Bivariate analysis of conception rates and test-day milk yields in Holsteins using a threshold-linear model with random regressions

Genotype by environment interactions on culling rates and 305-day milk yield of Holstein cows in 3 US regions

Abstract. The objective of this study was to estimate genetic parameters for milk yield and milk percentages of fat and protein in Iranian buffaloes. A total of 9,278 test-day production records obtained from 1,501 first lactation buffaloes on 414 herds in Iran between 1993 and 2009 were used for the analysis. Genetic parameters for productive traits were estimated using random regression test-day models. Regression curves were modeled using Legendre polynomials (LPs). Heritability estimates were low to moderate for milk production traits and ranged from 0.09 to 0.33 for milk yield, 0.01 to 0.27 for milk protein percentage and 0.03 to 0.24 for milk fat percentage, respectively. Genetic correlations ranged from −0.24 to 1 for milk yield between different days in milk over the lactation. Genetic correlations of milk yield at different days in milk were often higher than permanent environmental correlations. Genetic correlations for milk protein percentage ranged from −0.89 to 1 between different days in milk. Also, genetic correlations for milk percentage of fat ranged from −0.60 to 1 between different days in milk. The highest estimates of genetic and permanent environmental correlations for milk traits were observed at adjacent test-days. Ignoring heritability estimates for milk yield and milk protein percentage in the first and final days of lactation, these estimates were higher in the 120 days of lactation. Test-day milk yield heritability estimates were moderate in the course of the lactation, suggesting that this trait could be applied as selection criteria in Iranian milking buffaloes.

Genetic Parameter Estimation for Milk Yield over Multiple Parities and Various Lengths of Lactation in Danish Jerseys by Random Regression Models

The objective of this study was to assess the health status and the most common health problems occurring in beef cattle in the Czech Republic. Thirty five beef herds of different breeds were monitored from 1 January to 31 December 2006. The health status of 4872 animals (2601 cows and 2271 of their calves) was analyzed. Herds of up to 50 cows and those over 50 cows were evaluated both separately and together. Farm management data were collected by means of a questionnaire completed by the farmers. Both geographic and herd characteristics were evaluated, as well as the course of calving, mortality and morbidity in calves, and disease occurrence in cows. Calving was unassisted in about 80% of the cows, and the conception rate was approximately 90%. More difficult courses of calving were reported from the small herds than from the large ones (p < 0.001). Total calf losses were 10% on the average. Most calf deaths occurred during the first week of life (p < 0.01), the most common cause of death being diarrhoea (p < 0.001). The situation was similar in large and small herds. Diarrhoea was also most often diagnosed in those calves that survived the early life stage. At the age of 120 days, the calves that had suffered from diarrhoea showed a lower body weight by 12.6 kg than the calves of the same age from the same herd that did not have diarrhoea. The occurrence of diarrhoea in small and large herds was 12.1% and 6.7% per herd, respectively (p < 0.05). Also, other health disorders were more often reported from small herds, in calves as well as in adult cows (p < 0.001).

A descriptive study of teat morphology, milking machine characteristics, and milking practices in a sample of Brazilian dairy herds.

How do free-ranging domestic herbivores reduce competition within owner-determined herds?

Bovine viral diarrhoea (BVD) is a worldwide viral cattle disease. Percentage of seropositive animals, especially in the countries with intensive cattle breeding ranges from 60-90%. This infection on our epizootiology area, as well as on area in our surrounding, was for the first time described by OEuriåkoviñ et al. (1966) based on clinical pictures and pathomorphological findings. This was proved by antibody detection by Cvetnić et al. (1968). In the last few years a large number of serology examination was done on the presence of BVDV infection in our area. In 2004 an examination on virus neutralisation antibodies in sera of breeding dairy cattle older than 6 months was carried for the purpose of determining the prevalence of BVDV infection in large and small herds in Southern Bačka and Srem districts. There were 7577 sera samples from small herds, out of which 3457 were from Southern Bačka (26.31% out of total population in all 9 municipalities), and there were 4120 samples from Srem district (25.17% out of total population in all 8 municipalities). The examination included the animals from all settlements (156). From large cattle herds there were 3019 sera samples, out of which 2721 were from 18 large farms in Southern Baåka (38.65% out of total population), and 298 from 4 large farms in Srem district (29.22% out of total population). This examination encompassed animals from 22 large farms on this area. Virus neutralisation test (VN) was carried out according to the standard procedure described in ’’Manual of Diagnostic Tests and Vaccines for Terrestrial Animals’’ Office International des Epizooties (2004) with slight modifications. For test NADL strain of BVD virus and MDBK cell culture were used. The sera were examined in double dilution from 1:2 to 1:512. Virus neutralisation antibodies for NADL strain BVDV were detected in 1833 (24.19%) in the samples from small herds. Out of this number there were 1082 (31.30%) seropositive animals from Southern Baåka and 751 (18.53%) from Srem district. The largest number of seropositive animals in Southern Baåka district were detected in Titel municipality (68.07%) and the lowest in Bački Petrovac municipality (6.63%). In Srem district the largest number of seropositive animals was in Beoåin municipality (34.16%) and the lowest in Irig municipality (7.62%). When comparing all the settlements, the percentage of BVDV seropositive animals ranged from 0% (i.e. settlements with no seropositive animals) up to 86.67% (Krnjeãevci). Virus neutralisation antibodies for BVDV NADL strain were detected in 1667 (55.22%) samples from large cattle herds. Out of this number there were 1500 (55.13%) seropositive animals from Southern Bačka, and 167 (56.04%) seropositive animals from Srem district. The prevalence of seropositive animals in large herds from Southern Baåka district ranged from0%(5 large herds) up to 96.61%. High prevalence (70%) was detected in 7 out of 18 examined herds. The prevalence of seropositive animals originating from large herds in Srem district ranged from 0% (1 large herd) to 96.96%. High prevalence (70%) was detected in 2 out of 4 examined herds. Detected variation in the percentage of seropositive animals in some areas and herds most probably is the result of animal origin and management on the farms, i.e. movement of animals with introduction of new animals into a herd, what also means that the virus enters into a herd and outbreaks of BVDV infection occur. The titre ofVNantibodies in a certain number of animals, especially on certain areas and in some herds ranged up to 1:512 and even more, what was a clear indication of current or recent presence of persistently infected animals in these herds. High percentage of seropositive animals (70%) in 9 large herds most probably is the result of uncontrolled animal movement, entering of BVD virus and frequent outbreaks of BVDV infections in these herds, but this also indicates probable presence of persistently infected animals in the herds. The obtained results point on high prevalence of BVD infection in the examined area. This prevalence is not equal, what point on existence of areas where the infection is not present, or is present only sporadically.

Opinions and Practices of Wisconsin Dairy Producers About Biosecurity and Animal Well-Being

Genetic parameters of milking frequency and milk production traits in Canadian Holsteins milked by an automated milking system

Genetic and phenotypic parameters of lactations longer than 305 days (extended lactations)

Simple SummaryParatuberculosis is widespread in cattle throughout the world and is an economically important disease, especially in dairy cattle. It is caused by Mycobacterium avium subsp. paratuberculosis and is problematic due to complex transmission and unreliable diagnostic tests. The disease is present in Slovenia, where milk production is one of the most important sectors of agriculture. Our aim was to understand the disease spread in a typical Slovenian dairy herd of about 17 cows. To our knowledge, this is the first study specifically looking at the dynamics of disease spread in a small dairy herd. We relied on real data from the competent authorities on herd structure and data from the literature on disease spread, as well as expert opinion. The results showed that herd size has an influence on disease spread and that the prevalence in a small herd is probably lower than in larger herds because farmers tend to sell and buy animals frequently, which allows for the elimination of diseased animals from small herds. However, this can also reintroduce the disease into the herd. The results suggest that different assessments should be used to study the spread and control of this disease in herds of different sizes.This study aimed to investigate the possible dynamics of paratuberculosis or Johne’s disease in a typical Slovenian dairy herd of about 17 cows. Paratuberculosis is a worldwide endemic disease of cattle caused by Mycobacterium avium subsp. paratuberculosis (MAP) and is associated with significant economic losses. We developed a stochastic compartmental model with two pathways of disease progression, infections of adult cows and infections of young animals through horizontal and vertical transmission, and transmission through animal movements. The average proportions of subclinically and clinically infected cows were 4% and 0.47%, respectively. The prevalence within the herd, which included latently infected animals, averaged 7.13% and ranged from 0% to 70.59%. Under the given circumstances, the results showed a relatively high rate of spontaneous elimination (0.22 per herd per year) of the disease and a high rate of reinfection (0.18 per herd per year) facilitated by active animal trade. To our knowledge, this stochastic compartmental model is the first to be developed specifically to represent a small dairy herd and could apply to other countries with a similar structure of dairy farms. The results suggest that different models should be used to study MAP spread in herds of various sizes.

Fertility in dairy cows has decreased over the last fifty years while milk production per cow has increased. Furthermore, dairy herds become larger resulting in fewer employees per cow, which might also influence reproductive performance. To elucidate the situation in Germany, selected parameters (conception rate, service rate, pregnancy rate, days to first insemination and days open) were studied using data on 148 herds. For statistical analysis the herds were categorized concerning milk yield: (1) < 30 kg, (2) 30‒35 kg, and (3) > 35 kg/cow/day as well as concerning herd size: (1) < 200, (2) 200‒400, (3) 400‒1000 and (4) > 1000 milking cows. There was no difference in conception rate among herds. That means on dairy farms of larger size or with high milk yield the chance of an inseminated cow to become pregnant is the same as in small herds or in herds with low milk yield. Small herds (< 200 cows) had lower pregnancy rates than larger herds (200–400 cows). The pregnancy rate in herds with different milk yield was not statistically different. Though there was a trend that dairy farms with higher milk yield (> 30 kg) had higher pregnancy rates. The statistical differences and trends of pregnancy rates are due to higher service rate in larger herds as well as in herds with high milk yield. Therefore, service rate is the key factor for high reproductive performance on dairy farms. Poor fertility is not associated with high milk yield on herd basis or large herd size but may represent inappropriate farm management.

South Africa implemented test-day models for genetic evaluations of production traits, using a Fixed Regression Test-Day Model (FRTDM), which assumes equal variances of the response variable at different days in milk, the explanatory variable. Data at the beginning and at the end of lactation period, have higher variances than tests in the middle of the lactation. Furthermore, first lactations have lower mean and variances compared to second and third lactations. This is a deviation from the basic assumptions required for the application of repeatability models. A modification was therefore implemented to reduce the effect of deviating from this assumption. Test-day milk, butterfat and protein yield records of Jersey cows, participating in the South African Milk Recording Scheme, were therefore pre-adjusted such that the variances are on the same scale. Variance components estimated using the adjusted records were higher than using unadjusted records. Convergence of breeding value estimation is reached significantly faster when using adjusted data (± 4000 iterations) compared to unadjusted records (± 15 000 iterations). Although cow and bull rankings were not influenced much, significant changes in breeding values for individual animals and genetic trends of especially young animals, were found. South African Journal of Animal Science Vol. 36(3) 2006: 165-174

A random regression model was applied for the first time for the analysis of test day records and to study the genetic persistency of first lactation milk yield of Indian Murrah buffaloes.Wilmink's Function was chosen to describe the shape of lactation curves.Heritabilities of test day milk yield varied from 0.33 to 0.58 in different test days.The highest heritability was found in the initial test day (5 th day) milk yield.Genetic correlations among test day milk yields were higher in the initial test day milk yield and decreased when the test day interval was increased.The magnitude of genetic correlations between test day and 305 day milk yield varied from 0.25 to 0.99.The genetic persistencies of first lactation milk yield were estimated based on daily breeding values using two methods.P 1 is the genetic persistency estimated as a summation of the deviation of estimated daily breeding value on days to attain peak yield from each day after days to attain peak yield to different lactation days.P 2 is the genetic persistency estimated as the additional genetic yield (gained or lost) from days to attain peak yield to estimated breeding value on different lactation days relative to an average buffalo having the same yield on days to attain peak yield.The mean genetic persistency on 90, 120, 180, 240, 278 and 305 days in milk was estimated as -4.23, -21.67, -101.67,-229.57,-330.06 and -388.64,respectively by P 1 , whereas by P 2 on same days in milk were estimated as -3.96 (-0.32 kg), -23.94 (-0.87 kg), -112.81 (-1.96 kg), -245.83(-2.81 kg), -350.04 (-3.28 kg) and -407.58(-3.40 kg) respectively.Higher magnitude of rank correlations indicated that the ranking of buffaloes based on their genetic persistency in both methods were similar for evaluation of genetic persistency of buffaloes.Based on the estimated range of genetic persistency three types of genetic persistency were identified.Genetic correlations among genetic persistency in different days in milk and between genetic persistencies on the same day in milk were very high.The genetic correlations between genetic persistency for different days in milk and estimated breeding value for 305 DIM was increased from 90 DIM to 180 DIM, and highest around 240 DIM which indicates a minimum of 240 days as an optimum first lactation length might be required for genetic evaluation of Indian Murrah buffaloes.

The objectives of the present study were to explore the trend in preweaning mortality (PWM) and related measurements such as piglets born alive (PBA), stillborn piglets, herd productivity and herd size in sow herds over a 10-year period; and 2) to examine the relationships between PWM and the related measurements. Herd-level annual data from 2007–2016 for 91 herds in Spain were abstracted from a sow database compiled by a veterinary consultancy firm. The database software automatically calculated herd-level PWM (%) as follows: the total number of piglets born alive to a sow completely weaned during a year (TPBA) minus the total number of piglets weaned by the completely weaned sow during the year divided by TPBA x 100. All the statistical analyses were performed using SAS University Edition. A growth curve model was applied to incorporate correlations for all of the observations arising from the same farm. Herd means of PWM (SD) increased from 11.9 (4.1) % to 14.4 (3.2) %, and mean PBA increased by 1.9 pigs. Mean age of piglet death during lactation increased by 3.8 days, and there was a significant effect of increased year on herd size and the number of piglets weaned per sow per year (PSY; P < 0.05). Higher PWM was associated with more PBA, more stillborn piglets and small herds (lower than the median size: < 570 sows; P < 0.05). Also, as PBA increased from 9 to 14 pigs, PWM in large herds (> 570 sows) increased by only 6.6%, compared with 9.6% in small herds. Furthermore, as PWM decreased from 18 to 8%, herd productivity measured as PSY increased by 2.2 pigs in large herds, but only by 0.6 pigs in small herds. In conclusion, the effect of increased PBA on PWM was alleviated more in large herds than in small herds. Also, the impact of decreased PWM on herd productivity was greater in large herds than in small herds.