Control of Rate and Extent of Protein Degradation

Broderick, G.A.; Wallace, Robert John; Ørskov, E. R.

doi:10.1016/b978-0-12-702290-1.50030-8

Cited by 115 publications

(94 citation statements)

References 209 publications

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“…This will not only maintain the rate of microbial protein synthesis, but may in fact increase its efficiency (Cotta and Russell, 1982;Argyle and Baldwin, 1989;Griswold et al, 1996). Broderick et al (1991) demonstrated that rapidly degraded proteins may result in the accumulation of peptides and AA within the first 2 h after feeding, suggesting that rates of peptidolysis and deamination play an important role in the control of protein degradation. Cardozo et al (2004) also found in continuous culture fermenters receiving a typical dairy ration that the concentration of peptides, AA and ammonia were within the same range (50 to 10 mg N/l) for up to 8 h after feeding.…”

Section: Microbial Protein Synthesismentioning

confidence: 99%

Strategies for optimizing nitrogen use by ruminants

Calsamiglia

Ferret

Reynolds

et al. 2010

Animal

251

165

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The efficiency of N utilization in ruminants is typically low (around 25%) and highly variable (10% to 40%) compared with the higher efficiency of other production animals. The low efficiency has implications for the production performance and environment. Many efforts have been devoted to improving the efficiency of N utilization in ruminants, and while major improvements in our understanding of N requirements and metabolism have been achieved, the overall efficiency remains low. In general, maximal efficiency of N utilization will only occur at the expense of some losses in production performance. However, optimal production and N utilization may be achieved through the understanding of the key mechanisms involved in the control of N metabolism. Key factors in the rumen include the efficiency of N capture in the rumen (grams of bacterial N per grams of rumen available N) and the modification of protein degradation. Traditionally, protein degradation has been modulated by modifying the feed (physical and chemical treatments). Modifying the rumen microflora involved in peptide degradation and amino acid deamination offers an alternative approach that needs to be addressed. Current evidence indicates that in typical feeding conditions there is limited net recycling of N into the rumen (blood urea-N uptake minus ammonia-N absorption), but understanding the factors controlling urea transport across the rumen wall may reverse the balance to take advantage of the recycling capabilities of ruminants. Finally, there is considerable metabolism of amino acids (AA) in the portal-drained viscera (PDV) and liver. However, most of this process occurs through the uptake of AA from the arterial blood and not during the 'absorptive' process. Therefore, AA are available to the peripheral circulation and to the mammary gland before being used by PDV and the liver. In these conditions, the mammary gland plays a key role in determining the efficiency of N utilization because the PDV and liver will use AA in excess of those required by the mammary gland. Protein synthesis in the mammary gland appears to be tightly regulated by local and systemic signals. The understanding of factors regulating AA supply and absorption in the mammary gland, and the synthesis of milk protein should allow the formulation of diets that increase total AA uptake by the mammary gland and thus reduce AA utilization by PDV and the liver. A better understanding of these key processes should allow the development of strategies to improve the efficiency of N utilization in ruminants. Keywords: ruminant, nitrogen efficiency ImplicationsRuminants have a low efficiency of N utilization compared with non-ruminants. This low efficiency has implications not only for production performance and economic efficiency but also for the emission of contaminants to the environment. The efficiency of N utilization can be improved through the understanding and modification of factors regulating the efficiency of N utilization in key processes, including N capture in the rumen, ...

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Section: Microbial Protein Synthesismentioning

confidence: 99%

Strategies for optimizing nitrogen use by ruminants

Calsamiglia

Ferret

Reynolds

et al. 2010

Animal

251

165

View full text Add to dashboard Cite

show abstract

“…The effectiveness of the heat treatment depends on the time and temperature applied, but the optimal conditions vary with the protein concentrate (Broderick et al, 1991;McNiven et al, 2002). Thus, Calsamiglia and Stern (1995) observed a decrease of intestinal digestibility by heating the soybean meal at 165°C for more than 2.5 h, whereas milder heating resulted in an increase of protein digestibility.…”

Section: Implications and Methodsmentioning

confidence: 99%

“…However, if the thermal impact is excessive Maillard irreversible condensation reactions are produced between the free amino groups of protein and the aldehyde groups of sugars (Broderick et al, 1991;NRC, 2001;Arroyo, 2012). These irreversible reactions cause significant losses of certain AA and decrease protein digestibility in the small intestine, thus generating "overprotected proteins" (Van Soest, 1994).…”

Section: Implications and Methodsmentioning

confidence: 99%

“…There are different methods to decrease the ruminal fermentation of protein, which can be classified into physical and chemical treatments (Windschitl and Stern, 1988;NRC, 2001). Most of these methods are based on the application of heat, chemical agents or a combination of both for modifying the characteristics of the protein and increasing their resistance to microbial degradation (Broderick et al, 1991).…”

Section: Implications and Methodsmentioning

confidence: 99%

“…A reduction in the ruminal protein degradation of high-quality proteins can increase protein utilization and reduce N environmental emissions. The treatment of protein-rich feeds with heat and/or acid solutions has proven to be useful for protecting proteins from microbial degradation in the rumen, but the efficacy of these treatments varies with different factors, such as the type and concentration of acid and the heat intensity and duration (Broderick et al, 1991). Previous in vitro and in situ studies have demonstrated the efficacy of a combined treatment with malic acid and heat to increase the protein value of sunflower meal (SM) and spring peas (Arroyo et al, 2011;Díaz-Royón et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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