Short communication: Utilisation of n-alkanes to estimate feed intake in horses fed known amounts of a labelled concentrate supplement

The assessment of feed intake in stabled horses is a difficult task to accomplish. Faecal markers, namely n-alkanes, have been used successfully for the estimation of this important nutritional parameter. This usually involves the dosing of synthetic n-alkanes via different matrices, a laborious task that may also influence the animal normal foraging behaviour. An experiment was conducted to evaluate a relative simple methodology to quantify feed intake in horses, based on the provision of measured amounts of a concentrate supplement labelled with beeswax and the utilisation of n-alkanes as faecal markers. Four Lusitano horses were used in three consecutive experimental periods. Animals were fed on cereal straw and different proportions of a previously prepared beeswax-labelled concentrate supplement (BLCS; 0.05, 0.10 and 0.20, DM basis). Beeswax labelling was performed to provide a distinct n-alkane profile for the concentrate feed. Prior to feed intake calculations, proportions of labelled concentrate supplement in the diets were estimated using n-alkanes C₂₅ to C₃₃ by least-square optimisation procedures. Results showed that the beeswax labelling resulted in high n-alkane concentrations in the concentrate feed, especially for the odd-chain n-alkanes. Estimates of diet composition did not differ from the measured values, except for the diet with highest BLCS incorporation, with an underestimation of 10%. DM intake was accurately estimated by the “labelled supplement method” in all diets. However, for the lowest BLCS incorporation, DM intake was underestimated by 16% whereas for the higher levels of BLCS in the diet, measured and estimated DM intake values were almost identical with a slight overestimation of only 0.7 and 0.2% (10 and 20% of BLCS, respectively). Results indicate that both diet composition and feed intake can be accurately estimated in horses using the “labelled supplement method”, even when very low levels of the labelled concentrate supplement are included in the animals’ diet. This method eliminates the need for daily dosing with external synthetic markers, providing advantages in terms of minimising animal management and interference with their normal foraging behaviour.     

Tree retention in cattle ranching systems partially preserves dung beetle diversity and functional groups in the semideciduous Atlantic forest: The role of microclimate and soil conditions

The disturbance of natural environments affects, among others, the diversity of dung beetle assemblages, which could have serious consequences for the ecological processes regulated by these insects. The objective of this study was to evaluate and compare species diversity and functional groups of dung beetle assemblages both in the native forest and in three livestock systems that differed in their structure and composition of vegetation: a livestock system with native trees, a livestock system with exotic trees (Pinus taeda), and traditional open pastures, in the semideciduous Atlantic forest of Argentina, in an area previously covered by continuous forest and currently with a heterogeneous landscape of native forest and different land uses. Pitfall traps baited with cow dung were used in the natural forests and the livestock systems studied. A total of 2461 beetles belonging to 38 species were captured. Treed livestock systems showed the highest species richness (⁰D) and diversity (¹D and ²D). Twelve functional groups were identified. The native forest showed the highest functional group richness, while open pastures had the lowest. In general, livestock systems showed a low proportional abundance of telecoprid, diurnal and large beetles. Microclimate (average temperature and humidity) and soil conditions (soil composition: sandy or clayey) were closely associated with the species and functional group composition. Results confirm that cattle ranching with tree retention preserves dung beetle diversity, and suggest that cattle systems without canopy cover have higher impact (negative effects) than silvopastoral systems on both species and functional groups.     

Immunological cross-reactivity between the vaccine and other isolates of Streptococcus bovis and Lactobacillus

Recent studies have showed that immunisation with Streptococcus bovis (Sb-5) and Lactobacillus (LB-27) may confer protection against lactic acidosis in sheep and cattle. The present study was designed to determine the degree of immunological cross-reactivity between Sb-5 and eight other strains of Streptococcus bovis; and between LB-27 and four other isolates of Lactobacillus. The cross-reactivity index (CRI, a low CRI indicates a high degree of immunological cross-reactivity) ranged from 7.3 to 56.1% between the strains of S. bovis (the encapsulated strains with CRIs ranging from 7.3 to 12.4%). For isolates of Lactobacillus the CRIs ranged from 11.5 to 72.2%. The results indicate that all the isolates tested have a certain degree of immunological homology with Sb-5 and LB-27, and suggest that the vaccine may cross-react with a large number of strains of S. bovis and Lactobacillus which may cause lactic acidosis. As most of the S. bovis strains in the rumen are encapsulated, the high degree of homology between Sb-5 and encapsulated S. bovis strains further suggests that the vaccine containing Sb-5 may be effective against a wide range of strains of S. bovis in sheep and cattle.     

Einfluß des Gehaltes nativer Rohfaser in Diäten von Ratten auf die Aminosäurenresorption

Abstract

Mykotoxine sind Stoffwechselprodukte von Schimmelpilzen und weisen unterschiedliche chemische Strukturen sowie unterschiedliche toxische Wirkungen auf.

Desoxynivalenol (Vomitoxin) stellt in der Schweineproduktion aufgrund der Wachstumsdepression und Immunsuppression einen bedeutenden wirtschaftlichen Faktor dar. Im Alleinfutter für Schweine soll gemäß den Ergebnissen der Literaturstudien die Grenze von 1 mg/kg Futter nicht überschritten werden. Untersuchungen über Detoxifikationsmethoden erbrachten bisher keinen entscheidenden Erfolg.

Zearalenon weist eine Östrogenwirkung auf und kann beim Schwein bereits im Bereich von μg/kg Futter zu Fruchtbarkeitsstörungen und erheblichen wirtschaflichen Schäden führen. Empfehlungen über tolerierbare Höchstgrenzen können aufgrund der vorliegenden Ergebnisse nicht gegeben werden.

Das nierentoxische Ochratoxin A ist in der Schweine- und Geflügelhaltung von Bedeutung und stellt wegen der Akkumulierung im Gewebe eine mögliche Gefahrenquelle für den Menschen dar. Da eine mögliche kanzerogene Wirkung des Toxins nicht ausgeschlossen werden kann, sollte der Gehalt im Tierfutter möglichst niedrig gehalten werden. Mykotoxine stellen beim Wiederkäuer insgesamt keine besondere Gefahrenquelle dar, da diese Stoffe von der Pansenflora ab- bzw. umgebaut werden können.

Mycotoxins are metabolic products of mycotoxins which have various chemical structures and show various toxic effects.

Deoxynivalenol (vomitoxin) is an important economic factor in pig production due to growth depression and suppression of the immune system. Previous studies have shown that the 1-ppm limit in the sole feed for pigs should not be exceeded. Studies of methods of detoxification have as yet not produced conclusive results.

Zearalenon has an tolerable effect and may lead to fertility disturbances on the oestrogen production in pigs and can cause remarkable economic damage even in the ppb range. Recommendations of upper limits cannot be made on the basis of the available results.

The kidney toxin ochratoxin A is of importance in pig and poultry breeding and — due to its accumulation in the tissue — represents a possible source of danger to man. Since a possible carcinogenic effect of the toxin cannot be excluded, its content in animal rations should be kept as low as possible. For ruminants mycotoxins as a whole do not represent a particular source of danger as these substances can be degraded or converted by rumen flora.