Variations in the response of sheep to experimental magnesium deficiency.

Hypomagnesaemia was induced in adult sheep by changing their diet from chaff given orally to a milk diet, low in Mg, infused via the abomasum. All sheep given the milk diet developed hypomagnesaemia and four out of 19 developed nervous convulsions similar to the natural disease grass tetany. Analysis of the sequential changes in plasma Ca, P and Mg revealed a striking positive correlation between Ca and Mg and hypocalcaemia thus appeared to be a general response to Mg deficiency. Many sheep appeared to adapt to the deficiency since after a period of about 11 days the decline in plasma Mg (and Ca) was either alleviated or reversed. However the four sheep which developed convulsions all showed a rapid and substantial decline in plasma Mg associated with a decline in plasma Ca.     

Zinc bioavailability in soybean meal

A phytate-containing soy protein concentrate (SPC) diet (13.5 mg Zn/kg) and a phytate-free egg white diet (.3 mg Zn/kg) were used to determine the relative bioavailability (RBV) of Zn in dehulled soybean meal (SBM) based on Zn depletion-repletion growth bioassays in young chicks. After a 4-d Zn depletion period, chick weight gain responded linearly (P < .01) to graded increments of supplemental Zn (0 to 10 mg/kg) from ZnSO4 x 7H2O, whether added to the Zn-deficient SPC or egg white diet. Slope, however, was over twice as great for the standard curve relating weight gain to supplemental Zn intake for the egg white diet as for the SPC diet. Addition of 7 to 10 mg Zn/kg from SBM to either Zn-deficient diet increased (P < .01) weight gain, but a similar SBM addition to either diet made adequate in Zn did not increase weight gain. Using standard-curve methodology, RBV of Zn in SBM was 78% when the the SPC diet was used, but it was only 40% when the egg white diet was used. The phytate contained in the SPC basal diet therefore markedly reduced the efficiency of utilizing the supplemental inorganic Zn from ZnSO4 x 7H2O. This lowered the slope of the standard curve so that, on a relative basis, the Zn in SBM had a higher RBV value than was the case for Zn utilization in SBM with the phytate-free egg white diet. The 78% Zn RBV value in SBM would seem to have the greatest relevance for practical-type corn-SBM diets.     

The effects of citric acid on phytate-phosphorus utilization in young chicks and pigs

Several bioassays were conducted with young chicks and pigs fed phosphorus (P)-deficient corn-soybean meal diets. With diets for chicks containing .62% Ca and .42% P (.10% available P), graded doses of a citric acid + sodium citrate (1:1, wt:wt) mixture (0, 1, 2, 4, or 6% of diet) resulted in linear (P < .01) increases in both weight gain and tibia ash. Relative to chicks fed no citric acid, tibia ash (%) and weight gain (g/d) were increased by 43 and 22%, respectively, in chicks fed 6% citric acid. Additional chick trials showed that 6% citric acid alone or sodium citrate alone was as efficacious as the citric acid + sodium citrate mixture and that 1,450 U/kg of phytase produced a positive response in bone ash and weight gain in chicks fed a diet containing 6% citrate. Varying the Ca:available P ratio with and without citrate supplementation indicated that citric acid primarily affected phytate-P utilization, not Ca, in chicks. Moreover, chicks did not respond to citrate supplementation when fed a P-deficient (.13% available P), phytate-free casein-dextrose diet. Young pigs averaging 10 to 11 kg also were used to evaluate citric acid efficacy in two experiments. A P-deficient corn-soybean meal basal diet was used to construct five treatment diets that contained 1) no additive, 2) 3% citric acid, 3) 6% citric acid, 4) 1,450 U/kg phytase, and 5) 6% citric acid + 1,450 U/kg phytase. Phytase supplementation increased (P < .01) weight gain, gain:feed, and metatarsal ash, whereas citric acid addition increased only gain:feed (P < .05) and metatarsal ash (P < .08). A subsequent 22-d pig experiment was conducted to evaluate the effect of lower levels of citric acid (0, 1, 2, or 3%) or 1,450 U/kg phytase addition to a P-deficient corn-soybean meal diet. Phytase supplementation improved (P < .01) all criteria measured. Weight gain and gain:feed data suggested a response to citric acid addition, but this was not supported by fibula ash results (P > .10). The positive responses to phytase were much greater than those to citric acid in both pig experiments. Thus, dietary citric acid effectively improved phytate P utilization in chicks but had a much smaller effect in pigs.     

Limiting order of amino acids and the effects of phytase on protein quality in corn gluten meal fed to young chicks

An amino acid deletion assay, a protein efficiency ratio (PER) assay, and a slope-ratio growth assay were used to establish the limiting order of AA, and to determine the effects of microbial phytase on protein utilization in corn gluten meal (CGM) fed to chicks during the period of 8 to 21 d posthatching. In Assay 1, a 12% CP CGM diet was fortified with AA to fulfill the digestible AA ideal profile (only Phe + Tyr, Leu, and Pro exceeded requirements) for young chicks. Amino acids were then individually deleted, and all diets were fortified to 23% CP, with Glu varying as necessary. A Met-fortified 23% CP corn-soybean meal diet served as a positive control. No weight gain or feed efficiency differences were observed between the fully fortified CGM basal diet and the corn-soybean meal positive-control diet. The limiting order of AA established in CGM was 1) Lys, 2) Trp, 3) Arg, 4) Thr, 5) Val, 6) Ile, 7) His, 8) cystine, and 9) Met. In Assay 2, diets with 10% CP furnished by CGM or casein were fed in the presence and absence of 1,200 U/kg phytase. A protein source x phytase interaction (P < 0.05) was observed for weight gain, gain:feed, and PER, indicating positive responses to phytase when casein was fed but negative responses to phytase when CGM was fed. In Assay 3, graded levels of protein (8, 16, and 24% CP) furnished by CGM were fed in the presence and absence of 1,200 U/kg phytase. Weight gain and gain:feed increased linearly (P < 0.05) as a function of protein intake, but phytase supplementation had no effect on weight gain or gain:feed slopes. These results indicate that 1,200 U/kg phytase did not increase either CP or AA utilization in CGM for young chicks.     

Experimental Inoculation of Pregnant Swine with Type 1 Bovine Viral Diarrhoea Virus

The ability of bovine viral diarrhoea virus type 1 (BVDV‐1) to induce transplacental infection in pigs was evaluated. Control pigs (n = 4) were sham‐inoculated while infected pigs (n = 4) were intranasally inoculated with BVDV‐1 on day 65 of gestation. Blood samples were tested throughout the study for BVDV and antibody to BVDV. On day 110 of gestation, a Caesarean section was performed. Serum was obtained for virus isolation and antibody determination from all piglets, and all experimental animals were killed. Tissues were collected for virus isolation and histopathology. Bovine viral diarrhoea virus was isolated on days 5 and 7 after infection and seroconversion was demonstrated in all infected gilts; however, BVDV was only isolated from one fetus from an infected pig. Viraemia and seroconversion were demonstrated in the pregnant gilts; however, transplacental infection at day 65 of gestation in the pig was not consistently demonstrated.     

Effect of experimentally induced type II bovine viral diarrhea virus infection on platelet function in calves

OBJECTIVE: To evaluate platelet aggregation responses in calves experimentally infected with a thrombocytopenia-inducing type II bovine viral diarrhea virus (BVDV) isolate (BVDV 890). ANIMALS: 9 neonatal male Holstein calves. PROCEDURE: 5 calves were inoculated with BVDV 890, and 4 were used as controls. Platelet aggregation studies and attempts to isolate BVDV from platelets were performed 2 days before, the day of, and every 2 days for 12 days after inoculation. Platelet function was assessed by means of optical aggregometry, using adenosine diphosphate and platelet-activating factor as agonists. Bovine viral diarrhea virus was isolated from purified platelet preparations by use of an immunoperoxidase monolayer assay. RESULTS: Maximum percentage aggregation and slope of the aggregation curve decreased over time in calves infected with BVDV. Bovine viral diarrhea virus was not isolated from platelets from control calves, but it was isolated from infected calves from 4 through 12 days after inoculation. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that platelet function may be depressed in calves infected with type II BVDV. Although the mechanism for altered platelet function was not determined, it likely involved an increase in the percentage of aged platelets in the circulation, a direct virus-platelet interaction, or an indirect virus-platelet interaction. Platelet dysfunction, in addition to thrombocytopenia, may contribute to the hemorrhagic syndrome associated with acute type II BVDV infection in calves.     

Effects of non-genetic factors on responses to gastro-intestinal nematode infections in Ethiopian sheep

The effects of non-genetic factors on responses to gastrointestinal nematode infections were examined in artificially infected indigenous Horro and Menz lambs in the central highlands of Ethiopia. The experiment involved lambs of two sexes, infection and monitoring regimens (3 levels), dam parity (4 levels) and birth types (2 levels). A total of 152 weaner lambs (103 Menz and 49 Horro) were used. Endoparasite challenge involved three infection periods (primary, secondary and tertiary) each separated by an anthelmintic treatment. Data were collected on faecal egg counts (FEC), packed cell volume (PCV), worm count, and weight gain. Female lambs were found to harbor lower numbers of T. colubriformis counts and had lower (p < 0.01) FEC in tertiary infection compared to males. Younger animals were more susceptible to the nematode infections than older animals as measured by all the parameters studied (p < 0.01). Twins had higher FEC in both secondary and tertiary infections compared to singles. Lambs born to dams of first parity had higher PCV and lower FEC values during the tertiary infection compared to other parities. These results would be used as basic information in designing a more rational control strategy and should also help to advise on better management care for less resistant sheep.     

Differential induction of redox sensitive extracellular phenolic amides in potato

This study focuses on the differential induction of extracellular phenolic amides that accumulate in potato cell suspensions during the first few hours of the interaction between these plant cells and either bacterial pathogens or pathogen-related elicitors. Using suspension cells of Solanum tuberosum we identified 4 hydroxycinnamic acid amides that accumulate in the extracellular environment. Treatment of the suspension cells with pathovars of the plant pathogens Pseudomonas syringae or Ralstonia solanacearum or with pathogen-related elicitors changed the composition of the extracellular phenolic amides within hours and the composition differed for each treatment. Some of the phenolic amides were sensitive to oxidative stress; when suspension cells were treated with bacterial strains or elicitors that triggered an oxidative burst, the phenolics were oxidized and depleted for the duration of the burst. Other critical parameters that affected the qualitative and quantitative makeup of these phenolic amides were plant cell age and density.     

Assurance bonds: A tool for managing environmental costs in aquaculture

Abstract

The environmental costs associated with coastal aquaculture, though poorly understood, can in some cases be quite large. The presence of risk, uncertainty and insufficient monitoring can greatly reduce the power of traditional economic instruments such as environmental taxes and tradable permit systems to internalize these costs. Using the Texas shrimp farming industry as a specific example, this article explores the potential of environmental assurance bonds (EABs) as an alternative economic instrument to internalize environmental costs of aquaculture production under such conditions. Drawing from previous literature, an explicit distinction is made between two mechanisms simultaneously incorporated in the EAB: a deposit‐refund incentive and social insurance. The article discusses the role of each of these mechanisms in shifting the environmental costs of production back to firm. Practical application of EABs in the Texas coastal shrimp farming industry is then examined.