Milking Intervals Research Articles

Effect of pre- versus postmilking supplementation on traffic and performance of cows milked in a pasture-based automatic milking system

Cows milked in a pasture-based automatic milking system tend to have a lower daily milking frequency in comparison with cows milked in indoor systems. Milking events with intervals beyond 16h have been reported to have a negative effect on milk yield and udder health, and therefore it is important to minimize their occurrence. As feed is the main incentive to encourage cow traffic around the system, a study was conducted to compare pre- (PRE) versus postmilking (POST) supplementary feed placement strategies in a pasture-based automatic milking system. We hypothesized that PRE cows would have a stronger incentive to walk voluntarily from the paddock to the dairy facility to get milked (due to the reward being more immediate), thereby reducing their milking interval and increasing daily milking frequency and milk yield. The PRE cows returned to the dairy facility sooner (PRE=11.9 vs. POST=13.27h) but had longer milking intervals (PRE=15.3 vs. POST=14.28h). This was due to the additional time spent in the prefeeding area (PRE=56 versus POST=23min) combined with a longer average time spent in the premilking waiting yard (PRE=97 versus POST=77min). Treatment did not affect daily milk yield per cow. The result of this study demonstrates the potential of manipulating feeding management strategies to influence cow behavior and traffic in voluntary milking systems.

Attachment accuracy of a novel prototype robotic rotary and investigation of two management strategies for incomplete milked quarters

Throughout 2009 and 2010, FutureDairy (Camden, NSW, Australia) was involved in testing a novel prototype robotic rotary (RR). The commercial version RR is expected to be capable of carrying out 90 milkings per hour. To achieve the high throughput the rotary rotates the cow to the cup attachment robot and then around the platform in a stop–start fashion. The robot does not remain with the cow during the entire milking process. When not all teat cups are attached during a milking session there is an opportunity for cows to be sent back to the waiting yard for a second milking attempt. The study presented here was designed to test whether or not the extension of the interval to a second milking attempt improved milking success of incompletely milked cows. It was expected that with an increased milking interval between the two subsequent milkings the changes to the udder conformation could positively affect the attachment success at the second attempt. The 1h milking interval treatment (1h) simulated cows being drafted directly back to the pre-milking waiting yard, whilst the 3h milking interval treatment (3h) was designed to simulate cows being drafted back after accessing post-milking supplementary feed on a feedpad. The results presented in this manuscript showed no significant difference between the frequencies of successful attachment in the second attempt between the 1h and 3h treatments indicating that a reasonable level of flexibility exists with management of incompletely milked cows and dairy layout designs. Milk production level affected the probability of success at second attempt, which was about 7.5 times higher in cows with an average milk production level greater than 19.3kg than those with less than 10.8kg. When looking at the total proportion of cows successfully milked after two attempts, it was found that successful milking was more likely in multiparous cows compared to primiparous cows.

Alteration of the nutrient uptake by the udder over an extended milking interval in dairy cows

Little is known about modifications of the mammary utilization of nutrients circulating in blood plasma when milk yield is strongly decreased by once-daily milking. A trial was carried out to describe the mammary nutritional adjustments linked to the downregulation of milk synthesis as milk accumulated over an extended milking interval in the bovine udder. Three Holstein dairy cows yielding 34.0kg/d of milk were fitted with an ultrasound flow probe around the left external pudic artery and with catheters inserted into the left carotid and milk vein to estimate mammary blood flow (MBF) and mammary uptake of acetate, β-hydroxybutyrate, nonesterified fatty acids, glycerol, glucose, O2, and CO2 release. The trial was carried out over 2 consecutive weeks, with wk 2 repeating wk 1. Cows were milked twice daily at 12-h milking intervals. On d 3, cows were milked at 0630h and were not milked for 36h until d 4 at 1830h. Over the following days, twice-daily milking was resumed using 12-h milking intervals. Each half-udder was milked separately. Secretion rates of milk and milk proteins decreased 67% during the 12-to-36-h interval of milk accumulation, whereas that of milk fat fell 30%. Timing of changes in MBF and lactose levels in blood plasma was concomitant and significant after 19.5 and 21.5h of milk accumulation in the udder, respectively. The MBF decreased, most likely because the usual increases in MBF no longer occurred when the udder was full of milk. After 24h of milk accumulation, MBF did not increase further when cows lay down, and did not increase as usual 3h after a meal, suggesting a possible physical effect of milk accumulated in the udder on MBF, complementing metabolic regulation. Mammary uptake or release of nutrients was lowered before 24h for glucose, acetate, and β-hydroxybutyrate and after 24h for total glycerol, O2, and CO2, mostly associated with the impaired MBF. However, these decreases ranged from 12 to 17%, and cannot entirely explain the −45 and −20% decreases in milk secretion rates observed during the entire 36h of milk accumulation, thus confirming the primary role of intramammary metabolic regulation in the downregulation of milk secretion. The larger amount of nutrients taken up by the udder could explain the enhanced milk fat levels, involving a strongly modified metabolic fate of nutrients.

Two years of experience with an automatic milking system. 2. Milk yield, milking interval and frequency

The introduction of an automatic milking unit (AMU) changes milking procedures and routines: cows can be milked more than twice a day, and continuously over the day. Three milkings result in increased daily milk yield (MY) (Klei et al., 1997); however, the automatic milking system (AMS) is very different from the three milkings system, because there are not fixed intervals between two consecutive milkings and because the daily milking frequency (DMF) varies among cows and among days. A long milking interval (MI) has a detrimental effect on MY. To maintain the maximum of milk secretion, the udder ought to be empty before the reaching of critical value of intra-mammary pressure. Irregular milking causes a reduction in milk yield (Kelly et al., 1998). In AMS, some cows tend to have DMF less than two because of health problems, low MY or individual attitude.......

The effect of a single prolonged milking interval on inflammatory parameters, milk composition and yield in dairy cows

A technical stop in automatic milking systems may result in a severely prolonged milking interval (PMI) with subsequent impact on milk somatic cell count (SCC). This study investigated the inflammatory reaction, milk composition and yield during SCC peak observed in composite milk after exposing cows to a single PMI of 24 h. At the first milking after the PMI, a sharply increased proportion of milk polymorphonuclear leukocytes (PMN) but marginally increased SCC were observed. The peak in SCC was not seen until morning milking day 2 after the PMI, notably, concomitantly with a decreased PMN proportion. An increase in blood lactose, milk bovine serum albumin and serum amyloid A (SAA) and a drop in milk alpha lactalbumin (ALA) were seen concomitantly with the peak in PMN. All parameters mentioned, had returned to base line after day 2. The changes in SCC and SAA had the longest duration. Lactate dehydrogenase in afternoon milk was decreased during the whole study as was also afternoon milk yield. Interleukin-1β could not be detected in milk at any time. SAA and ALA, respectively, may influence chemotaxis and the changed concentrations observed after the PMI might have contributed to the increased migration of PMN to milk.

Increasing the revenues from automatic milking by using individual variation in milking characteristics

The objective of this study was to quantify individual variation in daily milk yield and milking duration in response to the length of the milking interval and to assess the economic potential of using this individual variation to optimize the use of an automated milking system. Random coefficient models were used to describe the individual effects of milking interval on daily milk yield and milking duration. The random coefficient models were fitted on a data set consisting of 4,915 records of normal uninterrupted milkings collected from 311 cows kept in 5 separate herds for 1 wk. The estimated random parameters showed considerable variation between individuals within herds in milk yield and milking duration in response to milking interval. In the actual situation, the herd consisted of 60 cows and the automatic milking system operated at an occupation rate (OR) of 64%. When maximizing daily milk revenues per automated milking system by optimizing individual milking intervals, the average milking interval was reduced from 0.421 d to 0.400 d, the daily milk yield at the herd level was increased from 1,883 to 1,909 kg/d, and milk revenues increased from €498 to €507/d. If an OR of 85% could be reached with the same herd size, the optimal milking interval would decrease to 0.238 d, milk yield would increase to 1,997 kg/d, and milk revenues would increase to €529/d. Consequently, more labor would be required for fetching the cows, and milking duration would increase. Alternatively, an OR of 85% could be achieved by increasing the herd size from 60 to 80 cows without decreasing the milking interval. Milk yield would then increase to 2,535 kg/d and milk revenues would increase to €673/d. For practical implementation on farms, a dynamic approach is recommended, by which the parameter estimates regarding the effect of interval length on milk yield and the effect of milk yield on milking duration are updated regularly and also the milk production response to concentrate intake is taken into account.

Comparison of parametric, orthogonal, and spline functions to model individual lactation curves for milk yield in Canadian Holsteins

Test day records for milk yield of 57,390 first lactation Canadian Holsteins were analyzed with a linear model that included the fixed effects of herd-test date and days in milk (DIM) interval nested within age and calving season. Residuals from this model were analyzed as a new variable and fitted with a five parameter model, fourth-order Legendre polynomials, with linear, quadratic and cubic spline models with three knots. The fit of the models was rather poor, with about 30%–40% of the curves showing an adjusted R-square lower than 0.20 across all models. Results underline a great difficulty in modelling individual deviations around the mean curve for milk yield. However, the Ali and Schaeffer (5 parameter) model and the fourth-order Legendre polynomials were able to detect two basic shapes of individual deviations among the mean curve. Quadratic and, especially, cubic spline functions had better fitting performances but a poor predictive ability due to their great flexibility that results in an abrupt change of the estimated curve when data are missing. Parametric and orthogonal polynomials seem to be robust and affordable under this standpoint.

Effects of milking interval and cisternal udder evaluation in Tunisian Maghrebi dairy dromedaries (Camelus dromedarius L.)

Effects of 4 different milking intervals (8, 12, 16, and 24h) on milk yield and milk composition were studied in Tunisian Maghrebi dairy dromedaries (n=6) at late lactation [240±14 days in milk (DIM), 5.84±1.62 L/d]. Camel-cows suckled their calves for 2 mo, were hand milked while suckling until mo 4 of lactation (calf weaning) and machine milked thereafter. Intravenous injection of oxytocin was administered before machine milking at each experimental milking to induce complete milk ejection and to avoid carryover effects of milking intervals. Cisternal and alveolar milk were measured at 380±16 DIM for a 24-h milking interval. Milk accumulated logarithmically (R2=0.95) in the udder from 8- to 24-h milking interval without reaching a plateau. Consequently, milk secretion rate decreased exponentially (R2=0.93) according to milking interval. Compared with 12-h milking interval (6.1 L/d), estimated daily milk yield was 113, 87, and 70% for 8-, 16-, and 24-h intervals, respectively. Total milk solids, milk fat content, and milk pH decreased with increasing milking interval, showing the greatest value at 8-h intervals (14.1±0.4%, 4.6±0.5%, and 6.66±0.05, respectively) and the lowest at 24-h intervals (12.3±0.9%, 2.9±0.6%, and 6.54±0.02, respectively). Milk protein (3.9±0.1%), lactose (4.5±0.2%), ash (0.84±0.01%) and density (1.028±0.01) remained constant for all milking intervals. Milk K, Ca, and Mg contents increased as milking interval increased, but Na content did not change (0.06±0.01%, on average). Milk Na:K ratio tended to decrease from 0.35 (1:2.9) to 0.22 (1:4.5) for the extreme milking intervals. Plasma lactose concentration steadied from 8- to 16-h (67±32 μmol) but increased dramatically at 24-h intervals (338±118 μmol), indicating that mammary tight junctions became permeable after 24h of milk accumulation. Camel udders showed small cisterns (19.3% of total milk in the udder at 24h) when compared with other dairy animals; we recommend the use of prestimulation for machine milking and selection for larger udder cisterns. Alveolar milk contained more fat (5.16 vs. 1.75%; SEM, 0.39%) and protein (3.23 vs. 2.73%; SEM, 0.15%) than cisternal milk. Despite the increase of plasma lactose during tight junction leakiness, the tendency for the Na:K ratio to decrease may be indicative of a camel's specific regulatory mechanism for controlling Na and K concentrations in milk and delaying the inhibitory effect of milk stasis on milk secretion rate. In conclusion, this short-term study proved the low storage capacity of the Tunisian Maghrebi camel udder but also showed their moderate ability to adapt to extended milking intervals at late lactation.

Is there a special mechanism behind the changes in somatic cell and polymorphonuclear leukocyte counts, and composition of milk after a single prolonged milking interval in cows?

BackgroundA single prolonged milking interval (PMI) e.g. after a technical stop in an automated milking system is of concern for the producer since it is associated with a short-lasting increase in milk somatic cell count (SCC), which is a major quality criterion used at the dairy plants. The content of polymorphonuclear leukocytes (PMN) and how the milk quality is influenced has not been much investigated. The SCC peak occurs without any obvious antigen challenge, possibly indicating a different leukocyte attraction mechanism after a PMI than we see during mastitis.MethodsComposite cow milk samples were taken at the milkings twice daily during 7 days before and 5 days after a PMI of 24 h. Milk was analyzed for SCC, PMN, fat, protein and lactose, and at some occasions also casein and free fatty acids (FFA).ResultsDuring the PMI the proportion of milk PMN increased sharply in spite of marginally increased SCC. The peak SCC was not observed until the second milking after the PMI, in the afternoon day 1. However, the peak SCC value in morning milk did not occur until one day later, concomitantly with a decrease in the proportion of PMN. After declining, SCC still remained elevated while PMN proportion was decreased throughout the study as was also the milk yield, after the first accumulation of milk during the PMI. Milk composition was changed the day after the PMI, (increased fat and protein content; decreased lactose, whey protein and FFA content) but the changes in the following days were not consistent except for lactose that remained decreased the rest of the study.ConclusionThe PMI resulted in increased SCC and proportion of PMN. Additionally, it gave rise to minor alterations in the milk composition in the following milkings but no adverse effect on milk quality was observed. The recruitment of PMN, which was further enhanced the first day after the PMI, appeared to be independent of milk volume or accumulation of milk per se. Hence, we suggest that there is a special immunophysiological/chemoattractant background to the increased migration of leukocytes into the milk compartment observed during and after the PMI.

Performance of dairy cows milked twice daily at contrasting intervals

The time constraints of the classic twice-daily milking routine are less easily endured by individual dairy farmers, because of their impact on quality of life. Our aim was to evaluate milk production responses by dairy cows milked twice daily at contrasting intervals. In experiments 1 (20 cows) and 2 (28 cows), four milking regimes were compared during a 3-week period beginning after the peak of lactation. Three groups of five cows were milked twice daily (TDM) with milking intervals of 11 : 13, 7 : 17 and 3 : 21 h in experiment 1, and three groups of seven cows at 11 : 13, 5 : 19 and 2.5 : 21.5 h in experiment 2. One group (five and seven cows respectively) was milked once daily (ODM) in each experiment. In experiment 3 (three groups, 12 cows per group), one group was milked at 10 : 14 h and one at 5 : 19 h, and the third group once daily. Milking treatments began during the second week of lactation and continued for an average of 23 weeks. In experiments 1 and 2, daily milk yields were reduced by 4.1%, 11.5% and 28%, for the 5 : 19, 3 : 21 and ODM milking treatments compared with the 11 : 13 h interval. In experiment 3, the decrease in daily milk yields for 5 : 19 h and ODM was 10% and 40% compared with the 10 : 14 h time interval. In the average daily milk, fat and protein contents and somatic cell counts were not different between the TDM groups, and the ODM group had (or tended to have) a higher fat and protein content. For a given milking, milk fat content decreased from about 60 to 32 g/kg as the preceding milking interval increased from 2.5 to 3 h up to 12 h. It then levelled out and even increased, mainly after 18 to 20 h. Somatic cell count showed a similar trend, and protein content did not change steadily. Dry matter intake, body weight and body condition score were not affected by contrasting milking intervals. After resumption of TDM with conventional intervals, productions of milk, fat and protein no longer differed between the TDM groups. Milk yield of previously ODM cows remained lower by 2 kg/day (P = 0.15) in experiments 1 and 2, and by 7 kg/day (P < 0.05) in experiment 3. These results suggest that TDM at contrasting intervals up to 5 : 19 h is feasible as it decreases milk yield only moderately, especially if implemented from peak of lactation.

Yield and quality of milk and udder health in Martina Franca ass: effects of daily interval and time of machine milking

Twenty asses of Martina Franca breed, machine milked twice a day, were used to assess the influence of milking interval (3-h, 5-h, and 8-h; N=5) and time (700, 1200 and 1900) on milk yield and udder health. Individual milk samples were taken to determine fat, protein and lactose content. Sensory analysis profile was also assessed. Milk’s total bacterial count (TBC), somatic cell content (SCC) and udder’s skin temperature were considered to assess udder health. Milk yield increases by 28.4% (P<0.01) with a milking interval from 3-h to 8-h and is higher (P<0.01) at morning milking. The maximum milk yield per milking corresponds to 700 milking (1416.9 mL) thus indicating a circadian rhythm in milk secretion processes. Milking intervals of 5 and 8 hours cause a decrease (P<0.01) in milk fat and lactose content. The 8-h interval leads to an increase (P<0.01) in SCC but without any significance for the health udder. No alterations about CBT, clinical evaluation and temperature of udder were observed. Milk organoleptic characteristics were better in the 3-h interval milking.

The effects of different milking intervals and milking times per day in jennet milk production

In their first 150 days of lactation, nine Ragusana jennets were investigated at the ‘Istituto Sperimentale Zootecnico per la Sicilia’ (ISZS) in Palermo, to study the effects of different milking typologies on milk production. The jennets were kept in a paddock and were fed hay ad libitum and concentrate (3.5 kg jennet/day). From post-foaling day 21, every 3 weeks individual milk amounts were recorded, and individual milk samples were collected and analyzed for the main qualitative parameters. The compared theses were: two daily milking times with 6- and 3-h intervals; and two, three and eight daily milking times with 3-h interval. The jennets were manually milked. The foals were separated from the jennets at 0800 h, and after the last milking the foals were housed with the jennets. During the day with eight milkings, the milk yield from the jennets was fed to their respective foals, through bottles. The 6-h milking interval produced more milk (+19%) per session than the 3-h interval (P ⩽ 0.01). The fat content per session, with the eight-time milking frequency (P ⩽ 0.001), was greater than the others. For each milking typology, the lactation stage had a similar effect on almost all the considered variables. When observing the eight-milking times, the fat content (%) increased from 1100 to 0500 h (P ⩽ 0.001). The milk yield and the fat percentage produced by two-, three- and eight-milking times were positively correlated.

Comparison of calculation methods of daily milk yield, fat and protein contents from AM/PM milkings

For prediction of daily milk yield (DMY), daily fat percentage (DFP), and daily protein percentage (DPP) from alternate AM/PM recording scheme, three different methods were tested. The data comprised information on 483 813 test-day records. Methods were compared on the whole data set or just on the upper or the lower quartile of the records according to DMY, DFP, DPP, and milking interval (MI). Method 1 included DMY, DFP or DPP as a dependent variable in regression analysis. In Method 2 ratio of partial AM/PM to daily yield was included as a dependent variable, whereas Method 3 is based on doubling milk yield from AM/PM milking while DFP and DPP are expected to be the same as the AM or PM milking. The bias on the whole data set was low. With respect to high DMY, DFP, and DPP on the upper quartile of data set bias in underestimation of records was noticed for Method 1 whereas with this method, data from the lower quartile of data set were overestimated. With respect to the short MI on the average DMY was underestimated whereas DFP and DPP were overestimated with Method 3. DMY with long MI were overestimated on the average with Method 3 while DFP and DPP were underestimated. That kind of bias was not detected with Method 2.

Changes in Alveolar and Cisternal Compartments Induced by Milking Interval in the Udder of Dairy Ewes

The aim of this work was to evaluate the effects of milking interval (4, 8, 12, 16, 20, and 24h) on cisternal size and milk partitioning (cisternal and alveolar) in the udders of dairy ewes. Twenty-four dairy ewes (Manchega, n=12; Lacaune, n=12) were used in a 2-wk experiment during mid-lactation. Cisternal and alveolar milk yields were measured and milk samples from each udder fraction were collected for analysis. Cisternal milk was obtained after i.v. injection of an oxytocin receptor antagonist, and alveolar milk was obtained after i.v. injection of oxytocin. Enlargement of the cisternal compartment due to milking intervals was measured by ultrasonography for each half udder. Volumes of cisternal and alveolar milk differed according to breed, being greater in Lacaune (888±43 and 338±25mL, respectively) than in Manchega ewes (316±43 and 218±25mL, respectively). Alveolar milk increased linearly to 16h in Manchega and 20h in Lacaune and remained constant thereafter. Cisternal milk accumulated linearly to 24-h milking intervals in both breeds. Cisternal area (values per udder half) increased as milking interval increased, reaching a plateau at 20h in Manchega (21±1cm2) and 16h in Lacaune (37±1cm2). Correlation between cisternal area and cisternal milk was the greatest at 8h (Manchega: r = 0.70 and Lacaune: r = 0.56). Cisternal area correlated with total milk (r = 0.80). Milk fat content varied markedly with milking intervals, increasing in alveolar milk (until 12h in Manchega, 8.90±0.18%; and 20h in Lacaune, 8.67±0.19%) and decreasing until 24h in cisternal milk (5.74±0.29% and 4.85±0.29%, respectively). Milk protein content increased in alveolar milk until 24h (Manchega, 6.46±0.11%; Lacaune, 5.95±0.11%), but did not vary in cisternal milk. Milk lactose content only decreased at the 24-h milking interval in the cisternal milk of Manchega ewes (4.60±0.04%). In conclusion, our results suggest that cisterns play an important role in accommodating secreted milk during extended milking intervals. Thus, long milking intervals could be a recommended strategy for large-cisterned dairy sheep. Evidence indicates that ultrasonography provides accurate estimations of udder cistern size and could be used as an indicator for selecting large-cisterned dairy ewes.

Evaluation of Milk Enzymes and Electrolytes, Plasma Metabolites, and Oxidative Status in Twin Cows Milked in an Automatic Milking System or Twice Daily in a Conventional Milking Parlor

The aim of this paper was to evaluate the effects of automatic milking (AM) on milk enzymes and minerals related to mammary epithelial integrity in comparison with twice-daily conventional milking (CM). One cow from each of 6 pairs of twins was assigned to be milked with AM or with CM throughout first lactation. Milk production was recorded and milk samples were collected at 4, 11, 18, 25, 32, and 39 wk of lactation (WOL) to determine fat and protein content, somatic cell count, pH, plasminogen (pl) and plasmin (Pl) activities, Na, K, and Cl. Body condition score was monitored; blood samples were collected to determine energy-related metabolites in the first third of lactation (14 WOL), and plasma oxidative status throughout lactation. Overall mean and standard deviation of milking frequency (MF) in AM were 2.69 and 0.88, respectively. Milk production, fat and protein contents, and somatic cell count did not differ between milking systems. The pl and pl+Pl activities were lesser in AM than in CM. Milk pH was greater in AM than in CM. Milk Na, K, Na/K ratio, and Cl did not differ across the whole lactation. Milk pH had a positive correlation with milk Pl activity (r=0.41), Na (r=0.37), and Cl (r=0.40) concentration, and negative correlation with the log10 of pl/Pl ratio (r=−0.47). The milk Na/K ratio had a positive correlation (r=0.55) with milk Pl activity. Milking system (MS) did not seem to affect mammary epithelial permeability. The differences in enzymatic (proteolytic) activity due to the MS, probably related to daily MF, lead one to suppose that the quality of the protein fraction for the cheese-making process was preserved better with AM than with CM, even if differences in pH might negatively interfere. No difference was detected in BCS, and in plasma concentration of triglycerides and nonesterified fatty acids, whereas plasma cholesterol concentration during the first 10 WOL was lesser in AM than CM. Oxidative status, measured by plasma reactive oxygen metabolites and thiol groups, did not differ between MS throughout the whole lactation. These results suggest that early lactation of AM primiparous cows may give rise to crucial situations: for milk production, when a low MF may impair further mammary cell proliferation; for milk quality, if an irregular MF, with prolonged milking intervals, leads to an increased milk pH with increased conversion of pl to Pl.

Disponibilidade de matéria seca, composição química e consumo de forragem em pastagem de capim-elefante nas estações do ano

Em pastagem de capim-elefante cv. Napier (Pennisetum purpureum Schum.) foram avaliadas, no período de fevereiro/1999 a novembro/2001, a disponibilidade de matéria seca (MS) acima da altura de resíduo pós-pastejo, a composição química, a digestibilidade in vitro da MS (DIVMS) e o consumo de forragem por vacas Holandês x Zebu lactantes, durante as estações do ano. Adotou-se o regime de lotação rotacionada, com três dias de ocupação e 30 de descanso dos piquetes. Estimativas da disponibilidade de forragem e da composição química foram realizadas mensalmente, enquanto o consumo, em dez ocasiões do período experimental. Durante a seca, as vacas receberam silagem de milho no período entre as ordenhas. A maior disponibilidade de MS de capim-elefante foi estimada em dezembro (3.402kg/ha). Entre maio e setembro, estimaram-se valores de 558 e 1.122kg/ha, evidenciando a acentuada estacionalidade na produção de forragem. Os teores de proteína bruta (PB) e a DIVMS do pasto não diferiram entre as estações do verão, outono e primavera, mas foram menores no inverno. Os teores de fibra em detergente neutro foram menores no verão, outono e primavera, quando comparados ao valor obtido no inverno. O consumo de capim-elefante foi maior no verão, outono e primavera e menor no inverno, em decorrência da baixa quantidade de forragem na pastagem. Entretanto, o consumo de MS total não diferiu entre as estações do ano, devido à suplementação com silagem de milho.

Effect of Milking Interval on Milk Secretion and Mammary Tight Junction Permeability in Dairy Ewes

Twenty-four lactating ewes (Manchega, n = 12; Lacaune, n = 12) in mid lactation were used to assess the short-term effects of different machine milking intervals (4, 8, 12, 16, 20, and 24h) on milk yield, milk composition, and tight junction (TJ) permeability of mammary epithelia. Milk samples were analyzed for chemical composition, somatic cell count (SCC), and plasmin activity. Plasma lactose, and milk Na and K concentrations were used as indicators of TJ permeability. Milk accumulated linearly for up to 24h, showing a different rate according to the milk yield of the breed (Manchega, 38mL/h; Lacaune, 87mL/h). Milking interval affected milk fat content, which decreased markedly from 4 to 24h in both breeds, but no differences were observed in milk protein content. The milk contents of casein, true protein, lactose, and total solids also varied according to milking interval. Values of SCC did not vary by breed (175×103cells/mL, on average), showing the lowest log10 values for the 4-and 24-h milking intervals in both breeds. Plasmin activity in milk increased with milking interval until 20h of udder filling in both breeds, and was poorly but positively correlated with SCC content (r = 0.39). Plasma lactose increased dramatically after 20h of milk accumulation, indicating enhanced permeability of mammary TJ. As a result, an increase in Na concentration and in the Na:K ratio, and a decrease in K concentration, were observed in the milk of Manchega ewes. On the contrary, no differences in Na and K concentrations in milk were detected in Lacaune ewes. In conclusion, our results proved that Manchega and Lacaune dairy sheep could maintain high rates of milk secretion during extended milking intervals in the short term, with no effects on udder health and few negative effects on milk yield. Increased TJ permeability, caused by the effect of udder filling, induced changes in milk composition that were more marked in Manchega than in Lacaune ewes.

Management systems with extended milking intervals in ruminants: Regulation of production and quality of milk1,2

This paper aims to compare different adaptive responses of the mammary gland of cows, ewes, and goats submitted to extended milking intervals in different systems of management. Depending on the species, these extended milking intervals can be characterized by the following milk removal approaches; 3 milkings every 2 d, elimination of 1 milking per week (i.e., 13 vs. 14 milkings per week), and once-daily milking with additional suckling (i.e., dual purpose system of suckling and milking) or without suckling (exclusive once-daily milking). All the high-yielding animals and breeds adapted without problems to being submitted to intervals between milking less than 20 to 21 h. Under these conditions, all ruminant species demonstrated only low and transitory variations in milk production and quality. Thus, management systems using such an interval are good tools for the dairy producer who wants to save time without important adverse economic impact. When animals have good mammary gland health, these management systems can be applied without preliminary adaptation. However, goats and some breeds of dairy ewes seem to adapt to once-daily milking better than cows. Additionally, goats and ewes with higher production levels demonstrate a lower reduction in milk yield. With goats, there is only a limited variation in milk quality and cheese-making capacity of the milk produced, but ewes and cows show a significant enrichment of milk constituents, especially in fat. This indicates some differences in the regulation of lactose, protein, and fat synthesis depending on the duration of the milking interval and provides interesting models for physiological studies on milk secretion and synthesis regulation. Anatomical and physiological characteristics of lactating cows and ewes, in terms of cisternal vs. alveolar volumes within the mammary glands, could contribute to different abilities in adaptation to different milking systems. In goats, however, other mechanisms, such as compliancy of the mammary gland and regulation of tight junction impermeability, could be involved in milk secretion regulation and, thus, could become new targets for genetic selection of animals better adapted to accept extended milking intervals.

Supplementary feeding at milking and minimum milking interval effects on cow traffic and milking performance in a pasture-based automatic milking system

In extensive pastoral dairy farming systems herds graze 12 months of the year with the majority fed a near-100% pasture or conserved pasture diet. The viability of automatic milking in these systems will depend partly upon the amount of supplementary feed necessary to encourage cows to walk from the pasture to the milking unit but also on the efficient use of the automatic milking system (AMS). This paper describes a study to determine the importance of offering concentrate in the milking unit and the effect of minimum milking interval on cow movement and milking performance in a pasture-based AMS. The effects of feeding rate (FR0=0 kg or FR1=1 kg crushed barley/d) and minimum milking interval (MM6=6 h or MM12=12 h) on cow movement and behaviour during milking were studied in a multi-factorial cross-over (feeding level only, 4 weeks per treatment) experiment involving 27 mixed-breed cows milked through a single AMS. Feeding 1 kg barley in the milking unit resulted in a higher visiting frequency to the pre-selection unit (FR0=4.6 visits/d, FR1=5.4 visits/d, sed=0.35, P<0.05) and a higher yield (FR0=22.5 kg/d, FR1=23.6 kg/d, sed=0.385, P<0.01) but had no effect on milking frequency (FR0=1.6 milkings/d, FR1=1.7 milkings/d, sed=0.04, NS). Minimum milking interval was the major factor influencing milking frequency (MM6=1.9, MM12=1.4 milkings/d, sed=0.15, P<0.01). The absence of feeding in the milking unit had no negative effect on behaviour during milking or the number of cows that had to be manually driven from the paddock. The results show that automatic milking can be combined with a near-100% pasture diet and that milking interval is an important determinant for maximizing milk harvested per AMS.

Leptin in milk and plasma of dairy asses

Milk and plasma leptin levels have been studied in dairy asses machine milked according to two different routines: 20 pregnant, pluriparous asses, were divided into two groups subjected, every 28 d for 150 d, to two consecutive milkings carried out at different intervals, i.e. 20 vs. 4 hours interval, respectively for group A and group B. During the study, the declining total milk obtained by machine milking was unaffected by the different milking strategies; body condition score of asses as well did not vary between the groups. Different milking intervals did not significantly influence skimmed milk leptin content neither plasma leptin level. Moreover, we did not find significant variation in plasma leptin neither correlation with BCS, indicating that in donkey pregnancy inhibits the cross talk between hypothalamus and adipose tissue.