Physiological Justification of Udder Emptying in Highly Productive Cows

This study encompasses to measure frequency of physiologically motivated emptying of the udder by Holstein cows during lactation phase. With the recording of the hours of the day, the experiment shows that the first-born cows emptied the udder, on average, almost three times a day, the cows having second lactation emptied 2.5 times a day, and cows having 3rd and 4th lactations emptied udder three or more times a day. Analysis of the daily attending a robotic milking machine during lactation phase by first-born cows showed that the visitation frequency was relatively even, except for the maximum peaks from 11.00 to 12.00 o’clock and from 21.00 to 23.00 o’clock. Similarly, among the cows having 2nd lactation there were two maximum peaks of milking or udder emptying – at night from 22.00 to 01.00 o'clock and in the day from 12.00 to 17.00 o'clock. For cows having 3rd lactation, there were two maximum peaks of udder emptying - one from 21.00 to 01.00 o'clock at night and the second from 12.00 to 17.00 o'clock in the afternoon. Cows under 4th lactation had three relatively high maxima: the first from 01.00 to 04.00 o'clock at night, the second from 10.00 to 12.00 o'clock in the afternoon, and the third from 18.00 to 22.00 o'clock at night. This study concludes that high milk productivity of cows needs emptying (milking) of the udder at least three times a day. Since almost a third of udder emptying occurs at night, at that time it is necessary to provide animals with adequate water and feed on the feed table.


Introduction
As part of milk production process, the frequency of milking the cows, the intervals between two milking, and the time of milking operation within a day (Zaharian, 1968) have always been important aspects to be considered by dairy industry.Currently, three-and two-time milking frequencies are used.Reducing the number of milking in a day, according to Kurak (2006), reduces the labour costs by 25-30%.However, in practice, the transition to two-time milking often leads to a decrease in milk productivity of cows (Lopatko and Pesotckiy, 2010;Palianova, 1974).
Various scientists and practitioners have supported repeated milking of cows.Dorovskih and Zharikov (2019) found that 4 times milking, compared to 2 times, increases amount of milk by 9.9% apart from the content of fat in the milk.Rivel (1909) proved that 4 times milking, compared to 3 times milking, increased milk yields by 6-8%.According to the research by Guglia and Vorobiov, 1987), the transition from twotime milking to three-time milking allowed to increase the average annual milk yield of a cow by approximately 200 kg.
Research on the effectiveness of 4-and 6-times milking of cows (Lopatko, 2010), and the causes of "attenuation" of the effectiveness of repeated milking, showed that the cause of declining effectiveness is not connected to physiological features of the udder, but to animal feeding conditions.It means, the cows moved to repeated milking must be provided with an appropriate level of nutrition.It has been established by Ovcharenko and Cherniaeva (2006) and Lopatko (2010) that frequent milking is advantageous mainly from the point of view of the physiology of lactation.The advantages in terms of the productivity of such cows are because of the stimulating effect of additional milking on the process of milk secretion, especially in the second half of lactation (Naumova and Palianova, 1976).The act of milking, that is stimulating the lactogenic function of the neuroendocrine system (prolactin secretion), helps increase milk productivity and the development of a capacious udder system.In most cases, 3-times milking increased the milk productivity of cows by 5-30%, but decreased milk's quality.Thus, the fat content in milk decreased by 4.55% in case of two-time milking, and by 4.01% in case of three-time milking.The protein content also decreased, but to a lesser extent, from 3.64% to 3.40% (Naumova and Palianova, 1976).It shows that the effect of additional milking is positive when it is carried out throughout the lactation period.
Conversely, when changing from more frequent milking of cows to three-or two-times milking, the opposite phenomenon is observed -the milk yield of cows is drastically reduced.However, even though after coming to two-time milking in the first days there is often a decrease in milk yield, but after a few days the productivity reaches the previous level (Merts, 1970).The more frequent milking than three-time milking per day received sufficient attention only during the last 20-30 years.The automation and robotization have added to attracting scientific attention.More frequent milking is now considered as one factor in increasing the stability of the lactation curve, improving the quality of milk and enhancing its technical properties (Ovcharenko and Cherniaeva, 2006).
Further, development of dairy farming in Ukraine is impossible without the introduction of modern technological solutions for milk production (Golubenko, 2014).The advent of milking robots in animal husbandry is a technological breakthrough in dairy industry (Naumenko, 2011).The robotic system of milking the cows is a complex technological operation, especially when the new system uses animals that were previously milked using traditional milk production systems (Myronova, 2015).
The system of milking among cows ensures that the animal excretes milk in accordance with the physiological needs, with its optimal accumulation in the udder, and not in accordance with the daily routine set by human.Experience in the operation of milking robots shows that the implementation of the milking operation, which is based on motivational milking, is quite reasonable, which implies that the animal itself comes to the milking for physiological needs (Meskens and Mathijs, 2002;Sarapkin, 2003;Sarapkin, 2004).To provide full stimulation to obtain milk yield and milk excretion, the system of "voluntary" milking should functionally meet the physiological needs of the animal, as its productivity and health depends on it.Such milking should not cause stress to the cow because it may otherwise affect the optimal course of lactation, especially at the beginning of lactation period and for first-born cows.Therefore, taking into consideration the complexity of automated equipment, where the preparation of cows for milking and milking operation are carried out without human involvement, the requirements and specifications are high to the systems of "voluntary" milking and to dairy cattle productivity.However, the practice of milking the cows using milking machines demonstrates that the animals are less stressed, and automated milking process is in line with their physiological needs (De Koning, 2010).
A literature source (Gorelik et al., 2018) indicates that the cows visit the milking robot from 2 to 4 times a day.The cows visit the milking robot twice a day for 2 days, three times a day for 24 days, and four times a day for 4 days.Kiseliov et al. (2019) found out that the frequency of visits of the milking robot was almost evenly distributed over the periods of the day: the number of visits during the specified periods differed by no more than 20%, and the difference was only between 0 and 4 and 4 and 8 hours.To what extent does the "natural" physiologically determined udder emptying correspond to the norms set up by man?Unfortunately, there is no consensus among scientists and practitioners on this issue till now (Batyr, 2014).
With the above backdrop, aim of this research was to study how and under what conditions of "voluntary" milking, cows of different productivity and age during lactation phase regulate the frequency of udder emptying during the day, and how to adhere to the time of udder emptying during lactation phase.

Methodology
This study on the milking using robot was conducted on emptying the udder in Holstein Friesians cows1 of different ages in lactation phase.The milk productivity was tested by ALC (Additional Liability Company) "Terezine" based in Kyiv region.An automatic milking control system mounted in a milking machine DelPro VMS -20122 was used.Automated data collection system operating with electronic flow meters "Fullflow" was used to fetch the following data: date and time of milking, the personal number of the animal, the weight of milk, average and maximum intensity of milk production, duration of milking, absolute and relative milk yield, and other lactational and physiological parameters of each cow.The electronic system is controlled by a microprocessor mounted in the terminal.At the same time, this equipment performs automatic control of the milking robot including stimulation of milk production, milking, removal of glasses, as well as control of the inlet and outlet gates.When the milking robot is connected to the udder of the next cow, the previous display is canceled.All the animals under study were kept in similar feeding conditions.
The size of the experimental group of cows kept on farm was 68.Depending on the quantitative distribution by lactations, the method of randomized (random) sampling was applied and the cows were selected in the following manner: 7 first-born cows, 8 cows under 2nd lactation phase, 4 cows under 3rd lactation phase, and 3 cows under 4th lactation phase.The average milk yield during full lactation phase of the studied cows was 8,100 kg of milk for first-born, 9,600 kg for cows under the 2nd lactation, more than 10,000 kg milk for cows under the 3rd lactation and more than 9,500 kg of milk for cows under 4th lactation.Due to the automated control system of the robot, capturing or accumulating milk is just on time with accurate duration and frequency.The milk from selected animals was recorded, accumulated and processed accurately.The nutrition supply to the cows was calculated based on standard set for obtaining maximum milk yields of cows on daily basis.A mix diet chart was followed round the year to feed the cows in equal quantities.
The processing of the obtained primary data was performed statistically using analytical techniques.

Results and Discussion
Analysis of the attendance of milking robot by first-born cows (Figure 1) shows that, during the 9 months of lactation, cows emptied their udder, on an average, almost three times a day, and on the 3rd month of lactation, almost four times a day.From the 10th month of lactation, the frequency of cows' visits to the milking robot has decreased to three times a day.Thus, in the 10th and 11th months, compared to the 9th month, it decreased by 11.4%; in the 12th month, it decreased by 22.5%; in the 13th month, it decreased by 26.2%; and in the 4th month, it decreased by 27.3%.It implies that functional emptying of the udder for first-born cows is three times a day, which does not confirm the current practice of two-time milking per day.The results of the frequency of visits to the milking robot by cows having the 2nd lactation (Figure 1) reflect that, only during the 1st and 2nd months of lactation, cows visited the milking robot on average three times a day.Subsequently, from 4th till the 10th month of lactation, cows visited the milking robot, on an average, 2.5 times a day.In the following months of lactation, compared to the 10th month, the decrease in attendance to the milking robot was insignificant and ranged from 3.2% to 16.7%.Thus, the multiplicity of functionally induced udder emptying during 2nd lactation was 2.5 times, which confirms the need for the introduction of 3 times milking, especially to high-yielding cows.
The milking of cows during 3rd lactation (Figure 1), on average, was three or more times per day in the 7th month.But from 8th to 11th months of lactation, the reduction in the frequency of visits to the milking robot was not significant and ranged from 2.5% to 9.3%.Therefore, the multiplicity of milking by three times a day should be functionally due to udder emptying in 3rd lactating cows.
Similarly, the multiplicity of udder emptying during 4th lactation of cows (Figure 1) was noted during the first 8 months of lactation, and it occurred, on average, three or more times per day.The decrease in the 9th and 13th months, compared to the 8th, was insignificant and ranged from 2.0% to 7.5%.That is, for cows under the 4 th lactation, as well as for cows under the 3rd lactation phases, functionally caused emptying of the udder was not less than three times a day.
Conclusively, to obtain high milk productivity from cows, the functionally determined frequency of emptying (milking) of the udder should be at least three times a day.
Analysis of the nature of daily visits to the milking robot by cows of different ages during lactation indicates that it differs significantly from the regimes used by humans.Thus, during lactation of first-born cows (Figure 2), percentage of visits have relatively even pattern, except for maximum peaks from 11.00 to 12.00 o'clock and from 21.00 to 23.00 o'clock.Some decrease of cows' visits to the milking robot was observed from 08.00 to 10.00 o'clock.It might be due to the distribution of feed at that time, which means the cows' attention to food predominates their attention to lactation.It was also noted that the first-born cows were quite active in visiting the milking robot at night, especially from 21.00 to 03.00 o'clock.The second active phase of visitation was observed in the afternoon from 15.00 to 19.00 o'clock.At night, attendance to the milking robot accounts for more than 28%.So, their daily number of visitations is physiologically motivated; therefore, it is necessary to provide animals at this time with the appropriate amount of feed on the feed table and lighting of at least 150-200 lux.This should be done because, after emptying the udder, cows are usually sent to a drinking point to replenish fluids in the body, and then to the feed table (feeder) to replenish the nutrients needed to secrete new portions of milk.Assessment of the pattern of the daily visit to the milking robot by cows of the 2nd lactation (Figure 3), the first-born cows have visits at two peaksat night from 22.00 to 01.00 and in the day from 12.00 to 17.00 o'clock.There is also a qualitative decrease in the visitation to the milking robot from 08.00 to 10.00 o'clock due to the distribution of feed.Like the first-born cows, the cows of the 2nd lactation actively emptied the udder at night.Thus, from 21.00 to 06.00, 43% of daily udder emptying occurs.To ensure a high level of milk productivity from such animals, it is necessary to create appropriate conditions for feeding and keeping them.
Analysis of the nature of daily visits to the milking robot by cows of the 3rd lactation (Figure 4) also showed the presence of two, somewhat shorter, maxima.One maximum visitation of cows was observed from 21.00 to 01.00 at night, and the other from 12.00 noon to 17.00 o'clock.In addition, the 3rd lactation cows had two minimums in terms of attending the milking robot: the first from 09.00 to 10.00 o'clock was associated with the time of distribution of feed, and the second from 19.00 to 20.00 o'clock.At the same time, nocturnal emptying of the udder by cows of the 3rd lactation accounted for 29.6%, or almost a one-third part of daily milking.This implies that there is a need to create optimal conditions for such animals for feeding and keeping them to realize their genetically determined level of productivity.The assessment of the nature of daily visits to the milking robot of cows under 4th lactation (Figure 5) demonstrate three relatively high peaks.The first is observed from 01.00 to 04.00 o'clock at night, the second highest peak from 10.00 to 12.00 o'clock in the afternoon, and the third peak from 18.00 to 22.00 o'clock at night.The minimum number of visits was observed from 05.00 to 09.00 o'clock in the morning.At night (from 21.00 to 05.00 o'clock), emptying of the udder by cows under 4th lactation accounted for 37.1% of daily bowel movements.In this case, more than a third of visits to the milking robot occurs during the hours when technological process cannot be controlled.

Conclusions
Following conclusions can be drawn from the findings of this experimental study.1.To achieve a genetically determined level of high milk productivity of cows, the functionally determined multiplicity of emptying (milking) of the udder should be at least three times a day.
2. Functionally determined nature of udder emptying by a cow does not correspond to the regime of milking used by man.
3. Since almost a third of udder emptying occurs at night, at that time it is necessary to provide animals with adequate water and feed on the feed table where the light intensity should be at least 150-200 lux.More fundamental studies of this nature are required to ascertain the visits of cows to the milking robot, especially by involving other breeds of cows or livestock.
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Figure 1 :
Figure 1: Distribution of the frequency of visits by cows to the milking machine by months of lactation

Figure 2 :Figure 3 :
Figure 2: Daily distribution of visits to the milking robot by first-born cows

Figure 5 :
Figure 5: Daily distribution of visits to the milking robot by cows of the fourth lactation day, hours/minutes Grassroots Journal of Natural Resources, Vol.5, No.2 (June 2022), p.138-147 | ISSN 2581-6853 | CODEN GJNRA9 Doi: https://doi.org/10.33002/nr2581.6853.050209145 Vasyl Ivanovych Kostenko Specify the exact number of experimental units allocated to each group, and the total number in each experiment.Also indicate the total number of animals used.b.Explain how the sample size was decided.Provide details of any a priori sample size calculation, if done.Describe any criteria used for including and excluding animals (or experimental units) during the experiment, and data points during the analysis.Specify if these criteria were established a priori.If no criteria were set, state this explicitly.b.For each experimental group, report any animals, experimental units or data points not included in the analysis and explain why.If there were no exclusions, state so.c.For each analysis, report the exact value of n in each experimental group.