Browsing by Author "Burger, Abraham Johannes Hendrik"
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- ItemThe effect of a potential protein binder on ruminal and post-ruminal protein digestion responses(Stellenbosch : Stellenbosch University, 2020-03) Burger, Abraham Johannes Hendrik; Cruywagen, C. W.; Van Zyl, Johan Hendrik Combrink ; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.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.