Season and location effects on serum and liver mineral concentrations of Senepol cattle on St Croix,virgin islands

Summary Serum and liver concentrations of selected macro-and trace minerals were determined in Senepol cattle at 8 sites (4 each in a high and low rainfall region) during the dry and wet season on St Croix. At each site an average of 15 mature, lactating cows, grazing native grass/legume pastures without supplementation were blood sampled each season. Liver samples were collected (n=51) at slaughter from mature animals originating from the same sites. A preliminary analysis indicated no differences in serum mineral concentrations between mature lactating cows and growing heifers. There were differences between sites for serum magnesium (Mg) (P<0·001), copper (Cu) (P<0·05) selenium (Se) (P<0·001) and zinc (Zn) (P<0·01) in the dry season, and for Cu (P<0·01), iron (Fe) (P<0·001) and Zn (P<0·01) in the wet season. Higher (P<0·001) serum concentrations of Mg, Cu, Fe and Zn were observed in the dry season, while Se was higher (P<0·001) in the wet season. Liver concentrations of Cu and Fe were lower (P<0·01) and liver molybdenum (Mo) (P<0·001) and Se (P<0·05) higher during the dry season. The seasonal differences in serum Cu, Se and Zn concentrations have not been observed in other studies in the Central American region. More than 50% of serum samples were deficient in phosphorus (P) regardless of season, and in Cu and Zn during the wet season. Mineral supplementation should be considered.

---

Resumen Se determinó la concentración de minerales (macro y trazas) seleccionados, en ganado Senepol en ocho sitios: cuatro de ellos en una región de alta precipitación y los otros cuatro en regiones de baja precipitación pluvial, durante la estación seca y lluviosa en la isla de Sta Cruz. En cada sitio, un promedio de 15 vacas lactantes, pastoreando pasto nativo y pasturas con leguminosas sin suplementación, se sangraron en cada estación. Se colectó tejido hepático (n=51) en el matadero local, de animales maduros provenientes de los sitios estudiados. Un análisis preliminar, no indicó diferencias en concentraciones séricas de minerales entre animales maduros lactandos y novillas en crecimiento. Hubo diferencias en cuanto a localización respecto al magnesio sérico (Mg) (P<0·001), cobre (Cu) (P<0·05) selenio (Se) (P<0·001) y zinc (Zn) (P<0·01) en la estación seca y para Cu (P<0·01), hierro (Fe) (P<0·001) y Zn (P<0·01) en la estación lluviosa. Se observaron concentracionas séricas màs altas (P<0·001) de Mg, Cu, Fe y Zn en la estación seca, mientras que el Se fue más alto (P<0·001) en la estación lluviosa. Las concentraciones hepáticas de Cu y Fe fueron bajas (P<0·01) y las de molibdeno hepático (Mo) (P<0·001) y Se (P<0·05), fueron altas durante la estación seca. Las diferencias estacionales en concentraciones de Cu, Se, y Zn sérico, no habian sido observadas en otros estudios en la región centroamericana. Mas de 50 por ciento de las muestras de suero fueron deficientes en fósforo (P) sin tener en cuenta la estación y en Cu y Zn durante la estación lluviosa. Se sugiere la necesidas de suplementación mineral.

---

Résumé Les auteurs ont déterminé les concentrations sériques et hépatiques d'un certain nombre d'oligo éléments et de sels minéraux sur des bovins Senepol éléves sur 8 sites (quatre pour chaque région à forte et faible pluviométrie) pendant la saison humide et la saison sèche sur l'lle Sainte Croix. Sur chaque site, des prélèvements de sang ont été effectués pendant chaque saison sur la base d'une moyenne de 15 vaches adultes en lactation, paturant sur des parcours naturels de graminées/légumineuses, sans complémentation. Les prélèvements de foie (n=51) ont été collectés à l'abattoir sur des animaux adultes originaires de ces mêmes endroits. Une analyse préliminaire n'a indiqué aucune différence dans les concentrations minérales du sérum entre les vaches adultes en lactation et les génisses en cours de croissance. Il y avait des différences entre les sites pour le magnésium sérique (Mg) (P<0,001), le cuivre (Cu) (P<0,05), le sélénium (Se) (P<0,001) et le zinc (Zn) (P<0,01) en saison sèche et pour le cuivre (Cu) (P<0,01), le fer (Fe) (P<0,001) et le zinc (Zn) (P<0,01) en saison humide. En saison sèche, des concentrations plus élevées (P<0,001) on été observées pour Mg, Cu, Fe et Zn alors que le sélénium (Se) était plus abondant en saison humide. Les concentrations hépatiques en Cu et Fe étaient plus basses (P<0,01) mais celles en Molybdène (Mo) (P<0,001) et en sélénium (P<0,05) plus élevées au cours de la saison sèche. Les différences saisonnières entre les concentrations sériques de Cu, Se et Zn n'ont pas été observées en Amérique centrale par d'autres auteurs. Plus de 50 p. 100 des échantillons de sérum étaient carencés en phosphore (P) quelle que soit la saison, et en Cu et Zn pendant la saison humide. Il conviendrait de prendre en considération la complémentation minérale.

     

Management options to decrease phosphorus and sediment losses from irrigated cropland grazed by cattle and sheep

In southern New Zealand, grazing of forage crops is common practice to satisfy feed requirements of animals in winter when pasture growth is limited. This practice has been shown to cause soil physical damage and increased loss of surface water contaminants sediment and phosphorus (P) to water bodies. Strategies to mitigate the loss of sediment and P were trialled on a Pallic soil type (Aeric Fragiaquept) in the North Otago Rolling Downlands of New Zealand. All sites were irrigated and measurements were made of losses in overland and sub‐surface flow from intensive cattle or sheep grazed, winter forage crops, and sheep grazed pasture. Two mitigations (restricted grazing of crop to three hours and the application of aluminium sulphate) were assessed for their potential to decrease contaminant loss from cropland. Volumes of surface runoff and loss of total P, filterable reactive P and sediment showed significant differences (P < 0.05) between the control treatments (i.e. no mitigation) with cattle crop (88 mm surface runoff) > sheep crop (67 mm) > sheep pasture (33 mm). The contribution of irrigation water to overland flow water, as a result of saturation‐excess conditions, varied between treatments with more loss under cattle crop (20% of total) compared with sheep crop (15%) and sheep pasture (11%). These differences are probably an effect of soil physical condition and highlight the importance of accurate irrigation scheduling to keep soil moisture below field capacity. Restricted winter grazing and alum application after grazing significantly (P < 0.05) decreased P losses in surface runoff under cattle (from 1.4 to 0.9 kg P/ha) and sheep (from 1.0 to 0.7 kg/P/ha) grazed crop plots by about 30%. In cattle grazed plots, restricted grazing also decreased suspended sediments (SS) by 60%. The use of restricted grazing is suggested as a means of decreasing P and SS loss from grazed winter forage crops. The use of alum shows some promise for decreasing P losses, but requires further work to determine its long‐term effectiveness and use in other soils and management regimes.     

Titres of precocene ii (6, 7-dimethoxy-2, 2- dimethylchromene) and its metabolites in the haemolymph of larvae of the african armyworm Spodoptera exempta (walker) following topical treatment with the compound

No precocious metamorphosis or other morphogenetic effects were seen following topical treatment of fifth instar Spodoptera exempta with pre- cocene II. [3H]-Precocene II penetrated the larvae rapidly following topical application. An uptake of 47% was recorded in the first hour and an average of 27% for the first 3 h. Radioactivity in the haemolymph reached a maximum 4 h after treatment at 6–8% of the applied dose. A maximum titre of precocene of 1.1 × 10^?4 _M was observed 2 h after treatment and a biological half-life of around 1 h was recorded for the first 6 h. The metabolite precocene 11–3, 4-dihydrodiol appeared in the haemolymph with a maximum titre of 1.1 × 10^?4 _M at 4 h suggesting metabolism via the 3, 4-epoxide. At the same time an unidentified metabolite was observed possibly corresponding to the 6- and 7-(O)-desmethylated products described by others. Very large quantities of highly polar materials were observed in the haemolymph throughout the experiment and it is thought that these corresponded to conjugates. The evidence suggests that peripheral detoxication mechanisms do not operate sufficiently rapidly to prevent the establishment of a high titre of precocene. This, however, did not affect the corpora allata in this insect, whereas in a sensitive species that has been studied by other workers, necrosis of the glands would have resulted. Alternative explanations for insensitivity are discussed.     

Effects of gossypol from cottonseed meal and dietary vitamin E on the reproductive characteristics of superovulated beef heifers

Superovulated Hereford-Angus crossbred heifers (average 397 kg BW) were used to test the effect of feeding cottonseed meal (gossypol) and vitamin E on embryo quality and ovarian characteristics. Twenty-four heifers were assigned randomly to four treatments with six heifers per treatment. Treatments were the following dietary supplements: 1) SBM (soybean meal + 30 IU vitamin E/kg of diet DM); 2) SBM+E (soybean meal + 4,000 IU vitamin E x animal(-1) x d(-1)); 3) CSM (cottonseed meal + 30 IU vitamin E/kg of diet DM); and 4) CSM+E (cottonseed meal + 4,000 IU vitamin E x animal(-1) x d(-1)). Supplements based on cottonseed meal provided 43.5 g of total gossypol/d (37% negative isomer (-) and 63% positive isomer (+)). Blood samples were collected at the start of the experiment and every 3 wk thereafter up to 12 wk. Plasma a-tocopherol (alpha-T) concentration was affected by treatments (P < 0.05). Heifers supplemented with cottonseed meal had greater (P < 0.05) alpha-T concentration in plasma than heifers supplemented with soybean meal at each concentration of vitamin E. Supplementation at 4,000 IU vitamin E x animal(-1) d(-1) increased (P < 0.05) the concentration of a-T in plasma. Weight gain, hemoglobin and hematocrit were not affected by treatment. Erythrocyte osmotic fragility (EOF) increased (P < 0.05) in cottonseed meal-fed animals; however, EOF was lowered (P < 0.05) with vitamin E supplementation. Heifers fed CSM and CSM+E supplements had greater (P < 0.01) concentrations of (-)-, (+)-, and total-gossypol in plasma, corpora lutea (CL), liver, and endometrium than heifers fed SBM and SBM+E supplements. Tissue alpha-T concentration increased with increased dietary supplemental vitamin E, particularly in great amounts in the CL. Because there was no adverse effect of gossypol on superovulation response or embryo development despite concentrations of gossypol in endometrium that are toxic to embryos, it is likely that systems exist in the reproductive tract to limit gossypol toxicity.     

Effect of ammonium sulfate fertilization on bahiagrass quality and copper metabolism in grazing beef cattle

To assess the impact of S fertilization on bahiagrass (Paspalum notatum) quality and Cu metabolism in cattle, two studies were conducted during the summer grazing season (1999 and 2000). Pasture replicates (16.2 ha; n = 2/treatment) received the same fertilizer treatment in each growing season, consisting of 1) 67 kg N/ha from ammonium sulfate (AS), 2) 67 kg N/ha from ammonium nitrate (AN), and 3) control (no fertilizer; C). Forage sampling was conducted at 28-d intervals following fertilization by the collection of whole plants (four samples/pasture) in randomly distributed 1-m2 grazing exclusion cages and analyzed for CP, in vitro organic matter digestibility, S, P, Ca, K, Mg, Na, Fe, Al, Mn, Cu, and Zn. To determine the effect of fertilizer treatment on liver trace mineral concentrations in grazing cattle, random liver tissue samples were collected (n = 12; four/treatment) at the start and end of the study period in 2000. Ammonium sulfate fertilization increased (P < 0.001) forage S concentration in both years. Plant tissue N concentrations were increased by N fertilization, regardless of source, in 2000, but not in 1999. Cows grazing AS pastures had lower (P < 0.05) liver Cu concentrations at the end of the study period in 2000 compared to AN and C. In Exp. 2, 37 Cu-deficient heifers grazing AS fertilized pastures were obtained from the same location and allocated to one of two treatments, consisting of supplements providing 123 mg/d of either inorganic (Cu sulfate; n = 12) or organic (Availa-Cu; n = 15) Cu. Treatments were delivered for 83 d. Liver Cu increased over time in all heifers regardless of treatment; however, heifers supplemented with Availa-Cu tended (P = 0.09) to have higher mean liver Cu concentrations than those receiving Cu sulfate. The results of these studies indicate that AS fertilization of bahiagrass increases forage S concentrations. When provided free-choice access to a complete salt-based trace mineral supplement, cows grazing AS-fertilized pastures had lower liver Cu concentrations than cows grazing pastures fertilized with AN; upon removal from high-S pastures, cattle were able to respond to Cu supplementation.     

Passive immunisation of neonatal lambs via colostrum and milk of ewes previously immunised with live attenuated Salmonella typhimurium protects neonatal lambs from experimental salmonellosis

Lambs sucking non-immunised ewes or ewes immunised 4-5 weeks before lambing with live attenuated, aromatic-dependent (aroA) Salmonella typhimurium (strain CS 332) were challenged orally at either 2, 4 or 7 days of age with virulent S. typhimurium (strain CS 94) at doses ranging from 10⁹ to 10¹³ colony forming units. No lambs displayed signs of clinical salmonellosis and all survived challenge but those sucking immunised ewes had organisms of the challenge strain in their faeces for much shorter periods of time than lambs of the control ewes. High titres of specific antibodies were measured in colostrum and milk of immunised ewes in comparison with very low titres measured in samples from control ewes; these differences were reflected by the titres of antibodies in the sera of corresponding lambs. At 2 days after lambing, the major antibody isotype in the colostrum of immunised ewes and sera of their lambs was IgM whereas at 7 days IgG1 was the predominant isotype. While it was clear that vaccination of pregnant ewes with the live attenuated vaccination conferred protection against experimentally-induced salmonellosis in their lambs, considerable protection was observed in control lambs in spite of there being very low titres of antibodies in the mammary secretion of their dams. The latter observation could be related to the presence of contain non-antibody potent bactericidal factors previously described in colostrum and milk.

Résumé

Des agneaux qui tètent des brebis non immunisées, ou bien immunisées, 4 à 5 semaines avant la mise bas avec un vaccin atténué constitué d'une souche de Salmonelle typhimurium dépendente pour sa croissance de la presence de composés aromatiques (souche aro A CS 332) ont reçu, à l'âge de 2, 4 ou 7 jours, par voie orale, des doses allant de 10⁹ à 10¹³ Salmonella (souche virulente CS 94). Aucun agneau n'a présenté de signes cliniques et tous ont survécu à cette administration, mais les agneaux des brebis immunisées ont excrété la souche d'épreuve dans leur fécès pendent moins longtemps que les agneaux des brebis non vaccinées. Des titres plus élevés d'anticorps sont détectés dans le colostrum et le lait des brebis vaccinées et comparés aux brebis témoins. Cette différence est également notée pour les titres d'anticorps présents dans le sérum des agneaux issus de brebis vaccinées ou non. Deux jours après la mise bas, la classe des anticorps majoritaires, tant au niveau du colostrum des brebis vaccinées que du sérum de leurs agneaux, est la classe des IgM, alors qu'après 7 jours, les IgG1 prédominent. Bien qu'il soit clair que des brebis pleines vaccinées à l'aide d'un vaccin vivant atténué, apportent à leurs agneaux une protection vis à vis d'une Salmonella expérimentale, une réelle protection est également observée chez les agneaux témoins, malgré les titres faibles d'anticorps présente dans les sécrétions mammaires de leur mères. Cette dernière observation peut être mise en rapport avec la présence d'agents bactériodes ne contenant pas d'anticorps, déjà décrits dans le colostrum et le lait.     

Direct inhibition of maintenance respiration in western hemlock roots exposed to ambient soil carbon dioxide concentrations

Root respiration often exhibits a direct and immediate decline with increasing concentrations of ambient soil carbon dioxide concentration ([CO(2)]), and recent evidence suggests this decline may be attributable to a decline in maintenance respiration within the root. If true, this concept could provide a clue to the biochemical process underlying respiratory inhibition as well as improve our knowledge of the timing and degree to which this inhibition occurs in nature. To test the hypothesis that maintenance respiration exhibits a direct, negative response to increasing [CO(2)], we measured total respiration in intact root systems of western hemlock (Tsuga heterophylla (Raf.) Sarg.) seedlings grown at different relative growth rates and exposed to soil [CO(2)]s ranging from 91 to 7008 &mgr;mol mol(-1). Analysis of covariance was used to separate maintenance from total respiration. Total respiration declined exponentially with increasing [CO(2)]. Maintenance respiration, which comprised 85% of total respiration over all treatments, also declined exponentially with increasing [CO(2)]. Growth respiration was not inhibited at any [CO(2)]. These findings may explain why roots of some fast-growing species do not show [CO(2)] inhibition.     

Estimating CO(2) flux from snowpacks at three sites in the Rocky Mountains

Soil surface CO(2) flux (F(s)) is the dominant respiratory flux in many temperate forest ecosystems. Snowpacks increase this dominance by insulating the soil against the low temperature to which aboveground components are exposed. However, measurement of F(s) in winter may be impeded by snow cover. Likewise, developing annual F(s) models is complicated by seasonal variation in root and microbial metabolism. We compared three methods of measuring sub-snow F(s): (1) dynamic chamber measurements at the upper snowpack surface (F(snow)), (2) dynamic chamber measurements at the soil surface via snowpits (F(soil)), and (3) static estimates based on measured concentrations of carbon dioxide ([CO(2)]) and conductance properties of the snowpack (F(diffusional)). Methods were compared at a mid-elevation forest in northeastern Washington, a mid-elevation forest in northern Idaho, and a high-elevation forest and neighboring meadow in Wyoming. The methods that minimized snowpack disturbance, F(diffusional) and F(snow), yielded similar estimates of F(s). In contrast, F(soil) yielded rates two to three times higher than F(snow) at the forested sites, and seven times higher at the subalpine meadow. The ratio F(soil)/F(snow) increased with increasing snow depth when compared across all sites. Snow removal appears to induce elevated soil flux as a result of lateral CO(2) diffusion into the pit. We chose F(snow) as our preferred method and used it to estimate annual CO(2) fluxes. The snowpack was present for 36% of the year at this site, during which time 132 g C m(-2), or 17% of the annual flux, occurred. We conclude that snowpack CO(2) flux is quantitatively important in annual carbon budgets for these forests and that the static and dynamic methods yield similar and reasonable estimates of the flux, as long as snowpack disturbance is minimized.     

Prevalence and Characteristics of Salmonella in the Beef Chain in the Republic of Ireland

The study investigated the prevalence, concentration and characteristics of Salmonella spp. in the Irish beef chain. A total of 900 samples including bovine hides, carcasses and ground beef were examined for the pathogen over a 2‐year study (July 2007–June 2009). Salmonella prevalence was low in all sample types; bovine hide (0.75%, 3 of 400); carcasses (0.25%, 1 of 400); and ground beef (3%, 3 of 100). All positive samples contained the pathogen in low concentrations (<10 CFU per cm² or per g). Serovars recovered were S. Dublin from hide and carcasses and S. Braenderup in ground beef. All isolates were susceptible to 13 anti‐microbials. The study highlights that Salmonella can be found at low levels at all stages of beef chain production, processing and retail and that there is a need for multiple hurdle interventions and practices along the beef chain, which will reduce consumer exposure to this pathogen.     

Occurrence,Virulence Genes and Antibiotic Resistance of Enteropathogenic Escherichia coli (EPEC) from Twelve Bovine Farms in the North‐East of Ireland

Cattle faecal samples (n = 480) were collected from a cluster of 12 farms, and PCR screened for the presence of the intimin gene (eae). Positive samples were cultured, and colonies were examined for the presence of eae and verocytotoxin (vtx) genes. Colonies which were positive for the intimin gene and negative for the verocytotoxin genes were further screened using PCR for a range of virulence factors including bfpA, espA, espB, tir ehxA, toxB, etpD, katP, saa, iha, lpfA_{O157/OI‐141} and lpfA_{O157/OI‐154.} Of the 480 faecal samples, 5.8% (28/480) were PCR positive, and one isolate was obtained from each. All 28 isolates obtained were bfpA negative and therefore atypical EPEC (aEPEC). The serotypes detected included O2:H27, O8:H36, O15:H2, O49:H+, O84:H28, O105:H7 and O132:H34 but half of the isolates could not be serogrouped using currently available antisera. Twenty‐two (79%) of the isolates carried the tir gene but only 25% were espB positive, and all other virulence genes tested for were scarce or absent. Several isolates showed intermediate resistance to ciprofloxacin, kanamycin, nalidixic acid, minocycline and tetracycline; full resistance to nalidixic acid or tetracycline with one isolate (O?:H8) displaying resistance to aminoglycosides (kanamycin and streptomycin), quinolones (nalidixic acid) and sulphonamides. This study provides further evidence that cattle are a potential source of aEPEC and add to the very limited data currently available on virulence genes and antibiotic resistance in this pathogenic E. coli group in animals.