Quarter-milking-, quarter-, udder- and lactation-level risk factors and indicators for clinical mastitis during lactation in pasture-fed dairy cows managed in an automatic milking system

Objectives To identify risk factors and indicators at quarter‐milking and other levels for clinical mastitis during lactation in pasture‐fed cows managed in an automatic milking system. Design A retrospective nested case–control study using data collected over a 31‐month period. A total of 803,948 quarter‐milkings from 249 cows were available for analysis, of which 245 were selected as clinical mastitis quarter‐milking cases and 2450 unaffected quarter‐milkings were selected as controls. Most of the diagnoses of clinical mastitis had been made after clinical assessments of quarters following automated alerts by the milking system. Potential risk factors and indicators were assessed using univariable and multivariable multilevel logistic models. Results Quarters that are milked infrequently and have low yield, fast peak milk flow rates, blood in the milk and/or elevated milk conductivity are at increased risk of clinical mastitis. Quarters were also at increased risk between days 10 and 29 of lactation, and during higher parity lactations. Milk fat and protein concentrations and the fat : protein ratio were not significantly associated with the development of clinical mastitis. Neither quarter position (fore or rear) nor side (left or right) was associated with clinical mastitis occurrence. Quarters that had been clinically affected more than 30 days previous in the current lactation were not at increased risk of redeveloping clinical mastitis. Conclusions Under the study conditions, the risk of clinical mastitis increased for quarter‐milkings in quarters that were milked less frequently in the previous 7 days, were low‐yielding, had fast peak milk flow rates and had more milkings in which blood was detected in milk and/or the milk conductivity was elevated. Risk was also increased in days 10–29 of lactation and in higher parity lactations.     

Prediction of cow's fertility based on data recorded by automatic milking system during the periparturient period

The results of most studies show the beneficial effect of milking automation on production parameters of dairy cows, but its effect on fertility traits is debatable. Therefore, a study was undertaken to predict cow fertility – services per conception (SC) and calving interval (CI) – based on automatic milking system (AMS) data collected in the periparturient period subdivided into the second and first week before calving, 1–4, 5–7, 8–14, 15–21 and 22–28 days of lactation. SC and CI were predicted using daily indicators such as concentrate intake, number of milkings, cow box time, milking time, milking speed, colostrum and milk yield, composition, temperature and electrical conductivity. The study material was derived from the AMS management system and from the SYMLEK milk recording system. The analysis covered data for 16,329 milkings of 398 Polish Holstein-Friesian (PHF) cows, which were used in three AMS herds. The collected numerical data were statistically analysed by correlation analysis in parallel with decision tree technique (SAS statistical package). The present study showed that due to the low, mostly non-significant coefficients of correlation between AMS data collected between 2 weeks before and 4 weeks after calving, it is not possible to predict cow fertility based on single traits. It has been established that the decision tree method may help breeders, already during the postcalving period, to choose the level of factors associated with AMS milking, which will ensure good fertility of cows in a herd. The most favourable number of services per conception is to be expected from cows that were milked <1.6 times per day from 1 to 4 days of lactation and electrical conductivity of their colostrum did not exceed 69 mS during that time. In turn, shortest CI (366 days) will be characteristic of the cows whose average daily colostrum yield did not exceed 20.2 kg and their daily concentrate intake from 8 to 14 days of lactation was at least 5.0 kg.     

Artificial long-day photoperiod in the subtropics increases milk production in goats giving birth in late autumn

Two experiments were conducted to determine whether exposure to a photoperiod of artificial long days in autumn increased milk yield in subtropical goats milked once (Exp. I) or twice daily (Exp. II). In Exp. I, starting at d 10 of lactation, 1 group of does was kept under naturally decreasing photoperiod (DD1X; n = 8), whereas the other group was submitted to an artificial photoperiod of long days (LD1X; n = 8; 16 h light:8 h darkness). The kids were weaned 28 d after parturition, and dams were manually milked once daily. Milk yield and milk components (fat, protein, and lactose) were assessed up to 140 d of lactation. From d 0 to 28 of lactation (suckling phase), mean daily milk yield did not differ between DD1X and LD1X goats (2.3 ± 0.2 kg vs. 2.4 ± 0.2 kg; P = 0.717). However, between d 29 and 84 (early milking phase), mean daily milk yield was greater in LD1X does than in DD1X does (2.6 ± 0.1 kg vs. 2.1 ± 0.1 kg; P = 0.001). Finally, between d 85 and 140 (late milking phase), mean daily milk yield was greater in LD1X goats than in DD1X goats (P ≤ 0.05) only during the first 2 wk. In Exp. II, one group of goats was exposed to a photoperiod of naturally decreasing days (DD2X; n = 8) and another group was submitted to an artificial photoperiod of long days (LD2X; n = 7). In both groups, kids were weaned on d 28 of lactation and the dams were manually milked twice daily. During the nursing phase, mean daily milk yield did not differ between the DD2X and LD2X groups (2.5 ± 0.3 kg vs. 2.6 ± 0.2 kg; P = 0.767). In the early milking phase, mean daily milk yield was greater in LD2X than in DD2X goats (3.3 ± 0.2 kg vs. 2.8 ± 0.2 kg; P = 0.022), whereas during the late milking phase, milk yield did not differ between the 2 groups (P = 0.946). In both experiments, milk composition was not significantly influenced by exposure to long-day photoperiod. We conclude that, in subtropical female goats that start lactation in late autumn, exposure to an artificial long-day photoperiod stimulates milk yield, even if goats are milked once daily. In addition, combining exposure to long days with twice-daily milking will increase further milk yield in such goats without affecting milk components.     

The acyclic period postpartum in automatic and conventional milking

The acyclic postpartum period in cows is prolonged due to frequent suckling when compared with twice daily milking. In conventional milking systems twice daily milking is common, while in automatic milking systems (AMS) three or more milkings are performed in early lactation. In this study, the hypothesis was tested that an increased milking frequency in AMS causes a delay in resumption of ovarian cyclicity postpartum and increases days open in German Fleckvieh cows (n = 124). Calvings were equally distributed throughout the 1-year experimental period. All cows were housed in one barn. Sixty-three cows were milked in an AMS (AC) and 61 cows were twice daily milked in a conventional milking parlour (PC). Forty-two AC and 36 PC remained in the herd until conception. After parturition, milk samples were analysed for progesterone twice weekly to record the ovarian activity until pregnancy was diagnosed. The first and the second ovulation were determined by the progesterone profile of each individual cow. The mean milking frequency during the first 3 weeks after parturition was higher in AC (3.17 +/- 0.09 milkings/day) than in PC (milked twice daily). The individual mean milking frequency of AC for the first 3 weeks of lactation ranged from 2.0 to 5.9 daily milkings. The time span from parturition until the first and second ovulation did not differ between AC and PC. However, first ovulation was observed earlier in primiparous (23 +/- 1 days) than in multiparous cows (29 +/- 1 days, P < 0.05). Within AC no relationship between milking frequency and duration of the acyclic period was observed. Days open did not significantly differ between AC and PC and between primiparous and multiparous cows. In conclusion, the increased milking frequency in AMS did neither cause a delay in resumption of ovarian cyclicity postpartum nor did it increase days open.     

Effect of an automatic milking system on milking traits

Recent studies in Japan of the effect of automatic milking systems (AMS) on the behavior of dairy cows have confirmed the labor-saving aspect of AMS, but have not solved some of the problems affecting milking traits. The influence of AMS on milking was examined in 39 Holstein cows at Iwate Agricultural Research Center from June 1998 to December 1999, by measuring and recording the yield per milking, milking finish time, milking frequency, and daily yield of milking. Four milking traits were analyzed separately as the objective variable in a linear model, with parity, days in milking, month after installation of the AMS as independent variables. Primiparous cows milked more frequently in the middle and late stage of lactation, yielded less per milking and less per day in the early stage of lactation than multiparous cows with the AMS. Lower frequencies were observed at noon and midnight for cleaning of the bulk tank. By contrast, higher milking frequency in the forenoon was shown. The yield per milking rose and declined, following a normal lactation curve. However, milking frequency rose slowly, and declined gradually in the late stage of lactation. After installing a one-way gate, the cows milked more frequently, with a lower yield per milking and a greater daily milk yield, than before installation.     

Evaluation of maternal performance of daughters from high and low milk EPD sires

Angus bulls (n = 24) were selected for either high or low milk EPD, but with similar growth EPD and mated within location (n = 6) at random to Angus cows. Daughters from these matings were bred to calve first at 2 yr of age to common reference sires across locations. Lactation records for 192 daughters were used to evaluate 12-h milk yield, percentage of milk fat and protein, and weaning weight of offspring. Milk production was measured four times during the lactation at regular intervals within location. Dams were separated from their calves the night before milking and milked with a portable milking machine the next morning to estimate 12-h milk yield. A sample of the milk was collected from each cow and analyzed for percentages of milk fat and protein. Data were analyzed as repeated records of the dam. Fixed effects were location, genetic line of sire, gender of calf within location, and milking period, with postpartum interval used as a covariate. Fixed effects and the random effects of sire of dam nested within line, sire of calf, and year were estimated by REML. Genetic line was an important source of variation for milk yield (P < 0.01) and percentage of milk fat (P = 0.03) but not for percentage of milk protein (P = 0.49). Location was significant for all three milk variables (P < 0.01), but the interactions between line and location were not significant. Gender of calf was significant for milk yield (P = 0.04) but not for percentage of milk fat or protein. Line (P = 0.02), location (P = 0.01), calf gender (P = 0.01), and age at weaning (P = 0.01) were significant sources of variation for weaning weight but the interaction of line and location was not (P = 0.69). The correlation coefficient between the sire's milk EPD and 12-h milk yield was significantly different from zero (r = 0.56). The difference between the least squares means for high and low lines for milk yield was 0.66 kg/12 h and the difference was 15.3 kg for weaning weight. The results indicate that there was not evidence for a genotype by environment interaction in milk production for daughters from divergent sires selected for high or low milk EPD.     

Lactation persistency: insights from mammary cell proliferation studies

A persistent lactation is dependent on maintaining the number and activity of milk secreting cells with advancing lactation. When dairy cows are milked twice daily, the increase in milk yield from parturition to peak lactation is due to increased secretory activity per cell rather than to accretion of additional epithelial cells. After peak lactation, declining milk yield is due to loss of mammary epithelial cells by apoptosis. During lactation, only 0.3% of mammary cells proliferate in a 24-h period. Yet this proliferative rate is sufficient to replace most mammary epithelial cells by the end of lactation. Management practices can influence lactation persistency. Administration of bovine somatotropin may enhance persistency by increasing cell proliferation and turnover, or by reducing the rate of apoptosis. Increased photoperiod may also increase persistency of lactation by mechanisms that are as yet undefined. Increased milking frequency during the first weeks of lactation increases milk yield, even after return to less frequent milking, with increases of approximately 8% over the entire lactation. A mammary cell proliferation response to frequent milking during early lactation appears to be involved. Conversely, advanced pregnancy, infrequent milking, and mastitis increase death of epithelial cells by apoptosis. Regulation of mammary cell renewal provides a key to increasing persistency. Investigations to characterize epithelial cells that serve as the proliferative population in the bovine mammary gland have been initiated. Epithelial cells that stain lightly in histological sections are evident through all phases of mammary development and secretion and account for nearly all proliferation in the prepubertal gland. Characterization of these cells may provide a means to regulate mammary cell proliferation and thus to enhance persistency, reduce the effects of mastitis, and decrease the necessity for a dry period.     

Estimation of daily and total lactation milk yield of Chios ewes from single morning or evening records

Linear models were developed and evaluated for the estimation of daily (24 h) and total lactation milk yield of dairy sheep from single morning (am) or evening (pm) milking records. A total of 22,908 individual test-day milk records of 5110 ewes of the Chios breed, raised in 46 flocks, were used. Depending on the model, different daily milk yield estimates were derived for each ewe, accounting for lactation number, stage of lactation, season of previous lambing and interval between successive milkings. Daily milk yield was also estimated from doubling the single am or pm record. Actual and estimated yields were compared using root mean square errors (RMSEs), mean absolute differences, an accuracy parameter defined as the ratio of the actual yield variance over the sum of the variances of actual yield and absolute difference, and the product moment correlation between estimated and actual yield. Results were validated on independent datasets. Linear models resulted in less biased and more accurate estimates of the daily milk yield than simply doubling the am or pm record. Root mean square errors decreased by 7-37% and the mean absolute difference was reduced by 1-4% of the average daily yield. Higher accuracy and correlation were obtained from linear model application than doubling. Total lactation milk yield was predicted based on actual daily yield and compared to predictions based on estimated daily yield from am or pm records, as well as directly on single milking records. Root mean square errors obtained when daily yield had been estimated with linear models were 26-35% lower compared to doubling the am or pm yield and 0-13% lower compared to estimating the total lactation yield directly from single milking records. Linear model application also resulted in lower mean absolute difference and higher accuracy and correlation than doubling the am or pm record. Recording the yield of a single milking (am or pm) instead of both can benefit milk recording by reducing its cost and increasing farmer participation. In this context, linear models developed in the present study can be used for the accurate estimation of daily (24 h) and total lactation milk yield from single milking records.     

Effect of milking interval on milk yield and quality and rate of recovery during subsequent frequent milking

Forty mid-lactation, pasture-fed dairy cows were used to study the effects of milking interval on milk yield and quality and whether effects could be reversed during a short period of subsequent frequent milking. Following a 2-day pre-experimental period of normal twice-daily milking (TDM), cows were milked again after 6, 12, 18, 24 or 30 h, with each milking interval followed by 24 h of frequent milking (i.e., every 6 h). Milk yield increased linearly until 18 h and then started to plateau. Similarly, milk quality (serum albumin and proteolytic enzyme activity) became adversely affected after 18 h. These changes coincided with increased permeability of mammary tight junctions (TJ), starting after a milking interval of 18 h. A brief period of frequent milking helped restore milk yields to pre-experiment levels, even after the longest milking interval.     

New developments on the galactopoietic role of prolactin in dairy ruminants

In most mammals, prolactin (PRL) is essential for maintaining lactation and its suppression strongly inhibits lactation. However, the involvement of PRL in the control of ruminant lactation is less clear because inconsistent effects on milk yield have been observed with short-term suppression of PRL by bromocriptine. By contrast, in vitro studies have provided evidence that PRL helps to maintain the differentiation state and act as a survival factor for mammary epithelial cells. Therefore, a series of experiments were conducted to assess the galactopoietic role of PRL. In a first experiment, daily injections of the PRL inhibitor quinagolide reduced milking-induced PRL release and induced a faster decline in milk production. Milk production was correlated with PRL released at milking. Quinagolide reduced mammary cell activity, survival, and proliferation. During the last week of treatments, differential milking (1× vs 2×) was applied. The inhibition of milk production by quinagolide was maintained in the udder half that was milked 2× but not in the udder half milked 1×, suggesting that the response to PRL is modulated at the gland level. In a second experiment, cows were injected with quinagolide, quinagolide + injection of bovine PRL at milking time, or water. As in the first experiment, quinagolide reduced milk, protein, and lactose yields. Although PRL injections at milking time were not sufficient to restore milk yield, they tended to increase milk protein and lactose yields and increased the viability of milk-purified mammary epithelial cells. Recently, we investigated the use of quinagolide at drying off. Treating late-lactation cows with quinagolide decreased milk production within the first day of treatment and induced faster increases in somatic cells and bovine serum albumin content in mammary secretions after drying off, which indicates an acceleration of mammary gland involution. In conclusion, these data, combined with data from other studies, provide a good body of evidence indicating that PRL is galactopoietic in dairy cows. However, the response to PRL appears to be modulated at the mammary gland level.     

Forecasting the milk yield of cows on farms equipped with automatic milking system with the use of decision trees

The purpose of this paper was to utilize the decision trees technique to determine the factors responsible for high monthly milk yield in Polish Holstein‐Friesian cows from 27 herds equipped with milking robots. The applied statistical method—the decision tree technique—showed that the most important factors responsible for monthly milk yield of dairy cows using robots were, in descending order of importance: milking frequency, lactation number, month of milking, and type of lying stall. At the same time, it has been ascertained that the highest monthly milk yield (47.24 kg) can be expected from multiparous cows kept in barns with a deep bedding that were milked more frequently than three times per day. On the other hand, the lowest milk production (13.56 kg) was observed among dairy cows milked less frequently than two times a day, with an average number of milked quarters lower than 3.97. The application of the decision trees technique allows a breeder to select appropriate levels of environmental factors and parameters that will help to ensure maximized milk production.     

A comparison of the direct and residual response of dairy cows to once or twice-daily milking, in late lactation

Two experiments were undertaken to examine the direct and residual responses of late lactation (mean of 232 days calved) autumn calving dairy cows (Experiment 1), and late lactation (mean of 240 days calved) spring calving dairy cows (Experiment 2), to once-daily milking. Experiments 1 and 2 involved 50 and 44 Holstein–Friesian dairy cows respectively. In each of the two experiments, cows were milked either once daily (ODM) or twice daily (TDM), during the late lactation period (mean of 79 and 66 days in Experiments 1 and 2 respectively). Cows in Experiment 1 were managed within a grazing system, and were offered 3.0 kg of concentrate/day, while cows in Experiment 2 were housed, and offered grass silage supplemented with 6.0 kg concentrate/day. Forty-one cows from Experiment 1, and 32 cows from Experiment 2, completed the first eight weeks of the subsequent lactation on a twice-daily milking regime. Food intakes were not measured in Experiment 1, while treatment had no significant effect on dry matter intake in Experiment 2 (P > 0.05). In each of Experiments 1 and 2, total milk output was increased with twice-daily milking (P ≤ 0.05), while milk fat (P ≤ 0.01) and protein (P < 0.001) concentrations increased with once-daily milking. Somatic cell counts were higher with animals milked once daily in Experiment 1 (P < 0.001), while not being significantly affected by milking frequency in Experiment 2 (P > 0.05). Milking frequency had no significant effect on cow live weight or on cow condition score at the point of drying off in either Experiment (P > 0.05). Milking time per cow during morning milking was unaffected by treatment in either experiment, while total daily milking time per cow (morning and evening combined) was significantly longer with the TDM treatment (P < 0.001). In Experiment 1, milk flow rates during the morning milking were higher with animals on the ODM treatment, compared to those on TDM treatment (P < 0.001), while being unaffected by treatment in Experiment 2 (P > 0.05). Neither daily milk yield, milk fat content, milk protein content, or somatic cell count during the subsequent lactation, were affected by previous lactation milking frequency in either of Experiments 1 or 2 (P > 0.05).     

The cell count in milk of goats]

Weekly milk samples were taken from mammary halves from 30 goats from 8 different herds each with from 2 to 5 experimental animals throughout their lactation periods. The physiological variations in the cell counts of goats milk during lactation were investigated by a projection microscope. Only small variations were found in the average cell counts in milk samples from goats in the same herd, but big variations from one herd to another (Table I and Fig. 3.). The curves of the average cell counts in milk samples of 5 herds showed a rise at the beginning of the season at pasture (Fig. 1 and Fig. 2). Also in the housed periods the cell count showed transitory rises. The herd with the lowest average cell count (220,000/ml) was milked by an ordinary bucket milking system, while the herd with the highest average cell count (1,490,000/ml) was milked by a pipeline milking system. Five herds milked by machine had an average cell count of 720,000/ml and three herds milked by hand 540,000/ml. All the herds in the material had an average cell count of 680,000/ml.     

Influence of milking technique and lactation on the bovine teat by means of ultrasonographic examination

The teats of Brown Swiss and Austrian Simmental cows, divided into two groups, one milked by means of an automatic milking system, the other using a conventional milking parlour, were examined monthly by ultrasonography. Aim of the study was to compare the effects of two different milking machines upon the structures of the bovine teat canal and wall by ultrasonography and thereby evaluate ultrasonography as a research tool for visualisation of different influences on the bovine teat. Length and thickness of the teat canal and teat wall thickness were measured and analysed. During lactation, teat canal length and thickness increased in both groups, teat canal length decreased in conventional milked cows at the end of lactation. Shorter and narrower teat canals were observed in automatic milked cows. Differences between the groups in teat canal length and thickness were determined in early lactation. During lactation teat wall thickness showed a slight increase. Automatic milked cows displayed thinner teat walls than cows milked in the milking parlour. Teat morphology was influenced by the number and duration of lactations, milk yield, quarter of the udder and time and date of examination. It was concluded that the effect of the two different milking machines caused significant differences in bovine teat morphology and that ultrasonography proved to be an appropriate method for visualising influences of the milking technique on the bovine teat.     

Lactation curves of commercial ewes rearing lambs

Three-hour milk production measurements determined by machine milking at 3-d intervals throughout a 63-d lactation period were used to describe lactation curves for crossbred ewes lambing at 1 and 2 yr of age and rearing single and twin lambs. Age of ewe, type of rearing, and day of lactation affected (P < 0.05) milk production. Over the 63-d lactation, average daily milk production was 2.56 and 2.63 kg, respectively, for 1- and 2-yr-old ewes rearing single lambs and 2.73 and 3.47 kg, respectively, for 1- and 2-yr-old ewes rearing twins. Milk production of 2-yr-old ewes rearing twin lambs peaked at 21 d of lactation, and that of 1- and 2-yr-old ewes rearing singles peaked between 27 and 30 d of lactation. The largest differences in the lactation curves among age and rearing ewe classes were found in early lactation. These differences were reduced by midlactation, and by late lactation, milk production for all ewes was similar. Diurnal variation in milk production by ewes was evaluated in an 8 x 8 Latin square design. Diurnal variation in milk yield measurements of eight mature ewes, each bearing and rearing twin lambs, was similar between d 21 and 24 of lactation. Time of milk production measurements within a day did not affect yield determinations. Extrapolation from 3-h production estimates to daily milk production is valid in determining a ewe's milk contribution in support of lamb growth.     

Effects of short periods of frequent milking on the persistency of milk yield and SCS in Turkish Saanen goats

The major purpose of this study was to investigate if increasing milking frequency for a short period of 3 weeks had any effects on the persistency of milk yield and the persistency of the somatic cell score (SCS). The methyl green–pyronin method was used for the direct microscopic SCS, converted to SCS for the analyses. Two groups were formed (control, n = 14 and treatment, n = 14). The treatment group was milked four times a day for 3 weeks after weaning. Both groups were milked twice a day outside this 3‐week period, throughout lactation. For the milk yield, persistencies were higher in the treatment group when the distance between the test days was equal to or less than 3 months. The exact opposite was true for the SCS; that is, the treatment group had higher persistencies when the distance between the test days was more than 3 months. Overall, persistencies related to milk yield were higher than persistencies related to SCS. For fat corrected milk yield, treatment persistencies were always higher than the control group persistencies, regardless of the distance between the tests. The same was true for the fat content. Increasing milking frequency for a short period of time (3 weeks) after weaning may help to increase the persistency of the milk yield, fat corrected milk yield and fat content. A 3‐D plot of least squares means indicated that the milk yield tended to show a classical lactation curve in lower SCS values while forming an unstable curve in higher SCS values.     

An automated in-line clinical mastitis detection system using measurement of conductivity from foremilk of individual udder quarters

AIM: To assess a novel method for automatic in-line detection of clinical mastitis.

METHODS: For a brief period at the start of milking for each cow, electrical conductivity of foremilk was measured for each quarter in turn, using a single sensor installed in the long milk tube (LMT) about 1.5 m downstream from the milking-machine claw. Sequential separation of flow between udder quarters was achieved by control of pulsation to individual teatcups within a conventional cluster. The ratio of conductivity values between quarters was used as an indicator of mastitis status. The concept was evaluated initially in a pilot trial in a 200-cow herd milked in a 23-stall swing-over herringbone milking parlour. It was then tested rigorously in a field trial in a 640-cow herd milked in a 50-stall rotary milking parlour. Both trials were conducted in the Waikato region of New Zealand. In the latter trial, sensor results were compared with visual inspection of a commercial in-line mastitis filter fitted to each milking unit. These filters were inspected for clots immediately after every cow's milking, for 3 weeks. The dataset of approximately 27,000 individual milkings was tested against several published or potential alter- native ‘gold standards’ for diagnosing clinical mastitis.

RESULTS: In the pilot trial, 12–14 clinical events were detected out of 19 true clinical quarters, with a false-alert rate of between three and five false electrical-conductivity alerts per 1,000 individual milkings. In the more rigorous field trial, sensitivity ranged from 68 to 88%, and the false-alert rate (false-alert episodes per 1,000 individual milkings) ranged from 2.3 to 7.0.

CONCLUSION: The novel clinical mastitis detection system, based on separation of the flow and measurement of electrical conductivity from foremilk of individual udder quarters, has the potential to provide a new tool for helping farmers to monitor clinical mastitis in herds milked with conventional clusters.     

不同挤奶次数对奶牛产奶量的影响分析

[目的]分析增加挤奶次数对不同阶段泌乳奶牛产奶量的提升,找出最佳挤奶管理方案,为有效提升牧场效益提供理论依据。[方法]将泌乳牛只随机分为两组,保证不同胎次、不同产犊阶段平均泌乳量相当,分组后两组分别保持3次挤奶和4次挤奶1个月。对牧场不同挤奶次数奶牛泌乳量进行统计汇总整理分析。[结果]增加挤奶次数能有效提高奶牛泌乳量（P<0.05）;泌乳量高于45 kg奶牛增加挤奶次数对产奶量的提升,显著高于泌乳量低于45 kg的奶量（P<0.05）;增加挤奶次数显著提升头胎牛产量2.33 kg,二胎牛产量2.31 kg,三胎及以上牛奶产量2.78 kg(P<0.05);不同泌乳阶段,增加挤奶次数能有效提高泌乳初期及产奶高峰期的产奶量（P<0.05）。[结论]增加挤奶次数能有效提升奶牛泌乳量,对高产及处于产奶初期及高峰期的奶牛提升效果最佳。     

Prospects for zero days dry.

Recent studies in high-producing dairy cows have demonstrated the dry period requirement is greatly influenced by parity and management practice. Multiparous cows that were continuously milked and treated with bST demonstrated negligible production losses in the next lactation. First-lactation heifers, however, demonstrated large reductions in milk yield. These reductions were not overcome by using bST or IMF the next lactation. No studies have been performed examining use of LDPP or SDPP in combination with bST and IMF on the dry-period requirement. Cows that are continuously milked demonstrated higher feed intakes during the peripartum period, which may greatly improve metabolic health. Future studies must examine potential benefits of continuous milking on health in the next lactation.     

Effects of short period frequent milking on milk yield and udder health in Turkish Saanen goats

The major purpose of this study was to investigate whether increasing milking frequency for a short period (21 days) increases milk yield and milk components and improves udder health throughout lactation in Turkish Saanen goats. Two groups were formed (control, n = 14, treatment, n = 14); balanced by parity, bodyweight and birth type to make them homogenous. Feeding and management practices were the same for both groups. The treatment group was milked four times a day (4×) for 21 days after weaning whereas the control group was milked twice a day (2×). All the animals were milked twice daily thereafter. The pyronin methyl green stain method was used to estimate the somatic cell count (SCC), which is an indication of udder health. This method provided a count that excluded RNA and background noise while including cells with DNA. Repeated measures analyses indicated that overall differences between the 2× and 4× groups were significant for the morning, evening and total test day milk yields, in that values for the 4× group were increased 14.7, 8.8 and 12.1%, respectively. Differences between the groups for SCC were not significant. The results of this study indicate that increasing milking frequency to 4×, even for a short time (21 days), increases overall milk yield throughout lactation in dairy goats.