N.C. Friggens

On the relationship between lactational performance and health: is it yield or metabolic imbalance that cause production diseases in dairy cattle? A position paper

The objective of this review was to explore the relationship between lactational performance and health. We focused on lactational incidence rates (LIR) of the production diseases that are of economic importance to the dairy industry. Based on a review of 11 epidemiological and 14 genetic studies we found little evidence that high yielding cows have increased risk of dystocia, retained placenta, metritis and left-displaced abomasum. Results for periparturient paresis were inconsistent. Whilst we found no phenotypical relationship between milk yield and the risk of ketosis and lameness, selection for higher milk yields will probably increase LIR for these diseases. Mastitis was the only disease where there was a clear relationship between milk yield and risk of infection. Continued selection for higher milk yields will worsen this situation. However, our overall conclusion is that reviewing existing literature, even with a structured literature selection, is inadequate to the task of elucidating the relationship between lactational performance and risk of production diseases. There are substantial problems with confounding effects and unaccounted for biological correlations. In the second part of the review we argue towards a common basis for addressing production diseases. We propose abnormal body mobilisation and immune competence as common currencies for metabolic and immune status and argue for the development of indicators of metabolic imbalance and the early development of diseases. Furthermore, we suggest the use of indicators of ‘imbalance’ to guide feeding according to the needs of individual cows with their specific genotype and management history. We believe that this approach has the potential to provide new diagnostic and decision support tools to improve animal health and reproduction, whilst simultaneously maintaining optimal production and efficiency. Further research is needed to identify and validate new indicators and individual feeding strategies.

Improved Detection of Reproductive Status in Dairy Cows Using Milk Progesterone Measurements

This study tested a model for predicting reproductive status from in-line milk progesterone ;measurements. The model is that of Friggens and Chagunda [Theriogenology 64 (2005) 155]. Milk progesterone measurements (n = 55 036) representing 578 lactations from 380 cows were used to test the model. Two types of known oestrus were identified: (1) confirmed oestrus (at which insemination resulted in a confirmed pregnancy, n = 121) and (2) ratified oestrus (where the shape of the progesterone profile matched that of the average progesterone profile of a confirmed oestrus, n = 679). The model detected 99.2% of the confirmed oestruses. This included a number of cases (n = 16) where the smoothed progesterone did not decrease below 4 ng/ml. These cows had significantly greater concentrations of progesterone, both minimum and average, suggesting that between cow variation exists in the absolute level of the progesterone profile. Using ratified oestruses, model sensitivity was 93.3% and specificity was 93.7% for detection of oestrus. Examination of false positives showed that they were largely associated with low concentrations of progesterone, fluctuating around the 4 ng/ml threshold. The distribution of time from insemination until the model detected pregnancy failure had a median of 22 days post-insemination. In this test, the model was run using limited inputs, the potential benefits of including additional non-progesterone information were not evaluated. Despite this, the model performed at least as well as other oestrus detection systems.

Influence of breed, parity, and stage of lactation on lactational performance and relationship between body fatness and live weight

The aim of this study was to characterise the effects of genotype, parity and nutrition on performance and the relationship between body condition and body weight. A total of 657 lactations from 322 cows were used. Three breeds were used, Danish Holstein, Danish Red and Jersey. Each breed was subdivided into two lines selected to differ in milk yield. Within line cows were randomly assigned to either a normal or low energy density total mixed ration. Three 1-week periods representing early lactation, peak milk yield and late lactation were identified for the analyses. For the analysis of the relationship between body weight and condition score, the dry period was also considered. There were significant effects of breed on all performance measures but no effect of line (with the exception of condition score). Cows fed the normal energy density diet had higher milk yield, fat percentage and condition score and weighed more than cows on the low feeding treatment. There was a highly significant relationship between body weight and condition score. In all periods except the dry period, there were significant effects of breed (P<0.001) and parity (P<0.05) on the intercept of the relation between body weight and condition score. However, there was no significant effect of breed or parity on the slope of the relationship between body weight and condition score.

Identification of potential markers in blood for the development of subclinical and clinical mastitis in dairy cattle at parturition and during early lactation

Our objective was to identify specific blood markers as risk factors for the development of mastitis during early lactation. We used a subset of cows from a larger experiment that consisted of a total of 634 lactations from 317 cows. Cows were of 3 breeds and ranged from parity 1 to 4. Blood samples were collected weekly from 56 d before expected calving date through 90 d in milk (DIM). Blood was analyzed for several hormones, metabolites, and enzymes, and energy intake and energy balance were calculated. Veterinary treatment records and daily composite milk somatic cell counts were analyzed and used to determine incidence and severity of mastitis in early lactation. Cows were separated into 2 groups: 1) WK0, consisting of cows that developed clinical mastitis (CM), cows that developed subclinical mastitis (SM), or cows that were healthy (H) during the first 7 DIM; and 2) EL, consisting of CM, SM, or H cows during wk 2 through 13 of lactation. Data were adjusted for numerous fixed effects (e.g., parity, breed, season, and DIM) before statistical analysis. The time of mastitis (TOM) was recorded as the DIM in which the first rise in somatic cell count was observed and was recorded as TOM = 0. The time before and after TOM was distinguished as +/- n wk relative to TOM = 0. Healthy cows were paired with either a SM or CM cow and the TOM for each H cow was equal to the TOM for its paired SM or CM cow. Data from wk -1 and -2 relative to TOM were analyzed for group WK0 and EL, respectively. For all parameters, SM cows did not differ from H cows from either group. The CM cows had higher nonesterified fatty acid levels and a tendency toward higher beta-hydroxybutyrate levels than H cows before mastitis for both groups. For group WK0, glucose was higher -1 wk relative to calving in CM than H cows. For group EL, aspartate aminotransferase was higher -2 wk relative to mastitis in CM than H cows during 8 to 90 DIM. All other variables were similar among CM, SM, and H cows for both groups. Our results indicate that substances in blood, especially nonesterified fatty acids and aspartate aminotransferase, may be potential markers for the risk of mastitis in early lactation.

The effects of low vs. high concentrate level in the diet on performance in cows milked two or three times daily in early lactation

Abstract The effect of concentrate:forage ratio in the diet and milking frequency on performance was investigated in a 2×2 factorial block design comprising 40 Danish–Holstein dairy cows from parturition to week 16 of lactation. One factor was concentrate level, either low (L: 25% concentrate) or high (H: 75% concentrate), in an ad libitum fed total mixed ration. The second factor was milking frequency, either two or three times daily milking during the first 8 weeks of lactation. From weeks 9 to 16 of lactation, all cows were milked twice daily. During weeks 0 to 8, the cows receiving diet H had a 4.2 units higher net energy intake (Scandinavian feed units), and a 15% higher milk yield compared with the cows receiving diet L. The cows being milked three times a day had an 8% higher daily milk yield, without an increase in DMI, than the cows milked twice a day. In the period from weeks 0 to 8 of lactation, the cows that were fed diet L and milked three times daily mobilised 70 kg, which was 11 to 18 kg more than in the other experimental groups. During weeks 9 to 16 of lactation, the cows receiving diet H maintained a higher feed intake and milk yield similar to that observed in the first 8 weeks of lactation. No positive carry-over effect was seen by changing from three to two milkings a day in early lactation. In conclusion, it seems that cows with high milk yield, achieved by increasing the milking frequency, will benefit from a high concentrate level in the diet.

Effect of changes in diet energy density on feed intake, milk yield and metabolic parameters in dairy cows in early lactation.

The purpose of this experiment was to investigate how early lactating cows adjust their metabolism and production to acute, but moderate changes in the energy density of the diet. Sixty dairy cows were randomly assigned to one of four treatments: two change-over groups (HNH and NHN) and two control groups (HHH and NNN), where H and N refer to a high and normal energy density in the total mixed ration (TMR), respectively. The experimental period covered the first 9 weeks post calving, which was split up in three 3-week periods. Thus, cows assigned to HNH or NHN shifted TMR in weeks 4 and 7 after calving while cows assigned to HHH or NNN were fed the same TMR for all 9 weeks. Results from cows on treatment HNH were compared with group HHH while cows on treatment NHN were compared with group NNN. When the diet changed from N to H and H to N, cows increased and decreased their dry-matter intake (DMI), respectively compared with control groups. Cows adjusted milk yield accordingly to changes in DMI, although not always significantly. Energy-corrected milk yield was not significantly affected by any of the changes in the energy density of the diet but generally showed same tendencies as milk yield. Non-esterified fatty acids (NEFA), beta-hydroxybutyrate in blood and milk and triacylglycerol and glycogen content in the liver were not significantly affected by changes in the energy density of the diet, except from NEFA at one change. Glucose increased more when the diet changed from N to H and increased less when the diet changed from H to N, compared with control groups, although not always significantly. Collectively, these results suggest that cows adjust their DMI and partly milk yield according to the energy density of the diet and therefore only limited effects were observed in physiological parameters.

An attempt to detect oestrus from changes in Fourier transform infrared spectra of milk from dairy heifers.

This study was carried out to investigate if there were systematic changes in milk Fourier transform infrared (FT-IR) spectra relative to stage of the oestrous cycle in cattle. Oestrous cycles of 22 lactating heifers were synchronized with two injections of prostaglandin F2alpha (PGF) administered 11 days apart. The heifers were milked twice daily, and milk samples were collected from each heifer at each milking for a period of 70 days, starting on the day of the second PGF injection. Oestrus was diagnosed by visual detection in conjunction with monitoring rectal temperature. Milk samples were analyzed by FT-IR spectroscopy and the spectra data were analyzed using partial least squares (PLS) methods in relation to time of observed oestrus in heifers. In this investigation, it was not possible to identify reliable changes in milk FT-IR spectra in relation to oestrus on a single heifer basis, though there was a weak correlation between FT-IR spectra and expected time of oestrus when the analysis was carried out across all the heifers.