Annalisa Stefani

Subacute ruminal acidosis and evaluation of blood gas analysis in dairy cow.

Subacute Ruminal Acidosis (SARA) corresponds to an imbalance between lactate-producing bacteria and lactate-using bacteria, which results in a change in ruminal pH associated with a prevalent consumption of rapidly fermentable carbohydrates. In our study, 216 primiparus and multiparus dairy cows were selected from 20 Italian intensive dairy herds and were divided into three groups based on the risk of SARA. All the dairy cows had high average milk production. After blood sampling, a complete blood gas analysis was performed. One-way ANOVA was performed to compare the three groups. O(2) Cont, PCO(2), blood pH, O(2)Hb, urinary pH, and rumen pH were significantly lower in cows with rumen pH < 5.5. These results indicate that blood gas analysis is a valuable tool to diagnose acidosis in dairy cows because it provides good assessment of acidosis while being less invasive than rumen pH analysis.

Effect of dietary supplementation with different sources of selenium on growth response, selenium blood levels and meat quality of intensively finished Charolais young bulls

The study aimed at comparing three strategies of supplementing selenium (Se) during the finishing period of Charolais young bulls: (1) administration of sodium selenite throughout the finishing (NaSe); (2) administration of an Se-enriched yeast strain (Saccharomyces cerevisiae NCYC R397) throughout the finishing (Se-Y); (3) administration of sodium selenite for 140 days replaced by Se-enriched yeast during the last 70 days of finishing (Switch). Eighty-four young bulls (mean initial BW=434.2±31.9 kg; mean age=382±52 days) were stratified by live weight and equally assigned to one of three Se treatments. Experimental groups were fed the same diets and the inclusion rate of the different treatments was targeted to achieve 0.3 mg of Se/kg of dry matter (DM) in the complete feed. The average daily gain of bulls was 1.36 kg/d and no differences due to Se treatment were recorded. Dry matter intake and feed conversion ratio were not affected by Se treatment resulting in, on average, 10.3 kg/d and 7.65, respectively. Repeated blood samples were taken at days 0, 120, 180 and 210 of finishing to assess the Se status of the animals. As compared to NaSe, both organic Se treatments (Se-Y and Switch) increased plasma Se in the last two sampling sessions according to a significant treatment×time interaction (P<0.001). A similar trend was observed for serum total antioxidant status of the young bulls, whereas there was only a significant time effect (P<0.001) on glutathione peroxidase activity that was raised by all Se treatments. The finishing period lasted 210 days and at the abattoir there were no differences across Se treatments in carcass weight and dressing percentage. A higher Se content in the Longissimus thoracis (LT) muscle was instead observed in Se-Y samples as compared with NaSe (0.85 v. 0.47 mg/kg DM; P<0.05). Meat quality evaluation was carried out on LT samples after 6 and 11 days of ageing under a vacuum package. Regardless of ageing time, meat from young bulls supplemented with Se yeast had higher colour lightness (L*) values than those receiving NaSe (38.1 v. 36.6; P<0.01) and showed a significant decrease in shear force (3.69 v. 4.22 kg/cm2; P<0.01). The outcomes of the study suggest that the provision of Se yeast throughout the finishing period is a strategy to increase the benefits of the replacement of sodium selenite with organic selenium in beef cattle.

Evaluation of thymus morphology and serum cortisol concentration as indirect biomarkers to detect low-dose dexamethasone illegal treatment in beef cattle

BackgroundCorticosteroids are illegally used in several countries as growth promoters in veal calves and beef cattle, either alone or in association with sex steroids and β-agonists, especially at low dosages and primarily through oral administration, in order to enhance carcasses and meat quality traits. The aim of the present study is to evaluate the reliability of the histological evaluation of the thymus, as well as the serum cortisol determination, in identifying beef cattle, treated with two different dexamethasone-based growth-promoting protocols and the application of different withdrawal times before slaughter.ResultsOur findings demonstrate that low dosages of dexamethasone (DXM), administered alone or in association with clenbuterol as growth promoter in beef cattle, induce morphologic changes in the thymus, resulting in increase fat infiltration with concurrent cortical atrophy and reduction of the cortex/medulla ratio (C/M). In fact, the C/M value was significantly lower in treated animals than in control ones, with both the protocols applied. The cut off value of 0.93 for the cortex/medulla ratio resulted to be highly effective to distinguish control and treated animals. The animals treated with DXM showed inhibition of cortisol secretion during the treatment period, as well as at the slaughterhouse, 3 days after treatment suspension. The animals treated with lower doses of DXM in association with clenbuterol, showed inhibition of cortisol secretion during the treatment period, but serum cortisol concentration was restored to physiological levels at slaughterhouse, 8 days after treatment suspension.ConclusionsThe histological evaluation of thymus morphology, and particularly of the C/M may represent a valuable and reproducible method applicable to large-scale screening programs, due to the easy sampling procedures at slaughterhouse, as well as time and cost-saving of the analysis. Serum cortisol determination could be considered as an useful in vivo biomarker of dexamethasone illegal treatment in beef cattle during the fattening period, whilst it does not appear to be a good biomarker at the slaughterhouse, since the protocol of DXM administration, as well as the withdrawal period could affect the reliability of the method.

Effect of induced ruminal acidosis on blood variables in heifers

BackgroundRuminal acidosis is responsible for the onset of different pathologies in dairy and feedlot cattle, but there are major difficulties in the diagnosis. This study modelled the data obtained from various blood variables to identify those that could indicate the severity of ruminal acidosis. Six heifers were fed three experimental rations throughout three periods. The diets were characterised by different starch levels: high starch (HS), medium starch (MS) and low starch, as the control diet (CT). Ruminal pH values were continuously measured using wireless sensors and compared with pH measurements obtained by rumenocentesis. Blood samples were analysed for complete blood count, biochemical profile, venous blood gas, blood lipopolysaccharide (LPS) and LPS-binding proteins (LBP).ResultsThe regression coefficient comparing the ruminal pH values, obtained using the two methods, was 0.56 (P = 0.040). Feeding the CT, MS and HS led to differences in the time spent below the 5.8, 5.5 and 5.0 pH thresholds and in several variables, including dry matter intake (7.7 vs. 6.9 vs. 5.1 kg/d; P = 0.002), ruminal nadir pH (5.69 vs. 5.47 vs. 5.44; P = 0.042), mean ruminal pH (6.50 vs. 6.34 vs. 6.31; P = 0.012), haemoglobin level (11.1 vs. 10.9 vs. 11.4 g/dL; P = 0.010), platelet count (506 vs. 481 vs. 601; P = 0.008), HCO3- (31.8 vs. 31.3 vs. 30.6 mmol/L; P = 0.071) and LBP (5.9 vs. 9.5 vs. 10.5 μg/mL; P < 0.001). A canonical discriminant analysis (CDA) was used to classify the animals into four ruminal pH classes (normal, risk of acidosis, subacute ruminal acidosis and acute ruminal acidosis) using haemoglobin, mean platelet volume, β-hydroxybutyrate, glucose and reduced haemoglobin.ConclusionsAlthough additional studies are necessary to confirm the reliability of these discriminant functions, the use of plasma variables in a multifactorial model appeared to be useful for the evaluation of ruminal acidosis severity.

Clinical biochemical and hormonal profiling in plasma: a promising strategy to predict growth hormone abuse in cattle

Recombinant bovine somatotrophin (rbST) is widely used in some countries to increase milk production. Since 1994, both marketing and use of this substance have been prohibited within the European Union. In this context, the targeted plasma biochemical and hormonal profiling was assessed as a potential screening strategy to highlight rbST (ab)use in cattle. Twenty-one routinely measured clinical blood parameters, representative of main biological profiles (energetic, proteic, etc.), were measured in the plasma of six lactating cows before and after rbST treatment throughout a 23-day study period. Appropriate multivariate statistical analyses [principal component analysis (PCA) and orthogonal partial least square (OPLS)] enabled discriminating animal samples before and after treatment (days 0 vs. 2 to 9, Pu2009=u20092.10−9) and highlighted the five most relevant blood parameters in this discrimination. Based on each five-analyte contribution, a simple mathematically weighted equation was suggested to predict the status of samples. A suspicious threshold was proposed, and the model was further tested with the status prediction of the supplementary samples from untreated (nu2009=u200920) and treated cows (nu2009=u200922). The calculated false-positive (10xa0%) and false-negative (4.5xa0%) rates were in accordance with the EU requirements for screening methods. Although the model needs to be further validated with additional samples, such targeted plasma biochemical and hormonal profiling already appears as a potential promising screening strategy to highlight rbST (ab)use in cattle.

Effect of feeding fine maize particles on the reticular pH, milk yield and composition of dairy cows

The particle size of cereal grains has been found to modulate the rate of passage from the rumen and the digestibility of starch and neutral detergent fibre (NDF), but few studies have examined its impact on reticular pH. The study aimed to evaluate the effect of feeding finely ground maize on the risk of ruminal acidosis, milk yield and composition. Twelve Holstein-Friesian cows were assigned to one of two experimental groups and fed according to a cross-over design. Diets were isoenergetic and isonitrogenous and were characterised by the same NDF and ADF, differing only in maize particle size. In the control diet (Ct), the maize meal was ground to 1.0 mm, whereas in the experimental diet, it was finely ground (Fg) to 0.5 mm. The pH and temperature of the reticulum were continuously measured in eight cows throughout the trial using indwelling sensors. Dry matter intake was higher in cows offered Fg diet than in Ct (19.0 vs. 20.3 kg/day; p = 0.067). However, milk yield (p = 0.855) and the 3.5% fat-corrected milk (FCM) (p = 0.724) did not show any differences between the diets. Casein (2.48 vs. 2.57%; p = 0.035) and crude protein (CP) (3.18 vs. 3.31%; p = 0.021) resulted higher in Fg. Similarly, starch digestibility increased in animals offered Fg diet versus Ct (0.94 vs. 0.98; p = 0.078). Among the reticular parameters, the Fg-fed cows spent a significantly higher time below the 5.5 pH threshold (15 vs. 61 min/day; p = 0.047) and had an average daily variation in reticular pH characterised by a lower nadir pH (5.95 vs. 5.72; p < 0.001) and a higher pH range (0.79 vs. 0.94; p = 0.003). In this study, grain particle size affected the risk of the onset of ruminal acidosis. Therefore, it should be carefully considered when formulating rations.

Effect of unsaturated fatty acid supplementation on performance and milk fatty acid profile in dairy cows fed a high fibre diet.

Abstract The influence of unsaturated fatty acid (UFA) supplement on productive performance, physiochemical properties and fatty acid (FA) profile of milk, was investigated in lactating dairy cows fed with high fibre diets. According to a cross-over design, twelve cows were assigned to two experimental settings characterized by different FA profiles. Cows received a high fibre diet (~42% NDF on DM basis) supplemented with soybean based mixtures with these FA compositions: 92.0% of saturated FA (SFA), 2.8% of monounsaturated FA (MUFA) and 5.2% of polyunsaturated FA (PUFA) in the control diet (C-diet); 19.1% of SFA, 20.9% of MUFA and 60.0% of PUFA in the experimental diet (E-diet). The E-diet did not affect dry matter intake nor milk yield. Milk composition and coagulation traits resulted similar between treatments, except for the lactose level, which was lower in the E-diet (5.0 vs 4.8%; P<0.05) and the freezing point (-0.546 vs -0.535 °C; P<0.05). As respects the milk FA profile, the E-diet significantly increased the percentage of UFA because of their greater amount in the ration; however the “transfer” of UFA in milk was limited by the high level of FA biohydrogenation (BH) at the ruminal level. UFA showed low values of carry over in milk (67.5 vs 39.7%; P<0.001) due to the saturation process; on the contrary SFA had a threefold increment (124 vs 323%; P<0.001), mostly due to a peak in the production of stearic acid. In this study, the percentage of CLA in milk (0.50 vs 0.62%; P<0.05) was quite low for both diets, if compared with other studies, and this was probably due to a low vaccenic acid supply at duodenal level.

Sub-therapeutic treatments of bulls with dexamethasone: direct and indirect markers of treatment

Dexamethasone is a potent synthetic corticosteroid synthesised as an anti-inflammatory agent, but also illegally used at low dosages as a growth promoter either alone or in combination with other steroids or β-agonists. The use of screening methods based on the detection of biological effects of growth promoters is a promising approach to assist residue monitoring. The advantage of such an approach is that it offers the possibility to discover illicit treatments even when the drug residues are not easily detectable by common analytical methods. The aim of this study was to determine the urinary elimination and tissue distribution of dexamethasone and to investigate whether endogenous corticosteroid profiling of urine could be used to establish a predictive tool for identifying any misuse of growth promoters in bulls. Urinary corticosteroid concentrations were assayed in bulls (nu2009=u20098) treated with dexamethasone (0.75u2009mg/animal/day), bulls (nu2009=u20098) treated with a combination of dexamethasone (0.66u2009mg/animal/day) and clenbuterol (from 2 to 6u2009mg/animal/day) and untreated bulls (nu2009=u20098). The distribution and elimination of dexamethasone and the urinary concentration of cortisone, cortisol and 6β-hydroxycortisol were determined by using LC-MS/MS at different time points both during treatments and after appropriate withdrawal times. The urinary concentration of endogenous corticosteroids in bulls decreased significantly (pu2009<u20090.001) upon the administration of dexamethasone alone, whereas it remained unchanged until the last sampling point in animals treated with dexamethasone and clenbuterol (pu2009<u20090.001). Nonetheless, dexamethasone administration significantly reduced (pu2009<u20090.01) the urinary 6β-hydroxycortisol/cortisol ratio in both treatment groups. Therefore, this ratio could be regarded as a candidate for an indirect screening assay for detecting glucocorticoid abuse in bull fattening to pick out farms where similar treatments are potentially in use and to suggest targeted sampling on remaining animals.

Glucose infusion response on some metabolicparameters in dairy cows during transition period

Abstract. The aim of this study was to evaluate the effect of glucose tolerance test (GTT) on glucose, insulin, non-esterified fatty acids (NEFA) and β-Hydroxybutyrate (BHB) concentration in dairy cows during prepartum and postpartum period. Forty Two clinically healthy Holstein cows were enrolled in two high producing dairy farms in the Northeast Italy. All animals were divided into two equal groups on the basis of the farm of origin: Group A (farm located in Vicenza) and Group B (farm located in Padua). Body condition score (BCS) was determined for both groups. GTT was performed 7 ± 5 days before and 7 ± 5 days after calving. Blood samples were collected from each animal before (T0) and after the administration of glucose at different times. Plasma concentration of glucose, insulin, NEFA and BHB was evaluated. Application of two way analysis of variance (ANOVA) showed no significant effect of farm and a significant effect of transition period (prepartum and postpartum) on BCS for both groups. Multivariate analysis of variance (MANOVA) was applied to determine significant effects of infusion glucose time, transition period and farm on glucose, insulin, NEFA and BHB. No significant difference was observed between Groups A and B and a significant effect of transi tion period and glucose infusion was found on all parameters studied. Results confirm that glucose is an important direct controller of metabolic response in dairy cows during the transition period because of the inappropriate energetic supply that characterizing this physiological phases.

Trend overtime of total haemoglobin, iron metabolism and trace minerals in veal calves fed high amounts of two different solid feeds

Abstract Fifty Polish Friesian veal calves were administrated high amounts of two different solid feeds (maize grain and a mix diet containing 10% of straw and 8% of soy) in addition to the traditional milk replacer diet. Compared to the mix diet, maize grain had a lower content of iron, copper and zinc and a minor fibre level. Effects of the two diets on calves’ blood haemoglobin, iron, iron metabolism parameters, copper and zinc concentrations were studied. Haemoglobin concentration resulted higher at the end of the fattening for calves fed the mix diet, as expected. Values remained, however, within ranges that allowed acceptable carcass paleness. Haematic iron, unsaturated iron binding capacity (UIBC) and total iron binding capacity (TIBC) levels were not significantly different between the two solid feeds. Lower copper and zinc blood concentrations resulted for calves fed the mix diet were likely due to the feed fibre interfering with the bioavailability of the two minerals, according to what happens for iron.