Month Of Calving Research Articles

Interaction of Age and Month of Calving with Year of Calving for Production Traits of Ontario Holsteins

Production records of 835,789 Ontario Holsteins calving between 1958 and 1990 were used to determine the presence of an interaction of the age and month of calving of cows with the year of calving for production of milk and fat and fat percentage. An animal model was employed including the effects of herd-year-season of calving, interaction of age and month of calving with year of calving, animal additive genetic effects, and permanent environmental effects. Tests for interactions of age with year within months of calving were significant for production of milk and fat, but not for fat percentage. Tests for interactions of month with year within age groups were significant for only a few age groups in the second and third parities. The implication of these findings on genetic evaluation is that an interaction of age and month of calving with year of calving should be included in the animal model for genetic evaluations rather than preadjusting production for age and month of calving.

Optimizing Model: Insemination, Replacement, Seasonal Production, and Cash Flow

Dynamic programming to solve the Markov decision process problem of optimal insemination and replacement decisions was adapted to address large dairy herd management decision problems in the US. Expected net present values of cow states (151,200) were used to determine the optimal policy. States were specified by class of parity (n = 12), production level (n = 15), month of calving (n = 12), month of lactation (n = 16), and days open (n = 7). Methodology optimized decisions based on net present value of an individual cow and all replacements over a 20-yr decision horizon. Length of decision horizon was chosen to ensure that optimal policies were determined for an infinite planning horizon. Optimization took 286s of central processing unit time.The final probability transition matrix was determined, in part, by the optimal policy. It was estimated iteratively to determine postoptimization steady state herd structure, milk production, replacement, feed inputs and costs, and resulting cash flow on a calendar month and annual basis if optimal policies were implemented. Implementation of the model included seasonal effects on lactation curve shapes, estrus detection rates, pregnancy rates, milk prices, replacement costs, cull prices, and genetic progress. Other inputs included calf values, values of dietary TDN and CP per kilogram, and discount rate. Stochastic elements included conception (and, thus, subsequent freshening), cow milk production level within herd, and survival. Validation of optimized solutions was by separate simulation model, which implemented policies on a simulated herd and also described herd dynamics during transition to optimized structure.

Genetic analysis of reproductive disorders in Israeli Holstein dairy cows

The heritability of common reproductive disorders was asessed in Israeli Holstein cows. Data were collected from 76,000 calvings on 102 collective farms (kibbuts) over a 36-mo period. The disorders considered were those of retained placenta, abnormal lochia, endometritis, anestrus, ovarian cysts with anestrus and ovarian cysts with nymphomania. The statistical model included fixed effects of herd-year, month of calving, duration of previous pregnancy, interaction between calving difficulty and sex of offspring, and the random effect of the sire. Herd-year effects consituted 0.68 of the explained variance of the incidence of retained placenta and approximately 0.89 of all the other disorders. Sire and calving-month effects were significant (P<0.05) for all the disorders. Heritability estimates of the disorders were 0.01 for retained placenta, abnormal lochia, and endometritis; 0.02 for anestrus; and 0.03 for all disorders. Correlations between any two disorders did not exceed 0.20. High genetic correlations were found between retained placenta and either abnormal lochia (0.90) or endometritis (0.70), while moderate genetic correlations were found among each of these and anestrus (0.30). Reproductive disorders occur as part of a complex which may be efficiently controlled by management measures. Nevertheless, breeding for resistance to reproductive disorders may also be feasible by using appropriate sires evaluated on a large number of daughters.

Genetic and phenotypic evaluation for reproductive performance of Egyptian buffaloes

ABSTRACTAn analysis of cow reproductive traits was carried out on 2057 lactation records of Egyptian buffaloes. A total of 651 daughters (paternal half-sisters) of 82 sires were available for the analysis. Reproductive traits analysed were age at first, second and third calving (AC), number of services per conception (NSC), gestation length (GL) and calving interval (CI). Year of calving affected most reproductive traits (P&lt; 0·001) while no important differences were detected among months of calving. Means of NSC, GL and CI decreased linearly (P&lt; 0·01) as parity advanced. Age of cow at calving exerted a pronounced effect (P&lt; 0·001) on NSC and CI. There was no systematic change in the estimates of heritability and sire components of variance for reproductive measures over the first three lactations. Heritability estimates for NSC and GL in the different parities were generally low, ranging between 0·04 and 0·18, while moderate estimates for AC and CI were obtained. Phenotypic correlations between reproductive traits were positive and relatively moderate or low. For most traits, positive and relatively high or moderate estimates of genetic correlations were observed. Mating bull was found to be an important source of variation for reproductive performance of Egyptian buffaloes. The highly significant effect of mating bull on reproductive traits could be considered as evidence for the importance of evaluating bull semen quality before the mating of cows

Prediction of conception rate in extensive beef herds in north-western Australia. 1. Seasonal mating and improved management

Statistical models for conception rate were developed using data collected at a mid dry season (August-September) muster from a controlled-mated and supplemented herd of 900 Brahman cross cows at Mt Bundey from 1980-84. Average conception rates were 74% for maidens, 25% for first-lactation cows, 51 % for 4-10-year-old lactating cows, 54% for &gt;10-year-old lactating cows and 96% for non-lactating cows. Although year effects dominated, they were partially explained by severity of the dry season and were consistent across levels of the other factors. Pregnant maiden heifers weighed 13 kg more than non-pregnant ones at the end of mating, after allowing for the weight of the fetus and gravid uterus. Conception rate of first-lactation cows was not affected by month of calving, adjusted mid dry season weight or condition score, possibly because of narrow ranges in these factors based on selection. For mature lactating cows the main effects on conception rate were month of calving (+11% for September to -16% for December or later), previous lactation (+6% for having reared a calf), adjusted mid dry season weight (-16% for &lt;300 kg to +9% for &gt;350 kg) and condition score (-17% for backward and store to +16% for good condition). Corresponding effects for aged lactating cows were +14% for September to -19% for December or later calving, +8% for previously rearing a calf, and -24% for backward store and store to +23% for good condition cows. The high conception rates for non-lactating cows corresponded with high liveweights and condition scores. A low cost, practical implementation of these models is based on previous lactation status and condition score in the mid dry season, with pregnancy diagnosis added at the next stage. Reproductive classes could be segregated on this basis for improved management and nutrition and to gain an economic return on capital invested in cattle control.

Milk Production and Somatic Cell Count in Michigan Dairy Herds

The established association between milk production and SCC in dairy cattle is increasingly used to estimate lost production due to mastitis. Such cost estimates are used to make decisions regarding cost effective mastitis prevention and control. It is therefore important to verify the relationship between SCC and milk production using data from different areas of the country and by using different analytical methodology. Our study used the 1985 to 1986 Michigan DHIA data base and analyzed daily milk production records rather than lactation summary records as used in the past. One advantage to our approach was that it did not give equal weight to all lactations, regardless of their duration. Also, it enabled inclusion of cows that had incomplete lactations caused by culling, or had other reasons for removal from the herd.A statistical model was constructed to predict milk production on the basis of herd, cow within herd, stage in lactation, month of calving, lactation, and SCC. The data base contained 397,172 milk test records obtained from Michigan DHIA from 504 Holstein herds in Michigan's lower peninsula. Our final model predicted 78% of the variation in milk production. Prediction of milk loss for each herd was highly correlated (r = .98) with the prediction model adopted by most DHIA organizations. Our model predicted that the mean herd lost a mean of 1.17kg of milk/cow per d associated with SCC.

Effects of Lactation on Various Blood Parameters In Holstein Cows. II. Serum Minerals and Enzymes

AbstractSixty-three Holstein cows were utilized to determine the effects of lactation on blood serum calcium, phosphorus, the calcium-to-phosphorus ratio, total and enzyme creatine phosphokinase, alkaline phosphatase, and glutamic-oxalacetic transaminase. Sampling consisted of monthly blood collections starting with the onset of lactation and continuing to the dry period. Blood values obtained were statistically analyzed by linear regression onlactation number, month of calving, month of lactation at conception, stage of lactation, milk yield, and milk fat yield.Serum calcium was significantly influenced by all lactation parameters examined except milk fat yield. Circulating phosphorus levels were influenced by all lactation parameters examined except lactation number and stage of lactation. The calcium-to-phosphorus ratio changed significantly withmonth of calving, month of lactation at conception, and milk fat yield. Serum total creatine phosphokinase was influenced by all lactation parameters examined except month of lactation at conception. Serum enzyme creatine phosphokinase was influenced by all lactation parameters examined except milk and milk fat yields. Circulating levels of alkaline phosphatase were influenced by all lactation parameters examined except milk fat yield. Levels of serum glutamic-oxalacetic transaminasechanged with lactation number, month of calving, and stage of lactation.

Effects of Lactation on Various Blood Parameters in Holstein Cows. I. Serum Protein and Protein Fractions

Summary Sixty-three Holstein cows were utilized to determine the effects of lactation on blood serum total protein, urea nitrogen, albumin, globulin, and the albumin to globulin ratio. Sampling consisted of monthly blood collections starting with the onset of lactation and continuing to the dry period. Blood values obtained were statistically analyzed by linear regression on lactation number, month of calving, month of lactation at conception, stage of lactation, milk yield, and milk fat yield. Serum total protein was influenced by all lactation parameters examined except milk fat yield. Circulating blood urea nitrogen levels varied with lactation number, month of calving, stage of lactation, and milk yield. Levels of serum albumin were influenced by month of calving. Serum globulin and the albumin to globulin ratio were influenced by all lactation parameters examined except milk and milk fat yield.

Additive Versus Multiplicative Precorrections of Dairy Records for Some Environmental Effects in Sire Evaluation

Additive and multiplicative correction factors were compared for precorrection of milk production records for effects of age at calving, month of calving, and pasture, using the data on 168,480 progeny of 70 proven sires of the Simmental breed. Criteria used for the comparison were unremoved variation, interactions of the mentioned effects with herd-year, residual variance ignoring interactions, and the bias in sire predictions. For age at calving and month of calving both types of correction factors were equally efficient in removing the variation in yields of milk and fat. Pasture effects were removed more effectively with additive than with multiplicative factors. The variances due to herd-year×month of calving and herd-year×pasture interactions were larger with multiplicative factors. The herd-year×age at calving interaction variances were similar with both types of corrections. Different criteria of the comparison showed that the differences in the efficiency of both types of correction factors were unimportant. A model of sire evaluation was found equally accurate with additive or multiplicative factors.

Postpartum ovarian activity, uterine involution and fertility in indigenous buffaloes at a selected village location in Sri Lanka

Reproductive events were monitored over a period of 30 months in a sample of 55 indigenous (Lanka) buffalo cows belonging to five farmers selected at random in a specific village in the dry zone low-country region of Sri Lanka. The animals were maintained under the existing traditional methods of extensive grazing management and low-intensity utilization for milk and draught power in a crop-livestock system. Annual calving rate was 87.2%, with 82.4% of all calvings occurring between December and March (peak calving season). Involution of the uterus, based on rectal palpation, was completed at an interval of (mean ± SD) 32.9 ± 8.2 days post-partum. The majority (70.8%) of first services postpartum were recorded between February and April. The interval from calving to first service was 57.3±49.2 days for 80 animals which calved during the peak calving season and 156.2 ± 95.6 days for eight animals calving outside the peak season (overall 66.4 ± 61.4 days, n = 88). The intervals to uterine involution and first service were correlated ( r=0.53, P < 0.01) and both were significantly influenced by month of calving, but not by age or parity of the cow. The interval from calving to palpation of the first corpus luteum was 52.3 ± 16.8 days, and to the first elevation of progesterone above 0.5 ng/ml of fat-free milk was 54.9 ± 17.9 days. Of the 36 cases where complete progesterone profiles and clinical data were available, first services were recorded in 27 (75%) before palpation of a corpus luteum or elevation of progesterone after calving, and conception to this service was confirmed in 24 (88.9%). Elevation of progesterone preceded first service in seven (19%); the resultant luteal phases were short in four and normal in three. Overall conception rate to first service was 77.7% and the number of services per conception was 1.29. The calving to conception intervals ranged from 23 to 502 days (mean 71.5 ± 66.2, mode 41–60, n = 82) and the calving intervals from 329 to 816 days (mean 384.9 ± 62.9, mode 351–370, n=79). These findings confirm that Lanka buffaloes are capable of maintaining high fertility under certain traditional systems of management. The major cause of long calving intervals was prolonged postpartum acyclicity, which occurred mainly in animals calving outside the peak calving season.

Adjustment of test-day milk, fat and protein yield for age, season and stage of lactation

The object of this study was to develop a method for the adjustment of test-day milk, fat and protein yield for age at calving, stage of lactation, and month of calving. Test-day records of 14 275 purebred Dutch Friesians were analysed by generalized least squares, (GLS). Functions of days in lactation and age in months were fitted to the age differences for different stages in lactation. A close fit to the GLS means was obtained for both milk fat and protein yield. From these functions, adjustment factors (CF ageI) were computed depending on the cow's age in months and number of days in lactation. A multiplicative adjustment for age and stage of lactation by CF ageI was compared with an adjustment using factors derived from the constant estimates (CF ageII). Comparison was on the F-variable and constant estimates for age after adjustment. When CF ageI was used instead of CF ageII, lower F-values were obtained and the constants showed a more regular pattern. Additive adjustment factors for month of calving were derived from the GLS constant estimates. After correction, month of calving was only significant for protein yield. The adjustment of test-day yields for age at calving and stage of lactation was improved by using mathematical functions.

A note on the value and methods of correcting milk records for calving interval or days dry

In formulating a genetic index for use in cow and sire evaluation, there is a need to account for all environmental factors which influence an animal's yield. To this end, milk production records are currently adjusted for, amongst other things, age at calving and month of calving. In Norway, Sweden and West Germany, records are corrected for calving interval, i.e. the number of days between subsequent calvings (Philipsson, Dommerholt, Fimland, Gaillard, Gjøl-Christensen, Lederer, McClintock and Mocquot, 1978), but in Britain no account is taken of calving interval or days dry. Analysis has shown (McClintock, 1982) that both these factors have a significant effect on yield, and hence further investigation into the value and methods of adjusting for these factors was required.

Cyclic Changes in Plasma Calcium and the Calcium Homeostatic Endocrine System of the Postparturient Dairy Cow

Plasma Ca, P, Mg, parathyroid hormone, and 1,25-dihydroxyvitamin D were measured in blood samples taken daily from d 5 before until d 15 to 30 after calving in 28 aged dairy cows (5 yr or older) and 9 first lactation cows. Subnormal plasma Ca concentrations were defined as being below the lower limit (2.18 mmol/L) of the 99% confidence interval for lactating cows outside the month of calving. A parturient minimum in plasma Ca and P concentrations occurred usually within 24h after calving in all animals.Plasma mineral changes very similar to those at parturition were observed in 50% of the aged cows at one, two, or even three later occasions during the 1st mo postpartum. Interval between subsequent subnormal Ca minima in these Ca-cycling cows was 7 to 10 d. The function of the Ca regulating endocrine systems appeared adequate.Calcium cycling with increased amplitude could be induced by feeding 200μg/d of 1,25-dihydroxyvitamin D3 for about 5 d around parturition (8 animals). The hypocalcemic episode was more pronounced than in untreated cows, and Ca cycling was traced throughout the 1st mo of lactation. Similar treatment also induced Ca cycling in 4 heifers, whereas 8 untreated heifers showed no tendency to Ca cycling in the postparturient period. The hypothesis is put forward that variations in intestinal Ca absorption induced by 1,25-dihydroxyvitamin D3 are the primary cause of the cyclic changes in plasma Ca postpartum of the aged dairy cow.

COMPARISON OF TWO MATHEMATICAL MODELS IN FITTING LACTATION CURVES FOR PURELINE AND CROSSLINE DAIRY COWS

Weekly milk yield of 2066 first, 1407 second, and 755 third lactation pureline and crossline cows was used to study environmental and genetic effects on the coefficients of the lactation curves derived by modified gamma and inverse polynomial functions. The inverse polynomial function provided a better fit than the modified gamma function based on comparison of R2 values. Coefficients of the two models were analyzed to evaluate environmental and genetic effects on the shape of the lactation curve. The model included station, year of calving, month of calving, age at calving, days open, line of sire, line of dam, interaction of line of sire with line of dam, and sires within line of sire. In addition, coefficients of the lactation curve were analyzed by another model which included station, year of calving, month of calving, age at calving, days open, breed additive, maternal, and heterosis effects. Effects of station, year of calving, month of calving, and days open were mostly significant (P &lt; 0.05); however the effect of age at calving was not significant on the coefficients of the lactation curves. Significant (P &lt; 0.05) line of sire and line of dam effects on the level of initial yield suggest that genetic improvement of this trait could be achieved through selection. Breed additive and maternal effects were mostly nonsignificant on the coefficients of the lactation curves indicating shape of the lactation curve could not be changed by selection. There was very little evidence of nonadditive genetic variation associated with the coefficients of lactation curves. Key words: Lactation curves, pureline, crossline, dairy cows

An Epidemiological and Genetic Study on Registered Diseases in Finnish Ayrshire Cattle

The epidemiology of clinical ketosis, hypocalcaemia and hypomagnesaemia was examined. In addition, the genetic variability of ketosis and parturient paresis was investigated. The data set consisted of the lactation records of 70,775 Finnish Ayrshire dairy cows. Each cow was under observation for 2 days before and for 305 days after calving. Lactation incidence rates (%) were: ketosis 6.0, parturient paresis 3.8, non-parturient paresis 0.6, hypomagnesaemic tetany, outdoor 0.6, and indoor 0.2. These diseases formed 22 % of all first treatments by veterinarians during farm visits. 92 % of the cases of ketosis occurred with 8 weeks of parturition, with the highest occurrence 3–5 weeks after calving. Four % of cases of parturient paresis occurred before, and 45 % within 24 h after calving. When cases were categorized by month of calving the risk of ketosis was higher during indoor feeding (October-April) than during outdoor feeding (May-September). The risk of parturient paresis did not significantly vary with month of calving. The occurrence of ketosis increased with parity up to the 4th and decreased thereafter. The occurrence of parturient paresis increased with parity. Both the increase in herd milk yield and the increase in individual milk yields were positively associated with the occurrence of ketosis and parturient paresis. The cows with a history of the reproductive tract infection had a higher risk of contracting ketosis. Heritability estimates for ketosis in various parity groups were from 1.6 % to 4.1 % on the binomial scale (corresponding to 7.3 %–14.4 % on the normal scale), and for parturient paresis from 3.5 to 10.5% (corresponding from 18.3 % to 27.4 %). The genetic correlation between ketosis and parturient paresis, and these and current milk production for all material were insignificant.

Studies on the replacement policies in dairy cattle. IV. Influence of seasonal variation in performance and prices

The optimum policy for inseminating and replacing cows, taking into account seasonal variation in biological factors and prices, was determined by the dynamic programming technique. The decision to inseminate a cow was based on comparing the expected income when the cow conceived with that when the cow was left open and replaced at the optimum time in the remainder of the lactation period. In the model, cows were characterised by their lactation number, stage of lactation, time of conception, milk production level and month of calving. The month of calving influenced the production of milk, fat and protein, the probability of conception, feed costs and the price of milk, calves and culled cows. Under Dutch conditions, heifers calving from September to November yielded the highest income while those calving in May or June gave the lowest. The difference in expected income between October and June was 277 Dfl. The minimum production for insemination to be optimum was largely dependent on the time of year. Lowest production was found when insemination took place from February to April. The consequences of the differences in the optimum policy in months of calving for the average length of the calving interval and the probability of replacement during the first lactation, and the expected herd life of heifers, were quantified. Seasonal differences in production, feed costs and calf prices were the main sources of the differences in the expected income from heifers. The optimum policy for inseminating and replacing cows was greatly affected by the seasonal variation in production and, to a much smaller extent, in calf prices and feed costs.

A note on the use of a categorical variable to explain seasonality deviation from the lactation curve

ABSTRACTThe addition of a categorical variable to the lactation model of Wood (1967) has been shown to be useful in the explanation of seasonality of milk production using data from an experimental herd. The technique is further investigated using monthly milk-yield data from 43 commercial herds in Northern Ireland in the years 1978 to 1982. Coefficients, d, of the categorical variable were estimated for each month of calving. The maximum value of d was 0·256 for the month of October and the minimum value was 0·022 for the month of March.

Effect of Sire of Fetus on Subsequent 90-Day Production of the Holstein Dam

Data on calving ease and 90-day milk, fat, protein, fat percent, and protein percent were available on 8,817 Holstein cows enrolled in the Quebec Dairy Herd Analysis Service. These observations were distributed in 802 herds, and they represented 124 service sires. Estimates of the variance components associated with the service sire (sire of fetus) were obtained by Minimum Norm Quadratic Unbiased Estimation procedures. Two models were fitted; one model included herd, month of calving, age of cow, and sire of cow as fixed effects and service sire and residual as random effects, whereas a second model included calving ease as an additional fixed effect. Variance components and percentages of variance accounted for by service sire were similar under both models. Proportions of variance accounted for by service sire were 1.1, .3, .5, .2, and .3% for 90-day milk, fat, protein, fat percent, and protein percent.

Estrus Detection and Subsequent Reproduction in Dairy Cows Continuously Housed Indoors

Records (1554) from 961 cows continuously housed indoors in two types of barns were analyzed for occurrence and detection of estrus and subsequent reproduction. Variables, percentage of cows observed in estrus by 55 days postpartum, days to first recorded estrus and first service, conception rates, service intervals, days open, and services per conception were analyzed by least squares procedures for year of calving, month of calving, genetic line, barn-type parity subclasses, and interaction of month by line.A higher percentage of multiparous cows in the tie-stall barn (60%) were observed in estrus by 55 days postpartum than those in the loose-housing barn (50%). Days to first recorded estrus and to first service, 54 and 81, were less for tie-stall cows than for loose-housing cows, 66 and 91. Conception rates at first service and overall conception, 54 and 91%, were higher for tie-stall cows than for loose-housing cows, 42 and 80%. A higher percentage of primiparous cows (69%) was in estrus by 55 days than multiparous cows (55%). Days to first estrus and first service were less for primiparous cows, 47 and 70, than multiparous cows, 60 and 80. Days open were less for primiparous cows. Primiparous cows required 1.9 services per conception compared with 1.7 for multiparous cows.

Association of Genetic Variants of Casein and Milk Serum Proteins with Milk, Fat, and Protein Production by Dairy Cattle

Polyacrylamide gel electrophoresis methods were used to phenotype caseins for 2045 cows and milk serum proteins for 3870 cows distributed in 63 Quebec dairy herds. Frequencies were: αs1-casein A .003, αs1-casein B .970, αs1-casein C .027; β-casein A1 .561, β-casein A2 .421, β-casein A3 .011, β-casein B .007; κ-casein A .744, κ-casein B .256; β-lactoglobulin A .387, β-lactoglobulin B .613; α-lactalbumin B 1.00. Overall unadjusted means for 305-day production in first lactation were: 5530±26.6kg, 197±1.0kg, 172±1.0kg, 3.58±.009, 3.12±.009 for milk yield, fat yield, protein yield, fat percentage, and protein percentage for 1687 cows for casein systems. Similar data for 2906 cows phenotyped for milk serum proteins were: 5412±20.6kg, 193±.8kg, 170±.7kg, 3.57±.007, and 3.13±007. Least squares analysis of variance showed that herd location, month of calving, age of cow at first calving, and protein variants had significant effects on production traits. αs1-Casein B and β-casein A phenotypes were associated with higher milk, fat, and protein yields than other variants in the two casein systems. Milk from κ-casein BB and β-lactoglobulin AA phenotypes contained .13 and .05% more protein than the AA and BB phenotypes with the AB phenotype intermediate.