Response in two commercial Holstein herds to addition of sodium bicarbonate to alfalfa hay-based diets

Feeding trials were conducted in two commercial dairy herds to evaluate the addition of .8% sodium bicarbonate to alfalfa hay-based diets. Approximately half of each herd served as controls and the other half was fed the same diet with sodium bicarbonate. A total of 1280 Dairy Herd Improvement Association lactation records were obtained in the two herds during the trials. Cows in herd 1 were milked three times daily and cows in herd 2 were milked twice daily. In herd 1, milk production from control and bicarbonate groups was: first lactation cows, 7491 and 7748 kg/cow; second lactation cows, 8363 and 8791 kg/cow; and third and higher lactation cows, 8713 and 9562 kg/cow. There were no differences in milkfat or solids-not-fat percentages between treatment groups. In herd 2, milk production from control and bicarbonate groups was: first lactation cows, 6800 and 7158 kg/cow; second lactation cows, 8487 and 8082 kg/cow; and third and higher lactation cows, 8807 and 8216 kg/cow. First lactation cows fed sodium bicarbonate had a lower milk fat percentage than controls. There were no other differences in milk fat or solids-not-fat percentages between treatment groups.     

Effect of Business and Dairy Herd Management Practices on the Variable Cost of Producing Milk

A Cobb-Douglas-type function was used to study the effect of several business and dairy herd factors on the variable cost of production per 45.4 kg milk in 410 New York State dairy herds. The model used was a recursive system of equations with milk sold per cow per year and total variable cost associated with milk production as endogenous variables. Solutions were obtained using the two-stage least squares procedure. Relationships were essentially linear between variable production cost per 45.4 kg of milk and average age of the herd, percent days in milk, average age at first calving, average body weight, average days dry, fat test, and kilograms of concentrates fed. For average days open, herd size, number of cows per worker, tillable acres per cow, percent cows leaving the herd, and capital investment per cow, relationships were curvilinear. A lower variable production cost was associated with those herds having fewer days open, younger age at first calving, higher percent days in milk, lower percent cows leaving the herd, and heavier cows. Average body weight of all cows, average days dry, cows per worker, and tillable acres per cow had very little relationship with the variable production cost.     

The impact of cooling ponds in North Central Texas on dairy farm performance

The objective of this study was to determine whether measurable differences existed between farms with and without cooling ponds. Data from Dairy Herd Improvement records for 1999 through 2002 were obtained on 42 herds located in North Central Texas. Nineteen herds had installed cooling ponds, whereas 23 herds had not. Monthly somatic cell counts for each herd were obtained from the Federal Milk Market Administrator. Data were analyzed using the PROC MIXED regression model of SAS. Within and across herd groups, milk production from June to October was significantly lower compared with milk production for the rest of the year. Although there was numerically higher average milk production per cow per day throughout the year for herds that used cooling ponds, differences between herd groups that used or did not use cooling ponds were significant only for August production. Herds without a cooling pond had 4.8 kg/d per cow lower production in August than in the cool-season months of November to May (26.4 ± 0.6 vs. 31.2 ± 0.5 kg/d), whereas the difference in August production was only 2.9 kg/d per cow in herds that used cooling ponds (29.0 ± 0.7 vs. 31.9 ± 0.6 kg/d). Differences caused by seasonal use of a cooling pond in culling, days to first service, days open, percentage of estruses observed, and somatic cell counts were not significant. Bulk tank milk samples cultured for 10 different bacteria showed no difference between cooling pond and noncooling pond herds in 2002. Also, there was no difference in incidence of violations from the Texas Department of Health for herds that used or did not use cooling ponds. However, herds with cooling ponds did have a lower percentage of successful breedings, fewer days dry, and a higher percentage of cows in milk compared with dairy herds that used other forms of cooling. Such differences may or may not be attributed to seasonal use of a cooling pond. Therefore, cooling ponds may provide relief from heat stress without adversely affecting most important measures of herd performance.     

Estimating milk loss based on somatic cell count at the cow and herd level

There is a direct relationship between elevated somatic cell count (SCC) in an individual cow milk production and milk loss. This relationship has been used at the herd level to estimate an overall herd milk loss due to subclinical mastitis and to use recovery of this lost milk as a financial benefit to cover the cost of intervention strategies to improve milk quality. The objective of this study was to estimate the recoverable milk revenue on a per cow basis for herds moving from one herd average SCC level to a newer, lower level. Test-day records from 1,005,697 dairy cows in 3,741 herds between 2009 to 2019 were used. Milk yield loss for each cow in each herd on test day was estimated using a mixed effects regression equation, and then summed to estimated total herd milk loss. These herd average daily milk loss estimates were then related to the bulk tank SCC, and the distribution of underlying individual cow SCC were examined. The distributions in daily herd milk loss for various bulk tank SCC values were generated, and estimates of recoverable milk loss were generated to simulate a herd moving from their current bulk tank SCC to a new lower level. The results indicate that estimates of total herd milk yield loss vary with the distribution of cow-level SCC and parity within the herd, so it is imperative that milk loss be calculated on a per cow basis. Further, the recoverable milk loss estimates based on moving to a lower bulk tank SCC where milk loss is still occurring was relatively small compared with the traditional assumption that all milk loss would be recovered, and less than most herd owners and advisors would expect.     

Economic effect of short (35-d) compared with conventional (60-d) dry period management in commercial Canadian Holstein herds

The Canadian dairy industry operates under a supply management system with production quotas (expressed in kilograms of butterfat per day) owned by dairy producers. Any management strategy influencing production responses must, therefore, be evaluated to estimate its effects on quota needed to sell the milk produced. In the present study, half of the cows from 13 commercial herds (850 cows, average of 70 cows per herd) were assigned to be managed for a short dry period (SDP; 35 d dry) and the other half was managed for a conventional dry period (CDP; 60 d dry) to evaluate the economic impact of a steady state involving either CDP or SDP. Economic variables included in the partial budget were: variations in revenues from milk and components as well as animals sold; costs related to feeding, reproduction, replacement, housing, and treatments. All variables were first estimated on a cow basis for each herd individually, and average results were used to calculate the partial budget for an average herd. Yearly milk and component yields per cow increased, which implies that fewer cows are required to produce the same amount of quota. Accordingly, 2 scenarios were investigated: in the first one, available quota was kept constant, and herd size was adjusted to avoid over-quota production. Consequently, the partial budget was calculated considering that 5 fewer cows were present in the herd. In this situation, switching to an SDP management increased net annual income for the farm by $2,677 (Can$), which represents $41.38 per cow. In the second scenario, the number of cows was kept constant, but additional quota (5.5 kg/d, $25,000/kg) was bought to allow selling all of the milk produced. In this case, net farm income was increased by $17,132 annually with SDP, which represents $245.18 per cow. This budget includes interest on the purchase of quota. A comparison of partial budgets for individual herds involved in the study revealed considerable variation among herds. Switching from a CDP to a SDP management would be beneficial for average dairy herds in eastern Canada.     

The association of herd milk production and management with a return-over-feed index in Ontario dairy herds

Associations of herd milk production and management variables to a return-over-feed (ROF) herd profit index were examined among 95 dairy farms. The ROF index is derived from 2 important determinants of profit on dairy farms: milk income and feed cost. All producers were participants in the Dairy Herd Improvement (DHI) ROF program in Ontario, Canada during 2002. Nutrition, housing, health, and other management data were collected through a phone survey of herd managers. Herd milk production, milk component percentages, and somatic cell count data were obtained from the Ontario DHI database. The linear regression model accounting for significant variation in ROF with highest R2 (0.66) included standardized milk production, milk protein percentage, milk fat percentage, and use of monensin in lactating cow rations. A 1-kg increase in standardized milk production (kg/d per cow) or a 0.1 percentage unit increase in milk protein was associated with $0.35/d per cow or $0.26/d per cow increase, respectively, in the ROF of the dairy herd. However, a 0.1 percentage unit increase in milk fat was associated with a $0.10/d per cow decrease in ROF, probably because of a negative association of milk fat with milk yield. Use of monensin in lactating cow rations was associated with a $0.39/d per cow increase in ROF. In a separate model (R2 = 0.27) that examined management factors independent of production variables, herds using 3 times daily milking had a $1.25/d per cow higher ROF vs. herds using twice daily, whereas use of an Escherichia coli mastitis vaccine was associated with $0.59/d per cow higher ROF. Production-related variables accounted for more variation in the ROF index than management variables, and the latter, e.g., use of monensin, only marginally increased R2 of production-based regression models.     

Sources of variation in milk urea nitrogen in Ohio dairy herds

The purpose of this study was to estimate the amount of variation in milk urea nitrogen (MUN) concentrations attributable to test-day, individual cow, and herd effects and to describe factors associated with MUN measurements in Ohio dairy herds. The data came from 24 Holstein herds, half of which were classified as low producing (LP) [rolling herd average (RHA) milk production < 7,258 kg] and half as high producing (HP) herds (RHA production > 10,433 kg). MUN concentration was measured from cow's monthly test-day milk samples. The data were analyzed using multilevel modeling technique in MLwiN, separately for LP and HP herds. The unadjusted mean MUN was 13.9 mg/dl for the HP herds and 11.3 mg/dl for the LP herds. The variance structure was different between the two groups. Most of the variability was found at test-day level in the LP herds, but at herd level in HP herds. MUN was lowest during the first month of lactation, and also season was associated with MUN in both groups. Test-day milk yield, milk fat percentage, and SCC were associated with MUN in the HP herds. With significant explanatory variables in the model, proportionally more of the variation was explained at herd level and less at test day level in both groups. Lower variability in MUN between test days in the HP herds may indicate more consistent day-to-day feeding and management within a herd. The great variability between test days should be considered when interpreting MUN and samples should be collected at the same time of the day to minimize day-to-day variability.     

Weekly balancing crude protein in diets for Holstein cows throughout lactation using one versus two grains.

Holstein cows (n = 72, 28 primiparous) were fed for ad libitum intake a forage mixture (corn and haycrop silages, 63:37 DM) and a 71:29 ratio of two grain mixtures (13.8 and 36.2% CP, DM basis) at 1 kg/2.5 kg of the previous day's milk during 1 to 28 DIM (covariate period). Thereafter, rations were balanced and adjusted for energy and CP weekly based on monthly DHI data, forage analyses, and NRC requirements. Cows were blocked by parity (1 vs. greater than 1) and assigned randomly to receive one grain (blend of 13.8 and 36.2% CP grains, herd mean) or two grains according to individual needs. Daily yields of milk, 4% FCM, SCM, and resulting intakes of grain were higher for cows fed two grains, but the increase in daily DMI and the decreases in daily forage intake and SCM:grain ratio were not significant. Fewer pluriparous cows (3 vs. 8 out of 19) on the two-grain treatment conceived after first service, but overall services per conception (1.97) were equal. Percentage of cows with SCC below linear score 4 (91%) was equal between treatments. Means adjusted by covariate 4% FCM resulted in more modest treatment effects. Advantage of two-grain versus one-grain treatment for milk per day was 7.7% for parity 1 and only 1.6% for parities greater than 1; corresponding responses (nonsignificant) for 4% FCM were 2.8 and 4.3, respectively. Forage DMI depressions on two-grain treatment were not significant. When covariate-adjusted means were used, the advantage in income over feed cost for individualized feeding of CP was $106 and $36/yr per cow in parities 1 and greater than 1 when cows produced 8209 kg (313 DIM) and 8527 kg (320 DIM) of milk, respectively.     

Effect of milk production on reproductive performance in dairy herds

The objective of the present study was to assess the relationship between individual cow milk yield and fertility, accounting for the contextual effect of the herd. A data set including 657,968 lactations from 677 dairy herds in Argentina from 2001 to 2012 was used. The odds of pregnancy by 100 d in milk (DIM) were assessed by a multilevel logistic model (with cow as the first and herd as the second hierarchical level), and time to pregnancy was assessed by a proportional hazards regression model. Multilevel logistic models included the fixed effects of milk yield by 80 DIM, parity, year, and calving season at cow level and quartiles of herd milk yield by 80 DIM as a contextual effect. The proportional hazards model included the effect of daily cow-level milk yield as time-dependent variable, with milk yield at herd level as the stratification variable. Cows producing 1 standard deviation over the mean milk yield of their herd had 1.3 percentage point lower pregnancy by 100 DIM (from 31.4 to 30.1%; odds ratio = 0.942) when in herds in the top quartile of milk yield, whereas they increased 0.5 percentage points (from 27.9 to 28.4%) when in herds in the lowest quartile of milk yield. Only 4% of the observed variation in pregnancy by 100 DIM was explained by the random effect of the herd. Similarly, cows producing 1 standard deviation (8 kg/d) greater than the herd mean daily milk had 1.3% lower hazard of pregnancy (hazard ratio = 0.987) at 63 DIM in herds in the top quartile of milk yield, whereas they had 14.8% higher hazard (hazard ratio = 1.148) in herds in the lowest quartile of milk yield. The magnitude of the negative association between the cow's daily milk yield and the hazard of pregnancy increased with DIM. In conclusion, the relationship between milk yield and reproductive performance is statistically significant, but the effect size is practically small and is modulated by herd production level.     

Associations between nondietary factors and dairy herd performance

Forty-seven dairy herds (approximately 3,129 lactating cows) from northeast of Spain that were offering exactly the same lactating ration were surveyed to determine the effect of nondietary factors on herd performance. The survey collected information on the profile of the owners (their future intentions, the number of workers, and time devoted to the enterprise), information regarding the animals (reproductive performance, incidence of pathology, culling rate, etc.), information on the facilities (number of feeders, waters, stalls, cleanliness, etc.) and information on management practices (numbers of daily milkings, feed deliveries, feed push-ups, cleaning frequency, etc.). In addition, the chemical quality of drinking water from each dairy enterprise was determined. Also, amount of feed delivered to each herd, daily total milk production, and milk quality were obtained for each herd for a period of 8 mo before the fulfillment of the survey. Mortality rate of calves tended to be lesser in herds that weaned progressively than in those that weaned abruptly. Age at first calving was negatively correlated with level of milk production (mainly due to the type of heifer rearing system used). Culling rate tended to be lower in herds that used a close-up ration than in those that did not. Using gloves and paper towels (instead of cloth towels) tended to reduce the somatic cell count in milk. Concentration of calcium in the drinking water tended to be negatively correlated with the number of days open and with the proportion of cows culled due to infertility problems. Despite that the 47 herds fed the same ration and shared a similar genetic base, average milk production per cow ranged from 20.6 to 33.8 kg/d. A positive relationship (r = 0.57) between the number of stalls per cow and milk production was found. The most important nondietary factors that affected milk production in these dairy herds were age at first calving, presence or absence of feed refusals, number of free stalls per lactating cow, and whether feed was pushed up in the feed bunk. These factors accounted for more than 50% of the observed variation, not attributable to the diet, in milk yield.     

Energy balance and reproduction on dairy cows fed to achieve low or high milk production on a pasture-based system

This study investigated the energy balance, metabolic changes, reproduction, and health in Australian Holstein-Friesian cows of average genetic merit fed to produce 6,000 L of milk/cow per lactation (restricted production; Rp) on a predominantly grazed pasture diet, or 9,000 L of milk/cow per lactation (high production: Hp) on a more intensive feeding regimen by using a partial mixed ration to supplement pasture. The mean 4% fat-corrected milk (FCM) and standard deviation achieved was 8,466 ± 1,162 L/cow per lactation for the Hp herd and 6,748 ± 787 L/cow per lactation for the Rp herd. During early lactation, the degree of estimated negative energy balance was less in the Hp cows than in the Rp cows (−16.1 vs. −29.1 MJ/cow per day, respectively). Consequently, the mobilization of body reserves was also lower in the Hp cows, and this was reflected in lower concentrations of nonesterified fatty acids (0.70 vs. 0.84 mmol/L) and β-hydroxybutyrate (0.51 vs. 0.69 mmol/L) and greater concentrations of glucose (3.51 vs. 3.34 mmol/L) and insulin-like growth factor-I (78.9 vs. 58.7 ng/mL) for Hp and Rp cows, respectively. After calving, body condition score and body weight decreased to a similar extent in both herds and did not reflect the differences in mobilization of body reserves between the 2 herds. Reproductive performance was not significantly related to level of milk yield. The mean interval from calving to first active corpus luteum was 33 (SD = 20) d postpartum, and there were 1.4 (SD = 0.8) estrus cycles before the beginning of the breeding period (>50 d postpartum). The interval from calving to pregnancy was 114 d, and the pregnancy rate after 12 wk of mating was 74%. The number of cows with ovarian abnormalities was also similar between the 2 herds. Cows with a long postpartum anestrus had the lowest concentration of insulin-like growth factor-I. The number of health-related disorders was also similar between the herds, with the exception of mastitis, for which the incidence was significantly greater in the Hp cows. The results indicate that the production per cow could be increased from 6,748 L of FCM/cow per lactation for cows grazing pasture and supplemented with concentrates only at milking to 8,466 L of FCM/cow per lactation, in one lactation, by supplementing pasture with a partial mixed ration. Despite the fact that production per cow increased substantially, the degree of estimated negative energy balance and the metabolic changes in early lactation were lower and reproductive performance was maintained.     

A method to analyze production responses in dairy herds

Milk production was simulated in a 50-cow herd averaging 8182 kg of 305-d milk with a standard deviation of 1364 kg. Herd demographics were 35% first lactation, 20% second lactation, and 45% third or greater lactation cows. A lactation model was developed with the Wood's equation (Milk/d = A*DIM*e(-c*dim)) to which random variation was added to be consistent with a coefficient of variation of 10% for daily milk production. Five sequential sampling periods, 30 d apart, were randomly selected for the experiment. For each of these sampling periods data were simulated for cow, lactation number, milk, and days in milk (DIM). To the third sampling period, a known input was pulsed into each cow record to simulate a change in milk production. Inputs and number of herds simulated were -1.140 kg and 15 herds, 0.909 kg and 30 herds, -0.455 kg and 20 herds, 0 kg and 65 herds, 0.455 kg and 21 herds, -0.909 kg and 47 herds, 1.140 kg and 20 herds, and 2.270 kg and 15 herds. Regression by cow was used to estimate milk production change for the known inputs: Milk(ijk) = Intercept + beta(i)*DIM(ij) + TRT(ik) + epsilon(ijk). Parameter estimates for each cow were submitted to analysis of variance with herd as a class variable. The least square mean of TRT (dummy variable for known input of milk volume change) for herd was tested for difference from zero based on a "t" statistic. Herd responses were classed as negative, not different from zero, and greater than zero based on P < 0.10. Herd responses were categorized based on the known input to assess the ability of the method to detect a change in production. The mean estimate of TRT from the regression analysis was used to assess the ability of the method to estimate the magnitude of the known input. The regression method was able to detect changes in production greater than 0.455 kg, but is more useful when changes of 0.9 kg or greater are shown. Adjustment for days postcalving on first test day is necessary to correct for the bias in linear regression to estimate response across the curvilinear milk production function.     

Evaluation of milk yield losses associated with Salmonella antibodies in bulk tank milk in bovine dairy herds

The effect of Salmonella on milk production is not well established in cattle. The objective of this study was to investigate whether introduction of Salmonella into dairy cattle herds was associated with reduced milk yield and determine the duration of any such effect. Longitudinal data from 2005 through 2009 were used, with data from 12 mo before until 18 mo after the estimated date of infection. Twenty-eight case herds were selected based on an increase in the level of Salmonella-specific antibodies in bulk-tank milk from <10 corrected optical density percentage (ODC%) to ≥70 ODC% between 2 consecutive three-monthly measurements in the Danish Salmonella surveillance program. All selected case herds were conventional Danish Holstein herds. Control herds (n=40) were selected randomly from Danish Holstein herds with Salmonella antibody levels consistently <10 ODC%. A date of herd infection was randomly allocated to the control herds. Hierarchical mixed effect models with the outcome test-day yield of energy-corrected milk (ECM)/cow were used to investigate daily milk yield before and after the estimated herd infection date for cows in parities 1, 2, and 3+. Control herds were used to evaluate whether the effects in the case herds could be reproduced in herds without Salmonella infection. Herd size, days in milk, somatic cell count, season, and year were included in the models. Yield in first-parity cows was reduced by a mean of 1.4kg (95% confidence interval: 0.5 to 2.3) of ECM/cow per day from 7 to 15 mo after the estimated herd infection date, compared with that of first-parity cows in the same herds in the 12 mo before the estimated herd infection date. Yield for parity 3+ cows was reduced by a mean of 3.0 kg (95% confidence interval: 1.3 to 4.8) of ECM/cow per day from 7 to 15 mo after herd infection compared with that of parity 3+ cows in the 12 mo before the estimated herd infection. We observed minor differences in yield in second-parity cows before and after herd infection and observed no difference between cows in control herds before and after the simulated infection date. Milk yield decreased significantly in affected herds and the reduction was detectable several months after the increase in bulk tank milk Salmonella antibodies. It took more than 1 yr for milk yield to return to preinfection levels.     

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 1.17 kg of milk/cow per d associated with SCC.     

Effect of concentrate level on enteric methane emissions,production performance,and rumen fermentation of Jersey cows grazing kikuyu-dominant pasture during summer

The effect of concentrate feeding level on enteric CH₄ emissions from cows grazing medium quality summer pasture is yet to be investigated. Sixty multiparous Jersey cows (9 rumen-cannulated) were used in a randomized complete block design study (with the cannulated cows in a 3 × 3 Latin square design) to investigate the effect of concentrate feeding level (0, 4, and 8 kg/cow per day; as-fed basis) on enteric CH₄ emissions, production performance, and rumen fermentation of dairy cows grazing summer pasture (17 cows plus 3 cannulated cows per treatment). Enteric CH₄ emissions were measured from 11 cows per treatment group during one 7-d measurement period using the sulfur hexafluoride tracer gas technique. Pasture dry matter intake (DMI) was determined parallel with the CH₄ measurement period using TiO₂ as an external marker, and milk yield, milk composition, cow condition, and pasture pre- and postgrazing measurements were also recorded. Daily total DMI (11.2 to 15.6 kg/cow), milk yield (9.1 to 18.2 kg/cow), energy-corrected milk (ECM; 11.2 to 21.6 kg/cow), and milk lactose content (44.1 to 46.7 g/kg) increased linearly, whereas pasture DMI (11.2 to 8.4 kg/cow) decreased linearly with increasing concentrate feeding level. Daily CH₄ production (323 to 378 g/d) increased linearly due to the increase in total DMI, whereas CH₄ yield (29.1 to 25.1 g/kg of DMI) and CH₄ intensity (35.5 to 21.1 g/kg of milk yield; and 28.8 to 17.6 g/kg of ECM) decreased linearly with increasing concentrate feeding level. Diurnal ruminal pH (6.45 to 6.32) and in sacco DM and neutral detergent fiber disappearance decreased linearly. Acetic and propionic acid were unaffected by treatment, whereas butyric acid (5.21 to 6.14 mM) increased linearly and quadratically with increasing concentrate feeding level. It was concluded that a high concentrate feeding level not only increases animal efficiency but is moreover a viable CH₄ mitigation option for dairy cows grazing kikuyu-dominant pasture in late summer when pasture is inherently fibrous.     

An Evaluation of Management Practices Used by Southern Dairy Farmers

Objectives were to examine the effect of using selected dairy farm management practices and other factors on average milk yield per cow and to evaluate characteristics explaining differences among dairy farmers in adopting practices. Data were obtained from 2712 operators of southern dairy farms. They were classified by management practices used including Dairy Herd Improvement records, artificial insemination, forage testing, balanced rations, and concentrate feeding methods. Feeding part of the concentrates at milking and part at other times showed increases of 190 to 259 kg yield per cow over feeding all the concentrate at milking. Compared with herds in which no identified practice was used, herds in which records or artificial insemination were used had 467 and 358 kg more yield per cow, respectively, and in herds in which all the practices were used the milk yield (per cow) was 1066 kg more.Factors affecting dairy farmer use of management practices were herd size, yield per cow, type of ownership, and education. A typical dairy farmer using all the management practices had a larger herd producing above the average, was younger than average, was in a farm partnership, and had a college education.     

A systems comparison of once- versus twice-daily milking of pastured dairy cows

The objective of this study was to compare the effect of milking frequency (once vs. twice-daily milking) and breed (Holstein-Friesians vs. Jerseys) on milk and milk solids (MS; milk fat + milk protein), yield per cow, milk composition, somatic cell count and lactation length; cow body weight, body condition score, and reproductive performance over a 4-yr period. Total cow numbers in each herd were 30, 35, 36, and 42 for Holstein-Friesians milked once or twice daily, and Jerseys milked once or twice daily, respectively. Forty hectares of pasture were subdivided into 4 smaller pastures of 10 ha each. Stocking rates for the once-daily herds were 16.7% greater than the twice-daily herd in their respective breed. An increased stocking rate was chosen to achieve equal milk and MS per ha from the 2 milking frequencies. Annual milk, fat, protein, and lactose yields per cow were less for once-daily than for twice-daily milking. Interactions were detected between milking frequency and breed for annual milk, fat, protein, and lactose yields per cow, because Jerseys were relatively less affected by once-daily than by twice-daily milking than Holstein-Friesians. Holstein-Friesian cows milked once daily produced 31.2% less milk and 29.4% less MS per cow than their twice-daily counterparts. In contrast, Jersey cows milked once daily produced 22.1% less milk and 19.9% less MS per cow than their twice-daily counterparts. Milk per ha was 17.7 and 9% less for the once-daily Holstein-Friesians and once-daily Jersey herds, respectively, compared with their twice-daily counterparts, because the greater stocking rate for the once-daily herds did not fully compensate for the milk loss per cow. Milking once daily increased somatic cell count throughout the year in both breeds. Cows milked once daily conceived 3 d earlier, took 5 d less from calving to conception, and needed 11% fewer controlled internal drug release devices than those milked twice daily. Milking once daily is a viable milking option for New Zealand farmers who are prepared to trade-off loss of MS income for increased time to accomplish other non-milking activities.     

Time to the occurrence of a decline in milk production in cows with various paratuberculosis antibody profiles

Infection with Mycobacterium avium ssp. paratuberculosis (MAP) in dairy cattle often results in reduced milk production and premature culling. Some test-positive animals can live for years without being affected by infection, whereas others are test negative when they die from the infection. Our objective was to describe the deviation in milk production of cows with various MAP antibody profiles compared with their repeatedly test-negative herdmates in the same parity. Data were obtained from herds participating in the Danish control program on paratuberculosis, for which 4 annual MAP antibody ELISA of individual cows were performed per herd per year. A total of 136,489 ELISA results from 38,998 dairy cows in 64 herds were used along with 484,285 test-day records on energy-corrected milk (ECM) yield. Cows were divided into 6 antibody groups based on their repeated milk ELISA results: A0) repeated ELISA negative; A1) ELISA negative, but only once; A2) ELISA negative on the last 3 tests, but with 1 previous positive result; A3) ELISA negative on the last test, but with 1 or more previous positive results; A4) last sample was ELISA positive, but all previous were negative; and A5) at least the last 2 samples were ELISA positive. The expected test-day kilograms of ECM by herd and parity were estimated for cows in antibody group A0. Deviations from expected milk production were then assessed for cows in the other antibody groups relative to the time of the first test-positive ELISA result (D 0). Cows in groups A2, A3, and A5 produced approximately 0.5 kg of ECM/d more than cows in group A0 at 300 d before D 0. Cows in group A4 had a decline in milk production from d 300 before D 0, with daily milk production reduced by 5 kg of ECM at 200 d after D 0. Milk production of cows in group A5 was reduced by 2.5 kg of ECM at 300 d after D 0 compared with 300 d before D 0, whereas cows in groups A2 and A3 produced 0.5 kg of ECM more than cows in group A0. The conclusions of the study were that 1) increasing the number ELISA tests increases the predictive value of ELISA for inference on milk production losses, 2) a combination of ELISA with assessment of observed milk production may be a valuable tool for decisions on culling, and 3) the declines in milk production attributable to MAP occurred over a long time period, and may not be realized by the herd manager without more advanced management tools such as the model proposed here.     

Yields and persistency of lactation in Friesian and Jersey cows milked once daily

Effects of milking cows once daily throughout lactation at high stocking rates (17% more cows/ha than for those milked twice daily) were studied in 2 Friesian and 2 Jersey herds during 3 lactations. Cows were allocated to 2 herds within breed and were milked either once or twice daily, based on age, genetic merit, and previous performance. Cows remained in their original herd and were milked at the same milking frequency during all lactations. Culled cows (20% per year) were replaced by 2-yr-old heifers. Yields of milk, lactose, protein, and fat were measured every 2 wk by commercial herd test. Cubic splines (5 knots) were used to approximate the lactation curve for each cow-yr to provide estimates of performance for each day of lactation. Yields of milk were greater for Friesian and Jersey cows milked twice daily (4,751 ± 89 and 3,067 ± 81 kg/cow) than for cows milked once daily (3,329 ± 80 and 2,431 ± 75 kg/cow), respectively. Cows milked once daily had lesser total and peak yields of milk, lactose, protein, and fat than cows milked twice daily. Friesians had greater total and peak yields than Jerseys. Peak production for all milk components occurred earlier in lactation for cows milked once daily than twice daily (d 24 to 39 vs. 32 to 44). Three measures of persistency of lactation were considered for each cow with 2 measures (Pers1 and Pers2) indicating that cows milked twice daily had better persistency than those milked once daily. Ranking of herds in persistency tended to match the ranking based on total yields. Measures of persistency (Pers1 and Pers2) were positively related to total yield in the Jerseys milked once daily and negatively related to peak yield in the Friesians. The third persistency measure (Pers3) ranked once-daily Jerseys first and twice-daily Friesians last, and was negatively correlated with total yield in the Friesian herds and negatively correlated with peak yield in all herds. For most performance measures, cows milked twice daily had better total yields and persistency than cows milked once daily.     

Relationship of Use of Dairy Herd Improvement Records to Herd Performance Measures,

Questionnaires and DHI herd summaries from 543 Ohio dairy farmers with Holstein cows were analyzed in relation to changes in herd performance measures, milk production, and herd size from 1976 to 1983. Milk production per cow increased 77.3 kg/yr and herd size increased by 11.8 cows during the period. Percent cows culled increased, but age at first and last calvings decreased significantly. Calving interval, days to first service, age at first calving, and age at last calving were significant contributors to change in milk production from 1976 to 1983. Respondents who agreed strongly that DHI records were worth the price increased production per cow by 816 kg from 1976 to 1983 compared with 254 and 63 kg for respondents who where neutral or strongly disagreed with the question. Percent changes in herd size and production were highest for younger farmers. Respondents with more productive herds thought they had adequate time to analyze their records.