Review: Strategies for enteric methane mitigation in cattle fed tropical forages.

Methane (CH4) is a greenhouse gas (GHG) produced and released by eructation to the atmosphere in large volumes by ruminants. Enteric CH4 contributes significantly to global GHG emissions arising from animal agriculture. It has been contended that tropical grasses produce higher emissions of enteric CH4 than temperate grasses, when they are fed to ruminants. A number of experiments have been performed in respiration chambers and head-boxes to assess the enteric CH4 mitigation potential of foliage and pods of tropical plants, as well as nitrates (NO3-) and vegetable oils in practical rations for cattle. On the basis of individual determinations of enteric CH4 carried out in respiration chambers, the average CH4 yield for cattle fed low-quality tropical grasses (>70% ration DM) was 17.0 g CH4/kg DM intake. Results showed that when foliage and ground pods of tropical trees and shrubs were incorporated in cattle rations, methane yield (g CH4/kg DM intake) was decreased by 10% to 25%, depending on plant species and level of intake of the ration. Incorporation of nitrates and vegetable oils in the ration decreased enteric CH4 yield by ∼6% to ∼20%, respectively. Condensed tannins, saponins and starch contained in foliages, pods and seeds of tropical trees and shrubs, as well as nitrates and vegetable oils, can be fed to cattle to mitigate enteric CH4 emissions under smallholder conditions. Strategies for enteric CH4 mitigation in cattle grazing low-quality tropical forages can effectively increase productivity while decreasing enteric CH4 emissions in absolute terms and per unit of product (e.g. meat, milk), thus reducing the contribution of ruminants to GHG emissions and therefore to climate change.

Use of Tithonia diversifolia (hemsl) A. Gray in the diet of growing lambs / [Uso de tithonia diversifolia (hemsl) A. Gray na dieta de cordeiros em crescimento]

Two assays were conducted to study the Tithonia diversifolia (Td) plant: (1) chemical analysis and in vitro dry matter digestibility (IVDMD) of plant parts and (2) productive performance of lambs fed a traditional diet or a Td diet (30% of Td plus 70% of the traditional diet). The plant parts studied were leaves (L), leaves and petioles (LP); and leaves, petioles and stems (LPS). Feed intake, weight gain and feed conversion were registered weekly during five weeks of experimentation. The L showed higher (P<0.05) crude protein content (26.7%) than LP and LPS (25.5 and 19.7%, respectively). Crude fiber (11.2%), neutral detergent fiber (45.4%), cellulose (16.9%) and hemicellulose (33.5%) were lower in L than in LP (12.5, 46.7, 18.0 and 35.7%, respectively) and LPS (22.6, 59.2, 27.0 and 43.5%, respectively). The L and LP showed the highest IVDMD (89.2 and 88.2%, respectively vs. 77.2% of LPS). The Td diet resulted in greater feed intake and weight gain and lower feed conversion than the traditional diet. Therefore, Tithonia diversifolia is a forage plant of good quality for lambs which does not affect the productive performance.(AU)

Dois ensaios foram realizados para estudar a planta de Tithonia diversifolia (Td): (1) análise química e digestibilidade in vitro da matéria seca (DIVMS) de partes de plantas e (2) desempenho produtivo de cordeiros alimentados com dieta tradicional ou dieta Td (30% de Td mais 70% da dieta tradicional). As partes vegetais estudadas foram folhas (L), folhas e pecíolos (LP); folhas, pecíolos e caules (LPS). O consumo de ração, o ganho de peso e a conversão alimentar foram registrados semanalmente, durante cinco semanas de experimentação. O L apresentou maior (P<0,05) conteúdo de proteína bruta (26,7%) que o LP e o LPS (25,5 e 19,7%, respectivamente). Fibra bruta (11,2%), fibra em detergente neutro (45,4%), celulose (16,9%) e hemicelulose (33,5%) foram menores em L do que em LP (12,5, 46,7, 18,0 e 35,7%, respectivamente) e LPS (22,6, 59,2, 27,0 e 43,5%, respectivamente). O L e o LP apresentaram o maior DIVMS (89,2 e 88,2%, respectivamente vs. 77,2% do LPS). A dieta Td resultou em maior consumo de ração e maior ganho de peso e menor conversão alimentar que a dieta tradicional. Portanto, Tithonia diversifolia é uma planta forrageira de boa qualidade para cordeiros que não afeta o desempenho produtivo.(AU)

Haemodynamic aspects of lower limb arterial reconstruction using Dacron and Goretex prostheses.

We have studied some haemodynamic consequences of vascular grafts of less than 8 mm diameter by animal studies on dogs before and after aortofemoral bypass with either knitted Dacron 5 mm internal diameter (6 dogs) or Goretex 6 mm internal diameter (7 dogs) prostheses between 17 and 24 cm in length. Both materials gave an increased velocity of pulse wave transmission for pressure and flow and an increase in resistance to pulsatile flow. The effects were more severe with Dacron than with Goretex. Pressure index and pressure pulsatility were not significantly altered, but flow pulsatility index, peak flow rate, and peak flow acceleration were all significantly reduced after both implants. These results are due to mismatching of mechanical properties leading to an increased impedance to pulsatile flow.

Validity of some methods of estimating circumferential elastance of vascular prostheses.

The two methods for tensile testing of vascular prostheses, cited in a Draft International Standard, have been compared on normal aorta, autologous vein, two knitted Dacron, expanded PTFE and elastomeric composite prostheses before and after implantation as an aorto-femoral bypass in the dog. With the exception of Gore-Tex expanded PTFE, tensiometric stressing and balloon distension are not equivalent techniques in 'as supplied' prostheses or in normal vessels, owing to the basic anisotropic properties of the different materials. The tensiometric method gave much lower estimates of circumferential elastance, ranging from 44.6% for CCV elastomeric to 80.4% for normal canine aorta of the elastance estimate using balloon distension. The differences between the two methods were much less marked on explant samples of synthetic prostheses, but remained for autologous vein. It is concluded that although the methods are equally valid for quality assurance purposes they are inappropriate to compare probable clinical performance, unless carried out on explant samples. The preferred method to cover all the prostheses studied, including autologous vein, should employ omnidirectional stressing. Manufacturers' specifications are, therefore, not necessarily related to clinical performance.