A Comparison Study of Milking Frequency- Once a Day Versus Twice a Day on Irish Dairy Farms

Contents

Introduction

Reduced milking frequency and the management implications

Reduction in milking frequency and feed allowance impact on the dairy cow’s immune system.

Cow comfort

Milk Composition and Milk Quality:

Effects of milking frequency on the Mammary Gland

Effects of milking frequency on the breed of the cow

Conclusion

A comparison study of milking frequency of milking frequency- Once a day versus twice a day on Irish dairy farms

Introduction

Once a day milking is becoming popular in Ireland and internationally in countries such as New Zealand. Farmers want to improve their herds by increasing profits and herd performance such as improving fertility (Hemming et., al). The objectives of carrying out this literature review is to find out if once a day milking have an impact on cow comfort. To find out does once a day milking frequency influence the milk composition and the quality of milk that is produced. To investigate if different milking frequency has an impact on the different breeds of dairy cows. To research if a reduction of milking intervals and feed allowance has an impact on the dairy cow’s immune system. Milking cows once a day can change the performance of the animal positively and negatively. Once a day milking can improve the cows energy balance especially after calving when cows are getting back into milk compared to a cow that is being milked twice a day after calving. Milking frequency has an impact on yield and also an impact on the quality of milk that is produced (Bortacki et al., 2017). The frequency of milking has also an impact on the cow’s immune system (O’ Driscoll et al., 2012). There is concern that cows milked once a day may suffer discomfort as the milking interval is longer then cows milked twice a day. As a result of once a day milking this can cause stress and discomfort in the locomotion system and the udder of the cows as the udder firmness can be effected (O’ Driscoll et al., 2011). Once a day milking first began in New Zeland in the 1980s, the reasons for this was to reduce farm labour and on some farms once a day milking was introduced after peak lactation to allow farmers and labour units to take holidays (Pomies et al., 2007). Genetic Parameters are also looked at with cows milked once a day and cows milked twice a day parameters such as milk yield and milk composition. At Present only 5% of herds in New Zealand are milked once a day for a whole lactation (Lembeye et al., 2016).

Reduced milking frequency and the management implications

Once a day milking has many benefits especially now that the climate is changing and summers are becoming much warmer. Once a day milking reduces heat stress on the cow as a result of less walking to be done leading to a decrease to lameness in the herd as cows are only walking to the milking parlour once a day therefore they have half the walking distance then a cow milked twice a day and less time is spent standing around in the collecting yard waiting to be milked. Once a day milking can have a positive impact on the body condition score of the cow after the cow calves a negative energy balance occurs and this increases the body condition score. Another huge benefit of once a day milk is that it can improve the reproductive performance of a cow, after calving the anoestrus interval is reduced. This reduces the hormone intervention. Which increases submission rates and the final rate of pregnancy (Stelwagen et al., 2013). Once a day milking also benefits the farmer from a management point of view. Once a day milking provides flexibility with regard to labour. Labour is becoming a huge issue. By milking cows once a day there is less time spent in the milking parlour. This reduces pressure on the farmer and creates more time to spend on doing other jobs around the farm yard such as grassland management, detecting animals for heat.  All of these aspects are essential to run a profitable dairy system (Bewsell et al., 2008).

The milk composition and milk traits can be different in cows milked once a day compared to cows milked twice a day. Farmers adapted to this system for a better lifestyle (Clarke et al., 2006) there is a huge variance in the production of milk. This variability can be changed due the fact of the frequency that the cows are milked be it once a day or twice a day. A study was carried out on herds of cows in New Zealand where cows milked once a day and cows milked twice a day performances were compared. The results that were constructed were cows that were milked once a day had a reduction in milk yield and a milk composition between 19% and 25%. This is compared to cows that have a milking frequency of twice a day (Lembeye et al., 2016). Increase in milking frequency increases the cow’s production, milk yield and milk composition immensely (Bortacki et al., 2017). In the early weeks of lactation cows that are milked more frequently can increase their production of milk by 8% for their full lactation even if milking frequency is reduced after the first 6 weeks (Bortacki et al., 2017). Increasing milk frequency has a positive effect on a cow’s milking lactation, as the milk yield is increased as a result of stimulation of the udder which increases cell proliferation in the mammary glands leading to a significant increase of 6-30% in the milk yield (Hale et al., 2003) when comparing once a day milking to twice a day milking, cows that are milked once a day have a decrease in milk yield by approximately 7-40%. There are obvious factors that may influence the reduction in milk yield such as the breed of the animal, the parity and the stage of lactation that the herd is at (Stelwagen et al., 2013).

Reduction in milking frequency and feed allowance impact on the dairy cow’s immune system.

The transition from milking twice a day to being milked once a day can be a stressful change for a cow.  To reduce the risk of stress the feed allowance should also be lessened limit the physiological stress that is caused during the transition to peak milk production. By carrying this out this will also improve the immune system in the cow (O’ Driscoll et al., 2012). Reducing milking frequency to once a day milking in the early stage of the lactation, this causes a reduction in milk yield but has a positive impact on the cow itself as it increases the energy balance of the cow and improves her metabolic status (McNamara et al., 2008). Having an increased energy balance and metabolism status this increase improves the body condition score of the cow immensely. Reducing milking frequency to once a day can cause a reduction in neutrophil and monocytes. The activity of the phagocytic neutrophils is reduced in cows milked once a day as a result of stress occurring as a result of an increase level of udder distension compared to cows udders that are milked twice a day (Llamas Moya et al., 2008). Cows that are fed on a high herbage diet mixed with concentrates increases milk yield throughout the lactation. This type of diet has also has a positive impact on the udder as it increases the score for udder firmness. Reducing the level of feed that is fed to the cows on a daily basis can help milk accumulation and reduce discomfort for cows that are milked once a day after calving (O’ Driscoll et al., 2012).  A study was carried out to assess the measures of the immune function. Cows milked once a day had a lower percentage of neutrophils and had a higher percentage of lymphocytes compared to cows that are milked twice a day and cows that are fed on a high allowance of feed. Cows that are milked once a day had a lower percentage of monocytes compared to the cows milked twice a day (O’ Driscoll et al., 2012).

Cow comfort

Once a day milking can be implemented for many reasons; the main reason is farm labour and labour costs (O’ Driscoll et al., 2011).  It is obvious to think that once a day milking less milk produced compared to cows milked twice or even 3 times a day (Ramond et al., 2004). There is also an advantage to once a day milking such as improving other parameters, improving performance of milk composition, increase reproductive performance as a result of increase fertility, improving live weight which leads to a good body condition score (O’ Driscoll et al., 2011).  There is a concern that cows may experience some discomfort in the udder due to holding a higher capacity of milk for a longer interval compared to cows milked twice a day (O’ Driscoll et al., 2010b). Animal welfare is also a concern for high yielding cows.  To overcome this welfare issue, cows may be milked twice a day at the beginning of lactation and a few weeks into the lactation reduce the milking interval to once a day milking (O’ Driscoll et al., 2011).  According to (O’ Brien et al., (2006) and (Hale et al.,2003) cows that are milked twice a day at the beginning of lactation and milked once a day for the duration of the lactation period can increase the production of milk as a result of the mammary cell proliferation increasing. From a welfare point of view if cow’s milk yield is increasing immensely when being milked once a day the interval should be increased to twice to ensure that the cow isn’t experiencing any discomfort. Every time a cow is milked the pressure that the cow’s udder is under is decreased at each milking. As the milk yield of the herd decreases then it is redeemed safe to go back to a once a day milking frequency. Once a day milking can benefit the feet of the cow as there is only half the walking distance as the cows are only coming back to the yard from pasture once a day. This may also increase the longevity of the cow to last in the herd for a longer period of time (O’ Driscoll et al., 2010b).  Once a day milking also reduces the need to have another labour unit employed to work on the farm especially during the calving season (O’ Driscoll et al., 2011).   A study was carried out to observe the locomotion, udder firmness and milk leakage score and lying behaviour of the cow milked when the cows milking frequency was changed from twice a day to once a day milking. When the changed occurred cows were lying down for a shorter period of time, as result of a longer milking interval the mammary pressure increased leading high level of milk leakage (O’ Driscoll et al., 2011).

Milking frequency has a huge impact on locomotion of the cow and the tension of the udder especially during the early stage of the lactation. Once a day milked cows have a higher locomotion score the cause of this is because of a higher abduction and adduction in the hind legs of the cow (O’ Driscoll et al., 2010b). The reason for the hind legs of a cow to become under such pressure is because the weight of the milk in a cow’s udder is carried by the back legs of the cow. Cows that are milked once a day will have a much bigger capacity of milk which puts pressure on the hind legs of the cow. Milk yield is at its highest from the time the cow calves until the cow hits peak lactation. Once a day cows have higher volume of milk during this period and this interrupts the normal movement of a cow back legs (O’ Driscoll et al., 2011).

Milk Composition and Milk Quality:

Once a day milking has an impact on the composition of the milk that the cow produces as cows milked once day has a higher percentage of milk fat and a higher percentage an increase protein content. The major drawback of once a day milking is a decline in milk production and a decrease in the output per hectare (Stelwagen et al., 2013). Another worry of once a day milking is an increase in somatic cell count (Lazzarini et al., 2017). An increase in SCC may lead to penalties in milk price leading to a reduction in profits. High SCC results in clinical mastitis which is Milking cows once a day has a negative impact on the lactose in the milk as the lactose percentage is decreased (Remond et al., 2012). Somatic cell count is known to be increased in cows that are milked once a day however this is not entirely accurate as the as the somatic cell count depends on hygiene factors and the condition of the cows udder.  A study was carried out to analysis milk yield and milk composition, Nutritional status, reproduction and pathology. A study was carried out over 12 week period where cows were milked once a day from the 15^th of January the results were as follows:

• Cows milked once a day from 15^th January produced 20% less milk then the cows that were milk twice a day for the 12 week duration.
• Cows milked once a day had a 14% decrease in milk fat and a decline protein by 17% compared to the cows that were milked twice a day.
• SCC was higher in once a day milking cows 79,433 cells/ml vs 50,110 cell/ml in the cows that are milked twice a day. it took 9 weeks until there was a difference detected in the  SCC (Grala et al., 2016)

Effects of milking frequency on the Mammary Gland

Milk yield can be affected by a number of different factors, the driving factor behind milk yield by the secretory mammary epithelial cells how active these cells are.  These parameters are the ones that respond to a change in milking frequency (Murney., et al 2015). There is also physical changes in the mammary gland as a result of extended milking interval. The blood flow and the nutrient uptake declines (Stelwagen et al., 2013).

Effects of milking frequency on the breed of the cow

The breed of the animal influences the production of milk that the animal will produce (Lembeye et al., 2016). A study was carried out on different breed of cows that are miked once a day. The breeds consisted of Holstein Frisian, jerseys and a Holstein Friesian crossed with a jersey. The breed f x J was the most efficient once a day milking cow compared to the purebred jersey and Holstein Friesian. The F x J breed has a lower milk production. The jersey breed is under less pressure compared to the Holstein Friesian cow. This is because the jersey breed has a lower milk production. Jersey cows have a better milk accumulation. This means that Jerseys can hold milk for a longer period of time compared to the Holstein Friesian (Lembeye et al., 2016).

The results achieved are as follows:

• At the beginning of the lactation the cows that were milked twice a day had a much higher milk yield then the cows milked once a day. These cows also had a higher percentage of milk fat and protein.
• The peak lactation for all 3 breeds occurred in around day 30 after calving.
• First lactating cows had a higher milk yield at the start of the lactation curve and became stable between day 30 and 100 of the lactation period.
• The constant decline then began after day 100 of the lactation.
• First lactating cows that were milked twice day did not decline until after 240 of the milking lactation. 

• Cows that were milked once a day produced 722 kg of milk less then cows milked twice a day, 28 kg less fat and 22.2 kg less protein.
• The breed that was most affected by the once a day milking was the Holstein Friesians  as there was a major decrease in the milk yield and milk composition.
• Holstein Friesians milked once a day have a lower milk yield by 24.7%, 18.9% less fat and 20.4% less protein compared to the Holstein Friesian milked twice a day.

• Jersey cows that were milked once a day had a decline in milk yield by 17.1%, 15.5% less fat and 14.6% less protein.
• The Jerseys milk yield and milk composition didn’t get affected as much as the Holstein Friesian cow. 
• The mature cows milked once a day declined in milk yield between 16% and 21%. This showed that the number of milk lactations and milking intervals had an impact on the performance of the cow (Lembeye et al., 2016).

Conclusion

In conclusion to carrying out a comparative study of milking frequency – once a day versus twice a day on Irish dairy farms, research has shown that there are many advantages and disadvantages to once a day milking. The main reason once a day milking is carried out is to improve management. Less time is spent in the milking parlour and more time is spent managing grass, and detecting cows for heat (Bewsell et., 2008). There is less stress on the farmer leading to a better lifestyle, more time for holidays and less labour units required. Once a day mi

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