Does intra-ruminal nitrogen recycling waste valuable resources? A review of major players and their manipulation

Abstract

Nitrogenous emissions from ruminant livestock production are of increasing public concern and, together with methane, contribute to environmental pollution. The main cause of nitrogen-(N)-containing emissions is the inadequate provision of N to ruminants, leading to an excess of ammonia in the rumen, which is subsequently excreted. Depending on the size and molecular structure, various bacterial, protozoal and fungal species are involved in the ruminal breakdown of nitrogenous compounds (NC). Decelerating ruminal NC degradation by controlling the abundance and activity of proteolytic and deaminating microorganisms, but without reducing cellulolytic processes, is a promising strategy to decrease N emissions along with increasing N utilization by ruminants. Different dietary options, including among others the treatment of feedstuffs with heat or the application of diverse feed additives, as well as vaccination against rumen microorganisms or their enzymes have been evaluated. Thereby, reduced productions of microbial metabolites, e.g. ammonia, and increased microbial N flows give evidence for an improved N retention. However, linkage between these findings and alterations in the rumen microbiota composition, particularly NC-degrading microbes, remains sparse and contradictory findings confound the exact evaluation of these manipulating strategies, thus emphasizing the need for comprehensive research. The demand for increased sustainability in ruminant livestock production requests to apply attention to microbial N utilization efficiency and this will require a better understanding of underlying metabolic processes as well as composition and interactions of ruminal NC-degrading microorganisms.

The Effect of Herbage Conservation Method on Protein Value and Nitrogen Utilization in Dairy Cows

“…represented the majority of bacteria, consistent with earlier observations [40]. The higher abundance in the ruminal fluid from cows fed SI compared to FH could be related to better accessibility of feed protein, as Prevotella are known for proteolytic and peptidolytic activity [41]. B. fibrisolvens also displays proteolytic activity [41] and was elevated through feeding FH compared to SI, but its overall relative abundances were low.…”

“…The higher abundance in the ruminal fluid from cows fed SI compared to FH could be related to better accessibility of feed protein, as Prevotella are known for proteolytic and peptidolytic activity [41]. B. fibrisolvens also displays proteolytic activity [41] and was elevated through feeding FH compared to SI, but its overall relative abundances were low. Carbohydrate-degrading bacteria F. succinognenes, R. albus, and R. flavefaciens showed together a high relative abundance, presumably reflecting the forage-only diet.…”

Rumen Virus Populations: Technological Advances Enhancing Current Understanding

“…This study was the first to demonstrate that not only were phages prevalent in the rumen, a finding subsequently confirmed using TEM (Hoogenraad et al, 1967), it also demonstrated that the phages found in the rumen differed from those present in other environments. This primary investigation was followed by numerous studies conducted in laboratories across the globe (Iverson and Millis, 1976a;Tyutikov et al, 1980;Hazlewood et al, 1983;Tamada et al, 1985;Nemcova et al, 1993;Styriak et al, 1994;Ambrozic et al, 2001). The majority of these studies were conducted in the 1980's and 1990's, with very few phage isolations reported in the literature beyond this era.…”

“…The final stages of viral replication results in the accumulation of intact viral particles inside the cells and fragmentation (lysis) of the cell membrane, causing cell death and the release of progeny viral particles. Lysis also releases remnants of the microbial cell, including cell wall fragments as well as proteins and nucleic acids, which may then be taken up and utilized by other rumen microbes, a process often described as intra-ruminal recycling (Firkins et al, 1992;Hartinger et al, 2018) (Figure 2A). The recycling of nutrients amongst microbes was initially regarded as being a negative consequence of viral activity, limiting the amount of microbial protein carried through to the lower intestine where it can be absorbed by the animal (Leng and Nolan, 1984).…”

Fermentation profile and nutritional quality of silages composed of cactus pear and maniçoba for goat feeding

“…The increase in nitrogen consumption is in line with the DMI presented by the animals fed increasing levels of maniçoba in the diets. The increase in faecal nitrogen may be related to the attempt to synchronize the availability of energy and protein for the rumen microorganisms, which may have increased the digestibility of the eliminated CPmainly through faeces (Hartinger et al, 2018). According to Getahun et al (2019), the N found in the faeces derives from the microbial cells formed in the large intestine, enzyme excretion and from food that has not been degraded in the gastrointestinal tract.…”