The effect of a potential protein binder on ruminal and post-ruminal protein digestion responses

Burger, Abraham Johannes Hendrik (2020-03)

Thesis (MScAgric)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: The objectives of this study were to determine the effect of a potential protein binder on in sacco and in vitro protein disappearance parameters, protein solubility, degradability of soluble protein and intestinal protein digestibility. Soybean, sunflower and canola oilcake meal (OCM) were the three protein feedstuffs used in the trials as they are commonly included in dairy cattle diets in South Africa. Substrates in all trials were treated with Bioprotect® at a rate equivalent to 0.5 L per tonne for each 1% CP (crude protein) in the substrate. Distilled water was used as the control treatment and was applied at the same rates. Ruminally cannulated lactating Holstein cows were used in an in sacco trial and were also used as rumen liquid donors for the in vitro trials. In the first trial, the in sacco procedure was used to determine degradation kinetic parameters over time. All three OCMs were used and rumen incubation was done in four cows. Incubation times were 0, 2, 4, 8, 16, 24 and 48 hours. For the 0 h values, samples were water washed and not incubated in the rumen. Dry matter and CP degradation data were fitted to a non-linear model to determine kinetic parameters and effective degradability. The protein binder did not increase resistance against microbial degradation. The 0 h values were increased after Bioprotect® treatment, resulting in higher model-derived a-values, which also resulted in higher effective degradability values for all three substrates compared to the control treatment. In the second trial, a DaisyII incubator (ANKOM Technology, New York) was used for the in vitro incubations. The same three OCMs were used as in Trial 1 and incubation times were also similar. Treatment * time interactions indicated that the protein binder reduced CP degradation of canola meal after 8 h (49.3 vs. 54.2% for Control; P = 0.022) and 16 h of incubation (63.3 vs. 67.5% for Control; P = 0.04). For soybean meal, treatment also tended (P = 0.06) to reduce 16 h CP degradability (72.6 vs. 77.9% for Control). It seems that Bioprotect® appears to increase CP solubility; however the effect of treatment on CP degradability was not conclusive because of different tendencies observed in the in sacco and in vitro trials. However, the difference between treatments in the magnitude of in vitro CP degradability observed from 4 to 16 h suggested that Bioprotect® may indeed have a reducing effect on the degradability of the potentially degradable fraction but this effect may be shadowed by the increase in the soluble fraction observed in the Bioprotect® treatment. The third trial was done to determine intestinal protein digestibility using the Ross assay. All three OCMs were used and rumen liquid was collected from six lactating Holstein cows. The first phase of the assay represented a 12 h rumen incubation, which was followed by a one-hour gastric digestion phase and finally, a 24 h intestinal digestion phase. Results showed no difference in protein degradability between treatments. The fourth trial investigated the effect of Bioprotect® treatment on the solubility of the substrate proteins. Each OCM with and without Bioprotect treatement was incubated in a borate-phosphate buffer for one hour. Samples were analysed for N only. Bioprotect® treatment increased protein solubility and the soluble protein content of soybean oilcake but had no effect on the other oil cakes. The soluble protein content of soybean oil cake was 20.2% for the Bioprotect® treatment vs. 13.1% for the Control (P < 0.001). The fifth trial determined the degradability of the soluble protein in soybean OCM. This was because it was the only substrate where the soluble protein content differed between treatments. After solubilising the protein using the same protocol as in Trial 4, the supernatant was added to a buffered rumen liquid incubation medium similar to that of the in vitro trial above. Samples were incubated at 39°C for 0, 2, 8 and 24 hours, followed by N analysis. Bioprotect® significantly reduced the rate and extent of the soluble protein degradation. Over the entire 0 – 24 h incubation period, the mean degradation rate (kd) was 0.028/h-1 for the Bioprotect® treatment and 0.036/h-1 for the Control treatment, clearly demonstrating the depressing effect of Bioprotect® on soluble protein degradation. The protein binder, Bioprotect®, seem to have some potential to reduce ruminal CP degradability in some OCMs as the degradation of soluble protein in soybean oil cake meal was clearly decreased by Bioprotect®. This may warrant further research as soybean oil cake is a major protein sources in dairy cattle. Further research with lactating dairy cows is warranted to investigate the effect of Bioprotect® on milk production response, especially when lowering the CP content of the diet.

AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die invloed van ‘n potensiële proteïenbinder op in sacco en in vitro proteïen-verdwyningsparameters, oplosbaarheid van proteïen, degradeerbaarheid van oplosbare proteïen en intestinale proteïenverteerbaarheid te bepaal. Drie proteïen-grondstowwe wat algemeen in melkbeesdiëte in Suid-Afrika ingesluit word, naamlik soja-, sonneblom- en kanola-oliekoekmeel, is in die proewe gebruik. Bioprotect® is as proteïen-binder gebruik en in al die proewe is die substrate met Bioprotect® óf gedistilleerde water (kontrole) behandel deur dit op die onderskeie substrate te spuit teen ‘n peil ekwivalent aan 0.5 L per ton vir elke 1% RP (ruproteïen). Rumen-gekannuleerde lakterende Holsteinkoeie is in ‘n in sacco proef gebruik en dieselfde koeie is ook gebruik as rumenvloeistofskenkers vir die in vitro proewe. In die eerste proef is die in sacco-prosedure gebruik om die kinetiese degradeerbaarheids-parameters oor tyd te bepaal. Al drie OKM substrate is gebruik en rumeninkubasies is in vier koeie gedoen. Inkubasietye was 0, 2, 4, 8, 16, 24 en 48 ure en die 0-ure waardes is verkry deur die onderskeie substrate in dacronsakkies in water te was. Droëmateriaal- en RP degradeerbaarheidsdata is met behulp van ‘n nie-lineêre model ontleed om die kinetiese parameters en effektiewe degradeerbaarhede te bepaal. Die proteïenbindmiddel het nie weerstand teen mikrobiese degradeerbaarheid verhoog nie. Die 0-ure waardes het wel verhoog ná Bioprotect® behandeling en dit het hoër model-afgeleide a-waardes tot gevolg gehad. In vergelyking met die kontrolebehandeling, is die effektiewe RP-degradeerbaarheid ook in al die substrate deur Bioprotect® behandeling verhoog. In die tweede proef is ‘n DaisyII incubator (ANKOM Technology, New York) vir die in vitro-inkubasies gebruik. Dieselfde drie OKM substrate is gebruik en inkubasietye was ook dieselfde. Behandeling * tyd interaksies het daarop gedui dat die proteïenbinder die RP degradeerbaarheid van kanolameel na 8 ure inkubasie verlaag het (49.3 teenoor 54.2% vir die Kontrole; P = 0.022), asook na 16 ure (63.3 teenoor 67.5% vir die Kontrole; P = 0.04). In die geval van soja OKM het die behandeling geneig (P = 0.06) om die RP degradeerbaarheid na 16 ure inkubasie te verlaag (72.6 vs. 77.9% vir die Kontrole). Die afleiding is gemaak dat Bioprotect® die RP oplosbaarheid verhoog, maar die invloed van behandeling op RP degradeerbarheid is onduidelik a.g.v. verskillende neigings wat in die in sacco- en in vitro-proewe waargeneem is. Die verskil in die ordegrootte van RP degradeerbaarheid wat vanaf 4 tot 16 ure inkubasie tussen behandelings waargeneem is, dui wel daarop dat Bioprotect® ‘n onderdrukkende invloed op die degradeerbaarheid van die potensieel degradeerbare RP fraksie mag hê, maar dat hierdie invloed moontlik oorskadu word deur ‘n toename in die oplosbare RP fraksie wat met die Bioprotect® behandeling waargeneem is. Die derde proef is gedoen om die invloed van behandeling op intestinale proteïen-verteerbaarheid te bepaal deur gebruik te maak van die Ross-analisemetode. Al drie proteïensubstrate is weereens gebruik en vir die ruminale inkubasiefase is rumenvloeistof van ses lakterende Holsteinkoeie verkry. Die eerste fase van die analise verteenwoordig ‘n 12-ure rumen-inkubasie, gevolg deur ‘n een-uur gastriese verteringfase en uiteindelik ‘n 24-ure intestinale verteringfase. Resultate het daarop gedui dat behandeling geen invloed op die totale intestinale proteïenvertering gehad het nie. Die vierde proef is gedoen om die invloed van Bioprotect®-behandeling op die RP oplosbaarheid van die onderskeie substrate te ondersoek. Elke OKM is geïnkubeer in ‘n boraat-fosfaatbuffer vir een uur. Monsters is daarna slegs ontleed vir N-inhoud. Bioprotect® behandeling het proteïenoplosbaarheid en die oplosbare proteïeninhoud van soja OKM verhoog, maar het geen invloed op die ander oliekoeke gehad nie. Die oplosbare proteïeninhoud van soja OKM was 20.2% vir die Bioprotect® behandeling teenoor 13.1% vir die Kontrole (P < 0.001). Die vyfde, en finale proef, is gedoen om die degradeerbaarheid van oplosbare proteïen te bepaal. Slegs soja OKM is in hierdie proef gebruik, aangesien dit die enigste substraat is waar die oplosbare proteïeninhoud deur behandeling beïnvloed is. Dieselfde prosedure is gevolg as dié in Proef 4 om oplosbare proteïen vir die hierdie proef te verkry. Die oplosbare proteïen supernatant is daarna by ‘n gebufferde rumenvloeistof-inkubasiemedium, soortgelyk aan dié van die in vitro proef hierbo beskryf, gevoeg en die monsters is vir 0, 2, 8 en 24 ure by 39°C geïnkubeer, gevolg deur N-analises. Bioprotect® het die degradeerbaarheidstempo, sowel as die hoeveelheid RP wat gedegradeer is, betekenisvol verlaag. Tydens die totale 0 tot 24-ure inkubasieperiode, was die degradeerbaarheidstempo (kd) 0.028/h-1 vir die Bioprotect®-behandeling en 0.036/h-1 vir die kontrolebehandeling, wat duidelik op die neerdrukkende effek van Bioprotect® op die degradeerbaarheid van die oplosbare proteïenfraksie dui. Die finale gevolgtrekking is gemaak dat die proteïenbinder, Bioprotect®, die potensiaal het om ruminale RP-degradeerbaarheid in sekere oliekoeke te verlaag. In die geval van soja OKM, wat een van die belangrikste proteïenbronne in melkbeesdiëte is, het Bioprotect®-behandeling die degradeerbaarheid van die oplosbare proteïenfraksie aansienlik verlaag. Verdere navorsing met lakterende melkkoeie is geregverdig om die invloed van Bioprotect® op melkproduksierespons te ondersoek, veral indien die RP-inhoud van die dieët verlaag word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/108306
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