Beef production and quality of Malawi Zebu steers fed diets containing rangeland-based protein sources under feedlot conditions

Thesis (PhD)--Stellenbosch University, 2018.

ENGLISH ABSTRACT: The current study evaluated smallholder farmers perceptions towards climate change, their identification of potential protein sources during drought, the nutrition profile of these protein sources and their actual production value when fed to Malawi Zebu steers under feedlot conditions. Using a structured questionnaire, 182 smallholder farmers were interviewed to determine socio-economic factors affecting their perceptions of impacts of climate change on beef production, and to identify potential protein sources they may use during drought periods in Malawi. All farmers were aware of the impacts of climate change on beef production including knowledge around the causes of deterioration of grazing rangelands, which culminated in poor animal reproduction and production performances. Perceptions of farmers were influenced more by the biophysical factors such as agroecological zone than socio-economic factors (P<0.05) indicating sensitivity of some areas to climate change in Malawi. Farmers had limited options to minimise the impacts of climate change on beef production including use of intake bulls to promote growth and increasing grazing hours. The indigenous oil-seeds and browse legume trees that farmers considered as potential protein supplements in the dry season included: Adansonia digitata (Baobab, 15% of respondents) seeds, Dolichos kilimandscharicus (wild lupin, 21%) and Vachellia polyacantha (White thorn tree) leaves 2%). Chemical composition and in vitro ruminal digestibility values of these potential rangeland-based protein sources were evaluated across two growing seasons: 2015 and 2016 and where applicable, compared to Glycine max (soybean) as a standard protein supplement. Regardless of season, soybean had the highest content of crude protein (CP) and starch followed by baobab seed (P<0.05). Crude fat content of baobab seed irrespective of season superseded all the assayed protein sources (P<0.05). The neutral detergent fibre (NDF) content was only affected by species (P<0.05), with soybean and baobab seed meals having the lowest NDF contents (P<0.05). Overall, leaves of V. polyacantha had the highest total phenols, tannins, calcium, iron and lowest in vitro NDF digestibility compared to other species across seasons (P<0.05). The largest content of phosphorus, copper and zinc was recorded in baobab seed collected regardless of season (P<0.05). Regardless of season, soybean meal had the highest content for most amino acids followed by baobab seeds, with V. polyacantha having the lowest contents (P < 0.05)Overall, irrespective of the season baobab seed had a better mineral profile and similar contents of CP, starch, NDF and amino acids compared to soybean. The effects of A. digitata seed and V. polyacantha leaf-meal on in vivo nutrient digestibility and microbial nitrogen supply, and growth performance, carcass and meat quality attributes were evaluated using Malawi Zebu steers. Three diets made up of rangeland hay and maize bran with either baobab seed meal, V. polyacantha leaf-meal or soybean meal (control) as protein source, respectively, were randomly allocated to 30 individually housed Malawi Zebu steers (182±21.4 kg and 29 months old) for 120 days. Feed offered and refused were measured daily and live weight of the steers were obtained every four weeks. Apparent in vivo nutrient digestibility was estimated usingn faecal grab samples which were collected over four days and in vitro indigestible neutral detergent fibre was used as an internal indicator. The rumen fluid was donated by a fistulated Malawi Zebu cow. Microbial nitrogen supply was calculated based on urinary purine derivative concentration of spot urine samples. On day 120, all steers were slaughtered and carcass measurements were recorded. The M. longissimus thoracic et lumborum (LTL) of each animal was sampled for meat quality measurements. Steers fed diets containing soybean and baobab seed meal had similar apparent total tract digestibility, DMI and ADG (P<0.05). However, steers fed baobab seed meal had the highest rumen microbial nitrogen supply followed by Soybean- and Vachellia-fed steers (P<0.05). Steers fed the diet containing baobab had the highest gross margins followed by steers fed V. polyacantha leaf-meal and soybean meal, in that order (P<0.05). Carcasses from Malawi Zebu steers fed baobab and Vachellia diets had higher ultimate pH than those animals fed the soybean diet (P<0.05). Muscle colour from animals fed the Soybean diet was brighter than that from animals on the baobab and Vachellia diets. During a 7-day retail display, Vachellia diet produced beef muscle with the highest resistance to browning (lowest hue angle values; P<0.05). Steers on baobab and Vachellia diets had muscles with higher (P<0.05) water holding capacity than those on soybean diet. Baobab-fed steers had muscle with the highest zinc and manganese contents compared to the other treatments. Overall, feeding steers with rangeland-based protein sources, especially baobab seed diet improved beef production and quality of Malawi Zebu steers. Although incorporation of V. polyacantha leaf-meal improved meat quality attributes, its inclusion should be minimal because of its adverse effects on animal performance. Data from the feeding trial, dry matter intake (DMI) and average daily gain (ADG) of the steers, was fitted into the two nutritional models to aid their predictions. The models used were the Beef Cattle Nutrient Requirements Model (BCNRM) and Large Ruminant Nutrition System (LRNS). The BCNRM was more accurate and precise in predicting the DMI (r2=0.95; mean bias, MB=2.5%; mean square prediction error, MSPE=0.16; and concordant correlation coefficient, CCC=0.96) than the LRNS (r2 =0.79; MB=11%; MSPE=0.19; CCC=0.82). Similarly, BCNRM was more accurate and precise in forecasting ADG (r2=0.87; MB=10%; MSPE=0.029; CCC=0.75) than LRNS (r2=68; MB=24%; MSPE=0.038; CCC=0.33). Overall, the BCNRM was more accurate and precise than the LNRS model in predicting DMI and ADG of Malawi Zebu steers fed rangeland based diets under feedlot conditions. To enhance adoption of strategies aimed at equipping smallholder beef producers to deal with climate change related feed shortages, it could be important to realign carcass classification and grading systems to suit smallholder beef production associated with rangeland-finished indigenous cattle breeds. Current beef carcass classification and grading systems in selected Southern African countries do not appropriately reward smallholder beef production associated with rangeland-finished indigenous cattle. Supportive policies and regulations have been recommended to promote value addition of rangeland-finished indigenous cattle breeds in the smallholder areas of Malawi.

AFRIKAANSE OPSOMMING: Die huidige studie het kleinboere se persepsies oor klimaatsverandering geëvalueer, hul identifikasie van potensiële proteïenbronne tydens droogte, die voedingsprofiel van hierdie proteïenbronne en hul werklike produksiewaarde geëvalueer wanneer Malawi Zebu ramme onder voerkraaltoestande met dit gevoer word. Met behulp van 'n gestruktureerde vraelys is daar met 182 kleinboere onderhoude gevoer om te bepaal hoe en tot watter mate sosio-ekonomiese faktore hul persepsies van klimaatsverandering op vleisproduksie beïnvloed, te identifiseer en vas te stel watter potensiële proteïenbronne hulle tydens droogtydperke in Malawi sal gebruik. Al die boere was bewus van die impak van klimaatsverandering op vleisproduksie, insluitend ook dat daar kennis heers oor die oorsake van die agteruitgang van weidingslande, wat gelei het tot swak lewering van geslag voortsetting en voortplanting, diereproduksie en algehele produksie vlakke. Die persepsies van boere is meer beïnvloed en bepaal deur die biofisiese faktore invloede soos die agro-ekologiese sone as sosio-ekonomiese faktore (P <0.05) wat duidelike aanduidings gee van die sensitiwiteit van sommige gebiede vir klimaatsverandering in Malawi. Boere het beperkte opsies gehad om die impak van klimaatsverandering op vleisproduksie te verminder. Pogings wat aangewend was sluit in die potensiaal om inheemse blare-peulvrugte asook blare te gebruik as proteïenbronne in die droë seisoen. Die mees algemeen beskikbare inheemse oliesade en blare wat hierbo genoem word, sluit in: Adansonia digitata (Baobab, 15% van die respondente) sade, Dolichos kilimandscharicus (wilde lupien, 21%) en Vachellia polyacantha (Witdoringboom, 2%) blare in die droë seisoen. Chemiese samestelling en in vitro-spatale verteerbaarheidswaardes van hierdie potensiële grondgebaseerde proteïenbronne is oor twee groeiseisoene geëvalueer: 2015 en 2016 en waar van toepassing, vergelyk met Glycine max (sojaboon) as 'n standaard proteïenaanvulling. Ongeag die seisoen, het sojabone die hoogste inhoud van ru-proteïen (CP) en stysel, gevolg deur kremetartsaad (P <0.05). Ruwe vetinhoud van kremetartsaad, ongeag die seisoen, het al die geasseseerde proteïenbronne (P <0.05) oorskrei. Die inhoud van die neutrale skoonmaakmiddelvesel (NDF) is slegs beïnvloed deur spesies (P <0.05), met sojaboon- en kremetartsaadmaaltye met die laagste NDF-inhoud (P <0.05). Oor die algemeen het blare van Vachellia polyacantha die hoogste totale fenole, tanniene, kalsium, yster en laagste in vitro NDF verteerbaarheid gehad in vergelyking met ander spesies oor seisoen tydperke (P <0.05). Die grootste inhoud van fosfor, koper en sink is aangeteken in kokaobab saad wat ingesamel is, ongeag die seisoen (P <0.05). Ongeag die seisoen het sojameel die hoogste inhoud vir die meeste aminosure gevolg deur kremetartaad, met Vachellia polyacantha die laagste inhoud (P <0.05) vlak. Oor die algemeen en ongeag die seisoen, het kremetartaad 'n beter mineraalprofiel en soortgelyke inhoud van CP, stysel, NDF en aminosure in vergelyking met sojabone gehad. Die effekte van A. digitata saad en V. polyacantha blaarmeel op in vivo voedingstof verteerbaarheid en mikrobiese stikstoftoevoer, en groeivoorstelling, karkas en vleiskwaliteit eienskappe is geëvalueer met behulp van Malawi Zebu ramme. Drie diëte wat bestaan uit heuwelhooi en mielies semels met onderskeidelik kremetartaad-ete, V. polyacantha-blaarmeel of sojameel (beheer) as proteïenbron, is nie-bepalend toegedien aan 30 individueel gehuisvestigde Malawi Zebu ramme (182 ± 21.4 kg en 29 maande oud) oor ǹ tydperk van 120 dae. Voedsel aangebied en geweier is daagliks gemeet en eintlike deurlopende gewigte van die ramme is elke vier weke gemeet en verhaal. Skynbare in vivo voedingstof verteerbaarheid is geskat met behulp van fekale gryp monsters wat oor vier dae versamel is en in vitro onverdiverbare neutrale skoonmaakmiddel vesel is gebruik as 'n interne aanwyser. Die rumenvloeistof is geskenk deur 'n gefistileerde Malawi Zebu-koei. Mikrobiese stikstofvoorsiening is bereken op grond van urinêre purien afgeleide konsentrasie van geteikende urine monsters. Op dag 120 is alle ramme geslag en karkasmetings is aangeteken. Die M. longissimus torakale et lumborum (LTL) van elke dier is bemonster vir vleiskwaliteitmetings. Ram gevoerde diëte wat sojabone- en kremetartaad-ete bevat, het soortgelyke skynbare totale kanaalverteerbaarheid, DMI en ADG (P <0.05) gehad. Ramme wat met kremetartaad-etes gevoer is het egter die hoogste speenmikrobiese stikstofvoorsiening gehad naas en gevolg deur ramme wat Sojaboon- en Vachellia-voer (P <0.05) ontvang het. Ramme wat met die dieet met kremetart gevoer is, het die hoogste bruto rig-wysigings perke gehad , gevolg deur ramme gevoed met V. polyacantha blaarmeel en sojameel, in daardie volgorde (P <0.05). Karkasse uit Malawi Zebu-ramme gevoer met kokaob-voeding en Vachellia-dieet het hoër uiteindelike pH gehad as die diere wat die sojaboon-dieet gevoer was (P <0.05). Spierkleur van die diere wat die sojaboon-dieet gevoer het, was helderder as dié van die diere op die kremetart- en Vachellia-dieet. Tydens 'n 7-dae kleinhandel vertoning, was aangedui dat die Vachellia dieet vleis spier die hoogste weerstand bied teen bruin etsing of bruin verkleuring of verbranding (laagste tint hoek waardes, P <0,05). Ramme op kremetart- en Vachellia-dieet het spiere gehad met hoër (P <0.05) waterhouvermoë as dié wat sojaboondieet toegedien was. Baobab-gevoerde ramme het spiere gehad met die hoogste sink- en mangaaninhoud in vergelyking met die wat ander behandeling ontvang het. Oor die algemeen het voedselsoorte met die oorsprong van proteïenbronne, veral kremetartaaddieet, die vleisproduksie en kwaliteit van die Malawi Zebu ramme verbeter. Alhoewel die inkorporering of insluiting van V. polyacantha-blaarmeel die eienskappe van vleiskwaliteit verbeter, moet die insluiting daarvan minimaal wees weens die nadelige gevolge daarvan op dier-prestasie. Data van die voedingstoets, droëstofinname (DMI) en die gemiddelde daaglikse wins (ADG) van die ramme is in die twee voedingsmodelle toegepas om hul voornemende voorspellings te bepaal en die uitwerking daarvan aan te help. Die modelle wat gebruik is, was die Beefvleisvoedingstofbehoeftesmodel (BCNRM) en die Groot Rundervoedingstelsel (LRNS). Die BCNRM was meer akkuraat en presies in die voorspelling van die DMI (r2 = 0.95; gemiddelde vooroordeel, MB = 2.5%; gemiddelde vierkantige voorspellingsfout; MSPE = 0.16; en ooreenstemmende korrelasiekoëffisiënt, CCC = 0.96) as die LRNS (r2 = 0.79; MB = 11%; MSPE = 0,19; CCC = 0,82). Net so ook was BCNRM meer akkuraat in die voorspelling van ADG (r2 = 0.87; MB = 10%; MSPE = 0.029; CCC = 0.75) as LRNS (r2 = 68; MB = 24%; MSPE = 0.038; CCC = 0.33). Oor die algemeen was die BCNRM meer akkuraat en presies as die LNRS-model in die voorspelling van DMI en ADG van die Malawi Zebu-ramme wat gevulde grondgebaseerde diëte onder voerkraaltoestande gevoer was. Om die aanvaarding van strategieë te verbeter wat daarop gemik is om kleinboerevleisprodusente toe te rus om die tekort aan voedseldoeleindes in verband met klimaatsverandering te hanteer, kan dit belangrik wees om karkasklassifikasie en graderingstelsels te hersien om kleinvee-beesvleisproduksie wat verband hou met inheemse beesrasse wat van herkoms afkomstig is, toegerus met wat paslik is, aanvaarding te bied. Huidige vleiskarkas klassifikasie en graderingstelsels in geselekteerde Suider-Afrikaanse lande beloon nie kleinvee-vleisproduksie wat geassosieer word met beweerde inheemse beeste. Ondersteunende beleide en regulasies is aanbeveel om waarde-toevoeging van inheemse beesrasse in die kleinboere van Malawi te verbeter.

Doctoral