The effect of different additives on the fermentation quality, aerobic stability and in vitro digestibility of pea/wheat bi-crop silages containing contrasting pea to wheat ratios

Studies were conducted to compare the effects of using two microbial inoculants, a sulphite salt‐based additive, formic acid and quebracho tannins, on the fermentation quality, nutritive value and aerobic stability of pea/wheat bi‐crop silages. Spring peas (Pisum sativum var. Magnus) and spring wheat (Triticum aestivum var. Axona) were drilled together at rates that gave high (HP/W; 3:1) or low (LP/W; 1:3) pea to wheat ratios. The peas and wheat were harvested at the yellow wrinkled pods and late milk/early dough maturity stage, respectively, and conserved in 1·5‐kg polyethylene bag, laboratory silos. The bi‐crops were conserved without treatment (control) or treated with either of two lactic acid bacteria‐based inoculants [Lactobacillus buchneri; applied at 10⁵ colony‐forming units (CFU) g^–1 fresh weight (FW) or Lactobacillus plantarum (applied at 10⁶ CFU g^–1 FW)], sulphite salts (applied at the rate of 1 ml sulphite solution kg^–1 FW), quebracho tannins (applied at 16 g kg^–1 FW) and formic acid (applied at 2·5 g kg^–1 FW). Six replicates were made for each treatment, and the silos were opened after 112 days of ensilage. The level of peas in the bi‐crop influenced the effectiveness of the additives. With the exception of sulphite salts, all the additives significantly reduced the soluble nitrogen (N) and ammonia‐N concentrations of all the silages. The ratio of lactic acid to acetic acid was generally lower in the LP/W silages than in the HP/W silages, and the additive treatments only increased the in vitro digestible organic matter in dry matter of the LP/W silages. Of all the additives evaluated, formic acid resulted in the least aerobic spoilage in HP/W bi‐crop silages. However, in the LP/W bi‐crops, additive treatment was not necessary for ensuring aerobic stability.     

Effect of condensed tannin ingestion in sheep and goat parotid saliva proteome

Saliva appears as a defence mechanism, against potential negative effects of tannins, in some species of animals which have to deal with these plant secondary metabolites in their regular diets. This study was carried out to investigate changes in parotid saliva protein profiles of sheep (Ovis aries) and goats (Capra hircus), induced by condensed tannin ingestion. Five Merino sheep and five Serpentina goats were maintained on a quebracho tannin enriched diet for 10 days. Saliva was collected through catheters inserted on parotid ducts and salivary proteins were separated by two-dimensional gel electrophoresis. Matrix-assisted Laser desorption ionization - time of flight (MALDI-TOF) and liquid chromatography tandem mass spectrometry (LC-MS/MS) were used to identify the proteins whose expression levels changed after tannin consumption. Although no new proteins appeared, quebracho tannin consumption increased saliva total protein concentration and produced changes in the proteome of both species. While some proteins were similarly altered in both species parotid salivary protein profile, sheep and goats also presented species-specific differences in response to tannin consumption.     

The influence of dietary chestnut and quebracho tannins mix on rabbit meat quality

Tannins were recently evaluated as feed additives in order to increase antioxidant compounds in animal diet, mainly to enhance resistance to lipid oxidation in meat. Rabbit meat is one of the most susceptible animal products, thus the main aim of this study was to evaluate the capacity of tannins to elongate shelf life of rabbit meat. Ninety hybrid rabbits were fed with three different diets: basal diet (control, C) and basal diet supplemented with 0.3% or 0.6% of tannins mix. Meat samples were refrigerated as raw at 4°C up to 11 days and analysed both as raw and cooked for physical‐chemical characteristics, fatty acids profile, lipid oxidation and antioxidant capacity. Results showed that dietary tannins affected meat colour of raw samples (mostly yellowness). Lipid peroxidation (TBARS) of raw samples was lower in tannins group than C group; a further inhibition of peroxidation was showed also in cooked samples only by the highest dose of tannins mix. Moreover, antioxidant capacity (ABTS) of raw samples increased with the percentage of tannins. In conclusion, supplementation with 0.6% of tannins mix seems to positively affect the lipid peroxidation and antioxidant capacity of meat without modifying the intrinsic characteristics of rabbit meat.     

Effects of supplemental dietary tannins on the performance of white‐tailed deer (Odocoileus virginianus)

Tannins are natural and nutritionally significant components of the diets of browsing ungulates. In trials on supplemented pastures and in drylots, we estimated dry matter intake (DMI), weight gain, and urea N, potassium, cortisol and creatinine in urine of captive white‐tailed deer fed pelleted diets that differed only in the respective quebracho tannin (QT) content. The low control, medium and high QT rations were 3.6, 63 and 152 g/kg DM respectively. There was no tannin‐free pellet option. Trials were divided into winter pasture, restricted choice and spring growth. In winter pasture trial on pasture using QT, deer reduced QT intake relative to that expected under random foraging. This aversion was also apparent during the spring growth trial. While DMI in the winter pasture trial remained similar among treatments (p > 0.05), averaging 130 g/kg^0.75/day, deer gained more weight (p < 0.05) when given a choice that included the high QT ration. During subsequent spring growth, DMI and weight gains generally exceeded those of the winter period. Unlike the winter pasture trial, weight gains in spring growth trial were higher (p < 0.05) in the low‐control QT treatment. In the restricted choice trial, weight gain was again higher (p < 0.05) for deer fed a low‐control QT diet. The urea N/creatinine ratio of deer fed the low‐control QT diet (0.0357) was over three times that of deer fed the high QT diet (0.0107). Neither potassium/creatinine nor cortisol/creatinine ratios were affected by diet (p > 0.05). Collectively, these results suggest that although deer do not avoid tannins, and even ingested up to 5% under the choice options in these trials, the effect of tannins on deer performance may vary by season as well as by foraging opportunities.     

Effect of tannin extracts on protein degradation during ensiling of ryegrass or lucerne

Eleven laboratory‐scale trials were undertaken in different years where ryegrass (Lolium perenne L.) or lucerne (Medicago sativa L.) were ensiled with different concentrations of tannin extracts (quebracho, Schinopsis balansae Engl., mimosa, Acacia mearnsii DE WILD.), and the effects on protein degradation were assessed. The dry‐matter (DM) content in grass silages ranged between 186 and 469 g/kg and in lucerne silages between 187 and 503 g/kg. Tannin extract, either quebracho or mimosa, was applied at 0–30 g/kg forage DM. Commercial additives such as Lactobacillus plantarum, formic acid or hexamine + NaNO₂ were applied in two of the grass trials and in six of the lucerne trials. Eight of the trials incorporated a maximum ensiling duration of 90 or 180 days in addition to replicates which were opened and evaluated at earlier stages. All trials included silages which were assessed after at least 49 days of anaerobic storage. The crude protein (CP) fraction A (non‐protein nitrogen, NPN) as proportion of total CP, served as the main indicator for proteolysis. In ryegrass, in general, the level of proteolysis was lower than in lucerne. A correlation of DM content in silages and degree of proteolysis was only evident for ryegrass. In both forages, the degradation of true protein slowed considerably after 24 days of ensiling. True protein was conserved most with the highest level of tannin extract addition. However, in lucerne, the combination of formate with lactobacilli was equally effective up to 330 g DM/kg, and deamination was further inhibited by formic acid compared to tannin extracts.