Digestibility, nitrogen balance and weight gain in sheep fed with diets supplemented with different seaweeds

9 páginas, 5 tablas.Three completely randomised design experiments examined the effects of the inclusion of three seaweed species (Ruppia sp., Ulva sp. or Chaetomorpha sp.) into the diet on digestibility and nitrogen balance in Barbarine sheep. Diets were composed of oat hay ad libitum supplemented with 600 g of concentrate. Seaweeds were incorporated into the concentrate at increasing levels (0, 200, 300 or 400 g seaweed kg−1 concentrate, dry matter (DM) basis) in replacement of other ingredients. Feed intake and water consumption were increased (P < 0.01) linearly with Ruppia supplementation. As the proportion of Ruppia was increased in the diet, the digestibility of organic matter decreased linearly (P < 0.01) from 0.698 (no seaweed) to 0.642 (400 g seaweed kg−1 concentrate). Increasing the level of inclusion of Chaetomorpha up to 300 g kg−1 did not affect the intake of concentrate. Organic matter digestibility decreased linearly (P < 0.001) from 0.685 with the control diet to 0.622 with the diet containing 400 g Chaetomorpha kg−1 concentrate. The level of inclusion of Ulva did not affect feed intake or water consumption, but decreased linearly (P > 0.001) organic matter digestibility from 0.637 with the control diet to 0.599 with the diet containing 400 g Ulva kg−1 concentrate. In all the experiments, nitrogen balance was positive and there were no differences among levels of seaweed supplementation in N retention or daily weight gain. These results suggest that seaweeds such as Ruppia, Ulva or Chaetomorpha can be incorporated into sheep concentrates up to 30% (DM basis) without adverse effects on feed digestibility or growth performance.The authors are grateful to the contribution of the director and the workers in the livestock industry of Tabarka (North of Tunisia). Special thanks to Mr. Boussbiaa and Mr. Mabrouk for their involvement

Aquatic plants and macroalgae as potential feed ingredients in ruminant diets

10 páginas, 6 tablas.The aim of this research was to investigate the nutritive value of three aquatic plants, the seagrass (Ruppia maritima) and two green macroalgae (Chaetomorpha linum and Ulva lactuca). Biomass from three aquatic plants collected from the lagoon Ghar el melh of Bizerte (northeast of Tunisia) was washed and dried, and tested alone (compared to barley grain and barley grass) or included at different levels in isonitrogenous concentrate mixtures. Four rumen cannulated Barbarine rams were used as donors of rumen fluid for in vitro incubations and as hosts for in situ nylon bags rumen incubations. Gas production, fermentation rate, gas produced after 24 h of incubation and apparent OM digestibility were greater for barley grain and grass than for the three aquatic plants (P  0.05). Inclusion of biomass of the three aquatic plant species studied as ingredients should not exceed 200 g kg in concentrate feeds, because the rate and extent of degradation of the mixture may be reduced with greater addition.The Canada Research Chairs Program (National Science and Engineering Council, Ottawa) is thanked for partial funding.Peer Reviewe

Effects of marine and freshwater macroalgae on in vitro total gas and methane production

This study aimed to evaluate the effects of twenty species of tropical macroalgae on in vitro fermentation parameters, total gas production (TGP) and methane (CH4) production when incubated in rumen fluid from cattle fed a low quality roughage diet. Primary biochemical parameters of macroalgae were characterized and included proximate, elemental, and fatty acid (FAME) analysis. Macroalgae and the control, decorticated cottonseed meal (DCS), were incubated in vitro for 72 h, where gas production was continuously monitored. Post-fermentation parameters, including CH4 production, pH, ammonia, apparent organic matter degradability (OMd), and volatile fatty acid (VFA) concentrations were measured. All species of macroalgae had lower TGP and CH4 production than DCS. Dictyota and Asparagopsis had the strongest effects, inhibiting TGP by 53.2% and 61.8%, and CH4 production by 92.2% and 98.9% after 72 h, respectively. Both species also resulted in the lowest total VFA concentration, and the highest molar concentration of propionate among all species analysed, indicating that anaerobic fermentation was affected. Overall, there were no strong relationships between TGP or CH4 production and the >70 biochemical parameters analysed. However, zinc concentrations >0.10 g.kg−1 may potentially interact with other biochemical components to influence TGP and CH4 production. The lack of relationship between the primary biochemistry of species and gas parameters suggests that significant decreases in TGP and CH4 production are associated with secondary metabolites produced by effective macroalgae. The most effective species, Asparagopsis, offers the most promising alternative for mitigation of enteric CH4 emissions