Effect of Chitosan and Naringin on Enteric Methane Emissions in Crossbred Heifers Fed Tropical Grass.

In order to meet consumer needs, the livestock industry is increasingly seeking natural feed additives with the ability to improve the efficiency of nutrient utilization, alternatives to antibiotics, and mitigate methane emissions in ruminants. Chitosan (CHI) is a polysaccharide with antimicrobial capability against protozoa and Gram-positive and -negative bacteria, fungi, and yeasts while naringin (NA) is a flavonoid with antimicrobial and antioxidant properties. First, an in vitro gas production experiment was performed adding 0, 1.5, 3.0 g/kg of CHI and NA under a completely randomized design. The substrate containing forage and concentrate in a 70:30 ratio on a dry matter (DM) basis. Compounds increased the concentration of propionic acid, and a significant reduction in methane production was observed with the inclusion of CHI at 1.5 g/kg in in vitro experiments (p < 0.001). In a dry matter rumen degradability study for 96 h, there were no differences in potential and effective degradability. In the in vivo study, six crossbred heifers fitted with rumen cannulas were assigned to a 6 × 6 Latin square design according to the following treatments: control (CTL), no additive; chitosan (CHI1, 1.5 g/kg DMI); (CHI2, 3.0 g/kg DMI); naringin (NA1, 1.5 g/kg DMI); (NA2, 3.0 g/kg DMI) and a mixture of CHI and NA (1.5 + 1.5 g/kg DMI) given directly through the rumen cannula. Additives did not affect rumen fermentation (p > 0.05), DM intake and digestibility of (p > 0.05), and enteric methane emissions (p > 0.05). CHI at a concentration of 1.5 g/kg DM in in vitro experiments had a positive effect on fermentation pattern increasing propionate and reduced methane production. In contrast, in the in vivo studies, there was not a positive effect on rumen fermentation, nor in enteric methane production in crossbred heifers fed a basal ration of tropical grass.

Role of Secondary Plant Metabolites on Enteric Methane Mitigation in Ruminants.

The rumen microbiome plays a fundamental role in all ruminant species, it is involved in health, nutrient utilization, detoxification, and methane emissions. Methane is a greenhouse gas which is eructated in large volumes by ruminants grazing extensive grasslands in the tropical regions of the world. Enteric methane is the largest contributor to the emissions of greenhouse gases originating from animal agriculture. A large variety of plants containing secondary metabolites [essential oils (terpenoids), tannins, saponins, and flavonoids] have been evaluated as cattle feedstuffs and changes in volatile fatty acid proportions and methane synthesis in the rumen have been assessed. Alterations to the rumen microbiome may lead to changes in diversity, composition, and structure of the methanogen community. Legumes containing condensed tannins such as Leucaena leucocephala have shown a good methane mitigating effect when fed at levels of up to 30-35% of ration dry matter in cattle as a result of the effect of condensed tannins on rumen bacteria and methanogens. It has been shown that saponins disrupt the membrane of rumen protozoa, thus decreasing the numbers of both protozoa and methanogenic archaea. Trials carried out with cattle housed in respiration chambers have demonstrated the enteric methane mitigation effect in cattle and sheep of tropical legumes such as Enterolobium cyclocarpum and Samanea saman which contain saponins. Essential oils are volatile constituents of terpenoid or non-terpenoid origin which impair energy metabolism of archaea and have shown reductions of up to 26% in enteric methane emissions in ruminants. There is emerging evidence showing the potential of flavonoids as methane mitigating compounds, but more work is required in vivo to confirm preliminary findings. From the information hereby presented, it is clear that plant secondary metabolites can be a rational approach to modulate the rumen microbiome and modify its function, some species of rumen microbes improve protein and fiber degradation and reduce feed energy loss as methane in ruminants fed tropical plant species.

Influence of energy supplementation on dietary nitrogen utilization and milk production in cows fed foliage of Leucaena leucocephala.

The aim of the study was to assess the effect of four energy supplements (two highly fermentable; two starch-based carbohydrates) on blood urea nitrogen (BUN), urinary urea excretion, and milk yield, in dual-purpose cows fed foliage of Leucaena leucocephala (Leucaena). Five Holstein-Zebu cows with 450 kg body weight in their second third of lactation were used in a 5 × 5 Latin square design. Cows were fed (dry basis) a mixture of 45% Leucaena and 55% Pennisetum purpureum grass. Treatments were supplementation with (i) sugarcane molasses (Mo), (ii) sorghum grain (So), (iii) fresh citrus pulp (CitP) or (iv) rice polishing (RP), all of them incorporated into the diet at 25 MJ of ME/cow/day. There was a control group (Cont) without energy supplementation. The study comprised five periods of 20 days (15 days adaptation, 5 days measurements). Dry matter intake (kg/day) was lower (P < 0.05) for Cont (9.4) compared with Mo (12.1), So (12.0), CitP (11.9) and RP (11.9) but no difference was observed among energy supplements (P > 0.05). Milk yield (kg/day) was higher (P < 0.05) in cows supplemented with starch supplements (4.7 for So; 4.9 for RP) compared with Cont (3.3). Milk yield from highly fermentable supplements (Mo and CitP) did not differ (P > 0.05) from Cont or other treatments. Milk protein, fat and lactose were not different among treatments (P > 0.05). Blood urea nitrogen and urinary urea excretion were both reduced (P < 0.05) by energy supplementation. Urinary urea excretion was not different (P > 0.05) among cows fed different sources of energy. It is concluded that in dual-purpose cows fed Leucaena foliage, supplementation with sugarcane molasses, citrus pulp or rice polishing reduced blood urea nitrogen and urinary urea excretion. Milk yield was increased by sorghum and rice polishing whereas energy supplementation did not affect milk composition.

Effect of Dried Leaves of Leucaena leucocephala on Rumen Fermentation, Rumen Microbial Population, and Enteric Methane Production in Crossbred Heifers.

The effects of dietary inclusion of dried Leucaena leucocephala leaves (DLL) on nutrient digestibility, fermentation parameters, microbial rumen population, and production of enteric methane (CH4) in crossbred heifers were evaluated. Four heifers were used in a 4 × 4 Latin square design consisting of four periods and four levels of inclusion of DLL: 0%, 12%, 24%, and 36% of dry matter (DM) intake. Results showed that DM intake (DMI), organic matter intake, and gross energy intake (GEI) were similar (p > 0.05) among treatments. Apparent digestibility of organic matter, neutral detergent fiber, and energy decreased with increasing levels of DLL in the ration (p < 0.05). In contrast, digestible crude protein (CP) was higher (p < 0.05) in treatments with 12% and 24% DM of DLL. The inclusion of DLL did not affect (p > 0.05) rumen pH and total volatile fatty acids. Rumen microbial community was not affected (p > 0.05) by treatment. There was a linear reduction (p < 0.05) in CH4 emissions as the levels of DLL in the ration were increased. Results of this study suggest that an inclusion of 12% DM of ration as DLL enhances digestible CP and reduces daily production of enteric CH4 without adversely affecting DMI, rumen microbial population, and fermentation parameters.

The Role of Chitosan as a Possible Agent for Enteric Methane Mitigation in Ruminants.

Livestock production is a main source of anthropogenic greenhouse gases (GHG). The main gases are CH4 with a global warming potential (GWP) 25 times and nitrous oxide (N2O) with a GWP 298 times, that of carbon dioxide (CO2) arising from enteric fermentation or from manure management, respectively. In fact, CH4 is the second most important GHG emitted globally. This current scenario has increased the concerns about global warming and encouraged the development of intensive research on different natural compounds to be used as feed additives in ruminant rations and modify the rumen ecosystem, fermentation pattern, and mitigate enteric CH4. The compounds most studied are the secondary metabolites of plants, which include a vast array of chemical substances like polyphenols and saponins that are present in plant tissues of different species, but the results are not consistent, and the extraction cost has constrained their utilization in practical animal feeding. Other new compounds of interest include polysaccharide biopolymers such as chitosan, mainly obtained as a marine co-product. As with other compounds, the effect of chitosan on the rumen microbial population depends on the source, purity, dose, process of extraction, and storage. In addition, it is important to identify compounds without adverse effects on rumen fermentation. The present review is aimed at providing information about chitosan for dietary manipulation to be considered for future studies to mitigate enteric methane and reduce the environmental impact of GHGs arising from livestock production systems. Chitosan is a promising agent with methane mitigating effects, but further research is required with in vivo models to establish effective daily doses without any detrimental effect to the animal and consider its addition in practical rations as well as the economic cost of methane mitigation.

Effects of energy supplementation on productivity of dual-purpose cows grazing in a silvopastoral system in the tropics.

The aim of the present work was to evaluate milk yield, postpartum (pp) ovarian activity and pregnancy rate in dual-purpose cows grazing Cynodon nlemfuensis and browsing L. leucocephala, with or without energy supplementation. Twenty-four Bos taurus × B. indicus cows were divided in two groups from calving to 70 days post-calving: supplemented group (SG) with ground sorghum grain offered at 0.4% of live weight at calving and control group (CG) without supplement. There was a trend for milk yield (kg day(-1)) to be greater (p = 0.08) for SG (10.55 ± 0.51) compared to CG (9.53 ± 0.61), although without differences in fat (0.42 ± 0.02 vs. 0.38 ± 0.03 kg day(-1)), protein (0.29 ± 0.02 vs. 0.29 ± 0.02 kg day(-1)) or lactose (0.49 ± 0.02 vs. 0.49 ± 0.03 kg day(-1)) concentration. Populations of large, medium and small follicles were similar between treatments. Percentage of cows which showed corpus luteum tended to be greater in SG (50%), compared to CG (33%). Supplemented cows tended to have a shorter calving-first corpus luteum interval (40 ± 10 vs. 51 ± 10 days) and had a significantly higher (χ (2) = 0.03) pregnancy rate (42% vs. 0%). It is concluded that energy supplementation helped to improve ovarian activity and pregnancy rate. Since supplementation did not avoid loss of body condition, the higher pregnancy rate in SG suggests beneficial effects of supplementation probably mediated by metabolic hormones.

Energetic efficiency of milk synthesis in dual-purpose cows grazing tropical pastures.

The aim of this study was to assess the energetic efficiency of milk synthesis by grazing dual-purpose cows with or without a starch-based supplement in tropical South Mexico. Forty-six Holstein × Zebu cows were used in a 2 × 2 × 2 factorial design. Factors analysed were diet (supplemented, unsupplemented), age (young: 1-2 calvings, mature: >3 calvings) and day of lactation (21 and 84 days post-calving). The supplement represented about 30% of estimated dry matter (DM) intake. Grass intake was measured using the n-alkane technique at 21 and 84 days post-calving when calculations of efficiency were performed. Efficiency for milk synthesis was reported as feed conversion efficiency (FCE, kilograms of milk per kilogram of DM intake), gross energetic efficiency (GEE, milk energy output/metabolisable energy (ME) intake) and efficiency of ME use for lactation (k(l), adjusted to zero energy balance). There were no interactions between factors. FCE and GEE were not different between diets, but supplemented cows had a lower (p < 0.01) k(l) value (0.62) than unsupplemented cows (0.67), suggesting a diverted partition of nutrients towards body tissue. Mature cows were more efficient (p < 0.001) than young cows in terms of FCE (1.13 vs 0.87) and GEE (0.34 vs 0.26), but equal in terms of k(l) (0.65). FCE (1.10 vs 0.90) and GEE (0.34 vs 0.27) were both higher on day 21 compared with day 84 post-calving, with a trend for a higher k(l) in early lactation. Dual-purpose cows used tropical grasses efficiently for milk synthesis, and higher milk yield observed in supplemented cows was due to a higher intake of nutrients rather than a higher energetic efficiency.