Genotype–environment interaction for age at first calving in buffaloes,using the reaction norm model

The objective of this study was to evaluate the genotype–environment interaction effect on age at first calving in buffaloes. The records were analysed using two approaches: (a) standard animal model and (b) reaction norm model. For the reaction norm analysis, two environmental gradients were formed, using age of first calving or milk yield group contemporary average. The results showed differences in the heritability estimates when using the two approaches. The reaction norm model indicated high heritability in more favourable environments and low magnitude genetic correlations between extreme environments. Based on our findings, we verified the significance of the genotype–environment interaction effect on age at first calving in buffaloes.     

Seasonal Divergence of Landscape Use by Heritage and Conventional Cattle on Desert Rangeland

Adopting livestock with heritage genetics may help to improve the sustainability of agriculture on rangelands with harsh, challenging conditions. In the Chihuahuan Desert, preliminary evidence suggests that heritage Raramuri Criollo exploit a greater variety of range resources than do conventional cattle. Accordingly, the use of Raramuri Criollo may help sustain vegetation and soils, as well as agricultural production. To explore these possibilities, we used Global Positioning System collars to track Angus × Hereford and Raramuri Criollo cows in a 1 535-ha pasture in southern New Mexico in June–December 2008. As predicted on the basis of past research, home range sizes of Raramuri Criollo exceeded those of Angus × Hereford during seasons with low forage availability—by 31.4 ± 6.5 ha during Pregreenup and 17.2 ± 6.5 ha during Drydown—but sizes converged during more productive seasons (Greenup 1, Greenup 2). Angus × Hereford allotted more daily time to resting, with the difference most pronounced during Drydown (71.1 ± 21.1 min day^{? 1}). Angus × Hereford had twice as many hotspots of use (locations with multiple visits of long duration), with seasonal timing and location corresponding with distribution patterns known to impact desirable natural resources. Raramuri Criollo more strongly preferred the Bare/Forbs ecological state with seasonal timing that possibly signals an ability to use nutritious forbs on open ground despite summer heat. Results are consistent with conjectures that compared with conventional cattle, Raramuri Criollo have greater daily mobility and wider spatial distribution during dry seasons. Although not directly measured, results also suggest that the heritage breed has superior heat tolerance and lower impact on desirable natural resources. These findings provide evidence that Raramuri Criollo can support sustainable livestock production in the Chihuahuan Desert, but direct measurements of profitability and environmental effects are needed before adoption can be recommended widely.     

Fundamental considerations about design and sample size in strain comparisons and their implications

Well‐known formulae for the calculation of the necessary number of animals in strain comparisons are presented. Their use is illustrated with an example with fish. Use of the formulae in the planning and design of strain comparisons is recommended. When the necessary number cannot be attained and the experiment is conducted with fewer animals than what the formulae indicate, or the animals originate from a low and thus most likely non‐random sample of parents, no inferences should be drawn about any observed between strain differences.     

The performance and impact of a bubble-wash bead filter in a recirculating green water larval culture system for delta smelt (Hypomesus transpacificus)

Delta smelt are cultured at the UC Davis Fish Conservation and Culture Lab (FCCL) for research purposes. The culture systems used are based on recirculation technology to ensure optimum water quality for the fish at each life stage. Larval culture takes place in recirculation systems with green water to which a Nannochloropsis algal concentrate is added to maintain a turbidity of approximately 9 NTU. A bubble-wash bead filter is used to remove total suspended solids (TSS) from the recirculation system. The performance of the bubble-wash bead filter has been evaluated by testing the TSS and particle size distribution in two parallel systems operated in the same way. The need for bubble-wash bead filter backwashing and the impact of the backwash method were evaluated also.The results show that the bubble-wash bead filter removed a great deal of the TSS, including the algae added to maintain the turbidity. An improper backwash method could result in a short term but significantly high TSS peak in the system immediately after the backwash event. Testing over an extended filtration period with a prolonged backwash interval showed that the TSS in the system remained stable up to 150 h post backwash, at which time it increased rapidly. The TSS accumulation in the system with a bubble-wash bead filter that was not backwashed was greater than that in a parallel system without a bubble-wash bead filter. No significant mortality increase was found in the system without a bubble-wash bead filter for 34 days, which provides a possible alternative in order to lower the rearing cost. Nevertheless, there are benefits of using a bead filter, and these are discussed in the paper.     

Routine oxygen consumption rates of california halibut (Paralichthys californicus) juveniles under farm-like conditions

Fish oxygen requirement is a fundamental variable of aquaculture system design and management, as it is the basis for determining water flow rates for sustaining stock. A study on oxygen consumption of California halibut (Paralichthys californicus) between 3.2 and 165.6 g was conducted in small raceways (2.41 m long, 0.28 m wide, and 0.22 m high; operational water depth between 0.05 and 0.10 m with a quiescent zone 19 cm long in the effluent section) working as open respirometers in a recirculating system under farm-like conditions. The fish were fed commercial dry pelleted feeds at a ratio of ～0.70–3.00% of body weight (BW) and stocked at densities between 94% and 316% percent coverage area (PCA). Oxygen consumption rates were determined by mass balance calculations. The mean and maximum oxygen consumption rates (g O₂/kg fish/day) for juvenile California halibut under the conditions tested can be expressed by M_day = 15.077W^?0.2452 and M_day = 17.266W^?0.2033, respectively, where W is fish weight in grams. The determination of oxygen consumption by California halibut in farm-like conditions provides valuable information on the oxygen requirement of these fish in an aquacultural setting. This information can be used for designing and sizing a rearing facility for the intensive culture of California halibut.     

Organizational learning through participatory research: CIP and CARE in Peru

Participatory research (PR) has been analyzed and documented from different points of view, with emphasis on the benefits generated for farmers. The effect of PR on organizational learning has, however, received little attention. This paper analyzes the interaction between a research and a development institution, the International Potato Center (CIP) and CARE in Peru, respectively, and makes the case that PR can contribute to creating a collaborative learning environment among organizations. The paper describes the evolution of the inter-institutional collaborative environment between the two institutions for more than a decade, including an information-transfer period (1993–1996), an action-learning period (1997–2002), and a social-learning period (2003–2007). Several lessons learned from each period are described, as are changes in institutional contexts and stakeholders’ perceptions. The case shows that research and development-oriented organizations can interact fruitfully using PR as a mechanism to promote learning, flexibility in interactions, and innovation. Interactions foster the diffusion of information and the sharing of tacit knowledge within and between organizations, which in turn influences behavior. However, the paper also argues that long-term inter-organizational interactions are needed to facilitate learning, which can be used to influence the way organizations implement their interventions in a constantly changing environment.     

Evaluation of carbohydrate/lipid ratios on growth and metabolic response in tropical gar (Atractosteus tropicus) juvenile

Five experimental diets with different carbohydrates/lipid ratio (CHO:L, 0.75, 1.28, 2.10, 2.52, 4.63) were formulated. Fish were randomly assigned by triplicate (10 fish per tank, 0.50 ± 0.01 g). Growth was registered every 15 days until end of the experiment (45 days). Samples were taken for analysis of chemical carcass composition, blood chemistry, glycogen and lipid liver content, digestive and metabolic enzyme activities. Results showed that survival, growth performance parameters and plasma glucose were not affected by treatments (p > 0.05). Lipids of carcass and liver, as well as triglycerides and plasma cholesterol increase significantly as CHO:L ratio decreased. While an inversely proportional tendency was observed for carcass protein and liver glycogen (p < 0.05). Digestive enzymes did not show significant differences among treatments (p > 0.05). Finally, Hexokinase (HK), glucokinase (GK), phosphoenol pyruvate carboxykinase (PEPCK) and fructose‐1,6‐biphosphase (FBPase) showed high regulation by carbohydrates up to the CHO:L ratio of 2.10 (p < 0.05), while pyruvate kinase (PK) activity was not significantly affected by the CHO:L ratio. By the other side, glucose‐6‐phosphate dehydrogenase (G6PD) tends to significantly increase as the CHO:L ratio increases. We conclude that A. tropicus fry have a high capacity to utilize carbohydrates substituting lipids as energy source in balanced diets.