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PubMed1981

Foraging differences in cattle: fecal analysis of three racial categories in a harsh environment.

Feces from three racial categories of cattle being raised together in degraded, desertic-thorn forest environment in northwestern Mexico were compared for plant epidermal cell content. There were statistically significant group differences for approximately one-third of the plant material found in the feces. The proportional fecal differences between racial categories were similar to those found previously for B-system blood types. The feces of Bos taurus-like cattle contained a greater variety of plants than did those of B indicus-like animals. The findings have implications for studies of behavioral evolution, the effects of cattle on ecology, and cattle husbandry.

Animals↗
PubMed1993

Dry Acacia sieberiana pods as a supplement to a low quality forage diet for growing lambs in northern Nigeria.

Twenty yearling lambs of mixed breed were grouped according to initial liveweight (20 +/- 2.7 kg), and each group was offered one of 5 concentrate rations as a supplement to a low quality, dry season Andropogon gayanus hay. Voluntary food intake and liveweight change were monitored over a 56 day growth period, after which 5 of the lambs were transferred to metabolism crates, in which digestibility and nitrogen balance studies were carried out. Ground Acacia sieberiana pods were substituted for maize offal in the experimental diets A, B, C, D and E at 0%, 15%, 30%, 45% and 60% respectively. Mean group intakes and growth rates were (913, 964, 1020, 1128 and 1004 g conc. DM/day) and (111, 120, 149, 165 and 119 g liveweight gain/day) respectively. A decline in both intake and growth rate were recorded as the level of A. sieberiana was increased beyond 45% of the supplement. This corresponded to a daily dry matter intake of Acacia pods in excess of 500 g, or 43 g/kg W0.75. This decline may have been due to the toxic effects of the phenolic compounds present in Acacia. It appears that up to a certain critical level of intake, A. sieberiana is able to support growth rates equal to or better than those obtained when feeding maize offal to lambs. This makes A. sieberiana an attractive low cost alternative, supplementary feed during the dry season.

Acacia↗
PubMed1994

Effects of poor forage conditions on the behaviour of grazing ruminants.

This paper shows that the study of animal behaviour is a valuable aid to the improvement of the management of grazing livestock under extensive conditions. The food available to grazing animals in developing countries, and particularly in the dry season in the tropics, is often of very low quality and, in addition, is frequently available at low densities per unit area. Grazing ruminants attempt to adapt to these adverse conditions by increasing the time for which they graze each day and also by dispersing more widely. However, the time for which animals can graze may be limited by solar radiation and fly irritation in the day, and by the confining of the animals in pens at night. The adverse effects of the above limitations may be partially overcome when adapted local breeds are used. Dispersion of animals improves their ability to make use of extensive pasture and in order to encourage it, an understanding of the factors that affect it such as breed differences, social behaviour, adaptation and location of watering points and other unique environmental factors must be achieved. The paper concludes with recommendations of areas worth further research.

Adaptation, Physiological↗
PubMed2003

The effect of octopamine on behavioral responses of free-foraging bumblebees to a change in food source profitability.

The invertebrate neuromodulator octopamine is known to be involved in bees' associative learning, enhancing the responsiveness of a bee to a conditioned stimulus. In this study, we tested the effect of octopamine on the choice behavior of free-flying bumblebees using a two-phase experiment in an array of artificial flowers. During the first phase of the experiment, the bee was allowed to collect octopamine-laden sugar water from two types of equally rewarding flowers (yellow versus blue). In the second phase, one type of flower was set to be unrewarding. The behavior of the bee (proportion of visits to the unrewarding flowers) over the two phases was fitted to a sigmoid regression model. Our results show that octopamine had no significant effect on the bees' equilibrium choice or on the overall rate of the behavioral change in response to the change in reward. Rather, octopamine significantly affected the time interval between the change in reward status and the initiation of behavioral change in the bee.

Adrenergic alpha-Agonists↗
PubMed2005

Multicomponent floral signals elicit selective foraging in bumblebees.

Flower constancy, or the tendency of individual pollinators to visit sequentially a single flower type even when other equally rewarding types are available, has important implications for animal-pollinated plants. Yet, the proximal reason for the behaviour still remains poorly understood. Here I show that bumblebees visiting equally rewarding flowers that differ in size and odour are more flower constant and less efficient (visited fewer flowers per minute) than bees visiting flowers that differ in size only and odour only. These results are consistent with the view that flower constancy in pollinators is related to their inability to perceive, process or recall multicomponent floral signals. I discuss these findings in the context of pollinator behavioural mechanisms and the evolution of floral diversity.

Animals↗
PubMed2004

Effects of DL-malate on in vitro forage fiber digestion by mixed ruminal microorganisms.

The objective of this study was to evaluate the effects of 0, 4, 8, and 12 mM DL-malate on the in vitro mixed ruminal microorganism fermentation of alfalfa hay and Coastal bermudagrass hay. When alfalfa hay was the substrate, 4 and 8 mM DL-malate numerically increased propionate concentration, and 12 mM DL-malate increased (P < 0.10) propionate. All three concentrations of DL-malate decreased (P < 0.05) the acetate:propionate ratio. In Coastal bermudagrass hay fermentations, all three DL-malate concentrations increased (P < 0.05) propionate and decreased (P < 0.05) the acetate:propionate ratio, while 4 and 12 mM DL-malate numerically increased in vitro dry matter disappearance. When mixed ruminal microorganisms were incubated with 6.25 mM DL-lactic acid and alfalfa hay, 8 and 12 mM DL-malate increased (P < 0.05) final pH, and 12 mM DL-malate increased (P < 0.10) propionate and decreased (P < 0.10) the acetate:propionate ratio. DL-Malate treatment had little effect on in vitro dry matter disappearance. Addition of 8 and 12 mM DL-malate to Coastal bermudagrass hay plus DL-lactic acid fermentations increased (P < 0.05) final pH, and 8 mM DL-malate increased (P < 0.10) in vitro dry matter disappearance. Even though DL-malate treatment consistently increased final pH values in fermentations that included DL-lactic acid, there was not a corresponding increase in in vitro dry matter disappearance of either alfalfa hay or Coastal bermudagrass hay in the 48-h batch culture incubations.

Animals↗
PubMed2003

Genetic transformation of Dichanthium annulatum (Forssk)--an apomictic tropical forage grass.

Eleven Dichanthium annulatum (Forssk) plants were regenerated from embryogenic callus co-transformed with two plasmids encoding either the hygromycin phosphotransferase gene (hph) or the beta-glucuronidase (GUS) gene (uidA). Analysis of these putative transformants showed that three plants were transformed with the hph gene, showed the presence of the hph transcript and expressed hygromycin resistance after transfer to soil. Two of these also contained the uidA gene but did not express GUS and were shown to be the same transformation event. All three of the transformants set seed. Hygromycin resistance varied from 68-100% in the progeny of the three transformants. Transgene transmission appeared to have been mainly through apomixis.

Blotting, Southern↗
PubMed2004

Plant regeneration from protoplasts isolated from embryogenic calli of the forage legume Astragalus melilotoides Pall.

An efficient and reproducible protocol is described for the regeneration of Astragalus melilotoides protoplasts isolated from hypocotyl-derived embryogenic calli. Maximum protoplast yield (11.74 +/- 0.6x10(5)/g FW) and viability (87.07 +/- 2.8%) were achieved using a mixture of 2% (w/v) Cellulase Onozuka R10, 0.5% (w/v) Cellulase Onozuka RS, 0.5% (w/v) Macerozyme R10, 0.5% (w/v) Hemicellulase, and 1% (w/v) Pectinase, all dissolved in a cell protoplast wash (CPW) salt solution with 13% (w/v) sorbitol. First divisions occurred 3-7 days following culture initiation. The highest division frequency (9.86 +/- 0.68%) and plating efficiency (1.68 +/- 0.05%) were obtained in solid-liquid medium (KM8P) supplemented with 1.0 mg/l 2,4-dichlorophenoxyacetic acid, 0.5 mg/l 6-benzylaminopurine (BA), 0.2 mg/l kinetin, 0.2 M glucose, 0.3 M mannitol and 500 mg/l casein hydrolysate. Upon transfer to MS medium with 0.5 mg/l alpha-naphthaleneacetic acid and 1-2 mg/l BA, the protoplast-derived calli produced plantlets via somatic embryogenesis (56.3 +/- 4.1%) and organogenesis (21.6 +/- 0.6%). Somatic embryos or adventitious shoots developed into well-rooted plantlets on MS medium without any plant growth regulators or supplemented with 3.0 mg/l indole-3-butyric acid, respectively. About 81% of the regenerants survived in soil, and all were normal with respect to morphology and growth characters.

Astragalus Plant↗
PubMed2003

The effect of temperature on digestive and assimilation efficiency, gut passage time and appetite in an ambush foraging lizard, Cordylus melanotus melanotus.

In ectotherms, an increase in body temperature increases metabolic rate and may increase rates of digestive processes. We measured the thermal dependence of the apparent digestive and apparent assimilation efficiencies (ADE and AAE), gut passage time (GP) and appetite in Cordylus melanotus melanotus, a medium sized Crag Lizard, which is endemic to South Africa. Trials were conducted at 20, 22, 25, 30, 32 and 35 degrees C under controlled conditions. Trials lasted 14 days, during which, lizards were fed ca. 1 g mealworms per day. Glass beads were used as markers to determine GP at the beginning and end of trials. Faeces and urates were collected daily and oven dried at 50 degrees C. The energy content of egested matter was then measured using bomb calorimetry. ADE and AAE were not affected by temperature for either males or females. The mean+/-SE ADE and AAE were 94.4+/-0.3% and 87.2+/-0.6%, respectively. GP was not significantly different between males and females at any temperature, but decreased significantly with increasing temperature. Appetite was significantly different between the different temperatures measured. The decrease of gut passage time with increasing temperature was expected, since the digestive and assimilation efficiencies are similar over the range of temperatures tested. Lizards are thus assimilating a similar proportion of ingested energy, but at faster rates at higher temperatures. The results indicate that the digestive physiology of this species results in maximum energy gain per meal in environments where food is scarce.

Animals↗
PubMed2005

Woodrat (Neotoma) herbivores maintain nitrogen balance on a low-nitrogen, high-phenolic forage, Juniperus monosperma.

The acquisition of adequate quantities of nitrogen is a challenge for herbivorous vertebrates because many plants are in low nitrogen and contain secondary metabolites that reduce nitrogen digestibility. To investigate whether herbivores maintain nitrogen balance on plant diets low in nitrogen and high in secondary compounds, we studied the effect of juniper (Juniperus monosperma) ingestion on the nitrogen balance of two species of herbivorous woodrats (Neotoma stephensi and N. albigula). These woodrat species feed on the foliage of juniper: N. stephensi is a juniper specialist, whereas N. albigula is a generalist that incorporates some juniper in its diet. Based on the nitrogen contents of the natural diets of these woodrats, we predicted that the generalist would be in negative nitrogen balance on a juniper diet whereas the specialist would not be affected. We found that both species of woodrat had low-nitrogen requirements (334.2 mg N/kg0.75/day) and that a diet of 50% juniper did not result in negative nitrogen balance for either species. However, excretion patterns of nitrogen were altered; on the 50% juniper diet, fecal nitrogen losses increased approximately 38% and urinary nitrogen losses were half that of the control diet. The results suggest that absorption and detoxification of juniper secondary compounds may be more important for restricting juniper intake by the generalist than nitrogen imbalance.

Analysis of Variance↗
PubMed2005

Nitrate assimilation in the forage legume Lotus japonicus L.

Nitrate assimilation in the model legume, Lotus japonicus, has been investigated using a variety of approaches. A gene encoding a nitrate-inducible nitrate reductase (NR) has been cloned and appears to be the only NR gene present in the genome. Most of the nitrate reductase activity (NRA) is found in the roots and the plant assimilates the bulk of its nitrogen in that tissue. We calculate that the observed rates of nitrate reduction are compatible with the growth requirement for reduced nitrogen. The NR mRNA, NRA and the nitrate content do not show a strong diurnal rhythm in the roots and assimilation continues during the dark period although export of assimilated N to the shoot is lower during this time. In shoots, the previous low NR activity may be further inactivated during the dark either by a phosphorylation mechanism or due to reduced nitrate flux coincident with a decreased delivery through the transpiration stream. From nitrate-sufficient conditions, the removal of nitrate from the external medium causes a rapid drop in hydraulic conductivity and a decline in nitrate and reduced-N export. Root nitrate content, NR and nitrate transporter (NRT2) mRNA decline over a period of 2 days to barely detectable levels. On resupply, a coordinated increase of NR and NRT2 mRNA, and NRA is seen within hours.

Gene Expression Regulation, Enzymologic↗