Relationships between age at first calving and first lactation milk yield, and lifetime productivity and longevity in dairy cows

Lifetime records of 442 Holstein cows on one farm in North Queensland, Australia, were analysed to evaluate the effects of age at first calving (AFC) and first lactation milk yield on parities per lifetime, longevity, milk yield in subsequent lactations, lifetime milk production and the longevity index (LI), that is the proportion of a cow's life spent in active milk production. The mean daily yield in the first lactation was a reliable indicator of milk yield in subsequent lactations, estimated lifetime production, longevity and LI. The afc had no effect on lifetime days in milk. Neither the AFC nor the milk yield in the first lactation significantly affected the number of parities per lifetime. For the majority of cows, which produced less than 30 l/day in the first lactation, there was a significant positive relationship between longevity and AFC. However, none of the cows that produced more than 30 l/day in the first lactation survived for more than two lactations. The optimal AFC was thus two to two-and-a-half years, as these cows had the highest first lactation yield, estimated lifetime production and LI. The optimal mean daily yield in the first lactation was 20 to 30 l/day, as these cows lived longer and had a higher LI and lifetime production.     

Reductions in milk production after induced parturition in dairy cows from commercial herds in south-western Victoria

SUMMARY The milk production of cows after induced parturition was compared with that of non-induced cows with similar calving dates, in 37 winter-calving, pasture-fed, commercial dairy herds in south-western Victoria. Parturition was induced when most cows were between 27 and 35 weeks of pregnancy. Milk production was compared for the lactation that commenced immediately after induction. The percentage of cows whose lactations were terminated less than 120 days after calving was increased by induction. Mean percentages for untreated and induced groups were 3.0% and 5.4%, respectively . For cows with lactations of at least 120 days duration, lactation length was not affected by the prior induction of parturition. However, milk production during the subsequent lactation was 9.0% less in induced groups. Fat and protein concentrations were not substantially affected. The reduction in milk production was not affected by stage of pregnancy when cows were induced, but tended to be greater in herds that delayed milking of induced cows .     

The relationship between milk yield and cystic ovarian disease in cattle

Studies were conducted to understand the relationship, if any, between the amount and pattern of milk yield and the occurrence of cystic ovarian disease (COD) in dairy cattle. More than 70 cows with cysts were compared with herd mates of similar lactation number. Total milk yield in lactations when cysts occurred and in the preceding lactations were not different from the corresponding lactations in control cows. Patterns of monthly milk yield did not differ between the two groups of cows. However, weekly analysis in early lactation revealed differences. Both groups of cows achieved peak yields at a similar time (5.4 +/- 1.2 vs 5.7 +/- 1.9 weeks post partum in normal vs cows with COD). However, owing to an early decline in yield of cows with COD, their duration of peak yield was significantly shorter (P less than 0.05) than in the control cows (3.2 +/- 2.2 vs 5.6 +/- 2.4 weeks). Both the attainment and the decline of peak yield occurred 5.6 (range = 2-15) weeks before the cysts were diagnosed. It is concluded that COD is not particularly a disease of higher yielding cows and that COD has no discernible effect on the milk yield or its pattern. It is speculated, however, that some cows in early lactation, while trying to meet the requirements of sustained peak milk production, are more susceptible to minor environmental changes (such as new social interactions, or changes in diet). These events may lead to a drop in milk production and disruption of events controlling normal ovulation, resulting in the formation of ovarian cysts.     

Genetic evaluation of somatic cell score in dairy cattle considering first and later lactations as two different but correlated traits

A test‐day (TD) random regression model (RRM) was described for the genetic evaluation of somatic cell score (SCS) where first and later lactations were considered as two different but correlated traits. A two‐step covariance function procedure was used to estimate variance–covariances and associated genetic parameters. Analysis of estimated breeding values (EBV), ranking of top bulls and cows and some computational aspects were used to compare RRM with TD repeatability model (RPM) and lactation average model (LAM). Residuals were analysed to assess the relative fit of TD models. Comparison between RRM and RPM showed that RRM has lower mean squared error and gave better fit to the data. For young bulls and cows, the standard deviation (SD) of EBVs was highest for RRM and lowest for LAM implying efficient utilization of information on SCS, in terms of revealing more genetic variation. A much lower correlation of EBVs ranging from 0.80 to 0.92 and significant re‐ranking of top bulls and cows were observed between RRM and LAM. The lower across‐lactation correlation between RRM and LAM indicated that LAM is directed to give more weight to first lactation breeding values. The RRM, where SCS in the first and later lactations was considered as two different but correlated traits was able to make effective use of available information on young bulls and cows, and could offer an opportunity to breeders to utilize EBVs for first and later lactations.     

Eleven-year analysis of changes in the incidence and recurrence of cystic ovarian disease in a herd of dairy cattle in California

Individual card records of all cows that began 1 or more lactations between the inclusive dates of Jan 1, 1976 and Dec 31, 1986 were obtained from a California dairy herd. Calving date, lactation number, physical examination date, conception date, and clinical findings pertinent to cystic ovarian disease (COD) were extracted from the records. Lactation-specific data were organized into cohorts by quarter and year in which lactation began, and the following estimates were calculated for each of the 44 cohorts: separate actuarial cumulative incidences for cows in their first lactation, cows in the second or later lactation, and all cows combined; separate proportions of the incident cases that were in their second or greater lactation and that had recurred from any previous lactation; proportions of the incident cases that had recurrence of COD 1 or more times, and recurrence 2 or more times during the lactation; and the mean number of days in lactation at diagnosis of the incident case. Time-series analysis and multiple-regression modeling procedures were used to characterize changes in the overall incidence rate over the study period and to describe the contribution of additional measures to the dynamics of the incidence rates. The quarterly actuarial cumulative incidences of COD increased concurrently with the increased incidence among cows in the second or later lactation. Neither the proportion of incident cases that were diseased during a previous lactation nor the proportion of cases that were in the second or later lactation contributed to the observed changes in the overall incidence rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Epidemiology of Streptococcus uberis intramammary infections in a dairy herd.

From 1987 to 1991, almost 36,000 quarter samples of mammary secretion representing 1790 lactations of 510 dairy cows from a research herd were collected for bacteriological examination. The percentage of cows infected with Streptococcus uberis ranged from 12 to 16% of cows/year. S. uberis was isolated from 14.2% of lactations over the 5-year period. The prevalence of S. uberis intramammary infection (IMI) was significantly higher in cows with > or = 4 lactations than in cows with 3 or fewer lactations. Regardless of lactation number, the prevalence of S. uberis was highest before parturition, during early lactation and near drying off. The prevalence of S. uberis infected quarters ranged from 1.3 to 2.3% of quarters/year; the prevalence rate for the 5-year period was 2% of quarters. The quarter prevalence of S. uberis was lowest in cows with < or = 3 lactations, increased significantly with lactation number and was highest in cows with > or = 6 lactations. The percentage of quarters infected with S. uberis varied significantly by year. The majority (95%) of S. uberis IMI were subclinical. The ratio of subclinical IMI to clinical IMI was lowest during early lactation, and increased with days in milk, and with lactation age except for cows in their 5th and 6th lactations. Results of this epidemiological investigation suggest that opportunities exist where suitable control measures could be applied to reduce the impact of S. uberis infections in the dairy herd.     

Relation of milk production loss to milk somatic cell count.

Milk production loss was studied in relation to increased somatic cell count (SCC). Available data were weekly test-day milk yields and SCC (in 1,000 cells/ml), and mastitis incidences. In total, 18,131 records from 274 cows were used. Production loss was determined for test-day kg milk, kg protein, and kg energy-corrected milk. Least-squares analysis of variance was used to estimate the direct effect of Log10(SCC) on production. The recorded measures of production were first corrected for fixed effects, with adjustment factors estimated from a healthy data-set. The average daily milk yield was 19.7 kg/day in first lactation and 22.0 in later lactations. The geometric mean of SCC was 63.1 in first lactation and 107.2 in later lactations. The incidence of clinical mastitis treated by a veterinarian was 19.8% of the lactations-at-risk. Linear relationships were found between the production parameters and Log10(SCC). Quadratic and cubic effects were evaluated, but were found to contribute little to the overall fit of the models. The individual milk yield loss was 1.29 kg/day for each unit increase in Log10(SCC) for cows in first lactation. Milk yield decreased by 2.04 kg/day per unit Log10(SCC) for older cows. Corresponding values for protein yield were 0.042 and 0.067 kg/day for first and later lactations, respectively.     

Skin Injuries on the Body and Thigh of Dairy Cows: Associations with Season,Claw Health,Disease Treatment,and other Cow Characteristics

An epidemiological study was conducted in 18 dairy herds with the objective to characterize those groups of cows where skin injuries to the body and thighs occurred most frequently. Data were analyzed with multivariable logistic regression. The epidemiologic patterns were different in first and later lactations. In first lactation some degree of injury occurred among 7.7% of 1793 cows. For most cows occurrence of sole ulcer was positively associated with injury while occurrence of heel horn erosion was negatively associated with injury. The association between injury and body weight differed depending on month of calving (significant interaction). Injuries occurred most frequently among high yielding cows. Severe reproductive, metabolic, and/or infectious diseases were associated with injuries. In later lactations some degree of injury occurred among 13.4% of 832 cows in lactations 2 to 9 where severity of injury increased with lactation number. Injuries occurred least frequently at examinations made in the January to March. They occurred most frequently among cows with sole ulcers. Calving in March through October was associated with injuries especially if the cows were treated for limb disorders. Most cases of injuries occurred early or late in lactation or among high or very low yielding cows in lactations 2 to 9.     

Risk of abortion associated with Neospora caninum during different lactations and evidence of congenital transmission in dairy cows

OBJECTIVE: To examine the relationship between exposure to Neospora caninum and abortion in dairy cows during their first, second, third, and fourth or later lactations and to establish the main mode of transmission in female calves from birth until their first pregnancy was terminated by abortion or parturition. DESIGN: Prospective observational study. ANIMALS: 460 Holstein cows and 79 female calves. PROCEDURE: Cows were classified as seropositive or seronegative to N caninum within 7 days after calving; incidence of abortion was compared between groups during different lactations. Blood samples were collected from female calves before ingestion of colostrum and every 6 months until their first pregnancy was terminated by abortion or parturition; number of seropositive calves was compared between seropositive and seronegative dams. RESULTS: During the first pregnancy of their second lactation, risk of abortion for seropositive cows was 2.8 times that of seronegative cows. Among 10 calves born to seropositive cows, 4 were classified as seropositive at birth and thereafter. Among 69 calves born to seronegative cows, all were classified as seronegative at birth; 67 calves remained seronegative thereafter. CONCLUSIONS AND CLINICAL RELEVANCE: Exposure to N caninum alone was not significantly associated with abortion in cows during the first, third, and fourth or later lactations. Seropositive cows that have aborted previously may have subsequent abortions attributable to N caninum. Congenital infection was the main mode of N caninum transmission in a cohort of female calves.     

Epidemiology of Streptococcus uberis Intramammary Infections in a Dairy Herd

From 1987 to 1991, almost 36 000 quarter samples of mammary secretion representing 1790 lactations of 510 dairy cows from a research herd were collected for bacteriological examination. The percentage of cows infected with Streptococcus uberis ranged from 12 to 16 % of cows/year. S. uberis was isolated from 14.2 % of lactations over the 5-year period. The prevalence of S. uberis intramammary infection (IMI) was significantly higher in cows with ≥4 lactations than in cows with 3 or fewer lactations. Regardless of lactation number, the prevalence of S. uberis was highest before parturition, during early lactation and near drying off. The prevalence of S. uberis infected quarters ranged from 1.3 to 2.3 % of quarters/year; the prevalence rate for the 5-year period was 2 % of quarters. The quarter prevalence of S. uberis was lowest in cows with ≤3 lactations, increased significantly with lactation number and was highest in cows with ≥6 lactations. The percentage of quarters infected with S. uberis varied significantly by year. The majority (95 %) of S. uberis IMI were subclinical. The ratio of subclinical IMI to clinical IMI was lowest during early lactation, and increased with days in milk, and with lactation age except for cows in their 5th and 6th lactations. Results of this epidemiological investigation suggest that opportunities exist where suitable control measures could be applied to reduce the impact of S. uberis infections in the dairy herd.     

Disease frequencies in dairy cows in Sweden. v. mastisis

An epidemiologic study of mastisis in dairy cows in Sweden covering 137 002 calvings and subsequent lactations is presented and various risk factors identified.

Swedish Friesian breed (SLB) had a higher incidence of mastisis than Swedish Red and White breed (SRB). The incidence was higher during the first part of lactation and increased with parity until the seventh lactation in SRB and the sixth lactation in SLB.

Dystocia, retained placenta and parturient paresis increased the risk of mastisis during the first part of lactation in SRB, and retained placenta increased the risk of mastitis during the first part of lactation in SLB. No associations between these periparturient disorders and the occurrence of mastitis in the latter part of lactation could be found. The incidence of mastitis was increased among teat-tramp-positive cows, and a positive report of mastitis increased the risk of mastitis in subsequent calvings.

The influence of environmental factors on the occurrence of mastitis was demonstrated by a higher incidence during housing as opposed to pasture, and a decreased incidence in loose-housed cows when compared to tied zero-grazing cows during the later part of lactation. During the first part of lactation, no seasonal variation could be found, and loose-housed cows had only slightly decreased incidence during this part of lactation when compared to tied zero-grazing cows.

The removal rate was increased in the mastitis-positive cow population.     

Bovine tuberculosis and udder health in Irish dairy herds

The association between bovine tuberculosis (TB) infection status based on results from the single intradermal comparative tuberculin test (SICTT) and milk production has been described in dairy cows in TB-infected herds in Ireland. The biological basis was uncertain, but could be related to increased TB susceptibility among lower producing dairy cows. In this study, the relationship between somatic cell count (as an objective measure of udder health) and SICTT reactivity (as a proxy for TB infection status) was investigated. Somatic cell counts of TB infected cows, both during and prior to the lactation of diagnosis of TB infection, were examined and compared to non-infected cows. All Irish dairy herds restricted from trading between June 2004 and May 2005 as a result of two or more TB reactors (test positive) to the SICTT were considered for study. Data were collected on 4340 cows from 419 herds. Previous lactation data for the cows were taken into consideration and all lactations on a cow were analysed together with the years of lactations. There was an inherent hierarchical structure in the data, with lactations nested within cows and cows within herds and so a linear mixed model with two random effects was used to describe the data. Milk production (305-day milk yield) was also included in the model as a fixed effect. The results of the study showed that for all lactations and years under investigation, somatic cell counts for SICTT reactor cows when compared to the non-reactor cows were not significantly different. In this study population, TB infection status was not associated with udder health.     

Pre-pubertal measurements of the somatotrophic axis as predictors of milk production in Holstein-Friesian dairy cows

This study investigated possible relationships between measurements of the somatotrophic axis in pre-pubertal dairy calves and subsequent milk yields. Endogenous growth hormone (GH) release was measured through a fed and fasted period in fifty 6-month-old Holstein-Friesian heifers and they were then challenged with growth hormone-releasing factor (GRF) to assess their GH release pattern. Insulin-like growth factor-I (IGF-I), insulin and glucose concentrations were measured in relation to time of feeding. Cows were subsequently monitored through their first three lactations to record peak and 305-day milk yields. In the first lactation, milk energy output for the first 120 days of lactation was also calculated. The mean 305-day milk yield increased from 7417 +/- 191 kg in the first lactation (n=37) to 8749 +/- 252 kg in the third (n=25). There were no significant relationships between any measures of GH secretion and peak or 305-day yield in any lactation. A highly significant positive relationship was established between the GH peak measured 10 min post-GRF challenge and 120-day milk energy values in the first lactation. This relationship was, however, only present in the sub-population of 12 cows culled after one or two lactations and was absent in the 25 animals remaining for the third lactation. There were no significant relationships between pre-pubertal IGF-I and fed or fasted insulin or glucose concentrations and any subsequent measurement of yield. The usefulness of GH secretagogue challenges in calves as a predictive test for future milk production is thus limited but may have some bearing on nutrient partitioning and longevity.     

Effects of daily exercise on the health of tied dairy cows

The effect of daily exercise on tied dairy cows was ied in 65 initially first and second calvers of the Swedish Red and White dual-purpose breed in a 4 year experiment, starting in July 1985. Half of the group walked outdoors for 2–3 km day⁻¹ from May to October and 400–800 m day⁻¹ from November to April. The rest of the cows were constantly tied. Health in general was significantly and positively influenced by exercise, reducing the need for veterinary treatments. Analysis over time, within lactations, showed that the difference in the number of veterinary treatments occured entirely in Weeks 0–2 of lactation. During those weeks, non-exercised (NE) cows were more affected by calving-related diseases, mastitis and leg problems than the exercised (E) cows. The difference between groups increased with increasing lactation number. In addition, somatic cell count in the milk was higher for the NE cows in their first month of lactation. Among feeding-related diseases, the cases of bloat were notably more frequent among NE cows, whereas exercise did not influence the occurence of clinical or subclinical ketosis. Cases of non-infectious leg and hoof disorders were also notably more frequent in the NE group, which also showed a significantly more serious score for skin lesions on the hocks, measured on one occasion. Scores for sole ulcer were significantly higher for the E cows on one occasion of four, at which there were problems with the surface of the exercise area. The causes of exclusions strengthened the differences mentioned for treatments.     

Genetic analysis of fat‐to‐protein ratio,milk yield and somatic cell score of Holstein cows in Japan in the first three lactations by using a random regression model

We estimated the genetic parameters of fat‐to‐protein ratio (FPR) and the genetic correlations between FPR and milk yield or somatic cell score in the first three lactations in dairy cows. Data included 3 079 517 test‐day records of 201 138 Holstein cows in Japan from 2006 to 2011. Genetic parameters were estimated with a multiple‐trait random regression model in which the records within and between parities were treated as separate traits. The phenotypic values of FPR increased soon after parturition and peaked at 10 to 20 days in milk, then decreased slowly in mid‐ and late lactation. Heritability estimates for FPR yielded moderate values. Genetic correlations of FPR among parities were low in early lactation. Genetic correlations between FPR and milk yield were positive and low in early lactation, but only in the first lactation. Genetic correlations between FPR and somatic cell score were positive in early lactation and decreased to become negative in mid‐ to late lactation. By using these results for genetic evaluation it should be possible to improve energy balance in dairy cows.     

Bone mineral changes in growing, pregnant and lactating cattle

Bone mineral content (BMC) was determined in one or two coccygeal vertebrae by dichromatic photon absorptiometry in two sets of cattle: A. This set consisted of six fattening bulls. Their increases of BMC and weights were closely correlated. However, BMC increased slightly more than weight. B. There were 28 cows in this set. BMC was measured during lactation and pregnancy. It was found that BMC increased during the dry period and decreased during early lactation. There were great individual variations in BMC, and the skeletal turnover seemed to be great.     

荷斯坦青年牛初次配种妊娠月龄对头胎和二胎产奶量和繁殖性能的影响

旨在研究母牛初次配种妊娠月龄（age at first pregnancy,AFP）对其泌乳性能和主要繁殖性能的影响。本研究以我国北方地区2个规模化奶牛场13 927头荷斯坦母牛（A牧场8 091头,B牧场5 836头）的生产数据为基础,统计了母牛AFP、头胎和二胎的产奶量、产后首次发情时间、首次配种时间和首次受孕时间,然后将母牛根据AFP的早晚（12~19月龄）分为8组,对各试验组母牛的头胎和二胎产奶量和主要繁殖性能的数据进行比较分析。结果表明：1）2个规模化奶牛场荷斯坦青年牛AFP以13和14月龄为主（总占比70.1%）;2）AFP可显著影响荷斯坦青年牛头胎和二胎的305 d产奶量（P<0.05）,其中AFP为14月龄时A牧场头胎和二胎305 d产奶量均最高,分别为15 102和15 534 kg;3）AFP可显著影响荷斯坦青年牛头胎和二胎产后首次发情时间和受孕时间（P<0.05）,AFP为14月龄时头胎产后首次发情和受孕情况最优;4）对于产后首配时间,除A牧场头胎AFP为16月龄时产后首次配种时间显著高于AFP为17月龄时（P<0.05）外,其余各组间均无显著性差异（P ≥ 0.05）,并且各组间配种时间相差≤ 5 d;5）通过对A牧场在场牛（2 703头）与淘汰牛（660头）的AFP记录数据分析发现,在场牛的AFP为14.52月龄,显著高于淘汰牛的AFP（P<0.05）。因此,在北方地区现有的生产管理水平下,14月龄可能是荷斯坦青年牛最适宜的初次配种妊娠月龄,这对我国规模化奶牛场选择荷斯坦青年牛适宜的初次配种月龄具有一定参考价值。     

Somatic cell score genetic parameter estimates of dairy cattle in Portugal using fractional polynomials

Milk somatic cell count is an indicator trait for mastitis resistance. Genetic parameters for somatic cell score in the Portuguese Holstein-Friesian population were estimated by modeling the pattern of genetic correlation over the first 3 lactations (days in milk) with a random regression model. Data records from the first 3 lactations were from the national database of the Portuguese Holstein Association herds. Heritability estimates ranged from 0.05 at the beginning of the lactation for the 3 lactations, to 0.07 at the end of the lactation period for the first and third lactations, to 0.09 for the second lactation. This increase in the heritability values was due to an increase in the genetic variance and a decrease in the residual variances. Genetic correlations evaluated for monthly time points were high (0.65 to 0.99) for all 3 lactations, whereas phenotypic correlations were much less than the genetic correlations (0.13 to 0.62).     

Changes in daily energy amounts of main milk components (lactose, protein and fat) during the lactation of high-yielding dairy cows

The aim of this study was to examine the changes of the daily energy amount of lactose, protein and fat throughout the lactations, and compare them to each other. A total of 309 Israeli Holstein-Friesian cows from one kibbutz were investigated in three lactations, and information was given for a period of five years from 1996 to the end of 2000. The distribution of milk components and milk yield during lactation, and changes of the absolute and relative energy amount in the different milk components were calculated and evaluated. The results showed changes in the energy content of milk and its different components throughout the lactation. Each component (fat, lactose and protein) is dominant in different periods during the lactation. The energy amount from fat reaches a peak first, between days 40 and 50. Lactose has a peak at about day 66 of lactation, and protein reaches the peak last, approximately at day 104 of lactation. It seems that this peak sequence is constant and it is considered to be physiological. It might be suggested that there is a regulation governing the secretion of the different components at different times, and only one component is dominant in a given period. Each component exerts negative and positive influences on the secretion of the other components, which interact with each other and are not fully independent.     

Factors influencing somatic cell score in Swiss dairy production systems

The aim of this study was to analyse the influence of fixed effects on somatic cell score (SCS) in Swiss dairy production. Monthly milk recording results were investigated against the background of changing housing conditions from tie-stall barns to loose housing systems. Zone, housing system and calving age within lactation number had a significant effect on SCS, as well as the covariables milk yield per day, fat and protein percentage and days in milk. Highest SCS was observed in cows of valley situated farms. Concerning housing system, best values were recorded in tie-stall barns (2.53). SCS was 0.08 higher during the changing period (2.61), and 0.12 higher in loose housing systems (2.65). SCS increased continuously with lactation number, but the differences between the age classes within lactation number were not significant. The lactation curves for SCS resembled inverted milk yield curves and were different between the first lactation on the one hand and higher lactations on the other hand.