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Fodder shrubs are important dry season feed sources for livestock in semi-arid environments. It has been proposed that a mixture of leguminous with non-leguminous shrubs may increase rates of N cycling and improve biomass and fodder quality. The objective of the present study was to assess the biomass productivity and fodder quality of leguminous shrubs growing a mixture with non-leguminous shrubs. Three shrub species—the legume Leucaena leucocephala (Lam.) and the non-legumes Guazuma ulmifolia (Lam.) and Moringa oleifera (Lam.)—were grown as legume/non-legume mixtures and as monocultures. Total fodder production and quality were estimated over five harvests at three-month intervals. The Leucaena–Guazuma mixture had the largest fodder production (9045 kg ha−1 year−1), followed by the Leucaena monocrop (7750 kg ha−1 year−1). Total nitrogen accumulation in the foliage was also high in the Leucaena–Guazuma mixture, reaching 282 kg ha−1 year−1; the Leucaena monocrop accumulated 244 kg N, while the Moringa monocrop took up only 46 kg N ha−1. The concentration of polyphenols was high in Leucaena and Guazuma, while Moringa had the lowest value. The high survival and excellent growth rates, as well as the high foliage production observed in Leucaena and Guazuma, suggest that they have the potential to provide high-quality fodder for livestock.

Decomposition and N release pattern from the leaves of three shrubs species were studied under field conditions. Leaves of Leucaena leucocephala (Lam.), Guazuma ulmifolia (Lam.) and Moringa oleifera (Lam.) and two mixtures, Leucaena + Moringa and Leucaena + Guazuma, in a complete randomized block design, were studied during the dry and wet seasons. Litterbags were randomly distributed in each experimental block and placed on the soil surface, and residues were recovered after 2, 4, 8, and 16 weeks. Double exponential model decay was better fitted to describe the pattern of the decay of the release of various leaf constituents. Litter dry weight loss and N release were faster from Moringa, followed by the Leucaena + Moringa mixture, while the Guazuma leaf litter decomposed much slower. In the wet period, a rapid N release was observed for Moringa (60%) and Leucaena + Moringa (43%) in the first two weeks. In contrast, Guazuma and the Leucaena + Guazuma mixture released about 46% of N in 16 weeks. In the dry period, leaves released most of their N during the first 8 to 16 weeks. Moringa and Leucaena + Moringa ranked first, having lost 81 and 75% of its initial N, respectively. The ratios of condensed tannin and polyphenols to N were significantly correlated with the N released. It was concluded that the initial mass loss from the leaf litter was high and rapid in the rainy period in comparison to the dry period. The residue disappearance pattern of Moringa, Leucaena and Leucaena + Moringa followed an asymptotic model, with more than 80% of the original residue released during the 16-week study period.

There are mixed reports about the advantages and disadvantages of the presence of shade produced by trees over the understory-growing grasses; thus, it is urgent to test grass species and cultivars with potential to develop in shaded conditions associated with trees that occur in silvopastoral systems. The objective of the present study was to identify Brachiaria spp. ecotypes adapted for cultivation under tree shade, typical of silvopastoral systems. The study was conducted at Kampepen ranch, located 14 km south of Merida, Yucatan, Mexico. A factorial 6 (ecotypes) x 2 (sunlight intensities) treatment structure was used, arranged in split-plot design; with sunlight intensity levels being the plots and ecotypes the subplots, with three replications. The ecotypes were T1: Brachiaria hybrid cv. Mulato II, T2: Brachiaria hybrid cv. Cayman Blend, T3: Brachiaria hybrid cv. Talisman (BR05/1467), T4: Brachiaria hybrid cv. Camello Blend, T5: Brachiaria brizantha cv. Marandu and T6 (the control): M. maximus cv. Mombasa, while the two sunlight intensity levels were higher and lower sunlight reductions with respect to full sunlight (25% and 50% light transmission with respect to full sunlight, respectively). Variables were plant height, forage yield and chemical composition; leaf, stem and dead material fractions and leaf:stem ratio; plant canopy cover, plant maturity, and growth rate. Significant (p < 0.050) ecotype x sunlight intensity interactions were recorded for most of the studied variables. Independent of the shading levels, ecotype Talisman showed superior performance compared with the other assessed ecotypes, yielding up to 20 ton ha−1 under the highest light intensity, means across light intensities for crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) of 11.8%, 59.7%, and 34.7%, respectively, and more than 90% plant canopy cover. It is concluded that Talisman has promising characteristics for cultivation under silvopastoral systems, where tree shading is common, in the dry tropics of Yucatan, Mexico.

Background: Accurate estimations of aboveground biomass (AGB) based on allometric models are needed to implement climate-change mitigation strategies. However, allometry can change with tree size. Questions: Does allometry in a tropical dry forest change with tree size? Does combining different allometric equations provide better AGB estimates than using a single equation? Study site and dates: San Agustín Ejido, Yucatán, México, 2016. Methods: Forty-seven trees of 18 species with 2.5 to 41.5 cm in diameter at breast height (DBH) were sampled. Stems and branches were sectioned, and samples were dried and weighed to estimate tree AGB. Segmented linear regression was used to evaluate changes in allometry between DBH, height and AGB. Different equations were tested for each size category identified, and the best models and model-combinations selected. Results: A shift in the AGB-height relationship was found, defining two tree-size categories (2.5-9.9 cm and ? 10 cm in DBH), with the inflection point corresponding to the average canopy height (12.2 m). The best models were AGB = exp(-2.769+0.937ln(D2HPw)) for trees < 10 cm DBH and AGB = exp(-9.171+1.591lnD+3.902lnH+0.496lnPw) for trees ? 10 cm DBH (R2 = 0.85 and R2 = 0.92, respectively). The combination of these models produced more accurate AGB estimates than a single model or combinations involving regional models with larger sample sizes. Conclusions: These results highlight the importance of locally-developed models and suggest changes in allometry and resource allocation: towards height growth for small trees, thereby reducing the risk of suppression, versus towards AGB growth for larger trees, thereby maximizing stability and resource acquisition.

The objective of this study was to determine the effect of stocking rate (SR: 2, 3 and 4 cows/ha) upon standing dry matter variables, its quality and ingestive behavior of F1 Holstein x Zebu cows that grazed rotationally and considering the climatic seasons (S): Rainy, winter and dry in the north-central region of the State of Veracruz. A completely randomized design was used. The analysis of variance considered the fixed effects of SR, S and their interaction, being the season the repeated measurement and the experimental unit the subject. The standing dry matter (kg/ha) was affected by S (7140±637, 5341±524 and 4512±719, respectively), but not by SR. Grazing time (min/cow/d) was similar between 2 (428±71) and 4 (400±83) cows/ha, both different from 3 cows/ha (462±55). Ruminating time (min/cow/day) was affected by SR, averaging 372±104, 364±96, and 315±90 min/cow/d, respectively. In situ dry matter digestibility (%) went from 57.6±1.3 to 79.2±1.6 for leaves and from 62.6±2.0 to 78.8±0.5 for stems; either component increased their values as SR increased. Daily milk yield per cow was not affected by SR. It is concluded that que there is a significant effect of SR upon grazing and ruminating time, but these variables were not statistically related to pasture variables and individual milk yield, mostly due to the fact that forage availability never limited pasture intake in any of the three stocking rates utilized. Key words: Daily milk yield; biting rate; climatic period; standing dry matter; pasture management. RESUMEN El objetivo del estudio fue determinar el efecto de la carga animal (CA: 2, 3 y 4 vacas/ha) sobre el porcentaje de materia seca de gramas nativas, su calidad, y el comportamiento ingestivo de vacas F1 Holstein x Cebú, en pastoreo rotacional en época (E) de lluvia, nortes y seca; en la zona centro norte del estado de Veracruz. Se empleó un diseño completamente al azar. Tanto las variables de pastura como de comportamiento animal y producción de leche, se analizaron con un modelo estadístico que consideró los efectos de CA, E, y sus interacciones; además de mediciones repetidas en la unidad experimental. La materia seca total en pie (kg/ha) fue afectada por E (7140±637, 5341±524 y 4512±719, respectivamente) pero no por CA. El tiempo de pastoreo (min/vaca/d) fue idéntico entre 2 (428±71) y 4 (400±83) vacas/ha, y diferentes de 3 vacas/ha (462±55). El tiempo de rumia fue afectado por CA (2, 3 y 4 vacas/ha), promediando: 372±104, 364±96, y 315±90 min/vaca/d, respectivamente. La digestibilidad in situ de la materia seca (%) para hojas fue de 57.6±1.3 a 79.2±1.6, y para tallos de 62.6±2.0 a 78.8±0.5, en ambos componentes el valor es mayor conforme se incrementó la CA. La producción láctea (8.1±2.5) no se afectó por CA. Se concluye que existe un efecto de CA sobre el tiempo de pastoreo y rumia; aunque no hubo una relación alta entre este comportamiento, las variables de la pastura y la producción láctea debido al rendimiento similar de forraje obtenido. Palabras clave: producción láctea; tasa de bocados; periodo climático; rendimiento de materia seca; manejo de la pastura.