Text|Little Tiger History Talk
Editor|Little Tiger History Talk
In many countries, the decline in the reproductive performance of livestock is a serious breeding problem. To shed light on Norwegian cattle, we studied trends in reproductive performance using insemination reports from 1985 to 2005 and data based on herd records from 1989 to 2005.
The herd and animal numbers decreased from 14.718 to 360.289 and 309.452 to 1989.2005, respectively. From 60 to 68 years, the rate of non-return of 1 day after a single insemination.
The NR0 was higher in summer and lower in RR3-1989 compared to the winter of the whole period. The fertility index is calculated based on herd records for each year from 2005 to 12. The average FS index did not show a significant trend and calving intervals were fairly stable between 4.12 and 6.79 months. The average interval from calving to first and last insemination increased from 102 days and 86 days in 1990 to 108 days and 6 days in 2005, respectively.
Herd records from 1989 to 2005 were obtained from the age of heifer first insemination, the average number of days from calving to first insemination and trends in last insemination, the number of animals fertilized, the interval between calves and the animals culled due to reproductive failure. During this period, the number of recorded herds decreased from 21.588 to 14.718 and the number of animals from 360.289 to 309.452. From 1989 to 2005, the fertility index, i.e. fertility status, for each herd was also calculated annually from herd record files.
The number of first inseminations every 5 is from 1985 to 2005. The main part of insemination was carried out with the semen of the Norwegian red variety, ranging from 97% in 1985 to 92% in 3.2003. Other breeds of semen are various beef breeds, mainly used in NRF cattle and other dairy breeds. Heifer age 1 year holy 15 years old insemination time as low as 6.1991 months.
The average CFI interval increased from 79 days in 1990 to 86 days in 2005. The CFI interval between cows during the initial lactation period has been longer than that of cows in the late lactation period, from 78 to 84 days and 1990 to 2005 days, respectively. During this period, the average CLI interval also increased from a low of 102 days in 1990 to 108 days in 2005. The CLI interval of the first lactating cow was also consistently longer than that of the second and later lactating cows, from 106 to 113 days and 99 to 104 days, respectively.
Trends regarding NR60 and RR0-3. Average NR60 increased significantly from 68% in 1.1985 to 73% in 2002 before dropping to 72% in 2005. RR0-3 increased from 6% in 1985 to 12% in 2005. NR60 has a seasonal variation every 5 thousand years from 1985 to 2005. NR60 is consistently higher in summer than in winter. However, the difference between the highest month in summer and the lowest month in winter has dropped significantly from 10% in 1985 to 5% in 7.2005.
Seasonal variation of RR1985-2005 every 5 years from the first to the third year. RR0-3 is consistently higher in winter compared to summer. RR0-3 in 2005 reached a high of 2.7% in May and fell to a low of 8% in January. The overall average national capacity assessment decreased from 1.6 in 1985 to 96,849.1 in 2005. The NIA of heifers, the lactation period and lactation >127252 cows of the control animals were 5.1, 8.1 and 7.0, respectively.
Data from 1989 to 2005 showed similar differences in NIA between heifers each year, with the mean FS index and calving interval of control animals from 1989 to 2005. The FS index varied between 59.3 (1989) and 63.3 (1998) and did not show a specific trend. Over the same period, the average calving interval between 12.4 and 12.6 months in controlled animals did not show a specific trend.
Percentage of fertilized animals culled due to poor fertility. This percentage decreased from 6% in 1989 to 4.6.199% in 1996 and then rose to 6% in 2005. The percentage of heifers is lower compared to mammals and the trend is slightly different, from 3 to 5 years 1989, the proportion of heifers has remained around 5% in 1989, then increased to a high level of 5% in 2003.
To describe fertility trends, a 60-day non-return rate and the number of servings per fertilized animal were used, among other things. As a measure of fertility, as described by Salisbury et al., the non-return rate has some drawbacks. Once inseminated, cows may be intentionally or unintentionally culled, die, or reproduce naturally without being recorded and shown in the record as not restoring the original insemination. On the other hand, cows that are in heat and fertilized during pregnancy will appear in the record as a return.
The registration system in Norway is also considered very reliable, since insemination is carried out by technicians and veterinarians employed by a company, Geno (Norwegian Association for Breeding and Artificial Intelligence), and at the time of insemination registration, reports of herders undergoing insemination may be somewhat incomplete, even if it should be done routinely as agreed. However, because herders did not inseminate before 2002 and accounted for only a small fraction of insemination since then, the incomplete report of this group is of little significance to the study.
Basically, the AI reporting procedure has not changed in the last few decades. Thus, a positive trend in non-return rates may reflect a real improvement in fertility. This trend is consistent with the phenotypic and genotypic trends that Andersen-Ranberg et al. studied heifer and naglowing cows. However, this is in stark contrast to the global trend of declining non-return and pregnancy rates over the past few decades, and the non-return rate of Norwegian cattle over the past few decades may also reflect a positive trend in pregnancy rates. Unfortunately, there is no reliable data to date to confirm the close trend relationship between these two parameters.
A recent Norwegian field study showed that pregnancy rates after a single insemination were, on average, about 60% lower than overall NR12. In this study, the overall pregnancy rate after a single first insemination of NRF was 60.7%, and these results suggest that NRF has a relatively high pregnancy rate compared to studies in many other countries.
The improvement in NR60 can be caused by a number of reasons, one of which is breeding strategies, which increasingly focus on fertility and health traits. In Norway, fertility was highlighted in the 1970s in the Total Merit Index, which was based on offspring testing using large subgroups of NRF varieties. Other reasons may be the different exercises and courses on herd management, nutrition and reproduction that veterinarians and agricultural consultants typically offer to farmers.
Since the mid-1980s, the incidence of ketosis has declined dramatically, which may be the effect of these activities. The reduction in ketosis may have a positive effect on NR60, as a reduction in NR20 non-return rates was found in cows treated for ketosis.
The successful bovine virus diarrhoeal virus (BVDV) eradication programme in Norway may also have contributed to the subsequent increase in NR950. BVDV infection is a notifiable disease in Norway. BVDV infection is associated with delayed resumption of services and other reproductive diseases. However, a Norwegian study found no indication for a reduced risk of conception.
The growth trend of CFI and CLI is likely to be mainly caused by management factors and farmer decisions. However, part of the cause may also be caused by tiny and undesirable genetic alterations in CFI, which have been observed in primary lactating cows. In this study, the genetic correlation between protein production during first lactation and CFI was very unfavorable.
There has been considerable positive genetic change in protein production in Norwegian cows. However, during this period, the average annual milk production per cow only increased from 5,716 kg to 6,541 kg. Genetically speaking, this breed has a higher milk production potential.
This may be mainly due to the fact that many high-priming cows are less able to meet their nutritional needs during peak lactation and therefore need more time to resume ovarian cycle activity and show estrus after delivery.
Compared to other studies, cows had relatively short CFI and CLI intervals for primary and late lactation, and the increase in both parameters was relatively modest during the study period. The use of double insemination is mainly caused by the problem of not finding the best time to insemination.
Farmers may realize that they are inseminating animals prematurely while in heat and therefore order a second insemination a day or two later. Farmers in particular who calves strictly seasonally rely on their cows to conceive quickly and can therefore use double insemination to get closer to the optimal time of estrus.
The use of twin insemination is more pronounced in winter than in summer. This can be caused by different environmental conditions, such as nutrient management, light intensity, and photoperiod in winter. Double insemination is usually performed after hormone therapy is used to induce or synchronize estrus.
According to Norwegian health card statistics, cows with a record of all milk kept their disease diaries in barns, and from 1980 to 1990 an increase in treatment of cows in heat was not observed. However, since 1990, the number of such treatments has declined, while the use of double insemination has not decreased at the same time.
Studies have shown that Norwegian summer has higher reproductive performance compared to winter. This is in stark contrast to the decline in fertility of fertilized cows in many countries with subtropical and tropical conditions during the hot summer months, and the opposite is true in Norway. It can be caused by a variety of environmental factors, including climatic conditions, light intensity, nutrition (grazing versus indoor rearing) and barns, which are different in relatively cold temperate climates.
Summer heat stress does not appear to cause fertility problems in Norway, but cold and dark winters may suppress ovarian activity and estrus and may increase embryonic mortality. However, the NR10 difference between the highest summer month and the lowest winter month fell from about 5% in 1985 to 6-6% in 2005. The improvement in winter reproductive performance over the years may be caused by a variety of factors, improved indoor seasonal nutrient management, and winter exposure of cattle at high latitudes to dim light with a minimum photoperiod of 12 hours.
Another factor may be the fertility rate of women selected for the NRF since 1972, the non-return rate. This leads to genetic improvement and may not be most beneficial to animals with high reproductive performance in winter. During the observation period, the FS index has been fairly stable, although NR60 first increased. This is mainly due to the increase in the average CLI interval that has a high impact in the FS formula.
This is also mainly caused by the increase in CLI intervals. The percentage of fertilized animals reported culled for poor fertility is based on information provided by farmers. This information may not be accurate because farmers may have different understandings of what low fertility is, and if cows are culled for a combination of different reasons, the main cause may be reported more or less incidentally.
From 1989 to 1998, the decline in the percentage of animals culled due to low fertility was consistent with the increase in non-return over the same period, and the consequent increase in culling was not commensurate with the non-return rate. The proportion of cows culled due to poor fertility in Norway was 12% in 2005. This proportion was relatively low compared to other studies.
conclusion
Most fertility indicators of Norwegian cattle, mainly NRF breeds, have shown relatively high reproductive performance and positive (NR60, NIA) or relatively constant trends (calving interval, FS index) over the past two decades. This can be caused by a number of reasons, one of which is the breeding strategy, which places increasing emphasis on fertility and health characteristics.
During this period, the interval from calving to the first and last insemination increased slightly, respectively, and RR0-3 increased. Despite an increase in non-return rates and a decrease in the number of servings per fertilized animal, calving intervals are relatively stable, mainly because of the longer interval from calving to first insemination. This is the main reason why the FS index has been relatively stable. Compared to many countries in subtropical and tropical conditions, Norway has higher reproductive performance in summer than in winter.
bibliography
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