestinal microarchitecture of broilers during heat exposure, along with partial immune stimulation.

GBP6: differential expression in pulmonary alveolar macrophages under PRRSV infection and association with blood parameters of its missense mutation

The GBP6 gene belongs to the gene family of interferon-gamma inducible GTPases, and is located in a previously characterized QTL region of porcine reproductive and respiratory syndrome virus (PRRSV) resistance in SSC4. In the current study, RT-PCR assay revealed that the GBP6 gene was widely distributed but highly expressed in spleen and lung. Under PRRSV infection, the GBP6 gene was up-regulated and differentially expressed in the pulmonary alveolar macrophages (PAMs) of Large White and Tongcheng pigs. Multiple sequences alignment and phylogenetic analysis revealed that GBP6 is highly conserved across species. We validated and analyzed the polymorphism of a missense mutation (n.932A>G, rs322187731) in the F2 resource population of Duroc × Erhualian, which changed the Valine (V) to Methionine (M) in the 300th residue of porcine GBP6. Through a linear mixed effects model, the polymorphism of the mutation (n.932A>G, rs322187731) was significantly associated with five haematological traits, namely platelet count at 20 days (PLT-20), plateletcrit at 20 days (PCT-20), white blood cell at 33 days (WBC-33), neutrophil count at 33 days (NE-33) and red blood cell count at 80 days (RBC-80). The findings presented here provide basic information for the function and possible involvement of the GBP6 gene in immune regulation and disease resistance.

Intramuscular variation in mitochondrial functionality of beef semimembranosus

Intramuscular color stability variations in beef semimembranosus have been reported previously. Mitochondria remain biochemically active in postmortem muscle and can influence fresh beef color stability. However, the role of mitochondrial functionality in intramuscular color variations in beef semimembranosus is yet to be examined. We examined the functionality of mitochondria isolated from outside (OSM) and inside (ISM) regions of beef semimembranosus. Semimembranosus muscles (n = 5) were collected from inside rounds of beef carcasses 48 h post-mortem and were separated to OSM and ISM steaks. Color attributes were evaluated instrumentally and biochemically on days 0 and 4 of retail display, whereas mitochondrial oxygen consumption rate (OCR) was measured on day 0 using succinate as substrate using steaks frozen during fabrication. Mitochondrial OCR was significantly greater in OSM than in ISM on day 0. The ISM steaks exhibited significantly greater redness (a* value) than OSM steaks on day 0, but OSM steaks had significantly greater redness than the ISM counterparts on day 4. During retail display, ISM steaks exhibited greater lightness (L* value) than OSM steaks. However, OSM demonstrated significantly greater color stability and metmyoglobin reducing activity than ISM throughout the display. The observed differences in mitochondrial OCR between ISM and OSM steaks indicated that mitochondrial biochemistry possibly contributes to the intramuscular color variations in beef semimembranosus.

**Ractopamine-induced changes in sarcoplasmic proteome profile of post-rigor pork semimembranosus muscle**

Ractopamine is a beta-adrenergic agonist that increases leanness and carcass weight in finishing pigs. Our previous study observed that dietary ractopamine increased the abundance of several glycolytic enzymes in the sarcoplasmic proteome of post-rigor pork longissimus thoracis muscle. Pork semimembranosus is an economically important muscle and demonstrates differences in biochemistry compared with longissimus thoracis. Nonetheless, the effects of ractopamine on sarcoplasmic proteome of semimembranosus have not been evaluated yet. Therefore, this study examined the influence of ractopamine on sarcoplasmic proteome of post-rigor pork semimembranosus. Analyses of sarcoplasmic proteome of semimembranosus muscles from control (CON; diet without ractopamine) and ractopamine-fed (RAC; 7.4 mg/kg for 14 days followed by 10.0 mg/kg for 14 days) barrows revealed that haemoglobin subunit beta, alpha-crystallin B, and titin fragments were over-abundant in CON. In contrast, myosin light chain 1/3 and tripartite motif-containing protein 72 were over-abundant in RAC. The low abundance of haemoglobin subunit beta and alpha crystallin B in RAC could be attributed to fibre type shift (from oxidative to glycolytic) in response to ractopamine. The over-abundance of MLC 1/3 and tripartite motif-containing protein 72 in RAC could be due to the increased myofibrillar protein synthesis and muscle mass in ractopamine-fed pigs. Dietary ractopamine decreased the abundance of sarcoplasmic proteins involved in oxygen transport and chaperone activity, but increased the abundance of proteins involved in muscle contraction and plasma membrane repair in pork semimembranosus muscle.

Increasing zinc levels in phytase-supplemented diets improves the performance and nutrient utilization of broiler chickens

Three hundred and thirty-six day-old Ross-308 male broiler chicks were used in a 35-day trial to investigate the effect of different concentrations of dietary Zn and phytase on broiler performance and energy utilization. Twelve day-old birds were used for the initial slaughter group to provide baseline body compositional data, while the remaining 324 birds were randomly distributed to six experimental diets. The treatments consisted of a 3 x 2 factorial arrangement with three levels of Zn (low, mid, and high; 30, 40, and 50 mg/kg, respectively) and two levels (0, 500 FTU/kg) of microbial phytase. Each dietary treatment was fed to 6 cages (9 birds/cage). Low Zn diet significantly decreased feed intake and body weight gain at days 1 -24. Phytase supplementation improved body weight gain at d 24, irrespective of Zn level. The digestibility of P was improved in birds fed high-Zn diet with phytase supplementation, and the reverse was the case for Fe and Zn digestibility. High dietary Zn increased the Zn and Fe deposition in liver. The activity of AP, Ca-ATPase and Mg-ATPase in the jejunum was high in the phytase supplemented mid-level Zn diet. Phytase supplemented to the mid and high level Zn diets significantly improved most energy utilization parameters. This result indicate that the Zn concentrations used in this study were not inhibitory to phytase activity and broiler performance. Therefore, it can be concluded that dietary zinc level in phytase-supplemented diets could be increased up to 50 mg/kg without any negative effect on phytase-mediated broiler response.

**Growth performance, haemo-biochemical parameters and meat quality characteristics of male Japanese quails fed a Lippia javanica-based diet**

A total of 105 male Japanese quails (153.2 ± 10.21 g) (Cortunix cortunix japonica) were reared in an environmentally controlled house to investigate the effect of inclusion of Lippia javanica leaf meal on growth performance, haematological and serum biochemical parameters, and carcass and meat quality characteristics. The quails were randomly allocated to 15 pens, with each pen holding 7 quails. Pens were then randomly allocated to the following experimental diets: 1) commercial grower diet without antibiotics [NegCon]; 2) commercial grower diet with antibiotics, coxistac and olaquindox [PosCon]; and 3) commercial grower diet without antibiotics in which L. javanica was included at the rate of 25 g/kg [Ljav25]. Experimental diets and fresh water were offered ad libitum. Weekly feed intake and body weights were recorded to calculate feed conversion efficiency (FCE). At 9 weeks of age, quails were slaughtered at a local poultry abattoir for assessment of blood parameters, carcass and meat quality characteristics. Repeated measures analysis showed no significant week × diet interaction effect on average weekly feed intake (AWFI), average weekly weight gain (AWG) and FCE. Diet had no significant influence on AWFI, AWG, FCE, and haematological parameters. There was no dietary effect on overall FI, overall WG and overall FCE. Alanine transaminase (ALT) was the only serum biochemical parameter influenced by diet. Quails offered Ljav25 had higher ALT content (56.83 u/L) than those offered PosCon (18.0 u/L). Diets had no significant impact on carcass characteristics and internal organs, except for gizzard weights. Immediately after slaughter, diets caused no effect on meat quality parameters, except meat lightness (L*), whereas at 24 h post slaughter, diets had significant impact on meat yellowness (b*). No dietary variation was observed for peak positive force (PPF) values of quail meat. NegCon diet promoted the least cooking losses (16.51%) when compared to PosCon and Ljav25 diets, which significantly did not differ. It was concluded that inclusion of L. javanica in quail diets at 25 g/kg feed promoted similar growth performance, health status, and carcass and meat quality traits as the commercial grower diet containing antibiotics. Lippia javanica leaf meal, therefore, has potential as an alternative to antibiotic growth promoters in Japanese quails.

Effects of mannan-oligosaccharides' supplementation on hatching characteristics of four close-bred flocks of Japanese quail breeders

The present study was conducted to evaluate the effects of mannan-oligosaccharides' (MOS) supplementation on hatching characteristics of four close-bred flocks (CBFs) of Japanese quail (Coturnix coturnix japonica) breeders. A total of 960 Japanese quail breeders, aged 12 weeks old, were randomly selected and divided into four groups (n = 240) with twelve replicates (n = 20) in a completely randomized design (15 ♂ : 5 ♀). The birds were a fed corn-based basal diet (group D) or basal diet supplemented with MOS at the levels of 0.25 % (group A), 0.5 % (group B) and 1.0 % (group C) for 15 weeks. The collected data were analyzed by two-way ANOVA techniques using Statistical Analysis System. The fertility and hatchability of 0.50 % MOS-supplemented group was significantly higher than other treatment groups. Similarly, fertility and hatchability percent of fertile eggs of Kaleem flock was significantly higher than other flocks, while dead in-shells were significantly lower in Sadat flock. Conclusively, MOS supplementation positively influences the fertility and hatchability of quail breeders.

Performance of broiler chickens fed South African sorghum-based diets with xylanase

Two experiments were conducted to determine the influence of sorghum variety and xylanase on performance of broiler chickens. In Experiment 1A, a total of 240 day-old Ross broiler chickens were assigned to a 2 (sex) × 3 (sorghum variety) × 2 (with or without xylanase) factorial arrangement in a completely randomized design with 20 chickens per treatment. Gross performance measurements were assessed at 7, 14, and 21 days of age. Carcass yield and visceral organ weights were measured at day 21. In Experiment 1B, a total of 108 female Ross 308 broiler chickens were randomly assigned to a 3 (sorghum variety) × 2 (with or without xylanase) factorial arrangement in a completely randomized design with 6 treatments replicated 6 times. On day 25, all birds were euthanazed by intravenous injection of sodium pentobarbitone and digesta contents from the distal ileum were collected to determine the nutrient digestibility. Broiler chickens offered sorghum variety Pan8816 supplemented with xylanase had higher feed intake, weight gain, and similar feed conversion ratio at 1 - 7 days of age. Breast meat of broiler chickens was not affected by variety or xylanase. The small intestine was heavier in the Pan8625 and Pan8816 groups with xylanase than in the similar Pan8906 group. Enzyme inclusion increased the crude protein digestibility. When xylanase was included in all sorghum varieties, numerically, starch digestibility tended to improve. Sorghum variety affected the growth performance of broiler chickens. Furthermore, nutrient digestibility was affected by the differences in variety.

Comparison of on-farm progeny performances from local and imported boar semen used in the South African pig industry

The widespread use of artificial insemination in the pig industry has provided breeders with access to genetic material from superior boars from around the world. Selection of parent stock is based on estimated breeding values (EBVs), which are regularly computed in all countries performing genetic evaluations. The purpose of this study was to evaluate the value of foreign sires in the South African (SA) pig industry by comparing the on-farm performances of progeny for average daily gain (ADG), feed conversion ratio (FCR) and back fat thickness (BF) from progeny sired by USA and Canadian born sires to the performance of progeny from local sires and to progeny with paternal USA grandsires (F1-US sires). The breeds analysed comprised of Duroc, Landrace and Large White pigs. Males outperformed females for all traits measured (P <0.0001). Large differences (P <0.0001) were observed between on-farm performances which had similar climatic regions for all traits except Duroc BF (P <0.05). Farm differences were consequently attributed to management rather than environmental influences. The effect of country was significant (P <0.05) in all the models tested with the USA-sired progeny having the best overall performance. However, as measured by a stepwise R², country remained the smallest contributor to variation across all models (except BF in Landrace), with farm, sex and year-season contributing larger portions to the variation observed in the on-farm performances of progeny. These results indicate that most of the variation observed could be attributed to differences in farm as explained by management, rather than superiority of the imported boar semen.

Effects of protease on growth performance and carcass characteristics of growing-finishing pigs

A study was conducted to investigate the effects of dietary protease supplementation on growth performance and carcass characteristics of growing-finishing pigs that started with a lower bodyweight than pigs in the control group. A total of 96 growing pigs (initial bodyweight (BW) 31.6 ± 2.97 kg) were allotted to two dietary treatments (48 pigs/treatment, 8 pigs/pen) with different initial BW (34.37 vs. 28.78 kg). The dietary treatments were a control diet (CON), based on maize and soybean meal (grower diets) and wheat (finisher diets), and a protease diet (PRO), which was the CON diet to which 0.02% protease was added. Pigs were fed these dietary treatments (high BW-CON, low BW-PRO) for 12 weeks, comprising six weeks growing and six weeks finishing. In the growing period, PRO had higher average daily gain (ADG) and gain to feed (G:F) ratio than CON. The significant difference in bodyweight that was observed at the beginning of the experiment between the treatment groups was still observed at the end of the growing period. In the finishing period, PRO had reduced feed intake, average daily feed intake (ADFI), and increased G:F ratio compared with CON. At the end of the experiment, there was no significant difference in BW between the treatment groups as a result of lower feed intake and ADFI and higher ADG and G:F ratio. In addition, there were no differences in carcass characteristics between the groups. Therefore, standalone protease supplementation may positively affect the growth performance of growing-finishing pigs through improved feed efficiency without negative effects on carcass characteristics.

Effects of feeding corn silage, pelleted, ensiled, or pelleted and ensiled alfalfa on growth and carcass characteristics of lamb

Two experiments were conducted to evaluate the effects of corn silage (CS) and alfalfa (pelleted (AP), haylage (AH), or combination (APH)) on lamb growth and carcass characteristics. The objective of Experiment 1 (Exp. 1) was to compare AH to CS in lamb feedlot diets on lamb growth and carcass characteristics. Eighty lambs were used in a 56 day experiment with a randomized complete block design. The objective of Experiment 2 (Exp. 2) was to determine the effects of alfalfa form, AP, AH or AHP, on animal performance and carcass characteristics. Seventy two lambs were used in an 82 day experiment with a randomized complete block design. In Exp. 1, lambs offered AH consumed 23.5% more feed on a daily basis than lambs offered CS. However, lambs fed CS gained weight 21.3% faster than lambs fed AH (259 versus 213 g/day, respectively). Additionally, lambs fed CS were 50.4% more efficient in converting feed to gain compared with lambs offered AH (0.173 versus 0.115 kg gain/kg feed, respectively). In Exp. 2, AP resulted in a greater dry matter intake (DMI) and average daily gain (ADG), and fewer days on feed than with AH. The combination of pellets + haylage resulted in a greater DMI, ADG, and fewer days on feed compared to AH alone. Therefore, there was an inverse relationship between both forage particle size and diet moisture content with DMI. There was no difference in daily efficiency of gain due to the form of alfalfa. Average daily gain, days on feed, and DMI are economically important criteria that differ due to the form of alfalfa even when feed efficiencies are similar.

Genetic parameters for ewe reproduction with objectively measured wool traits in Elsenburg Merino flock

Reproduction is important for sustainable lamb production in Merino sheep. Data from a Merino flock maintained at Elsenburg Research Farm in the Western Cape, South Africa, were used to investigate the genetic parameters for ewe reproduction traits and their relationship with objectively measured wool traits. Traits included number of lambs born during the first lambing opportunity (NLB1), number of lambs weaned during the first lambing opportunity (NLW1), total weight of lamb weaned during the first lambing opportunity (TWW1), number of lambs born during a ewe's lifetime (NLB3), number of lambs weaned during a ewe's lifetime (NLW3), and total weight weaned per ewe's reproductive life (TWW3) Fixed effects of selection line, birth type, sex, age of the dam in years, year of birth, and the sex*birth year interaction had significant effects on all bodyweight and objectively measured wool traits. Only year of birth and selection line affected ewe reproduction traits. Heritability estimates amounted to 0.10 ± 0.03 for NLB1, 0.07 ± 0.02 for NLW1, 0.10 ± 0.04 for TWW1, 0.25 ± 0.04 for NLB3, 0.12 ± 0.03 for NLW3, and 0.18 ± 0.04 for TWW3. Wool traits were moderately heritable at 0.28 ± 0.05 (staple strength) to 0.60 ± 0.03 (clean yield (CY)) and coefficient of variation of fibre diameter (CVFD). Relationships among ewe reproduction traits were high, ranging from 0.74 between TWW1 and NLB3 to 1.00 between NLW1 and TWW1. The genetic relationships of ewe reproduction traits with wool weights and staple length were positive. Fibre diameter (FD) and CY were unfavourably related to ewe reproduction traits. It seems possible to improve ewe reproduction when selecting on NLB, NLW, and TWW in Merino sheep without unwanted correlated response to selection in wool traits, with the exception of FD and CY.

**Effects of various inulin levels on in vitro digestibility of corn silage, perennial ryegrass (Lolium perenne L.) and common vetch (Vicia sativa L.)/oat (Avena sativa L.) hay**

The aim of this study was to investigate the effects of various inulin levels on in vitro true dry matter digestibility (IVTD DM) and in vitro neutral detergent fibre digestibility (IVTD NDF) of corn silage (CS), perennial ryegrass (PR), and common vetch/oat hay (VO). Inulin was added to the fermenter at concentrations of 0 (CSC, PRC, VOC), 100 (CS100, PR100, VO100), 200 (CS200, PR200, VO200), and 300 (CS300, PR300, VO300) mg/litre of total culture fluid using an in vitro Daisy" incubator. Each fermenter contained 1600 ml buffer solution and 400 ml rumen fluid. The IVTD DM and IVTD NDF were determined with a Daisy" incubator and rumen fluid obtained from three cannulated Karayaka rams. The IVTD DM values (%) for PRC, PR100, PR200, and PR300 were 70.06 ± 1.133, 73.21 ± 4.153, 70.36 ± 0.506, and 66.69 ± 1.317, respectively. The effects of vNDaFrious inulin levels on IVTD DM and IVTD NDF values of PR were significant (P <0.05). The IVTD DM and IVTD NDF values for CS and VO were not significantly (P >0.05) different. Among the treatments, supplementation of inulin to CS and VO did not have a significant (P >0.05) effect on IVTD DM and IVTD NDF values. The high dose of inulin (PR300D reduced IVTD DM and IVTD NDF, whereas PR100 showed a statistically significant (P <0.05) increase on IVTD Mand IVTD NDF. However, in vivo studies with PR may be required to show the effects of various levels of inulin supplementation to support the IVTD findings of the current study.