Salivary amino acid concentrations in zebus (Bos indicus) and zebu hybrids (Bos indicus × Bos taurus) fed a tannin-rich diet

Many animals show adaptation to tannins in the form of tannin-binding salivary proteins (1). Among ruminants, such proteins have been demonstrated in saliva of several species (usually browsers and intermediate feeders) (2, 3, 4, 13). There is some circumstantial evidence to suggest that zebu cattle (Bos indicus) are different from temperate cattle breeds with respect to their salivary and digestive physiology. Apart from differences in susceptibility to heat and tropical disease (5), a difference in salivary anti-tannin defenses (and a resulting difference in rumen physiology) could be another reason zebu cattle are particularly suited for agricultural systems in the tropics, where available forages often contain high levels of tannins (6, 7). Although non-proline-rich proteins exist that also have affinity for tannins (1, 8), it is interesting to compare the proline content of different cattle breeds. Here, we report such a screening for a comparison of zebu cattle and zebu-Holstein- Friesian in the Jimma area located at 7°40′N and 36°50′E at 1760 masl in southwest Ethiopia

Effects of trace element supplementation on apparent nutrient digestibility and utilisation in grass-fed zebu (Bos indicus) cattle

Trace element deficiencies in cattle are omnipresent, both in developing and industrialised regions. Little information is available on the effect of dietary trace elements on nutrient digestibility and utilisation, in spite of many deficiency-related symptoms suggesting a relevant role, such as loss of appetite in Zn deficiency and severe diarrhoea in Cu deficiency. The present study aimed to identify the early effects of dietary trace elements on nutrient utilisation in grass-fed zebu (Bos indicus) cattle. Adult bulls (n=8) were randomly assigned to a treatment: control or trace element supplementation (Zn, Mn, Cu, Se, I and Co) during 28 days. Grass mineral analysis suggested deficient Cu (5.53-9.60. mg/kg) and Se (0.02-0.09. mg/kg) concentrations in combination with high S (2577-3855. mg/kg) and Mo (1.52-3.12. mg/kg) and very high Fe (619-1214. mg/kg) concentrations. Supplementation increased plasma Cu (0.82 vs. 0.61. mg/l), Zn (1.40 vs. 0.89. mg/l), Mn (0.30 vs. 0.05. mg/l) and Se (0.07 vs. 0.06. mg/l) concentrations (all P0.05). Also, no effects on apparent nutrient (dry matter, ash, protein, fat, and fibre) digestibility, apparent trace element absorption (except for Se and I) or plasma acyl carnitines (indicators of available energy substrates) were observed in this study (all P>0.05). Overall, despite clear improvement in trace element status - notwithstanding high concentrations of Cu antagonists in the grass diet - supplementation did not affect nutrient digestibility or utilisation in grass-fed zebu cattle. © 2013 Elsevier B.V.status: publishe

Amino acid profile of salivary proteins and plasmatic trace mineral response to dietary condensed tannins in free-ranging zebu cattle (Bos indicus) as a marker of habitat degradation

In the southern hemisphere, foraging areas of cattle are affected by overgrazing and soil erosion resulting in decreased availability of grasses and increased amounts of browse plants high in condensed tannins (CT). This study aimed to identify biomarkers in free-ranging zebu cattle (Bos indicus) for the habitat degradation, based on their salivary and trace mineral response to dietary CT. Saliva and blood samples were collected from 60 randomly involved free-ranging zebu bulls in six study sites, which were further grouped into two regions based on the average CT concentration in the plants regularly consumed by the cattle. Jugular venipunctures for blood sampling and the swabbing technique for saliva collection were used. Plasma samples were analyzed for Cu, Zn and Fe. Saliva samples were analyzed for total amino acid concentrations. Average CT concentrations in the plants ranged between 0 and 166 g CT/kg dry matter (P 0.05). In contrast to Cu, higher Zn concentration was found in the region rich in CT content (P <0.05). The proportion of proline of total amino acids, as main indicator of salivary proline-rich proteins in the saliva, was higher in the tannin-rich region (P <0.01). The ratio of proline to the sum of total amino acids was also higher in this region (P <0.001). Higher ratio of salivary arginine to ornithine was observed in the tannin-rich region (P <0.05), suggesting reduced ruminal protein synthesis due to reduced protein bio-availability. In conclusion, the increase in salivary proline concentration in free-ranging zebu cattle reflects the dietary CT load, which in turn suggests habitat degradation and lower availability of feed sources