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Biomedical subjects

N C Friggens

Publications and source records attributed to N C Friggens.

16 recordsLinked to original sources
PubMed2006

A model for detection of individual cow mastitis based on an indicator measured in milk.

A dynamic deterministic biological model was developed that generates, for a given cow on a given day, a value for her risk of having mastitis. The model combines real-time information from a mastitis indicator measured in milk with additional factors that are other known risk factors of mastitis but that are not reflected in the indicator. l-Lactate dehydrogenase (LDH), an enzyme whose activity is increased because of mastitis, is used as an example of a mastitis indicator. The additional factors incorporated in the model are days from calving, breed, parity, milk yield, udder characteristics, other disease records, electrical conductivity, and herd characteristics. The model is designed to run each time a new LDH value is recorded and can run in the absence of the additional factors. Electrical conductivity measurements and disease records, where available, also trigger the model to run. As an input, milk LDH activity values (micromol/min per L) are multiplied by milk yield (L) to produce the amount of LDH (micromol/min) and are then smoothed using an extended Kalman filter before being processed by the biological model. The output comprises a risk of acute mastitis and a relative degree of chronic mastitis. The model also produces a days-to-next sample value that allows sampling frequency to be either increased or reduced depending on the risk of mastitis. The days-to-next sample value was designed to make the best use of opportunities afforded by automated, inline sampling technology. The model functionality was investigated using simulated data, and real-farm data of naturally occurring mastitis were then used to validate the model. The results demonstrated that the model is robust to sampling frequency and random noise in the LDH measurements. It was able to detect mastitis reasonably well: Using a threshold mastitis risk of 0.7, sensitivity for detecting clinical mastitis was 82%. Specificity, that is, the ability to avoid misclassifying healthy observations as mastitis, was 99%.

Acute Disease↗
PubMed2005

Technical and economic effects of an inline progesterone indicator in a dairy herd estimated by stochastic simulation.

For several years progesterone in milk or blood has been recognized as an indicator of different cow states related to reproduction. For this study, an existing simulation model was modified in order to analyze the technical and economic effects of including information on progesterone status in an automatic inline monitoring system. Implementation of an inline progesterone indicator was assumed to directly affect the estrus detection rate, the period until treatment for post-partum anestrus and the number of mistimed AIs. Different implementations of an inline progesterone indicator were simulated in a typical Danish dairy herd with 120 cows and in other herd situations represented by: a herd with poor reproduction efficiency, a herd with a high estrus detection rate and a herd using a 9 week postponed AI period for primiparous cows. It was concluded that implementation of an inline progesterone indicator in a dairy herd previously using visual estrus detection has a break-even price of 3-81 euros per cow-year depending on differences in implementation type and herd reproduction management. The highest break-even price was found using the assumptions that simulated a herd with initially poor reproductive efficiency. With the assumptions that simulated a typical Danish herd the break-even price was 46 euros per cow-year. Attributable effects of using the indicator, including effects of labor time, are discussed.

Animals↗
PubMed2005

Predicting risk of ketosis in dairy cows using in-line measurements of beta-hydroxybutyrate: a biological model.

Automated monitoring of individual cows to determine health status is a potentially valuable management tool, especially in large dairy herds. Herein is described the rationale, structure, and functionality of a biological model to predict risk of ketosis in individual cows using in-line measurements of the ketone body beta-hydroxybutyrate (BHBA) in milk. The model also uses acceleration in milk yield, body fatness at calving, diseases in current lactation, and incidences of ketosis in earlier lactations as additional risk factors for ketosis. However, the model is designed to function merely on the basis of milk BHBA in the absence of other data. Values of milk BHBA are smoothed using a state space model before these are used in calculations in the biological part of the model. The model is designed to be updated each time a new BHBA measurement or a disease occurrence is available and then uses previous and current data. Outputs of the model are the risk of ketosis (value between 0 and 1, where 0 = no risk and 1 = clinical ketosis) and how many days until the next milk sample should be taken and analyzed for BHBA. At higher risks for ketosis, more frequent milk sampling is the recommended output. Test examples from cows for which BHBA has been measured extensively were used to show the functionality of the model. The model performed equally well when reductions in sampling frequency were applied, and it was also relatively robust to the addition of up to +/- 2 residual SD of random noise in the BHBA values. This model has the potential to provide the basis for a useful disease monitoring and management tool. However, thorough validation awaits a much larger dataset and testing of the model under a variety of on-farm situations.

3-Hydroxybutyric Acid↗
PubMed2005

A stochastic model simulating pathogen-specific mastitis control in a dairy herd.

The objective of this study was to develop a model simulating mastitis control in dairy herds and to investigate how sensitive the model is when varying the effect parameters according to the uncertainty. The model simulates 9 pathogen-specific mastitis types, each of which can be subclinical or clinical. The clinical cases can be 1 of 4 severities defined according to the effect of the mastitis case: mild, moderate, severe, and permanent effect. The risk factors include lactation stage, parity, yield level, previous diseases, season, and contagious spread of the infection from herd mates. Occurrence of mastitis is modeled to have direct effects on feed intake, body weight, milk yield, somatic cell count in the milk, subsequent mastitis cases within the cow and in herd mates, voluntary and involuntary culling, mortality, and milk withdrawal. Thirty-five scenarios were simulated to study model behavior and model sensitivity. The consequences per cow/yr of mastitis in the default simulated herd included 0.42 clinical mastitis occurrences, 0.56 subclinical mastitis occurrences, loss of 385-kg milk yield, a 1.3% reduced feed intake, 61-kg milk withdrawal and 146 in reduced economic net return. Based on scenarios demonstrating model behavior and sensitivity analysis, the model appears to produce valid consequences of mastitis control strategies. Representation of the effect of subclinical mastitis and of variation in mastitis severity was concluded in this study to be important when modeling mastitis economics in a dairy herd. The model offers the opportunity to study the long-term herd specific effects of a wide range of control strategies against mastitis.

Animals↗
PubMed2004

Effect of energy density in the diet and milking frequency on plasma metabolites and hormones in early lactation dairy cows.

The effects of energy density in the diet [low = 0.86 SFU/kg dry matter (DM) or high = 1.06 SFU/kg DM] and daily milking frequency (two or three times) in early lactation on plasma concentrations of metabolites and hormones were evaluated in 40 Holstein dairy cows arranged in a 2 x 2 factorial block design. The four treatment combinations were L2, L3, H2 and H3, and the experimental period comprised the first 8 weeks of lactation. Plasma glucose, insulin and insulin-like growth factor (IGF)-I concentrations were on average 8 (3.43 versus 3.19 mmol/l), 114 (41.6 versus 19.4 pmol/l) and 60% (91.9 versus 57.4 ng/ml) higher, whereas beta-hydroxybutyrate (BOHB), plasma urea nitrogen (PUN) and growth hormone (GH) concentrations were on average 18 (0.73 versus 0.89 mmol/l), 14 (7.18 versus 8.35 mmol/l), and 63% (1.0 versus 2.6 ng/ml) lower for cows fed diet H than for cows fed diet L. Cows milked three times daily had a 6% (3.20 versus 3.42 mmol/l) lower plasma glucose concentration and a 19% (0.88 versus 0.74 mmol/l) higher plasma concentration of BOHB compared with cows milked two times daily. Plasma non-esterified fatty acid (NEFA) concentration was not affected by either treatment. Overall, it is concluded that increasing the daily milking frequency creates a higher metabolic imbalance in early lactation. Cows in early lactation will benefit from receiving a high energy density diet and thereby avoid a too high metabolic imbalance when mobilizing body tissue in support of milk production.

3-Hydroxybutyric Acid↗
PubMed2004

Prediction of body lipid change in pregnancy and lactation.

A simple method to predict the genetically driven pattern of body lipid change through pregnancy and lactation in dairy cattle is proposed. The rationale and evidence for genetically driven body lipid change have their basis in evolutionary considerations and in the homeorhetic changes in lipid metabolism through the reproductive cycle. The inputs required to predict body lipid change are body lipid mass at calving (kg) and the date of conception (days in milk). Body lipid mass can be derived from body condition score and live weight. A key assumption is that there is a linear rate of change of the rate of body lipid change (dL/dt) between calving and a genetically determined time in lactation (T') at which a particular level of body lipid (L') is sought. A second assumption is that there is a linear rate of change of the rate of body lipid change (dL/dt) between T' and the next calving. The resulting model was evaluated using 2 sets of data. The first was from Holstein cows with 3 different levels of body fatness at calving. The second was from Jersey cows in first, second, and third parity. The model was found to reproduce the observed patterns of change in body lipid reserves through lactation in both data sets. The average error of prediction was low, less than the variation normally associated with the recording of condition score, and was similar for the 2 data sets. When the model was applied using the initially suggested parameter values derived from the literature the average error of prediction was 0.185 units of condition score (+/- 0.086 SD). After minor adjustments to the parameter values, the average error of prediction was 0.118 units of condition score (+/- 0.070 SD). The assumptions on which the model is based were sufficient to predict the changes in body lipid of both Holstein and Jersey cows under different nutritional conditions and parities. Thus, the model presented here shows that it is possible to predict genetically driven curves of body lipid change through lactation in a simple way that requires few parameters and inputs that can be derived in practice. It is expected that prediction of the cow's energy requirements can be substantially improved, particularly in early lactation, by incorporating a genetically driven body energy mobilization.

Animals↗
PubMed2004

Electrical conductivity of milk: ability to predict mastitis status.

Electrical conductivity (EC) of milk has been introduced as an indicator trait for mastitis over the last decade, and it may be considered as a potential trait in a breeding program where selection for improved udder health is included. In this study, various EC traits were investigated for their association with udder health. In total, 322 cows with 549 lactations were included in the study. Cows were classified as healthy or clinically or subclinically infected, and EC was measured repeatedly during milking on each quarter. Four EC traits were defined; the inter-quarter ratio (IQR) between the highest and lowest quarter EC values, the maximum EC level for a cow, IQR between the highest and lowest quarter EC variation, and the maximum EC variation for a cow. Values for the traits were calculated for every milking throughout the entire lactation. All EC traits increased significantly (P < 0.001) when cows were subclinically or clinically infected. A simple threshold test and discriminant function analysis was used to validate the ability of the EC traits to distinguish between cows in different health groups. Traits reflecting the level rather than variation of EC, and in particular the IQR, performed best to classify cows correctly. By using this trait, 80.6% of clinical and 45.0% of subclinical cases were classified correctly. Of the cows classified as healthy, 74.8% were classified correctly. However, some extra information about udder health status was obtained when a combination of EC traits was used.

Animals↗
PubMed2003

Potential for improving description of bovine udder health status by combined analysis of milk parameters.

The objective of this study was to assess the potential of a stepwise multivariate procedure to quantify cow-level udder health based on eight milk parameters: milk yield, protein percentage, fat percentage, lactose percentage, citrate percentage, somatic cell count (SCC), and two electrical conductivity parameters. The data were collected in one research herd and included 821 cow-level observations. In addition to milk parameters, disease recordings and bacteriology on quarter milk samples every eighth week throughout lactation were included. A multivariate mixed model was applied to the milk parameters in a healthy subset to adjust for the following systematic factors: total mixed ration (TMR) energy density, breed-line combination, parity, stage of lactation, and season. The proportion of variance accounted for by the mixed model ranged from 0.14 to 0.82 depending on milk parameter. The adjustments estimated in the healthy subset were applied to the whole dataset, including observations pertaining to nonhealthy cows. Combined description of the adjusted variation in the milk parameters was performed with a principal component analysis. The first principal component (Prin1) described 30% of the adjusted variation and was interpreted as being the main consequences of mastitis. Finally, cluster analysis based on Prin1 separated the observations into nine clusters, which were strongly associated with udder health in terms of increasing clinical and subclinical mastitis with increasing level of Prin1. It was concluded that a multivariate approach to assess udder health from milk parameters has the potential to substantially improve description of udder health.

Analysis of Variance↗
PubMed2002

Factors affecting the transfer of porcine parvovirus antibodies from sow to piglets.

The aim of the study was to investigate the effects of a number of environmental, behavioural and biological factors on passive immunization of piglets as assessed by transfer of porcine parvovirus (PPV) antibodies (ab) from the colostrum of PPV vaccinated mothers to the serum of the piglets. Twenty primiparous sows were housed in pens with peat, straw and branches for nest building. Half the sows were prevented from achieving feedback from a completed farrowing nest by repeated removal of the nest from 10 to 12 h after nest building had begun, whereas the other half kept their nests. Sow serum PPV-ab titres were positively related to colostrum PPV-ab titres at birth of the first piglet (BFP) (P < 0.001). Litter average piglet PPV-ab titre was positively related to both sow serum and colostrum PPV-ab titres (both P < 0.001). In addition, in the individual piglets. PPV-ab titres were reduced as time from BFP to birth and time from birth to first sucking increased and time spent sucking decreased (all P < 0.01). There were no effects of treatment, time spent in lateral recumbency by the sow, number of times the sow stood or piglet weight on day 1 on piglet serum PPV-ab titres. Preventing prolonged farrowing, while at the same time ensuring the piglets' access to the udder, is important for transfer of maternal immunity. Measurements of specific antibodies in sow serum during the periparturient period and in piglet serum at 28 days of age may provide a practical tool for evaluating transfer of maternal immunity from sow to piglets.

Animals↗
PubMed2001

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.

Animals↗
PubMed1998

Proportions of volatile fatty acids in relation to the chemical composition of feeds based on grass silage.

This experiment was designed to quantify the relationships between feed chemistry and the proportions of rumen volatile fatty acids (VFA) across a wide range of feedstuffs. In an experiment using 11 rumencannulated sheep, 16 test feeds were fed at three different inclusion rates in rations that were based on grass silage. The 17 periods of the experiment were each 14 d long. Eight rumen samples were taken every 24 h on d 13 and 14 of each period from which the mean daily proportions of VFA were derived. The effects of an increase in the proportion of test feed in the total feed on proportions of VFA were significant. The observed proportions of VFA were related to the chemical composition of the total feed by principal component regression. The inclusion of the amount of feed offered and the ratio of test feed to total feed in these regressions did not improve their precision; these terms were not significant. The significant terms in the regressions were crude protein, starch, sugar, and cellulose (calculated by difference). The R2 values achieved for the regressions between acetate, propionate, and butyrate (molar proportions) and feed composition were 77.5, 68.0, and 87.3%, respectively. These regressions provided an apparently robust basis for predicting molar proportions of VFA from feed chemistry in feeds based on grass silage.

Acetates↗
PubMed1998

Feed intake relative to stage of lactation for dairy cows consuming total mixed diets with a high or low ratio of concentrate to forage.

This experiment examined the effect of feed quality on the relationship between intake and stage of lactation in dairy cows. Two total mixed diets composed of grass silage and concentrate were formulated. The high concentrate total mixed diet was designed to meet energy requirements, and the low concentrate total mixed diet was designed to limit intake. Twenty-four Holstein-Friesian cows were offered the total mixed diets in a full 2 x 2 change-over design with control treatments. The changeover was at 153 d in milk (DIM). For the statistical analyses, two periods of 13 wk, one period before and one period after the changeover, were used. Dry matter intake (DMI), milk yield, body weight, and body condition score were significantly greater for cows fed the high concentrate total mixed diet than for cows fed the low concentrate total mixed diet. Significant interactions between total mixed diet and period were observed for DMI and milk yield. However, no significant residual effects of changing from one total mixed diet to the other were observed. The interactions were due to substantially different slopes of DMI and milk yield relative to DIM for cows fed the two different total mixed diets. For cows fed the low concentrate total mixed diet, there was no effect of stage of lactation on DMI; the slope was 0. For cows fed the high concentrate total mixed diet, there was a significant decline in DMI as lactation progressed.

Animal Feed↗
PubMed1998

Diet choice by dairy cows. 1. Selection of feed protein content during the first half of lactation.

Effects of weeks in milk and milk yield on diet choice were recorded during the first half of lactation. Low and high protein feeds were used, and both consisted of 30% concentrate and 70% grass silage (fresh matter basis). Both feeds contained similar amounts of energy, but the crude protein contents were 131 and 185 g/kg of dry matter (DM), respectively, for the low and high protein feeds. In a nutrient flow experiment with three cannulated lactating cows, the metabolizable protein yields of the low and high protein feeds were 75 and 114 g/kg of DM, respectively. Thirty-seven cows were divided into control groups for the low and high protein feeds, and a choice group had access to both the low and the high protein feeds. Intake of DM and milk yield by cows in the control group fed the high protein feed were higher than those by cows in the control group fed the low protein feed, but these measurements did not differ from those of cows in the choice group. Cows in the choice group consumed a mean of 683 g of high protein feed/kg of total intake, which differed from what would be considered random intake (500 g/kg total intake). Diet choice did not systematically change during the experiment and was not correlated with weeks in milk, milk yield, or milk protein output. We concluded that diet selection differed significantly from what would be considered random, which allowed cows in the choice group to perform well. However, diet choice did not reflect the estimated metabolizable protein requirements of the cows.

Ammonia↗
PubMed1998

Effects of feed composition and stage of lactation on the short-term feeding behavior of dairy cows.

Twenty Holstein-Friesian cows were assigned to one of four feeding groups throughout lactation in a full change-over experiment using two total mixed diets. The low concentrate total mixed diet contained 100 g of concentrate/kg of fresh matter, and the high concentrate total mixed diet contained 300 g of concentrate/kg of fresh matter. The remainder of the total mixed diet was grass silage. The two changeover groups switched total mixed diets at 153 d of lactation; the other two treatment groups remained on their assigned diets throughout lactation. For analysis of short-term feeding behavior, four periods of 3 wk each were identified. The midpoints of these periods were -102, -18, 18, and 102 d from the changeover. The concentrate content of the total mixed diet significantly affected dry matter intake and all short-term feeding behavior variables. Cows that consumed the high concentrate total mixed diet had fewer but longer visits to the feeders and ate more feed per visit than did cows consuming the low concentrate total mixed diet. With one exception, no significant effect of stage of lactation was detected for any of the short-term feeding behavior variables. Despite a highly significant decline in dry matter intake as lactation progressed for cows consuming the high concentrate total mixed diet, there were no interactions between total mixed diet and stage of lactation for any of the short-term feeding behavior variables. Large differences in feeding behavior were detected between cows consuming the same total mixed diet. These last two findings suggest that the use of short-term feeding behavior variables to predict daily intake is unlikely to be successful.

Animal Feed↗
PubMed1993

Interactions between major nutrients in the diet and the lactational performance of rats.

The effect on lactational performance of replacing feed carbohydrate with fat at two different protein levels was studied. Lactating Sprague-Dawley rats with a standardized litter size of thirteen pups were allocated one of eight feeds containing either 300 or 150 g protein/kg organic matter (OM) and ranging in fat content from 100 to 550 g/kg OM from day 2 until day 14 of lactation. Daily food intake, live-weight gains, and changes in body composition of both dams and litters were measured. Feeds of low protein content resulted in a significant decline (P < 0.001) in lactational performance despite a significant increase (P < 0.001) in maternal protein mobilization. Maternal lipid mobilization was not significantly affected by feed composition. Litter lipid gain was significantly increased (P < 0.05) as fat replaced carbohydrate in the high-protein feeds, due to an increase in maternal energy intake. In contrast, lactational performance was severely depressed (P < 0.001) as fat replaced carbohydrate in the low-protein feeds. This interaction between feed components on lactational performance was in accordance with the hypothesis that the heat production of lactating rats is maximal and, hence, constraining intake.

Animals↗