Drug and chemical residues in livestock

The problem of drug and chemical residues in foods of animal origin has become increasingly important to the entire livestock industry as growing consumer health concerns continue to erode the demand for these products. Although nearly 90 per cent of all drugs approved for use in livestock are available for over-the-counter sales, in the public's view, it is only the veterinarian who administers drugs to animals and who, therefore, is responsible for all drug residues in food. Congress has responded to these consumer concerns by applying increased pressure on the FDA to restrict the extra-label use of drugs by veterinarians. The veterinary profession now finds itself in a position in which it must reexamine its current drug-use policies and strive to develop policies that are more responsible to the consumer, both in appearance and substance.     

Non-enzymatic hydrolysis of fluorescein diacetate (FDA) in a Mediterranean oak (Quercus ilex L.) litter

We show the presence of interfering substances when the total microbial activity in litter samples is measured with fluorescein diacetate (FDA), and we propose some methodological modifications to avoid such interference. Three distinct litter layers (the OhLn, the OhLv and the OhLf) of evergreen oak (Quercus ilex L.) were characterized by ¹³C CPMAS NMR and the spectra show that the recalcitrant aromatic and phenolic compounds increase with the degree of degradation of litter. A wide range of sources of interference in the hydrolysis of FDA was found. To understand the origin of this interference, sterilized litter materials (i.e. γ‐irradiated or autoclaved) and a wide range of organic substances (i.e. amino acids, glucose, sorbitol and organic humic acids) were investigated. Insignificant differences on the FDA hydrolysis activity (FDA activity) were found in the γ‐irradiated and non‐irradiated OhLn litter, indicating that γ‐irradiation does not destroy enzymes. Conversely, after heat‐sterilization of litter, samples showed FDA activity corresponding to 60, 34.8 and 30.8% (in the OhLn, the OhLv and the OhLf layers, respectively) of that of control litters. This indicates the presence of non‐enzymatic interfering substances in the FDA assays. As the humification and litter depth increased, hydrolysis of FDA due to interferences decreased, indicating degradation and/or chelation of interfering substances. We hypothesize that lysine, arginine, histidine and cysteine are mainly responsible for the hydrolysis of FDA. We suggest that the use of phosphate buffer (50 mm , pH 7.0) with incubation < 30 minutes, in combination with a temperature between 30 and 40°C, produces insignificant interference in the determination of the final FDA activity in litter samples.     

Dietary supplementation with multienzyme preparations improves nutrient utilization and growth performance in weaned pigs

Two experiments with young pigs (25 d of age) were conducted to investigate the effect of multienzyme preparations on nutrient digestibility, growth performance, and P utilization and excretion. In Exp. 1, 24 pigs (six pigs per treatment) were used in a 28-d performance and digestibility trial using four diets: control (no enzyme) and control supplemented with enzyme preparation A, B, or C. The control diet was formulated to meet 95% of NRC (1998) nutrient specifications (except for available P, which was at 44% NRC) and composed of corn, wheat, wheat by-products, barley, soybean meal, canola meal, and peas. All three enzyme preparations contained xylanase, glucanase, amylase, protease, invertase, and phytase activities and differed in the type of plant cell wall-degrading activities; Enzyme A contained cellulase, galactanase, and mannanase; Enzyme B contained cellulase and pectinase; and Enzyme C contained cellulase, galactanase, mannanase, and pectinase. Pigs fed enzyme-supplemented diets had higher ADG (P = 0.02) and G:F (P = 0.01) than those fed the control diet. On average, and when compared with control diet, enzyme supplementation improved (P = 0.001 to 0.04) ileal digestibility of DM (60 vs. 66%), GE (62.8 vs. 70.4%), CP (62 vs. 72%), starch (86.7 vs. 94.2%), nonstarch polysaccharides (NSP; 10.1 vs. 17.6%), and phytate (59 vs. 70%). Compared with the control, total-tract digestibility of nutrients was increased (P = 0.001 to 0.01) owing to enzyme supplementation, with Enzyme C showing the highest improvement in DM, GE, CP, starch, NSP, phytate, and P utilization. Pigs fed enzyme-supplemented diets had decreased (P = 0.04) fecal P excretion. The benefit from improved nutrient utilization with enzyme supplementation was further substantiated in a 38-d growth performance study with 48 pigs. The control and Enzyme C-supplemented diets (same as Exp. 1) were assigned to six replicate pens (four pigs per pen). The study was conducted in three phases (Phase 1 = d 0 to 7; Phase 2 = d 7 to 21; Phase 3 = d 21 to 38). Individual BW and pen feed disappearance were monitored. Average daily gain and G:F were 231 and 257 g (P = 0.01), and 0.56 and 0.63 (P = 0.001) for the control and enzyme-supplemented diets, respectively. It is evident from this study that the use of enzyme preparations may allow for cost-effective and environmentally friendly formulation of young pig diets.     

Pine needle abortion in cattle: a review and report of 1973-1984 research

Research has verified field observations that cows grazing ponderosa pine needles may abort. The incidence and nature of the abortions produced experimentally simulate very closely those reported by livestock producers and veterinarians. The incidence of experimentally-produced abortions varied markedly from year to year even though the needles were collected in the same general area each year. This suggests that the abortifacient compound(s) in the needles vary from year to year, probably due to environmental and site conditions. The impact of stress (cold and nutrition) as a factor in the abortions was examined. It was concluded that the only effects would be on the willingness of cows to eat the needles. The pine needle abortion problem, what is known of the etiology, and mechanisms of the abortion are reviewed. The usefulness of bioassay systems to study pine needle abortions is discussed.     

The extraction particles from winter rapeseed with different glucosinolate fractions in swine with regard to the iodine supply. 3. Apparent digestibility of crude nutrients with special regard to the carbohydrate and nitrogen balance]

In two digestibility and N-balance experiments the following solvent extracted meals were examined in a grain (barley and wheat in equal parts) or in a starch diet with four female pigs/group fitted with urethra catheters during the 5 days sampling period: 48% soyabean meal (SBM) (1), 24% conventional rapeseed meal (RSM) (2), 24 (3) or 48% (4) RSM from a newly bred low glucosinolate variety, groups 1 to 4 with grain, 48% low glucosinolate RSM (5) or 48% SBM (6) both with starch. In numeric order of the groups 88, 85, 86, 84, 79 and 89% N were digested. Pigs responded to the additional faecal N excretion from RSM diets by a lower urinary N excretion and thus they reached the N-balance of the animals fed on SBM. In numeric order of the groups 86, 79, 80, 73, 73 and 92% of the organic matter of the solvent extracted meals were digested. In comparison with SBM even 48% RSM in the feed significantly lowered the digestibility of organic matter. Using detergents the additional faecal organic matter excretion of RSM versus SBM could quantified as two third lignin. In the case of 24% RSM in the diet--i.e. 15% of the carbohydrates given--the carbohydrate digestibility is estimated with a high error, that an energetic feed value should not calculated. Investigating 48% SBM or RSM respectively in a grain diet the net energy content was 9.8 MJ (666 Energetic Feed Units, EFU pig) or 8.3 MJ (569 EFU pig)/kg dry matter (DM). Based on the starch diet, however, little relevant for estimation of normal pig diets, there were evaluated 10.6 MJ (720 EFU pig) for SBM and 8.3 MJ (567 EFU pig) net energy/kg DM for RSM.     

Influence of environmental and plant factors on canopy photosynthesis and transpiration of apple trees

We estimated carbon and water flows, canopy conductance and the assimilation/transpiration ratio of fruiting and non-fruiting apple trees grown in the field, from daily gas exchange measurements taken during the summer with a whole-canopy enclosure device. The relationships between photosynthetic and transpirational responses and environmental conditions were also investigated, as well as the role of canopy conductance in controlling carbon dioxide and water vapor exchange. Light-saturated net photosynthetic rates, which were higher for the fruiting canopy than for the non-fruiting canopy, showed a general decrease in the afternoon, particularly for the non-fruiting canopy, compared with rates in the morning. When light was not limiting, the afternoon decrease in net photosynthesis appeared to be regulated more by non-stomatal factors than by changes in canopy conductance. Canopy conductance, which was higher for the fruiting canopy than for the non-fruiting canopy, may actively regulate photosynthetic activity and may also be modulated by feedback control in response to assimilation capacity. We conclude that adjustments in canopy conductance, which were partially dependent on the vegetative-reproductive status of the tree, control the equilibrium between photosynthesis and transpiration. We also demonstrated that whole-canopy chambers can be used to estimate photosynthetic and transpirational responses thereby overcoming the difficulty of scaling these physiological responses from the leaf to the whole-canopy level.     

Growth and nutritional responses of bareroot Jeffrey pine on a Sierra Nevada surface mine to minisite applications of fertilizer and lime

The effects of two controlled release fertilizers, Forestcote 22-4-6 + Minors and Dry Site 21-6-2 + Minors, and also dolomitic lime, on growth and nutrition of bareroot Jeffrey pine (Pinus jeffreyi Grev. & Balf.) were investigated. Forestcote, which consists of loose prills, and Dry Site, consisting of prepackaged prills, were administered with two rates, while a single liming rate was used. An acidic Sierra Nevada surface mine provided the study site, and all amendments were applied at outplanting to the backfill of augered planting holes. Without impacting survival, both fertilizer formulations enhanced seedling growth, particularly at a 16 g rather than an 8 g application rate, although Forestcote was marginally more effective in this regard. In contrast, liming at a 27 g rate induced severe mortality and offset much of the growth gains resulting from fertilization. Improvements in N and P nutrition, as revealed by foliar analysis, probably accounted for much of the growth stimulation exhibited by fertilized seedlings, but reductions in the uptake of potentially phytotoxic trace elements such as Mn and Al and increases in base cation/metallic element ratios likely also contributed. The high application rate was generally preeminent in eliciting these nutritional responses. Liming induced little alteration of seedling nutrition. Impaired water relations may have caused the unfavorable responses to this treatment.