Beef production and biopreservative effects of dietary citrus and winery by-products

Thesis (PhDAgric)--Stellenbosch University, 2020.

ENGLISH ABSTRACT: The overall objective of the current study was to compare citrus pulp and grape pomace as dietary supplements and biopreservative for beef production and quality. Angus steers were fed 150 g/kg of dried citrus pulp (DCP) or grape pomace (DGP) as alternative fiber sources to wheat bran (control). Twenty-four steers (7 months old) were assigned to three dietary treatments (8 steers/ treatment) in a completely randomized design. Steer was the experimental unit. Steers were adapted for 21 d before 7 d of collecting feed, refusals, faecal and urine samples for determination of nutrient digestibility and utilisation. The digestibility trial was followed by a growth performance trial, which lasted 90d. During this period, dry matter intake (DMI), average daily gain (ADG) and feed efficiency data were collected. Post-feeding, steers were slaughtered and the left longissimus thoracis lumborum (LTL) from each carcass was sampled for physico-chemical meat quality attributes, shelf-life, major pro-oxidant fatty and volatile compound analyses, while the right LTL was sampled for the evaluation of eating quality attributes. Overall, steers fed the DGP diet had the greatest intake of dry matter (DM), organic matter (OM), crude protein (CP), ash free neutral detergent fiber (aNDFom), ether extract and starch followed by steers fed the DCP and control diets (P ≤ 0.05). Apparent digestibilities of DM, OM and aNDFom were greater (P ≤ 0.05) for the DCP diet compared to the DGP and control diets. Feeding the DCP and DGP diets increased (P ≤ 0.05) ruminal concentrations of total volatile fatty acids, acetate, isovalerate, acetate to propionate ratio, and reduced propionate concentrations compared to the control diet. The steers fed the control diet had the greatest urinary excretions of allantoin, uric acid and total purine derivatives followed by those fed the DCP and DGP diets (P ≤ 0.05). The nitrogen (N) intake, faecal nitrogen, N retention and N efficiency utilization were DGP > DCP > control diets (P ≤ 0.05). Feeding the DGP and DCP diets resulted in greater (P ≤ 0.05) ADG and final weight compared to the control diet. Steers fed the DGP diet had greater (P ≤ 0.05) DMI, warm and cold carcass weights than those fed the DCP and control diets. Shear force and income over feed costs were greatest for the DGP diet followed by the DCP and control diets (P ≤ 0.05). The DCP diet resulted in the greatest concentration of α-tocopherol in beef muscle tissues, followed by DGP and control diet (P ≤ 0.05). The beef antioxidant activity was DGP > DCP > control (P ≤ 0.05). During retail display DGP- or DCP-fed beef had greater L* (P ≤ 0.05) and fewer (P ≤ 0.05) coliforms than control diet fed beef. Beef TBARS and carbonyl contents were DGP < DCP < control (P ≤ 0.05). Overall, antioxidant activity decreased (P ≤ 0.05) while bacterial loads, TBARS and carbonyl contents increased (P ≤ 0.05) during retail display regardless of the diet. Feeding the DGP or DCP diets increased (P ≤ 0.05) the proportions of 18:2 n-6, 18:3 n-3 and total polyunsaturated fatty acid (FA) in LTL muscle. Beef from steers fed the control diet had greater (P ≤ 0.05) concentrations of alcohol, ketones and aldehydes, and lower (P ≤ 0.05) concentrations of sulphur containing compounds compared to the DCP- and DGP-fed beef (P ≤ 0.05). Feeding the DGP and DCP diets produced about 10% less tender (P ≤ 0.05) beef than the control diet. Overall, DGP improved nutrient intake, retention and efficiency of N utilization, growth performance, carcass attributes, beef shelf life, increase proportions of the main pro-oxidant fatty acids, and reduced aldehydes, ketones and alcohols associated with oxidation without compromising beef physicochemical and sensory quality. The current finding suggests that DGP may be a better fiber substitute and natural preservative in beef finishing diets than DCP.

AFRIKAANSE OPSOMMING: Die algemene doel van die studie was om sitrus- en druiwepulp te vergelyk in terme van hulle potensiaal as voedingsaanvullings en biopreserveermiddels vir die produksie en kwaliteit van beesvleis. ‘n Porsie van 150 g / kg gedroogde sitruspulp (DCP) of druiwepulp (DGP) is aan Angus bulle gevoer as ‘n alternatiewe veselbron in die plek van koringsemels (kontrole). Vier-en-twintig bulle (7 maande oud) is lukraak ingedeel in drie dieetbehandeling groepe (8 bulle per behandeling) in 'n totaal ewekansige ontwerp, met ‘n bul as eksperimentele eenheid. Bulle is vir 21 dae aangepas voordat versameling van onbenutte voer, mis- en urienmonsters oor ʼn tydperk van 7 dae versamel is vir die bepaling van die verteerbaarheid en benutting van voedingstowwe. Die verteerbaarheidstoets is gevolg deur 'n groeiprestasieproef wat 90 dae geduur het. Gedurende hierdie periode is droëmateriaalinname (DMI), gemiddelde daaglikse gewigstoename (ADG) en voerdoeltreffendheidsdata versamel. Na voeding is die bulle geslag en die linker longissimus thoracis lumborum (LTL) is van elke karkas versamel vir die ontleding van fisies-chemiese vleiskwaliteit eienskappe, rakleeftyd, hoof pro-oksidant vetsure en vlugtige verbindings, terwyl die regter LTL versamel is vir die bepaling van die eetgehalte eienskappe. Oor die algemeen het die bulle op die DGP-dieet die grootste inname van droëmateriaal (DM), organiese materiaal (OM), ruproteïen (CP), mineraalvrye neutrale detergentvesel (aNDFom), eterekstrak en stysel gehad, in vergelyking met die bulle wat die DCP en kontrole diëte ingeneem het. Die oënskynlike verteerbaarheid van DM, OM en aNDFom was hoër vir die DCP-dieet in vergelyking met die DGP en kontrole diëte. Die voeding van die DCP- en DGP-diëte het ʼn verhoging van die totale rumen vlugtige vetsure asetaat, iso-valeraat en asetaat tot propionaat-verhouding en die propionaatkonsentrasies verlaag, wanneer dit met die kontrole-dieet vergelyk word. Die bulle wat die kontrole dieet ontvang het, het die grootste urinêre uitskeiding van allantoïen, uriensuur en totale purienderivate gehad, gevolg deur die bulle wat die DCP- en DGP-diëte gevoer was. Die stikstof (N)-inname, fekale stikstof, N-retensie en N- doeltreffendheidsbenutting was DGP> DCP> kontrole diëte. Die voeding van die DGP- en DCP-diëte het tot 'n beter ADG en finale gewig gelei in vergelyking met die kontrole-dieet. Bulle wat die DGP-dieet gevoer was, het ʼn verhoogde DMI en swaarder warm- en koue karkasgewigte gehad as dié wat die DCP- en kontrole diëte ontvang het. Die skeursterkte en inkomste bo voerkoste was die hoogste vir die DGP-dieet, gevolg deur die DCP- en beheerdiëte. Die DCP-dieet het gelei tot die hoogste konsentrasie van α-tokoferol in beesspierweefsel, gevolg deur die DGP- en kontrole dieet. Die antioksidant aktiwiteit van beesvleis was DGP> DCP> kontrole. Tydens kleinhandelvertoning het DGP- of DCP-gevoede beesvleis hoër L * waardes gehad en minder kolivorme as beesvleis van bulle wat die kontrole dieet ontvang het. Bees-TBARS en karbonielinhoud was DGP <DCP < kontrole. Oor die algemeen het die antioksidant aktiwiteit afgeneem terwyl bakterielading, TBARS en karbonielinhoud toegeneem het tydens kleinhandelvertoning, ongeag die dieet. Die voeding van die DGP- of DCP-diëte verhoog die verhoudings van 18: 2 n-6, 18: 3 n-3 en totale poli-onversadigde vetsure (FA) in die LTL-spier. Beesvleis van diere op die kontrole dieet het ʼn hoër konsentrasie alkohol, ketone en aldehiede gehad en laer konsentrasie swaelbevattende verbindings, wanneer vergelyk met die monsters versamel van die DCP- en DGP-gevoerde bulle. ʼn Metaalagtige vleis-aroma was meer prominent vir vleismonsters verkry van die DGP- en DCP-gevoerde bulle, in vergelyking met die kontrole dieet. Die voeding van die DGP- en DCP-diëte het ongeveer 10% minder sag beesvleis opgelewer as die kontrole-dieet. In die geheel het DGP voedingsinname verhoog, die retensie en doeltreffendheid van N-gebruik, groeiprestasie en karkaseienskappe verbeter. Die DCP – en DGP diëte het gelei tot ʼn verlengde rakleeftyd, die verhoudings van die belangrikste pro-oksidant vetsure verhoog en laer vlakke van aldehiede, ketone en alkohole, wat met oksidasie verbind word, tot gevolg gehad. Fisio-chemiese en sensoriese kwaliteit is nie beïnvloed nie. Die bevindinge dui daarop dat DGP 'n beter veselvervanger en natuurlike preserveermiddel in beesafronddiëte kan wees as DCP.

Doctoral