-Tannins represent one of the most abundant polyphenolic compounds in plants. Tannins exist as a multitude of chemically unique entities in nature. The most commonly occurring tannins are typically divided into two major classes based on chemical structure: hydrolysable (HT) or condensed tannins (CT). Hydrolysable tannins are esters of gallic or ellagic acid linked to a polyol core, typically glucose. Condensed tannins or proanthocyanidins consist of flavan-3-ol subunits linked together to form oligomers and polymers. Both HT and CT are defined as astringent, medium-to-high-molecular weight polyphenolic compounds that characteristically bind and precipitate soluble proteins. The objective of this paper was to present recent advances in CT-ruminant interactions, the limitations associated with understanding and using CT in ruminant animal production, and future needs for research to further advance our knowledge of the role of CT in optimization of ruminant animal production. Condensed tannins pose some anti-nutritional problems to ruminants due to their astringent property that reduces feed intake and, consequently, animal performance. Ruminants can, however, tolerate CT by slowly adapting the ruminal microbes to the toxic effects of CT and by releasing CT-binding salivary proteins. The protein-binding ability of CT has some benefits to the ruminant due to complexes formed with essential amino acids, preventing their degradation in the rumen, but releasing them in the lower gut for absorption by the animal. Recent data have suggested increased N retention when CT is given to growing animals. There are potential benefits of using CT and HT for anthelmintic purposes due to their ability to inhibit egg hatching and larval motility of gastrointestinal nematode parasites, especially in small ruminants. Condensed tannins also bind to minerals (Al, Ca, Co, Cu, Fe, Mg, Mn, P, and Zn). Although studies with ruminants have been contradictory, it has been reported that because the CT-metal ion complex is stable over a wide pH range, CT may reduce the bioavailability of minerals. Methane mitigation by feeding CT might be the most impactful benefit for ruminant production. Many empirical equations have been developed to predict ruminal methane emissions, but very few have included CT. Future research should focus on the improvement of methodology to assess CT biological activity, interaction with other plant-specialized metabolites, and associated physiological and nutritional impacts on ruminants.

The beneficial effects of forages containing condensed tannins (CTs) on ruminants are well documented, but the chemical features of CT that yield benefits have not been defined. Some evaluations of limited numbers of highly purified compounds have resulted in positive correlations between CT molecular weight (M W ) and biological activity, while others have failed to show a correlation. The objectives of this study were to determine if M W of CT could predict biological activity relative to protein precipitability. M W of condensed tannin, proteinprecipitable phenolics (PPP), and the amount of protein bound (PB) were determined for nine species of warmseason perennial legumes. There was no correlation between PPP or PB and M W (R 2 0.11 and R 2 0.02, respectively). However, CT concentration did correlate with PPP and PB (R 2 0.81 and R 2 0.69, respectively). It was concluded that CT M W does not explain the variation in protein precipitation by CT from the forage legumes surveyed.

Previous studies showed that a series of purified condensed tannins (CTs) from warm-season perennial legumes exhibited high variability in their modulation of methane production during in vitro rumen digestion. The molecular weight differences between these CTs did not provide correlation with either the in vitro CH4 production or the ability to precipitate bovine serum albumin. In an effort to delineate other structure-activity relationships from these methane abatement experiments, the structures of purified CTs from these legumes were assessed with a combination of methanolysis, quantitative thiolysis, 1H-13C HSQC NMR spectroscopy and ultrahigh-resolution MALDI-TOF MS. The composition of these CTs is very diverse: procyanidin/prodelphinidin (PC/PD) ratios ranged from 98/2 to 2/98; cis/trans ratios ranged from 98/2 to 34/66; mean degrees of polymerization ranged from 6 to 39; and % galloylation ranged from 0 to 75%. No strong correlation was observed between methane production and the protein precipitation capabilities of the CT towards three different proteins (BSA, lysozyme, and alfalfa leaf protein) at ruminal pH. However, a strong non-linear correlation was observed for the inhibition of methane production versus the antioxidant activity in plant sample containing typical PC- and PD-type CTs. The modulation of methane production could not be correlated to the CT structure (PC/PD or cis/trans ratios and extent of galloylation). The most active plant in methane abatement was Acacia angustissima, which contained CT, presenting an unusual challenge as it was resistant to standard thiolytic degradation conditions and exhibited an atypical set of cross-peak signals in the 2D NMR. The MALDI analysis supported a 5-deoxy flavan-3-ol-based structure for the CT from this plant.

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Low productivity and nutritive value of cool‐season perennial forages, such as tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] during summer necessitates the identification of warm‐season forages that improve nutritive value and yield of cool‐season‐based forage systems. A fast‐growing, warm‐season tropical legume sunn hemp (Crotalaria juncea L.) has the potential to accomplish this. Our objectives were to evaluate herbage accumulation and nutritive value (crude protein [CP], in vitro true digestibility [IVTD], neutral detergent fiber [NDF], acid detergent fiber [ADF], and NDF digestibility [NDFD, 48 h]) of sunn hemp harvested 35, 45, and 55 d after planting (DAP) at 10‐ and 15‐cm heights and to determine regrowth potential when harvested 20 d after each initial harvest over two consecutive years. Sunn hemp herbage accumulation averaged 1.9 and 3.1 Mg ha−1 at 45 and 55 DAP, respectively. Herbage accumulation of initial harvest increased linearly from 35 to 45 to 55 DAP by 119 and 57%, respectively. Herbage accumulation of regrowth after the 35 DAP initial harvest was 262 and 303% greater than the 45 and 55 DAP initial harvests, respectively. Cutting height did not affect (P > 0.05) any variables. The greatest CP (154 g kg−1 dry matter) was observed at 35 DAP and decreased linearly with DAP. Both NDF (P < 0.01) and ADF (P = 0.01) concentrations increased linearly with DAP for both initial and regrowth harvests. The IVTD of initial and regrowth harvests averaged 794 and 624 g kg−1 dry matter, respectively. Forage NDFD for initial and regrowth harvests averaged 487 and 392 g kg−1 NDF, respectively. Nutritive value and herbage accumulation of sunn hemp can be optimized by initially harvesting between 35 and 45 DAP, and leaving at least 10 cm of residue to allow for regrowth.

A study was conducted to determine how total phenolic (TP), protein precipitable phenolic (PPP), C, and N concentrations, and amount of protein bound (PB) by PPP in leaves of Desmodium paniculatum (panicled tick-clover; PTC) and Lespedeza cuneata (sericea lespedeza; SL) were affected by simulated herbivory and plant ontogeny. All PTC treatments resulted in a decrease (P ≤ 0.05) in TP, PPP, C, and N concentrations and PB between vegetative and seed set stages. All SL treatments resulted in increased (P ≤ 0.05) or stable TP and PPP concentrations from vegetative stage to seed set. The amount of PB was greatest (P ≤ 0.05) in SL plants submitted to 25% defoliation, and flowering and seed set stages had greater (P ≤ 0.05) PB than the vegetative stage. Ontogenesis and defoliation did not (P > 0.05) affect SL N and C concentrations. The protein binding characteristics of PPP from PTC, but not that of SL, appear to be altered in response to stress. Results might correspond with seed dispersal strategies of the two species, with PTC's epizoochory making increased palatability at seed set beneficial.

Achieving high animal productivity without degrading the environment is the primary target in pasture based-dairy farming. This study investigated the effects of changing the forage base in spring from grass-clover pastures to forb or legume-based pastures on milk yield, N utilization and methane emissions of Jersey cows in Western Oregon. Twenty-seven mid-lactation dairy cows were randomly assigned to one of three pasture treatments: grass-clover based pasture composed of festulolium, tall fescue, orchardgrass, and white clover (Grass); forb-based pasture composed of chicory, plantain, and white clover (Forb); and legume-based pasture composed of red clover, birdsfoot trefoil, berseem clover and balansa clover (Legume). Pastures were arranged in a randomized complete block design with three replicates (i.e., blocks) with each replicate grazed by a group of three cows. Production and nutritive quality of the forages, animal performance, milk components, nitrogen partitioning, and methane emissions were measured. Feed quality and dry matter intake (DMI) of cows were greater (P ≤ 0.05) for Legume and Forb vs. Grass, with consequent greater milk and milk solids yields (P &lt; 0.01). Cows grazing Forb also had more (P &lt; 0.01) lactose and linoleic acid in milk compared to cows grazing the other pastures, and less (P = 0.04) somatic cell counts compared to Grass. Cows grazing Forb had substantially less (P &lt; 0.01) N in urine, milk, and blood compared to cows grazing the other pastures, with a greater (P &lt; 0.01) efficiency of N utilization for milk synthesis calculated using MUN but also a larger (P &lt; 0.01) fecal N content, indicating a shift of N from urine to feces. Both Forb and Legume had a diuretic effect on cows, as indicated by the lower (P &lt; 0.01) creatinine concentration in urine compared to Grass. Methane emissions tended to be less (P = 0.07) in cows grazed on Forb vs. the other pastures. The results indicate Forb pasture can support animal performance, milk quality, and health, comparable to Legume pasture; however, Forb pasture provides the additional benefit of reduced environmental impact of pasture-based dairy production.

Strips of plate meat were sprayed with acetic acid, sodium hypochlorite, or tap water after they were washed with 0, 12.7, or 25.4 liters of tap water/min. Washing before sanitizing lowered bacteria counts significantly only when the higher volume of water, 1.4 ml/cm2, was applied, and this difference existed for samples taken immediately but not 48 h after treatment. Reductions in counts exceeded 99.9% when samples washed with 25.4 liters/min (1.4 ml/cm2) were sanitized with 3% acetic acid. This sanitizer was sprayed at the rate of 6.8 liters/min (1.9 ml/cm2) at a pressure of 14.0 kg/cm2 from a distance of 40 cm as the meat moved at 2 cm/sec through the spray. Under comparable conditions of application, both sodium hypochlorite (200 to 250 mg/liter) and tap water reduced counts by about 90%. Acetic acid had a much greater residual effect on numbers of viable bacteria than did hypochlorite. No effect of air drying was observed.