Olav Kärt

A comparison of the methods for determination of the rennet coagulation properties of milk

Abstract The objective of the present study was to compare two methods for measuring the rennet coagulation properties of milk: the Formagraph, and the Optigraph. The parameters used to describe rennet coagulation of 81 milk samples were rennet coagulation time (RCT, Formagraph, and R, Optigraph) and curd firmness 30 min after the addition of rennet (E30, Formagraph, and A30, Optigraph). New Optigraph system recipes were found: R slope = 1.784 and R offset = − 2.303. Using the above Optigraph system recipes, no statistically significant differences were found in rennet coagulation time measurements in either of the studied methods. Regarding curd firmness, the best approximation to describe the relationship between the methods was polynomial: E30= − 0.0357*A30 2+2.8795*A30 −5.2991 (R 2 =0.925). Such strong correlations indicate that the two techniques for detecting milk coagulation properties are comparable and that the data obtained by these methods allow for data interpretation in studies using either method.

Comparison of the metabolic profiles of noncoagulating and coagulating bovine milk

We hypothesize that, through milk composition and different milk metabolites, it is possible to characterize the technological properties (e.g., coagulation) of milk. In this research, liquid chromatography mass spectrometry was used to obtain profiles of low molecular weight organic compounds in 143 milk samples. The metabolic profiles of milk from cows were correlated with their coagulation properties. Using multivariate data analysis methods, we demonstrated that the metabolic profiles of the milk were correlated with coagulation ability. Several marker ions responsible for differential coagulation were found. Although not all affected metabolites could be identified, the most significant differences were found for carnitine and oligosaccharides. Exploitation of these results may increase the use of biomarkers to assess the coagulation ability of milk. This study represents the first large-scale metabolomic profiling of noncoagulating and coagulating bovine milk samples in Estonia.

Field trial on glucose-induced insulin and metabolite responses in Estonian Holstein and Estonian Red dairy cows in two herds

BackgroundInsulin secretion and tissue sensitivity to insulin is considered to be one of the factors controlling lipid metabolism post partum. The objective of this study was to compare glucose-induced blood insulin and metabolite responses in Estonian Holstein (EH, n = 14) and Estonian Red (ER, n = 14) cows.MethodsThe study was carried out using the glucose tolerance test (GTT) performed at 31 ± 1.9 days post partum during negative energy balance. Blood samples were obtained at -15, -5, 5, 10, 20, 30, 40, 50 and 60 min relative to infusion of 0.15 g/kg BW glucose and analysed for glucose, insulin, triglycerides (TG), non-esterified fatty acids (NEFA), cholesterol and β-hydroxybutyrate (BHB). Applying the MIXED Procedure with the SAS System the basal concentration of cholesterol, and basal concentration and concentrations at post-infusion time points for other metabolites, area under the curve (AUC) for glucose and insulin, clearance rate (CR) for glucose, and maximum increase from basal concentration for glucose and insulin were compared between breeds.ResultsThere was a breed effect on blood NEFA (P < 0.05) and a time effect on all metabolites concentration (P < 0.01). The following differences were observed in EH compared to ER: lower blood insulin concentration 5 min after glucose infusion (P < 0.05), higher glucose concentration 20 (P < 0.01) and 30 min (P < 0.05) after infusion, and higher NEFA concentration before (P < 0.01) and 5 min after infusion (P < 0.05). Blood TG concentration in ER remained stable, while in EH there was a decrease from the basal level to the 40th min nadir (P < 0.01), followed by an increase to the 60th min postinfusion (P < 0.01).ConclusionOur results imply that glucose-induced changes in insulin concentration and metabolite responses to insulin differ between EH and ER dairy cows.

Relationships between luteal activity, fertility, blood metabolites and body condition score in multiparous Estonian Holstein dairy cows under different management.

The objective was to compare the relationships between luteal activity and fertility, and relate these parameters to metabolic indices and body condition changes in multiparous Estonian Holstein cows on two commercial dairy farms under different management and levels of production and nutrition (higher, H, n=54 (71 lactations) and lower, L, n=39 (39 lactations)). For statistical analysis cows were categorized according to their milk progesterone (P4) profiles as follows: normal ovarian function; delayed start of cyclicity (DC) (interval from calving to first luteal response (P45 ng/ml up to and more than 50 d respectively, followed by regular cyclicity); cessation of luteal activity (prolonged interluteal interval, P4<5 ng/ml, with a duration of 14 d between two adjacent luteal phases); prolonged luteal activity (P4 levels 5 ng/ml for 20 d without preceding insemination). The Mixed procedure of the SAS system was used to compare milk production traits, blood metabolites (ketone bodies, non-esterified fatty acids, total cholesterol) and aspartate aminotransferase, body condition scores (BCS) and fertility parameters between the two farms, and also fertility parameters between the farms within P4 categories. Differences in milk fat/protein ratio, ketone body levels and BCS indicated a deeper negative energy balance (NEB) during the first month after calving on farm L. On both farms nearly 50% of the recently calved dairy cows suffered from ovarian dysfunction during the post-partum period. Delayed start of cyclicity was the most prevalent abnormal P4 profile, 25% and 28% on farms H and L, respectively. Prolonged luteal activity accounted for one-third of atypical ovarian patterns on farm H, and cessation of luteal activity on farm L. On farm L, DC cows had lower BCS values from day 10 to day 90 after calving compared with normal cows (P<0.01) and cows lost more BCS (1.2 units) during the 40 d after calving than normal resumption cows (0.75 units; P<0.05). On farm H with moderate NEB the delayed start of ovulation post partum did not impair subsequent reproductive performance.

Alterations in milk metabolome and coagulation ability during the lactation of dairy cows

Milk composition has been known to change during lactation. To help understand the changes in metabolic profile throughout the whole lactation, liquid chromatography mass-spectrometry was used to analyze 306 milk samples from 82 primi- and multiparous dairy cows. Changes in metabolic profile common to all cows throughout lactation were ascertained based on principal component and general linear model analysis. Sets of specific markers; for instance, 225, 397, and 641-642 m/z (positive mode), and 186, 241, and 601-604 (negative mode), with at least a 1.5-fold higher intensity during the first 60 d compared with the last 60 d of lactation were observed. The metabolome was affected by parity and milking time. Markers, identified as peptides differentiating parity, were observed. A significant increase for citrate was observed in evening milk. Milk coagulation traits were strongly animal specific. The curd firmness values were influenced by milking time. Sets of markers were associated with curd firmness in positive (197 m/z) and negative (612, 737, 835, 836, 902, 1000, 1038, and 1079 m/z) ion mode.

CRUDE GLYCEROL AS GLYCOGENIC PRECURSOR IN FEED, EFFECTS ON MILK COAGULATION PROPERTIES AND METABOLIC PROFILES OF DAIRY COWS

As grain prices rise, the search for alternative glycogenic precursors in animal feed becomes increasingly important, and this study was conducted to determine if the replacement of starch with glycerol, as an alternative glycogenic precursor, affects the milk metabolic profile and milk coagulation ability, and therefore the quality of the milk. Eight primiparous mid-lactation Holstein cows were fed during a replicated 4 × 4 Latin square trial with four different isoenergetic rations: (1) control (T0) fed a total mixed ration (TMR) with barley meal; (2) group T1, decreased barley content, replaced isoenergetically with 1 kg crude glycerol; (3) group T2, the barley meal was replaced with 2 kg of crude glycerol; and (4) group T3 the barley meal was replaced with 3 kg of crude glycerol. Rumen, blood and milk samples were collected at the end of every 21-d treatment period. Rumen samples were analysed for proportion of total volatile fatty acid (VFA), blood samples for insulin and glucose, and milk for metabolites (e.g. citric-acid cycle compounds). The change in glycogenic precursors had a positive effect on rumen VFA proportions; the proportion of propionic acid increased (P < 0.001). Milk protein (P < 0.001) and curd firmness (P < 0.001) both increased. The increase in milk protein concentration may have been due to an increase in microbial protein. Regarding the milk metabolic profiles, different signals were positively associated with coagulation ability and change in the diet. Based on this study, changing the glycogenic precursor in animal diet in this way is possible, and may have no immediate deleterious consequences on milk quality or cow health. Indeed, there is evidence for benefits from this substitution.