Calcium plus magnesium indicates digestibility: the significance of the second major axis of plant chemical variation for ecological processes.

Plant variation in nutrient concentrations encompasses two major axes. The first is connected to nitrogen (N) and phosphorus (P), reflects growth rate and has been designated as the leaf economics spectrum (LES) while the second follows the gradient in calcium (Ca) and magnesium (Mg) and mirrors cell structural differences. Here, we tested in grasslands whether the sum Ca + Mg concentrations is a better indicator of digestibility than LES constituents. Structural equation modelling revealed that the total effect size of N (0.30) on digestibility was much lower than that of Ca + Mg (0.58). The N effect originated predominantly from sampling date (biomass ageing), while the Ca + Mg effect largely from phylogenetic composition (proportion of monocots). Thus, plant variation in partially substitutable divalent cations seems to play a significant role in biomass digestion by ruminants. This finding contests, together with litter decomposition studies, the prominent role of the LES for understanding both fundamental ecological processes.

Anaerobic fermentation of rice bran using rumen liquor for desirable chemical changes as animal feed.

Objective: The objectives of this research are to overcome the limitations of rice bran (RB) and de-oiled rice bran (DORB) by fermentation anaerobically using inoculum from the rumen of a canulated sheep for desirable chemical changes. Materials and Methods: Initially, RB and DORB were fermented by 10% rumen liquor for 12 h at 39°C at different moisture levels (10, 20, 30, 40, 50, and 60% phosphate buffer). Again, DORB was fermented for 24, 48, and 72 h at 39°C using 10% rumen liquor at different moisture levels (10, 20, 30, 40, 50, and 60% phosphate buffer). Before and after fermentation, RB and DORB were analyzed for pH, proximate components, neutral detergent fiber (NDF), total-P, inorganic-P, and phytate-P. Results: Fermentation of RB and DORB for 12 h reduced (p < 0.05) pH, crude fiber (CF),NDF, and phytate-P, but increased (p < 0.05) the content of inorganic-P. Subsequent fermentation of DORB for 24, 48, and 72 h reduced pH, CF, and NDF. Total-P of fermented DORB remained similar till 72 h fermentation (p < 0.05). But, inorganic-P increased with the increasing duration (24, 48, and 72 h) of fermentation and increased (30, 40, and 50) moisture level (p < 0.05). Alternatively, phytate-P decreased with increasing duration and moisture level (p < 0.05). Conclusion: Inoculation of rumen microbes and incubation of RB (12 h) and DORB (24 h) at room temperature reduced phytate-P and fiber content (CF and NDF) when the moisture level was up to 50%; those are the indicators to reduce the limitation of RB and DORB to use as feed for non-ruminant animals like poultry and pigs.

Effect of Olive Cake and Cactus Cladodes Incorporation in Goat Kids' Diet on the Rumen Microbial Community Profile and Meat Fatty Acid Composition.

The olive cake (OC) and the cactus cladodes (CC) are two alternative feed resources widely available in the southern Mediterranean region that could be used in ruminants' diet. Their impact on the rumen bacterial ecosystem is unknown. This work aims to evaluate their effects on the microbial community and meat fatty acids of goat's kids. Forty-four goat kids were divided into four groups receiving diets with conventional concentrate, or 35% OC, or 30% CC, or 15% OC, and 15% CC. After 3 months, these animals were slaughtered, and the rumen liquor and longissimus dorsi and semimembranosus muscles samples were collected. Animals receiving a control diet had rumen liquor with high acidity than test groups (p < 0.001). Test rumen liquor was more adapted to digest efficiently their matching diet than control liquor (p < 0.05). These feedstuffs did not affect rumen bacteria abundance and alpha diversity (richness, evenness, and reciprocal Simpson indexes), and these results were confirmed by beta-diversity tests (NMDS plot, HOMOVA, PERMANOVA). The test diets slightly affected the individual fatty acids of meat (p < 0.05) without effect on fatty acids summaries, indexes, and ratios. Thus, these alternative feed resources could take place in goat kids' diet to diversify their feed and to reduce feed costs.

Rumen liquor from slaughtered cattle as inoculum for feed evaluation.

Use of nonlinear mathematical models has been majorly based on in vitro gas production (GP) data generated when substrates are incubated with rumen liquor from fistulated steers. However, existing evidence suggests that rumen liquor from slaughtered cattle of unknown dietary history also generates quantifiable in vitro GP data. Fitting and description of GP data obtained from 4 diets incubated with rumen liquor from slaughtered cattle was evaluated using single-pool exponential model with discrete lag time (EXPL), logistic (LOG), Groot's (GRTS) and Gompertz (GOMP) models. Diets were formulated by varying proportions of Rhodes grass (Chloris gayana) hay and a concentrate mixed on dry matter basis to be: 1,000 g/kg Rhodes grass hay (RGH) and 0 of the concentrate (D1), 900 g/kg RGH and 100 g/kg concentrate (D2), 800 g/kg RGH and 200 g/kg concentrate (D3), 700 g/kg RGH and 300 g/kg concentrate (D4). Dietary kinetics for the models were determined by measuring GP at 2, 4, 8, 10, 18, 24, 36, 48, 72, 96 and 120 h. Model comparison was based on derived GP kinetics, graphical analysis of observed versus predicted GP profiles plus residual distribution and goodness-of-fit from analysis of root mean square error (RMSE), adjusted coefficient of determination (Adj-R2) and Akaike's information criterion (AIC). Asymptotic GP, half-life and fractional rate of GP differed (P < 0.001) among the 4 models. The RMSE, Adj-R2 and AIC ranged from 1.555 to 4.429, 0.906 to 0.984 and 2.452 to 15.874, respectively, for all diets compared across the 4 models. Based on the goodness-of-fit statistical criterion, GP profiles of D1 were more appropriately fitted and described by GRTS and GOMP than the EXPL and LOG models. The GRTS model had the lowest AIC value for D2 (2.452). Although GRTS model had the most homogenous residual dispersion for the 4 diets, all the 4 models exhibited a sigmoidal behavior. Therefore, rumen liquor from slaughtered cattle of unknown dietary history can be used to derive nutritionally important feed parameters, but choice of the most appropriate model should be made based on fitting criteria and dietary substrates incubated.