Three times a day milking during the first half of lactation

Three milking frequency treatments were compared: twice daily milking; thrice daily milking until milk dropped below 24 kg; thrice daily milking until milk dropped below 31 kg. Three time milking was at least 45 days but no more than 150 days. Cows (12 to 14 per group) were managed alike except for milking frequency. In early lactation, increased milking had little effect. With time the superiority in yields increased such that cows on three times for 150 days were outproducing two time cows by 20%. Cumulative milk yields were greater for the thrice groups than for the twice group by 5% at 56 days, 11 and 8% at 154 days, 11 and 9% at 182 days, and 10% at 280 days. Fat percentage, adjusted for previous lactation fat percentage, averaged .2 to .3% lower for the cows milked three times until 24 kig but only .1% lower for cows milked thrice until 31 kg. Increased yield was primarily from prolonged peak yield and less subsequent decline. Switching from three to two milkings decreased yield 6 to 8% in the 1st wk. However, three time milking had a positive carryover, apparently due to higher starting yield at the point at which they were switched.     

Effects of continuous milking during the dry period or once daily milking in the first 4 weeks of lactation on metabolism and productivity of dairy cows

The objective was to compare the effects of 3 management systems in high-yielding dairy cows on metabolic profiles and milk production. Thirty-six multiparous Brown Swiss cows were randomly assigned to 1 of 3 treatment groups (n = 12 cows/group): the control (C) group, in which cows were dried off 56 d before calving and milked twice daily throughout next lactation (305 d); the once daily milking (ODM) group, in which cows were dried off 56 d before calving and milked once daily for the first 4 wk of lactation and twice daily for the remaining lactation; and the continuous milking (CM) group, in which cows were milked twice daily until calving and also during the subsequent lactation. Serum glucose concentrations decreased between wk 1 and 4 exclusively in C cows. Serum concentrations of NEFA and BHBA in the first 4 wk of lactation were highest in C cows compared with ODM and CM cows. Decreased backfat thickness during early lactation and reduction of body condition score were markedly more pronounced in C cows compared with ODM and CM cows. Mean lactational milk yield of C cows [11,310 ± 601 kg of energy-corrected milk (ECM)/305 d] was approximately 16% higher compared with ODM cows (9,531 ± 477 kg of ECM/305 d) and CM cows (9,447 ± 310 kg of ECM/305 d). The lactation curve of CM cows compared with C cows was characterized by a similar time of peak yield (wk 3), a reduced peak yield, and no obvious differences in persistency. Mean percentage of milk protein was significantly higher for CM cows (3.91%) compared with C cows (3.52%). In contrast, once daily milking was accompanied by a reduced and significantly delayed peak yield (wk 8) compared with the control treatment, whereas persistency was better and milk protein (3.79%) was higher in ODM cows than in C cows. In conclusion, continuous milking and once daily milking, targeting the interval before or after calving, respectively, substantially reduced the metabolic challenge of fresh cows and improved milk protein percentage. Continuous milking and once daily milking increased milk protein percentage markedly; furthermore, once daily milking during the first 4 wk of lactation improved the lactation curve.     

Modeling daily energy balance of dairy cows in the first three lactations

Daily energy balance was calculated for 111 Holstein cows in their first 3 lactations, based on combinations of smoothed preadjusted phenotypic records for milk yield, feed intake, live weight, and body condition score. Two energy balance traits were defined: one based on milk yield and feed intake (EB1) and the other on live weight and body condition score change (EB2). Bessel functions (BF), Legendre polynomials (LP), sinusoidal functions (SF), and cubic splines (CS) were used to model energy balance within and across lactations. Models with BF or LP fitted fixed regressions of order 1 to 6 and random regressions of order 1 to 10. Cubic splines were fitted at 5 to 30 equally spaced knot points. In within-lactation analyses with BF and LP models, likelihood ratio tests revealed that the fit improved significantly up to random regression order of 5 for EB1 and 4 for EB2, independently of the fixed regression order. For EB1 analyses with LP, improvement was marginal albeit significant even for higher random regression order. For CS models, optimal number of knot points was 13 and 12 for EB1 and EB2, respectively. Residual variance and comparisons between actual and predicted energy balance showed that LP of minimum order 8 and 5 modeled, respectively, EB1 and EB2 better than the other 3 functions. In across-lactation analyses with BF and LP models, likelihood ratio tests were significant as the random regression order increased, for any order of the fixed regression. For CS models, optimal number of knot points was 14 and 16 for EB1 and EB2, respectively. Residual variance and comparisons between actual and predicted energy balance showed that models fitting CS and high (>8) random order BF or LP provided the best fit to both traits. However, in an across-lactation analysis, even higher order of LP or BF will be required to provide as good a fit as within-lactation analyses.     

Effects of 6 times daily milking during early versus full lactation of Holstein cows on milk production and blood metabolites

An experiment was conducted to determine the effects of different milking frequencies on entire lactation production performance in Holstein cows. One hundred twenty Holstein cows were assigned to 3 milking treatments (35 multiparous and 5 primiparous cows in each): 1) milking 6 times daily for the entire lactation (6×); 2) milking 6 times daily for the first 90 d in milk (DIM) and switching to 3 times daily milking afterward (6×-3×); and 3) milking 3 times daily for the entire lactation (3×). Milk yield was recorded every other day during the first 60 DIM and on 2 consecutive days per week subsequently. Cows were weighed and scored for their body condition immediately after parturition and monthly afterward. Blood and milk samples were taken from each cow on 30, 60, 90, 120, 150, 210, and 270 DIM, with an additional blood sampling on 15 DIM. Milk and fat corrected milk yield was greater for 6× and 6×-3× cows than for 3× cows (36.82, 37.32, and 36.1, 36.75 versus 34.56, 35.33 kg/d, respectively) during the experimental period. Milk fat and lactose percentage were not different among treatments, but milk protein was lower in 6× cows than in 6×-3× and 3× cows. Blood glucose concentration was higher and blood nonesterified fatty acids and β-hydroxybutyrate concentration were lower in 3× cows than in 6× and 6×-3× cows during early lactation. Dry matter intake was greater in 6× cows than in 6×-3× and 3× cows (23.05, 22.58, and 22.45 kg/d, respectively). The 3× cows began to gain weight earlier than the 6× and 6×-3× cows, but there was no difference among groups for BW change regarding the entire experimental period. These results indicate that increasing milking frequency to 6 times daily increases milk yield only during early lactation and that there are no advantages of milking 6 times daily compared with 3 times daily during the mid and late lactation periods. Given the results of this study and the economical aspects of production, milking 6 times daily until 90 DIM and subsequently switching to milking 3 times daily is preferred.     

Genetic and phenotypic statistics of lactation cell counts in different lactations of Holstein cows

Between February 1977 and February 1982, 680,246 monthly test-day observations of somatic cell count were taken for Holstein cows having completed 79,124 lactations in 941 herds on the Quebec Dairy Herd Analysis Service. Data were transformed to natural log scale, and analyses were separate within five parity groups. Two lactational measures of cell count, geometric mean, and weighted (by test-day milk yield) mean of the log of monthly cell counts were calculated for each lactation. Maximum likelihood, iterative Minimum Norm Quadratic Unbiased Estimation, and multivariate Restricted Maximum Likelihood procedures were used for estimation of genetic and phenotypic parameters. Repeatabilities of log test-day cell counts and log of test-day cell counts corrected for milk yield were the same at each parity, .36, .41, .42, .42, and .42 in first, second, third, fourth, and fifth and later parities. Repeatabilities of lactational measures of cell count were .33 between first and second parities, .40 between second and third parities, .13 between first and third parities, and .27 between first, second, and third parities. Heritabilities of measures of lactational cell count were small from .06 to .14 in the five parities. Genetic correlations between measures of lactational cell count in different parities were close to unity, .90 to .97.     

Optimal timing and duration of unilateral frequent milking during early lactation of dairy cows

Increased milking frequency during early lactation can elicit immediate and persistent increases in milk yield; however, the timing and duration of frequent milking have not been optimized. Our objective was to use a half-udder model to determine the milk yield response to 2 wk of frequent milking imposed at 2 different times in early lactation. Multiparous Holstein cows were assigned at parturition to unilateral frequent milking [UFM; twice-daily milking (2×) of the left udder half and 4-times-daily milking (4×) of the right udder half] on d 1 to 14 (UFM-1-14) or 7 to 21 (UFM-7-21) of lactation (n = 10 cows per treatment). Cows were milked 2× before and after UFM. Half-udder milk weights were measured at 1, 3, 7, 14, 21, 28, and 35 d in milk, and then once every 3 mo for the remainder of lactation. For both treatments, the 4× udder halves produced more milk than the 2× udder halves during UFM, resulting in an average difference of 3.7 ± 0.7 kg/d in UFM-1-14 cows and 2.9 ± 0.9 kg/d in UFM-7-21 cows. After cessation of UFM, milk production of the 4× udder halves decreased in both treatments, but UFM-7-21 cows produced 1.5 ± 0.6 kg/d more milk from the 4× side than the 2× side for the remainder of the lactation. In UFM-1-14 cows, the difference was 1.2 ± 0.7 kg/d, which was significant overall, but not at 270 d in milk. In both treatments, the full-lactation yield of the 4× udder half was greater than the 2× half. Moreover, the total milk yield response to UFM observed in the current study did not differ from that observed in a previous study in which cows were assigned to UFM from d 1 to 21 of lactation. We conclude that UFM for a 2-wk interval during early lactation elicited a persistent increase in milk production of the frequently milked udder half. In addition, the overall milk yield responses observed for UFM-1-14 or UFM-7-21 were not significantly different than that previously observed for UFM on d 1 to 21 of lactation.     

Effect of milking frequency on lactation persistency and mammary gland remodeling in mid-lactation cows

The objective of this study was to evaluate the effect of milking frequency on milk production and composition, mammary cell proliferation, apoptosis, and gene expression. For this investigation, 10 Holstein cows that were being milked twice a day in mid lactation were selected. To study the effect of differential milking, 2 quarters were milked once daily and the other 2 were milked thrice daily for 8 wk. After that period, twice-daily milking was resumed for all quarters, and data were collected for an additional 6 wk. Mammary gland biopsies were taken 1 wk before differential milking (wk −1) and after 4 and 8 wk of differential milking. Milk samples were collected weekly throughout the experiment. Once-daily milking resulted in an immediate reduction in milk yield, whereas thrice-daily milking resulted in an increase in milk yield. During differential milking, the daily milk yield of the quarters milked once daily declined by 0.54 kg/wk, on average, but remained constant in the quarters milked thrice daily. Part of the difference in milk yield between the glands pairs persisted after twice-daily milking was reinitiated. In the quarters milked once daily, milk BSA concentration increased, indicating an increase in tight junction leakiness, and zymographic analysis of milk enzymes showed increased activity of several proteases. Reducing the milking frequency also increased mammary cell apoptosis and, surprisingly, mammary cell proliferation. Interestingly, milk concentrations of stanniocalcin-1 and insulin-like growth factor-I and mammary gland expression of several genes were also modulated by milking frequency. For example, expression of insulin-like growth factor I receptor was downregulated during once-daily milking. Last, expression of the short and long isoforms of the prolactin receptor and of CSN2 (β-casein) were upregulated during thrice-daily milking. Taken together, these data suggest that milking frequency not only affects mammary gland remodeling and the expression of paracrine factors but also modulates hormone sensitivity.     

Measurement of mastitis in first lactation heifers and third to fourth lactation cows

The influence of lactation stage on susceptibility to mastitis infection in Friesian dairy cows was investigated. The cattle studied included third to fourth lactation cows and both summer and autumn calving groups of heifers. No increase in vulnerability to invasion by mastitis pathogens in recently calved cattle was demonstrated. Analysis of raw milk samples using ATP bioluminescence produced variation in results, suggesting that further work to develop the technique is required.     

Energy balance profiles for the first three lactations of dairy cows estimated using random regression

Daily animal solutions were predicted using random regression analysis for feed intake, milk yield, live weight, and condition score recorded on 189 cows at the Langhill Dairy Cattle Research Centre. All cows had three successive lactations. Energy balance for days 1 to 305 of each of the three lactations was calculated both from daily measures of feed intake and milk output and from weekly measures of live weight and condition score. Cows returned to positive energy balance at days 72, 75, and 95 in lactations 1, 2, and 3, respectively, based on energy balance calculated from feed intake and milk output records (EB1), and at days 77, 83, and 73 based on energy balance calculated from body energy state changes (EB2). Correlations between energy balance at the same time in successive lactations ranged from 0.01 to 0.66 depending on the method of calculation and the stage of lactation. Energy balance over three lactations was modelled using sinusoidal functions which were associated with individual cows and allowed to vary between cows. The parameters of these curves are potentially useful since they have a biological interpretation. The phase relates to the period from calving to return to positive energy balance, and the amplitude relates to the degree of body energy loss (and recovery). The sinusoidal functions fitted to the curve removed a significant proportion of the variation, but accounted for only 45% and 40% of the variation in EB1 and EB2, respectively. The relationship between energy balance in the first three lactations is likely to be more complex than a simple linear function, but the profile of energy balance over the first three lactations may be a useful selection criteria in a multi-trait index. Energy balance profile over lactations one to three can be modelled with moderate accuracy using sinusoidal functions, and this warrants further research.     

Modeling lactation curves and estimation of genetic parameters for first lactation test-day records of French Holstein cows

Several functions were used to model the fixed part of the lactation curve and genetic parameters of milk test-day records to estimate using French Holstein data. Parametric curves (Legendre polynomials, Ali-Schaeffer curve, Wilmink curve), fixed classes curves (5-d classes), and regression splines were tested. The latter were appealing because they adjusted the data well, were relatively insensitive to outliers, were flexible, and resulted in smooth curves without requiring the estimation of a large number of parameters. Genetic parameters were estimated with an Average Information REML algorithm where the average information matrix and the first derivatives of the likelihood functions were pooled over 10 samples. This approach made it possible to handle larger data sets. The residual variance was modeled as a quadratic function of days in milk. Quartic Legendre polynomials were used to estimate (co)variances of random effects. The estimates were within the range of most other studies. The greatest genetic variance was in the middle of the lactation while residual and permanent environmental variances mostly decreased during the lactation. The resulting heritability ranged from 0.15 to 0.40. The genetic correlation between the extreme parts of the lactation was 0.35 but genetic correlations were higher than 0.90 for a large part of the lactation. The use of the pooling approach resulted in smaller standard errors for the genetic parameters when compared to those obtained with a single sample.     

Genotype and diet effects on energy balance in the first three lactations of dairy cows

Dairy cows make strategic use of body energy to support early lactation and replenish this lost energy later in lactation, thereby creating body energy profiles that vary both within lactation and across lactations. The interaction between genotype and diet energy content is interesting from a management viewpoint and from a cow survival viewpoint. In this study, we modeled energy balance over 3 lactations using a multivariate random regression model, for cows from the Langhill Dairy Cattle Research Centre. This herd has been selected for maximum production or to remain at the UK national average for production (control group) and has been fed 2 diets of different energy density (high or low concentrate). Cows in the various groups differed in body condition score and the way they lost and regained body lipid. Cows selected for maximum production on a low-concentrate diet lost the greatest amount of body lipid (0.54 condition score units) after 3 lactations. Cows selected for maximum production lost more than control cows on either diet, indicating that selection mainly for yield has predisposed cows to utilize body energy to support lactation on diets spanning the range used here. Cows selected for maximum production were heavier at first calving than control cows but lost more weight and regained more weight so that at the end of each lactation, cows in the 2 groups did not differ significantly in weight. Cows use body lipid to support lactation over 3 lactations and the profile of that use varies according to genotype and diet.     

Extended lactation in dairy cows: effects of milking frequency, calving season and nutrition on lactation persistency and milk quality

Twelve spring-calving and twelve winter-calving cows were managed for extended lactation cycles of 18-months duration, with the former group then completing a second extended lactation. Half of the cows were fed according to standard management practice for the herd; the other half received supplementary concentrate from week 9 of lactation onwards. Commencing at the same time, half of the udder of each cow was subjected to increased milking frequency (thrice daily rather than twice daily). Lactation persistency (and hence total milk yield) was significantly increased by frequent milking. Winter calving cows and supplemented cows also exhibited better persistency, but this was only evident up until the point of re-breeding, at around lactation week 33. Milk composition was measured in the spring-calving cows in both their first and second extended lactations. Composition altered during the course of the lactation, protein and fat percentages increasing and lactose percentage decreasing, irrespective of treatment. The quality of the milk for processing into cheese, fermented products, heat-treated products and cream liqueurs was assessed by calculation of casein number (casein protein as a proportion of total protein). Processing quality declined across the course of lactation in those groups that showed poor persistency but not in those that maintained a persistent lactation. Milk hygienic quality (somatic cell counts) showed parallel changes. Body condition score increased during the course of lactation but was not affected by supplementation; none of the cows became excessively fat. All cows remained healthy throughout the extended lactations and the majority (33/36) re-bred successfully. By demonstrating that lactation persistency is plastic and can be improved by simple management interventions, the results lend support to the economic arguments in favour of extended lactation cycles. The likely welfare benefits of extended lactation are also discussed.     

Estimating daily yields of cows milked three times a day

Factors to estimate daily yield from one or two sampled milkings of cows milked three times a day were derived with data for 21 mo from seven Pennsylvania herds and data for 1 yr from five Utah herds. Accuracy of estimation increased with number of milkings weighed; standard deviation of error was nearly halved when information was included from two milkings instead of one. Fat yield did not increase as much as milk yield with increased time between milkings (interval); therefore, fat percentage factors increased with interval. If fewer milkings were sampled than weighed, fat yield was estimated by adjusting sample-day fat percentage. Effect of interval on protein yield was nearly the same as on milk yield. Therefore, milk factors are recommended for protein, and no adjustment to protein percentage is necessary if fewer milkings are sampled than weighed. Factors derived for milk were tested on records from 53 California and Oregon herds. Standard deviations of errors were similar to those from Utah and Pennsylvania data.     

Effect of bull selection for somatic cell count in first lactation on cell counts and pathogens in later lactations

Somatic cell counts were measured one time on Meuse-Rhine-Ijssel cattle in The Netherlands. Experiment 1 involved 1,741 first lactation daughters of 31 bulls. Eleven bulls with daughters with either high or low average cell count were selected for further study of their daughters in third and fourth lactation. Cell counts and bacteriological tests were performed on 684 of the older daughters. A second experiment was conducted to measure daughters in second lactation and to obtain additional daughters in first lactation. This experiment recorded cell counts of 1,071 daughters of 10 of the bulls selected in Experiment 1. Heritability of the natural logarithm of cell count in first lactation was .081 based on daughters of 31 bulls in Experiment 1. Geometric daughter averages ranged from 206 to 700 X 10(3) cells/ml. Transmitting ability of bulls was estimated by the regressed least squares method. Ranking of bulls on first lactation cell count was different between the two experiments. Management factors and stage of lactation effects could be responsible for these differences. Within Experiment 2, the ranking of bulls on cell counts was nearly identical between first and second lactation. Daughter groups with low average cell count in first lactation in Experiment 2 had low averages in third and fourth lactation although some changes in ranking did occur. These results are consistent with a low to moderate genetic correlation between lactations for cell count. In general, daughter groups with higher average cell count had higher percentage of quarters with mastitis pathogens.     

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.     

Effect of milking frequency and pasture intake on milk yield and composition of late lactation cows.

Twenty-four monozygous twinsets in late lactation (> 210 d in milk) were used to examine the effects of feed restriction and milking frequency prior to drying off on milk yield and composition in a pastoral dairying system. Cows were assigned to one of four treatment groups for 26 d and were milked either twice or once daily and given either unrestricted or restricted access to feed. Dry matter intakes averaged 16 or 8 kg per cow per day, and diets comprised ryegrass and white clover pasture supplemented with 15% pasture silage. Feed restriction and once daily milking reduced milk yield and increased concentrations of milk fat and protein. Somatic cell count was increased by feed restriction only. Production losses caused by feed restriction were nearly threefold higher than were those for once daily milking. Yields of components that were mammary synthesized and serum derived were reduced by feed restriction, in accordance with milk volume reduction. Plasma lactose concentration increased with once daily milking only and indicated enhanced permeability of mammary tight junctions. Both feed restriction and once daily milking compromised milk quality, but increased leakage of serum components into milk via mammary tight junctions was deemed to occur only for once daily milking.     

Health and reproductive performance of dairy cows treated for up to two consecutive lactations with bovine somatotropin

Forty-three purebred Holstein cows were put on an rbST milk production trial. There were 15 control cows (saline-injected), 15 cows injected with 10.3 mg rbST/d and 13 cows injected with 20.6 mg rbST/d. Injections were initiated between wk 4 and 5 of lactation and continued for 266 consecutive days. Fourteen of the rbST-treated cows were treated with one of three dosages of rbST in the previous lactation (10.3, 20.6, or 41.2 rbST/d). The objective of this study was to determine the health and reproductive efficiency of cows treated with rbST for up to two consecutive lactations relative to control cows. The incidence of 11 health-related variables before, during, and after the 38-wk injection period were not different among treatment groups. Previous treatment with rbST had no effect on reproductive variables; however, there was evidence that injections with the highest dosage of rbST in the current lactation resulted in lowered reproductive efficiency. It is possible that the effects of rbST on early lactation energy and nitrogen balance have confounding effects on the estrous cycle.     

Effects of dietary amino acid balance on the response of dairy cows to an increase of milking frequency from twice to three times daily

An experiment was conducted to examine how the response of dairy cows to a change from twice to three times-daily milking is affected by deficiencies in the dietary supplies of three amino acids, His, Met, and Lys. Six cows were used in a 6 x 6 Latin square with 14-d periods. The three dietary treatments were: grass silage and a cereal-based supplement containing feather meal as the sole protein supplement; the same silage-cereal diet supplying similar amounts of metabolizable and rumen-undegradable protein but with additional amounts of His, Met, and Lys in the form of fish meal; and the fish meal diet with additional metabolizable energy in the form of an additional 2 kg/d of sugar beet pulp. Within each of these dietary treatments, the cows were milked twice and three times daily, making a total of six treatments. When cows were given the feather meal diet, even though dietary metabolizable energy was in considerable excess, a deficiency of specific amino acids prevented any increase in milk yield in response to increasing the frequency of milking from twice to three times daily. In contrast, when cows consumed a similar level of excess metabolizable energy and a similar level of rumen-undegradable protein for which the protein was of better amino acid balance (fish meal), the increased frequency of milking led to increased yield of milk and milk protein.