H.D. Hess

Supplementation of Acacia mearnsii tannins decreases methanogenesis and urinary nitrogen in forage-fed sheep

The objective of this experiment was to assess the effects of a partial replacement of ryegrass (Lolium perenne) by red clover (Trifolium pratense) or alfalfa (Medicago sativa) supplemented with 0 or 41 g Acacia mearnsii extract (containing 0.615 g/g condensed tannins)/kg dietary dry matter on nitrogen turnover and methane release by sheep, using the respiration chamber technique. Across all variables, there was no significant interaction between basal diet and tannin supplementation. The partial replacement of the grass by the legumes remained without effect on the amounts of nitrogen excreted through faeces or urine. Nitrogen and energy utilisation was lower (P < 0.05) with ryegrass-alfalfa than with ryegrass alone, and methane release (kJ/MJ gross energy intake) was higher (P < 0.05) with ryegrass-red clover than with ryegrass alone. Tannin supplementation decreased (P < 0.05) ruminal ammonia concentration and urinary nitrogen excretion without affecting body nitrogen and energy retention, and reduced (P < 0.001) methane release by 13% on average. The results suggest that supplemented Acacia mearnsii tannins can be useful in mitigating methane and potential gaseous nitrogen emissions, whereas a replacement of grass by legumes obviously shows no advantage in this respect.

Effect of the tropical tannin-rich shrub legumes Calliandra calothyrsus and Flemingia macrophylla on methane emission and nitrogen and energy balance in growing lambs

The objective of this study was to test whether the use of tannin-rich shrub legume forage is advantageous for methane mitigation and metabolic protein supply at unchanged energy supply when supplemented in combination with tannin-free legumes to sheep. In a 6 × 6 Latin-square design, foliage of two tannin-rich shrub legume species (Calliandra calothyrsus and Flemingia macrophylla) were used to replace either 1/3 or 2/3, respectively, of a herbaceous high-quality legume (Vigna unguiculata) in a diet composed of the tropical grass Brachiaria brizantha and Vigna in a ratio of 0.55 : 0.45. A Brachiaria-only diet served as the negative control. Each experimental period lasted for 28 days, with week 3 serving for balance measurement and data collection inclusive of a 2-day stay of the sheep in open-circuit respiration chambers for measurement of gaseous exchange. While Vigna supplementation improved protein and energy utilisation, the response to the partial replacement with tannin-rich legumes was less clear. The apparent total tract digestibilities of organic matter, NDF and ADF were reduced when the tannin-rich plants partially replaced Vigna, and the dose-response relationships were mainly linear. The tannin-rich plants caused the expected redistribution of more faecal N in relation to urinary N. While Flemingia addition still led to a net body N retention, even when fed at the higher proportion, adding higher amounts of Calliandra resulted in body protein mobilisation in the growing lambs. With respect to energy, supplementation of Vigna alone improved utilisation, while this effect was absent when a tannin-rich plant was added. The inclusion of the tannin-rich plants reduced methane emission per day and per unit of feed and energy intake by up to 24% relative to the Vigna-only-supplemented diet, but this seems to have been mostly the result of a reduced organic matter and fibre digestion. In conclusion, Calliandra seems less apt as protein supplement for ruminants while Flemingia could partially replace a high-quality legume in tropical livestock systems. However, methane mitigation would be small due to associated reductions in N and energy retention.

Modification of milk fatty acid composition by feeding forages and agro-industrial byproducts from dry areas to Awassi sheep

The study tested the hypothesis that certain underused forages and agro-industrial byproducts available in dry areas may positively influence fatty acid (FA) composition and antioxidative properties of milk by their contents of residual oil or phenolic compounds or both. Sixty multiparous fat-tailed Awassi ewes were allocated to 6 groups in a completely randomized block design. During 50 d, the ewes were group-fed 2.5 kg of dry matter/d per ewe 1 of 6 isonitrogenous and isoenergetic diets (forage:concentrate, 0.3:0.7). The test feeds, comprising 30% of the diets, replaced either barley straw [lentil straw, olive leaves, and Atriplex (saltbush) leaves, rich in phenolic compounds or electrolytes] or conventional concentrate ingredients (olive cake and tomato pomace; ∼10% lipids) from the control diet. The diets containing olive cake and tomato pomace were rich in oleic acid (18:1 cis-9; 27% of total dietary FA) and linoleic acid (18:2 cis-9,cis-12; 37%), respectively. Profiles of FA were determined in individual milk samples drawn on d 0 and in wk 1, 3, 5 and 7. Data was analyzed by repeated measurement analysis. No consistent treatment effects on yield and gross nutrient composition of the milk were observed, although some differences occurred. Milk resulting from the Atriplex leaf diet expressed the highest antiradical activity, which was low with control and olive leaves. Feeding the tomato pomace and olive cake diets decreased the proportions of short- and medium-chain FA, whereas oleic acid clearly increased in proportion to total FA. Olive leaves most effectively increased rumenic acid (18:2 cis-9,trans-11) and α-linolenic acid (18:3 cis-9,cis-12,cis-15) in milk fat. This also resulted in the highest α-linolenic acid transfer rate from feed to milk and suggests that olive leaves affect ruminal biohydrogenation at several steps. Several alternative feeds exist with an added value, as they enhance FA with potential health benefits and the stability of the milk with higher antioxidative activity, even though responses to test feeds differed largely. It remains to be investigated whether combinations of these feeds would be complementary in these beneficial effects.

Nitrogen and mineral balance of lambs artificially infected with Haemonchus contortus and fed tanniferous sainfoin (Onobrychis viciifolia).

Tanniferous temperate legumes are assumed to possess anthelmintic properties, but it is unclear whether this is the direct result of condensed tannins (CT) or is mediated indirectly via an improved metabolic protein supply. A metabolism experiment was conducted to differentiate between these factors by feeding the CT plant sainfoin (19.7% CP in DM) to lambs infected with the abomasal blood-sucking nematode Hemonchus contortus. A total of 18 infected lambs were fed sainfoin either untreated or treated with polyethylene glycol, a CT-inactivating agent, or a grass-clover mixture (13.2% CP in DM) over 3 wk (n = 6). Six uninfected lambs received the grass-clover mixture as a control. In addition to indicators of infection (fecal egg count, packed-cell volume, abomasal worm burden, and serum protein), nutrient digestibility, the balance of N and selected minerals, ruminal fluid characteristics, and plasma AA levels were determined mostly in the final experimental week. The specific effects of the sainfoin CT, the extra CP with sainfoin, and the infection were statistically evaluated by contrast analysis. The sainfoin CT exerted no beneficial effects on resilience to nematode infection and exerted only minor effects on ruminal ammonia or blood urea concentrations and the excretory pattern of N. Plasma alanine, aspartate, and proline concentrations tended to be greater (P < or = 0.09) because of the sainfoin CT, whereas the other AA remained unaffected. Intake of the mineral supplement was lower (P < 0.001) for lambs fed sainfoin compared with those fed sainfoin treated with polyethylene glycol. Feeding the high-protein sainfoin instead of the grass-clover mixture increased (P < 0.001) N retention and apparent OM digestibility, whereas digestibility of NDF and ADF were decreased (P < 0.001). Feeding sainfoin also decreased (P < or = 0.04) plasma alanine, glycine, isoleucine, and total nonessential AA compared with the grass-clover mixture. Although fecal egg count, worm burden, and packed cell volume were not affected by the greater CP supply associated with sainfoin feeding, serum albumin level was increased (P = 0.008). The lack of effects of sainfoin on resilience to nematode infection might have been the result of the unexpectedly low CT content (3.6% in DM) of the material used. It cannot be excluded that longer term feeding of this batch of sainfoin might have been effective.

Investigation of sainfoin (Onobrychis viciifolia) cultivar differences on nitrogen balance and fecal egg count in artificially infected lambs

Research in ruminant nutrition and helminth control with forages, which contain condensed tannins (CT), suggests that varying responses may depend not only on CT concentration but also on CT composition. An experiment was designed to test this by feeding 2 dried sainfoin cultivars (Visnovsky and Perly), which differed in CT properties, to lambs that were artificially infected with the abomasal blood-sucking nematode Haemonchus contortus. Twenty-four infected lambs received 1 of these 2 cultivars; the feeds were either untreated or treated with the CT-binding polyethylene glycol over 4 wk (n = 6). The 2 cultivars were also fed to 2 × 6 uninfected lambs. Nutrient digestibility, N balance, ADG, plasma urea, together with indicators of infection [fecal egg count (FEC), abomasal worm count, per capita female fecundity, erythrocytic indices, and serum protein], were determined. The specific effects of sainfoin cultivar, CT, and infection were evaluated by contrast analysis. Digestibility of both NDF and ADF were less (P < 0.001) with Perly compared with Visnovsky. The apparent nutrient digestibility was reduced (P < 0.001) by CT. However, no clear cultivar effects were evident on N excretion and retention. Condensed tannins reduced (P = 0.05) body N retention and shifted (P < 0.001) N excretion from urine to feces. Unlike cultivar and CT, infection decreased (P = 0.002) ADG. Plasma urea concentration was decreased (P = 0.007) in Perly- compared with Visnovsky-fed lambs and was decreased (P < 0.001) by CT. Plasma concentrations of essential and semiessential AA were increased (P < 0.001) by CT. The groups of infected lambs did not clearly differ in abomasal worm counts and erythrocytic indicators. In the last 2 to 3 wk of the experiment, FEC was decreased (P ≤ 0.01) when feeding CT. The lack of substantial cultivar effects suggests that the differences in CT properties may have been too small to result in nutritional and anthelmintic effects. The present results indicate that sainfoin CT had a mitigating effect on FEC and, consequently, pasture infectivity. However, the reduction was too small to expect any significant benefits in an Haemonchus-dominated system. Therefore, the use of sainfoin for controlling H. contortus should only be one component within an integrated worm control system.

In vitro evidence for the importance of cultivation conditions on the effects of Calliandra tannins on ruminal escape of soybean protein and its post-ruminal degradability

Purified condensed tannins (CT) extracted from the legume Calliandra calothyrsus (var. San Ramón CIAT 22310), harvested in the dry and the rainy season and cultivated with low or high level of fertilization were added to soybean meal in a ratio of 600 mg/g of the incubated crude protein (CP). Effects on degradation either in ruminal fluid only, or in ruminal fluid followed by incubation in HCl/pepsin, were evaluated using a modified two-step in vitro method. Season was found to have larger effects on in vitro ruminal and post-ruminal CP degradation than fertilization. Condensed tannins from the rainy season harvest reduced ruminal CP degradation less than that from the dry season harvest. They had also less negative effects on the degradability of rumen escape protein and enhanced the proportion of post-ruminally degraded CP more than CT from the dry season harvest. An increase in level of fertilization reduced ruminal CP degradation in CT from the rainy season plants but this was not associated with effects on post-ruminal degradation. The study demonstrated the importance of environmental factors for the efficiency of CT in modifying ruminal and post-ruminal CP degradation.