Results and Evaluation of Thirty Years of Health Recordings in the Norwegian Dairy Cattle Population

The results are based on the Norwegian Cattle Health Recording System, which has been in place for the entire country since 1975. The dairy breeds in Norway consist of 94% Norwegian Red and 4% crossbreeds with Norwegian Red. No other breed consists of more than 0.5% of the total population. During the past 30 yr, there have been 11,563,692 dairy cows within the recording system, corresponding to 8,633,532 cow-years and 8,632,516 calvings. This population consisted of 3,038,675 first-calving cows. Altogether, 8,435,704 different diagnoses were recorded from 4,444,485 different cows each year. The general trend for all recordings was an increase in the incidence rate of all cases from 0.74 per 365 d at risk (cow-year) in 1976 to 1.36 in 1990, and then a decrease to 0.62 in 2002. The corresponding figures for cows treated per cow-year were 0.44 up to a maximum of 0.82, and then a decrease to 0.46 per cow-year in 2002. The most common diseases were acute (severe to moderate) clinical mastitis, chronic (mild) clinical mastitis, ketosis, milk fever, teat injuries, retained placenta, silent heat or anestrous, indigestion, cystic ovaries, and metritis. Clinical mastitis increased from 0.15 cows treated per cow-year in 1975 to 0.44 in 1994, and then decreased to 0.23 in 2002. Ketosis began at 0.10 in 1975, increased to 0.24 in 1985, and then decreased to 0.05 in 2005. For several of the most common diseases, there was a reduction of more than 50% from the 1990s to the years after 2000. Validation processes confirmed that this fluctuation reflected the general trend in the population. The disease recording system also reflected the known outbreaks of bovine respiratory syncytial virus during 1976, 1989 to 1990, and 1995. A marked increase in malformation diagnoses could be seen in 1986 and in 1989 and 1990. These could be related to the Chernobyl nuclear power plant accident in April 1986. The diagnosis that showed the most stability throughout these 30 yr was retained placenta. The 3 main reasons for the large fluctuation for many of the diseases could be the following: a breeding effect, an effect of preventive work, and an effect of changing the therapeutic attitude. Many of the actions taken to bring about improvements would not have been possible without a functioning and practical recording system. Our experience is that an organ-related diagnosis system with up to 60 or 70 different diagnoses will meet the needs of the dairy industry.

Bovine Claw and Limb Disorders at Claw Trimming Related to Milk Yield

As part of a cross-sectional study of Norwegian Red Cattle, associations of lameness, lesions at the tarsus, claw shapes, claw lesions, and claw trimming with milk yield were examined. Fifty-five tie-stall herds and 57 free-stall herds were sampled by computerized systematic selection, and 2,665 cows were trimmed and limb and claw disorders recorded. After exclusions, 2,599 cows were included in this study. Monthly recordings of milk were extracted from the Norwegian Dairy Herd Recording System. Most claw lesions were mild (score 1). The prevalence of moderate and severe lesions (score 2 and 3) did not exceed 5% for any of the lesions. Associations with test-day milk yield were identified using regression analyses (Proc Mixed) with repeated measurements within lactation and herd as random effect. Lactation curves were fit to visualize differences in changes in milk yield throughout the lactation. Milk yield was generally higher in cows with lesions at the tarsus, heel-horn erosions, and hemorrhages of the white line and the sole than in cows without these lesions, whereas cows with dermatitis yielded less than cows without dermatitis. Cows in lactation 1 with corkscrewed claws had reduced milk yield, whereas cows in lactations 2 and above had increased milk yield compared with cows without corkscrewed claws in respective lactations. Cows in lactation 1 yielded 0.47 +/- 0.15 kg and cows in later lactations yielded 0.51 +/- 0.15 kg more milk on test days after claw trimming than they did before when adjusted for days in milk. In this study, where most disorders were mild, the most evident results were higher milk yield in cows with lesions at the tarsus, heel-horn erosions, and hemorrhages of the white line and the sole than in cows without these lesions. Cows yielded more milk after claw trimming than they did before trimming.

Progesterone concentrations in milk fat at first insemination--effects on non-return and repeat-breeding

The relationship between milk fat progesterone concentration at first artificial insemination (AI) and reproductive performance of Norwegian Red Cattle dairy cows was investigated in a field study. Fifteen AI technicians collected milk samples from 2250 cows from 458 herds and progesterone was analysed in the milk fat portion of the samples. Logistic regression revealed decreased probability of non-return, and increased likelihood of repeat-breeding, with increasing progesterone concentrations at insemination. The odds ratio for non-return and for repeat-breeding between the minimum and maximum value for milk fat concentrations between 4 and 32.2ng/ml was 4.5 (P < 0.01) and 3.2 (P = 0.01), respectively. The variable 'Technician' did not significantly influence non-return rate or repeat-breeding. Progesterone concentration at AI was positively related to calving to last insemination interval, and to number of inseminations per cow (P < 0.05). The association between the progesterone concentration at insemination and calving interval was only marginally significant. Technician was significantly (P < 0.01) associated with interval from calving to first AI, interval from calving to last AI (P = 0.05), and number of AI per cow (P = 0.01). Technician was not significantly related to the calving interval. We conclude that increased suprabasal progesterone concentrations at the time of first insemination, and higher return rate at AI may, at least partly, be due to endocrinological asynchrony at AI, a condition which may lead to decreased fertility.

To treat or not to treat: a proper use of hormones and antibiotics

Hormones and antibiotics are important remedies in animal reproduction. Compared to other areas of application, hormones are probably more used than antibiotics. The quantities of hormones applied in cattle reproduction are largely dependent on whether these drugs are extensively used for pharmaceutical control of breeding or not. Diseased animals should be treated both from an animal welfare point of view and to restore their production capacity. The treatment should be based on an accurate diagnosis. Some of the treatment methods used in animal reproduction do not seem to be well documented. When using antibiotics, it should be known that an infectious agent is present which will be susceptible to therapy. The use of hormones and antibiotics to solve or mask managerial problems should be avoided. Ideally, fertility and health traits should be included in a breeding programme. Therefore, all diagnoses and treatments performed should be recorded and these data made available for breeding purposes. Manipulation of the breeding cycle by pharmaceutical means should not disturb the natural reproductive performance of animals being progeny tested. Animal health and fertility should be improved by selection and good management rather than by extensive use of hormones and antibiotics. Cases of inappropriate use of pharmaceutical preparations have created a general scepticism among people concerning the use of hormones and antibiotics in modern farming. Evidence of increasing resistance to antibiotics in bacteria infecting humans has focused on the role that anti-microbial drug use in food-producing animals plays in the emergence of resistant bacteria. There is also a concern about possible residues in animal products. Further, the consumers have a growing interest in animal health and animal welfare issues, and they have ethical concerns regarding the use of hormones and antibiotics, in particular, as performance enhancers. In Europe, the number of farmers growing organically cultivated foodstuffs is increasing, and according to the regulations for organic farming, the use of hormones and antibiotics is limited. Even though the proper use of hormones and antibiotics does not have any known negative effect on animal welfare or public health, the consumers' concerns have to be taken into account in livestock production.

Use of semen from a bull heterozygous for the translocation in an IVF program

In cattle, a translocation of the Robertsonian type between the largest and smallest chromosome leads to a reduction in fertility. This is substantiated by reduced nonreturn rates in daughter groups of bulls carrying the 1 29 translocation and in the heterozygous bulls themselves. This reduction in fertility is thought to be due to the early death of embryos with unbalanced karyotypes. The influence of semen from a bull known to be heterozygous for the 1 29 translocation on the outcome of a bovine IVF program was investigated. There was a significant difference (P<0.005) in terms of cleavage rate (59.8 vs 71.1%) and blastocyst rate (12.0 vs 20.0%) between the carrier and control bull, respectively. There was no difference in blastocyst quality as measured by cell number. The results observed in vitro are consistent with the field fertility records of the 2 bulls in terms of nonreturn rates (59.2 vs 70.6%, for the carrier and control bull, respectively).

Immune function in dairy cows related to energy balance and metabolic status in early lactation

Two feeding experiments were carried out in 2 successive years with 28 cows of the Norwegian Red Cattle (NRF) in each experiment. The cows were randomly distributed into 4 groups and subjected to different feeding regimens from 1 month prior to calving until 12 weeks after calving. The experimental design was factorial (2 x 2) with respect to protein content of the concentrate (17.5% digestible crude protein (DCP) v.s. 12.5% DCP) and concentrate allowances (standard v.s. substandard allowances after calving). Silage was offered ad libitum. Samples for estimation of serum immunoglobulin-G, white blood cells and lymphocyte responses to the mitogens phytohemagglutinin, concanavalin A and pokeweed mitogen were collected 4 weeks prior to expected calving, and 2, 4 and 8 weeks after calving. The levels of milk immunoglobulin-G were estimated at calving and 2, 4 and 8 weeks after calving. A significant positive relationship was found between the estimated energy balance and the lymphocyte response to mitogens. Little evidence was found for the existence of a significant relationship between the immunologic parameters and plasma indicators of metabolic status. The lymphocyte response to phytohemagglutinin and levels of serum immunoglobulin-G increased, while levels of milk immunoglobulin-G decreased during the period from calving to 8 weeks after calving. Increased milk somatic cell counts were associated with a significant decrease in the lymphocyte responses to mitogens.

Levels of milk urea, plasma constituents and rumen liquid ammonia in relation to the feeding of dairy cows during early lactation

The study was undertaken to establish the relationships between milk and plasma urea levels and protein supply, using traditional and new measures of feed protein value. Samples of milk and plasma were taken before morning feeding twice weekly for the first 3 months post partum from 21 multiparous cows and 7 heifers. Samples of rumen fluid were collected every second week. The cows were distributed into 4 different feeding groups. Feeding regimens were factorial with respect to protein content of the concentrates (i.e. Low protein (Lp): 12.5% digestible crude protein (DCP) vs. High protein (Hp): 17.5% DCP) and concentrate allowances (i.e. Low energy (Le): substandard vs. High energy (He): standard). Silage was offered ad libitum. The within-animal coefficients of correlation between milk and plasma urea levels, and between milk urea levels and the levels of ammonia in the rumen fluid wer r = 0.88 (p less than 0.001) and r = 0.75 (p less than 0.001), respectively. Analysis of variance showed the following sources of urea variation to be significant: Protein balance in the rumen (PBV), intake of DCP, intake of amino acids absorbed in the intestine (AAT), intake of fattening feed units, and the individual animal factor. A similar tendency was found for the variation of ammonia in rumen fluid. The coefficients of determination (R2 model) were not increased by introducing protein balance (BADCP), the amount of PBV and AAT in the dry matter ingested, or the protein/energy ratio as alternative parameters of protein intake in the models. The levels of protein or energy intake did not significantly influence the levels of plasma albumin. The correlations between urea levels and other plasma indicators of metabolic status and liver function were generally low.

Variations in parameters of liver function and plasma progesterone related to underfeeding and ketosis in a dairy herd

Twenty-eight Norwegian Red Cattle dairy cows were fed silage ad libitum and restricted amounts of concentrates. Blood samples were collected before morning feeding, once or twice weekly, from 2 weeks before to 12 weeks after calving. Parameters of liver function, carbohydrate status and fertility were recorded in order to assess their interrelationships. Eight cows were treated for clinical ketosis. Four of these had to be treated 2 or 3 times. Aspartate aminotransferase and bilirubin showed the highest within-animal coefficients of correlation with acetoacetate. Analysis of variance revealed a significant effect of carbohydrate status (indicated by plasma acetoacetate levels) on the levels of aspartate aminotransferase, glutamate dehydrogenase and sorbitol dehydrogenase, though only a small part of the total variation was explained by this factor. The estimated volume density of liver fat in the 4th week of lactation averaged 6.0 +/- 6.4% (+/- SD) ranging from 0.1-25.1%. Liver fat content at this stage of lactation was not significantly correlated with other indicators of liver function or carbohydrate status. Cows treated for clinical ketosis had significantly lower plasma progesterone values at the time of first ketosis treatment than untreated multiparous cows. The frequency of high progesterone values (greater than 3 ng/ml) being significantly lower in treated than in untreated cows during the period from 3-5 weeks post partum, though not at later stages. In conclusion, the results revealed a significant relationship between carbohydrate status and liver function, and also between clinical ketosis and luteal function.

Variations in parameters of liver function and plasma progesterone related to underfeeding and ketosis in a dairy herd

Twenty-eight Norwegian Red Cattle dairy cows were fed silage ad libitum and restricted amounts of concentrates. Blood samples were collected before morning feeding, once or twice weekly, from 2 weeks before to 12 weeks after calving. Parameters of liver function, carbohydrate status and fertility were recorded in order to assess their interrelationships. Eight cows were treated for clinical ketosis. Four of these had to be treated 2 or 3 times. Aspartate aminotransferase and bilirubin showed the highest within-animal coefficients of correlation with acetoacetate. Analysis of variance revealed a significant effect of carbohydrate status (indicated by plasma acetoacetate levels) on the levels of aspartate aminotransferase, glutamate dehydrogenase and sorbitol dehydrogenase, though only a small part of the total variation was explained by this factor. The estimated volume density of liver fat in the 4th week of lactation averaged 6.0 +/- 6.4% (+/- SD) ranging from 0.1-25.1%. Liver fat content at this stage of lactation was not significantly correlated with other indicators of liver function or carbohydrate status. Cows treated for clinical ketosis had significantly lower plasma progesterone values at the time of first ketosis treatment than untreated multiparous cows. The frequency of high progesterone values (greater than 3 ng/ml) being significantly lower in treated than in untreated cows during the period from 3-5 weeks post partum, though not at later stages. In conclusion, the results revealed a significant relationship between carbohydrate status and liver function, and also between clinical ketosis and luteal function.

Levels of milk urea, plasma constituents and rumen liquid ammonia in relation to the feeding of dairy cows during early lactation

The study was undertaken to establish the relationships between milk and plasma urea levels and protein supply, using traditional and new measures of feed protein value. Samples of milk and plasma were taken before morning feeding twice weekly for the first 3 months post partum from 21 multiparous cows and 7 heifers. Samples of rumen fluid were collected every second week. The cows were distributed into 4 different feeding groups. Feeding regimens were factorial with respect to protein content of the concentrates (i.e. Low protein (Lp): 12.5% digestible crude protein (DCP) vs. High protein (Hp): 17.5% DCP) and concentrate allowances (i.e. Low energy (Le): substandard vs. High energy (He): standard). Silage was offered ad libitum. The within-animal coefficients of correlation between milk and plasma urea levels, and between milk urea levels and the levels of ammonia in the rumen fluid wer r = 0.88 (p less than 0.001) and r = 0.75 (p less than 0.001), respectively. Analysis of variance showed the following sources of urea variation to be significant: Protein balance in the rumen (PBV), intake of DCP, intake of amino acids absorbed in the intestine (AAT), intake of fattening feed units, and the individual animal factor. A similar tendency was found for the variation of ammonia in rumen fluid. The coefficients of determination (R2 model) were not increased by introducing protein balance (BADCP), the amount of PBV and AAT in the dry matter ingested, or the protein/energy ratio as alternative parameters of protein intake in the models. The levels of protein or energy intake did not significantly influence the levels of plasma albumin. The correlations between urea levels and other plasma indicators of metabolic status and liver function were generally low.

Thyroxine in blood plasma related to plasma levels of acetoacetate and glucose in ketotic and healthy cows

Plasma samples were taken before morning feeding twice weekly for the first 3 months post partum from 28 individually fed cows, of which 8 developed clinical ketosis. Feed rations consisted of grass silage ad libitum and concentrates. The high incidence of ketosis may be accounted for mainly by substandard amounts of feed energy, and by variations in the quality of the grass silage. The following sources of post-partum thyroxine variation were found to be statistically significant (p less than 0.001): The individual cow, the individual pre-calving thyroxine level, metabolic status estimated by plasma levels of acetoacetate or glucose, and elapsed time from partus. The post-partum decrease in thyroxine was greater in cows which developed ketosis (55%) than at the corresponding stage of lactation in those which remained moderately ketonaemic (33%). Extensive overlapping of ranges nevertheless indicates that the apparent hypothyroidism of ketosis is of limited importance for the etiology of the disease. Susceptibility to ketosis was not related to the thyroxine levels observed before partus or after recovery from the disease, in the third month of lactation. Evidence was obtained of a common glucose threshold of about 3.6 mmol/l, below which decreasing sugar levels were accompanied by progressive increments in acetoacetate and decreases in thyroxine. Above the threshold level, the average level of the hormone increased from the first to the third month of lactation in spite of a poor correlation to glucose.

Immune function in dairy cows related to energy balance and metabolic status in early lactation

Two feeding experiments were carried out in 2 successive years with 28 cows of the Norwegian Red Cattle (NRF) in each experiment. The cows were randomly distributed into 4 groups and subjected to different feeding regimens from 1 month prior to calving until 12 weeks after calving. The experimental design was factorial (2 x 2) with respect to protein content of the concentrate (17.5% digestible crude protein (DCP) v.s. 12.5% DCP) and concentrate allowances (standard v.s. substandard allowances after calving). Silage was offered ad libitum. Samples for estimation of serum immunoglobulin-G, white blood cells and lymphocyte responses to the mitogens phytohemagglutinin, concanavalin A and pokeweed mitogen were collected 4 weeks prior to expected calving, and 2, 4 and 8 weeks after calving. The levels of milk immunoglobulin-G were estimated at calving and 2, 4 and 8 weeks after calving. A significant positive relationship was found between the estimated energy balance and the lymphocyte response to mitogens. Little evidence was found for the existence of a significant relationship between the immunologic parameters and plasma indicators of metabolic status. The lymphocyte response to phytohemagglutinin and levels of serum immunoglobulin-G increased, while levels of milk immunoglobulin-G decreased during the period from calving to 8 weeks after calving. Increased milk somatic cell counts were associated with a significant decrease in the lymphocyte responses to mitogens.

Postpartum reproductive performance in dairy cows in relation to phosphorus status

The levels of inorganic phosphorus in blood samples from two cow populations were related to reproductive performance. Group I comprised 305 dairy cows from 17 herds with normal fertility. The herds were visited every 2–4 weeks. Blood samples were collected from animals between 4 weeks prior to expected calving and subsequent confirmed pregnancy.

The individual mean plasma phosphorus level in samples collected from 0–90 days after calving in cows which conceived following insemination (n = 262) was related to reproductive performance.

Group II comprised cows from 47 herds with reproductive problems. The herds were visited once during the indoor season for blood sampling. Mean herd serum phosphorus levels were related to herd reproductive performance registered during a period from 6 months before to 9 months after the time of blood sampling. Overall mean herd phosphorus levels were 1.51 ± 0.08 mmol/1 plasma (±SD) (Group I) and 1.77 ± 0.16 mmol/1 serum (±SD) (Group II). In Group I (indivu-dual cows), the coefficient of correlation between phosphorus levels and elapsed time from calving to pregnancy was low (r = 0.10, p<0.1). In Group II (herds) significant correlations were observed between the fertility status index (FS), the average number of days from calving to last insemination and phosphorus levels (rs = 0.32, P <0.05 and rs p <0.05, respectively).

The mean herd phosphorus levels were within normal limits in both groups. Although increased phosphorus levels were associated with lower fertility in both groups, the amount of the total fertility variation which could be explained by phosphorus levels was small.

Herd reproductive performance related to urea concentration in bulk milk

Bulk milk samples were collected from 256 dairy herds from 4 districts in Southern Norway: Gudbrandsdal (n = 35), Bergen (n = 15), Hedmark (n = 117) and Hardanger (n = 89).

A total of 6–8 samples were collected in each herd during the indoor season. Data concerning reproductive performance, milk production and nutrition were registered for a period of 15 months starting 7 months before the first milk sample was collected. The urea levels obtained during the sampling period were averaged generating a mean urea level of each herd. The mean urea levels were related to reproductive performance.

The urea levels within districts showed only minor variations during the sampling period. The mean urea level in Hardanger was significantly higher (p < 0.05) than in the other distrikts. This district also had the lowest fertility. Significant correlations between mean urea level and fertility were observed only in Hedmark. Fertility status (FS), an integrated index, and number of inseminations per animal inseminated were significantly affected by the interaction between mean urea level and district. Herds in Hardanger with cows treated for ovarian cysts had a significantly higher mean urea level (p = 0.02) than herds with non-treated cows.

The results appear to support the notion that a negative relationship may exist between bulk milk urea levels and reproductive performance. The great district variations observed indicate, however, that the practical value of such measurements is limited.

Urea concentration in bulk milk as an indicator of the protein supply at the herd level

Levels of urea in bulk milk from 80 herds were analysed twice monthly during 1 year to study herd variations and effect of season (Experiment 1). The overall (mean ± s) was 4.7 ± 1.3 mmol/1 ranging from 1.4 to 10.0 mmol/1. Generally, the urea levels were high in summer and early autumn and during this period there were 3 peaks, the first one at the beginning of June, the second one in the middle of July and the third one at the end of September. The peaks reflected feed changes and use of fertilizers commonly practized in the area.

In another study samples of bulk milk were obtained from 49 herds using single forage diets with fresh grass silage and standardized concentrate mixtures (Experiment 2). In these herds all feed components given on the day of urea sampling were weighed as accurately as possible and a sample of the silage was taken for chemical analyses and determination of in vitro digestibility. Mean level of crude protein (CP) in silage dry matter was 15.6 ± 2.2 % and average dietary digestible crude protein (DCP) per feed unit (FU) was 146 ± 16 g. In all herds the protein levels in the total daily ration were equal to or above recommended standards. Urea concentration in bulk milk was significantly affected by the GP content in silage, level of dietary DGP and amount of DCP/FU. In energy deficient herds relatively high urea values were obtained without any great surplus of protein. Yield did not significantly affect the urea concentration in bulk milk.

Low fertility in daughters of bulls with 1/29 translocation

Non-return rates at different stages after insemination were compared in daughters (n = 21,212) of five translocation heterozygous sires with all cows and heifers (n = 610,714) represented in the Norwegian Red Cattle (NRF) breeding statistics during the period October 1970 to September 1972. The daughters of the carrier bulls showed statistically significant lower non-return rates for 0–30, 30–60, 60–90, 90–120, 120–150, 150–180 and 180–270 days as compared with the control animals. The decline in non-return percentage for the daughters of translocation sires was greater than in the control animals during the period from 0–30 to 60–90 days indicating higher losses of fetuses during the early period after insemination.

Daughter groups of carrier bulls consisting of adult cows only showed higher non-return rates than groups comprising both cows and heifers.

Urinary excretion of oestrone and oestradiol-17alpha in cows with cystic ovaries

Using a method comprising fluorimetry the urinary excretion of oestrogens was determined daily for an extended period of time in two cows with ovarian cysts. The excretion patterns were characterized by wide peaks separated by relatively narrow minima spaced over 2–4 weeks. During the repetitive periods of high excretion rates the urinary contents of oestrone as well as of oestradiol-17α were considerably larger than those associated with an ovulatory follicular phase in normal cows.

The oestrogen excretion in the abnormal animals decreased to low levels after ovariectomy which was performed after an observation period of about 10 weeks.

Plasma progesterone in gilts during the prepuberal period and the first oestrous cycle

The progesterone concentration of peripheral plasma in pigs has previously been studied during the oestrous cycle and in early pregnancy (Tillson & Erb 1967, Stabenfeldt et al 1969). The present study was undertaken to obtain some information on the concentration of plasma progesterone during the prepuberal period and during the first oestrous cycle in the pig.