The genetic diversity of Agave plants is threatened by clonal commercial reproduction and climatic change. Sexual reproduction is uncommon and research on seed germination is scarce. The present study evaluated the seed germination of Agave lechuguilla, Agave striata, Agave americana var. marginata, Agave asperrima, Agave cupreata, Agave duranguesis, Agave angustifolia ssp. tequilana and Agave salmiana at constant temperatures (10, 15, 20, 25, 30, 35 and 40°C). Initial imbibition (after the first 12 h) was significantly variable among species, positively correlated with seed weight (r = 0.6560, P < 0.001) and increased with temperature (from 35% at 10°C to 66% at 40°C). Temperature affected maximum imbibition (83-150%) for A. asperrima, A. lechuguilla, A. salmiana and A. striata; other species averaged 110%. Most germination kinetics best fitted a logistic model, whereas only a few treatments fit a Weibull model. The time to germination onset diminished (P < 0.05) from 125-173 h at 15°C to 68-84 h at 25°C, and then ascended to 84-196 h at 35°C. The mean germination rate and seed germination percentage after 312 h peaked at 25°C (0.50-0.95% seeds/h and 85-99%, respectively) and fell (P < 0.05) to near zero at 10 and 40°C. Temperatures of 10, 35 and 40°C were partially lethal to A. asperrima, A. duranguensis and A. salmiana seeds. The time to germination onset, seed germination percentage after 312 h and mean germination rate are best described by a Gaussian distribution, with its optimum at approximately 25°C. Thus, optimum temperatures are related to the ecological characteristics of each species area.

This study evaluated the effect of dietary supplementation with Amaranthus dubius on carcass characteristics and meat quality of fattening rabbits. One hundred and six New Zealand White rabbits, weaned at 35 d of age, were assigned to three experimental diets including 0%, 16% and 32% of A. dubius (A0, A16 and A32), and were fed ad libitum until their slaughter at 87 d of age.

The aim of this study was to quantify mucilages, pectins, hemicelluloses, and cellulose of nopalitos (edible, as vegetable, young cladodes of flat-stemmed spiny cacti) of most consumed Mexican cultivars, and sweet and acid cactus pear fruits of Opuntia spp. The hypothesis is that, regardless of their unavailable polysaccharides diversity, nopalitos and cactus pear fruits are rich sources of soluble and insoluble dietary fiber. Twelve cultivars of Opuntia spp. were used. Nopalitos had a significant variation in structural polysaccharides among the cultivars: mucilages (from 3.8 to 8.6% dry matter (DM)) averaged near a half of pectins content (from 6.1 to 14.2% DM) and tightly bound hemicelluloses (from 2.2 to 4.7% DM), which were the less abundant polysaccharides, amounted 50% of the loosely bound hemicelluloses (from 4.3 to 10.7% DM). Acid fruits (or 'xoconostle') had significantly higher unavailable polysaccharides content than sweet fruit, and contain similar proportions than nopalitos. Unavailable polysaccharides represent a high proportion of dry tissues of nopalitos and cactus pear fruits, composition of both of these soluble and insoluble polysaccharides (total dietary fiber) widely vary among cultivars without an evident pattern. Nopalitos and cactus pear fruit can be considered an excellent source of dietary fiber.

Abstract:The effects on performance and digestibility in growing rabbits were studied by comparing 3 diets containing increasing inclusion rates of amaranth (Amaranthus dubius Mart. ex Thell.): 0 (A0), 160 (A16) and 320 g/kg (A32 diet). Diets were formulated isoproteic and isocaloric to meet the nutrient requirements of growing rabbits. One hundred and thirteen weaned New Zealand White rabbits (mean±standard deviation weight: 760±102 g), individually caged, were randomly assigned to one of the 3 experimental diets. Rabbits were fed ad libitum from 35 to 87 d of age, and health status and performance traits were monitored. The coefficients of total tract apparent digestibility of the diets were measured between 42 and 46 d of age in 12 rabbits per treatment. Amaranthus dubius contained 209 g/kg dry matter (DM) of crude protein and 398 g/kg DM of neutral detergent fibre. There were no significant differences between treatments in weight gain (mean 21.6 g/d) and live weight at the end of the fattening period (mean 1883 g). Daily feed intake was higher (P<0.05) in A0 than in A16 and A32 diets (85.4 vs. 73.7 and 69.9 g/d, respectively), and feed conversion rate improved with increased inclusion of A. dubius in the diet (from 3.84 to 3.28 for A0 and A32 diets, respectively; P<0.05). Health status was not affected by the amaranth inclusion rate. Total tract apparent digestibility showed high values, with no differences among diets except for ether extract. Thus, A. dubius could be considered as an alternative source of protein and fibre for rabbit feeding in tropical and subtropical regions.

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Anatomical root variations in response to water deficit: wild and domesticated common bean (Phaseolus vulgaris L.

Amaranthus dubius is an alternative source of fibre and protein for the feed formulation for growing rabbits, although its effects on their health status are yet unknown. Therefore, this study aimed to evaluate the effects of three dietary levels (0, 160 and 320 g/kg) of A. dubius on haematological, serum biochemical and histopathological parameters of fattening rabbits. One hundred and thirteen New Zealand White rabbits were fed ad libitum from weaning (35 days) to slaughter (87 days). The health status of the animals was monitored, and mortality was recorded. Before slaughtering, 30 rabbits were randomly selected for haematological and serum biochemical analysis. During slaughter, 18 rabbits were randomly selected for histopathological study in heart, liver, lung and small intestine. The health status of rabbits was good, with no differences among treatments in mortality. Diet and sex did not affect the values of most haematological and serum biochemical parameters. Fibrinogen, glucose and high-density lipoprotein values increased significantly from 0 to 320 g/kg A. dubius diets. The white blood cell count and glutamic oxaloacetic transaminase values decreased significantly from 0 to 320 g/kg A. dubius diets. The organs showed histologically well-structured tissues. However, in all experimental groups several samples with lesions were observed, always highly focalized in small tissue areas. The main lesions observed, probably related to conditions of thermal stress affecting the rabbits, were cholesterolosis (heart), steatosis (liver), inflammatory lymphoplasmacytic infiltrate (lung) and chronic inflammatory tissue damage (small intestine). In conclusion, the inclusion of up to 320 g/kg A. dubius in diet did not jeopardize the health status of growing rabbits. Therefore, A. dubius can become an alternative raw material for the formulation of feeds in tropical and subtropical countries where this plant is widespread.

The objective of this study was to test the hypothesis that root of maguey (Agave salmiana Otto ex Salm-Dyck) seedlings reacts during the first 24 h to low substrate water potential (Ψ W), by anatomical modifications. Three-4 cm root length seedlings were planted in vermiculite for 24 h at Ψ W between-0.03 and-2.35 MPa. Root dimensions, proline content and anatomy were evaluated. Substrate Ψ W between-0.65 and-2.35 MPa did not significantly affect longitudinal root growth. However, proline content significantly increased from 1.6 to 2.1 μmoles mg-1. Significant reductions of transverse root area (41 %), thickness of mucilage covering the epidermis (47 %), thickness of epidermis (between 15 and 46 %), area of the parenchyma (between 35 and 41 %) and number of vessels (up to 28 %) were observed with Ψ W of-2.35 MPa. In contrast, thickness of xylem wall, diameter of xylem vessels and the number of cells of the cortex of the differentiation root region significantly increased (64, 17, and 97 %, respectively). The anatomical changes associated with low substrate Ψ W indicate a net increase of root apoplatic paths; structures involved in water conduction increased their diameter under low substrate Ψ W conditions and anatomical changes occurred during the first 24 h of water stress.