Optihouse: Small changes can lead to big improvements in calf performance and health

Date published: 25 July 2023

Area of Expertise:

The recently completed AFBI Optihouse project has found that simple changes to cleaning practices and management of the environment can double the likelihood of being within target hygiene range and offer potential improvements in growth of 140g/day.

Example of milk feeding equipment found on NI dairy farms as part of the Optihouse project.


The overall aim of Optihouse project which was funded by the Department of Agriculture and Rural affairs (DAERA) was to improve calf performance and labour efficiency in NI calf rearing enterprises through optimising the rearing environment and management of calves. One of the main elements of the projects was to gain a better understanding of conditions in NI calf rearing houses e.g. building design, hygiene practices and calf nutrition, with the aim of identifying the key factors linked to poor environmental conditions and failure to deliver expected growth.

Do the dishes!

Good management of hygiene within calf housing is of key importance to minimise the risk of disease transmission in pre-wean calves, which can have a negative impact on calf performance. As part of the Optihouse project, AFBI alongside the CAFRE Dairy advisors completed hygiene assessments on 66 dairy farms, with samples of feed, bedding and feeding equipment collected as these are all likely sources of infection in calves. The samples were analysed for hygiene indicators including total viable count (TVC), which gives a general indication of bacteria load in the environment, coliforms (TCC) and E.coli, both of which are linked to faecal contamination, and were compared with pre-defined targets that were deemed an acceptable level.

An overview of hygiene results found on the participating farms is reported in Table 1, and as can been seen, levels of bacterial contamination found pose a real risk to calf health and performance. Of particular concern were the high levels of contamination found in drinking water that was available to calves, with around 90% of samples above target hygiene levels for coliforms and E.coli. Water is a key nutrient for pre-wean calves and a driver for concentrate intake and rumen development and providing water with high levels of bacterial contamination is a real risk factor for enteritis. Within this study, it was found that the source of water, either mains or borewell, had no impact on probability of samples being within target TVC, TCC or E.coli levels, this meaning that the contamination is likely coming from unclean drinkers. Water offered in buckets was more likely to be within the acceptable range for TVC and TCC than self-fill drinkers. Water samples were also more likely to be within target TVC levels where the facilities had an improved ease of cleaning score. These results highlight that making facilities easy to clean through implementation of simple cleaning procedures and building design choices can really help to reduce the risk of bacterial contamination. For example, if drinkers are located where they are more easily seen and accessed, they are more likely to be cleaned out.

Data from the Optihouse project also revealed that practices for cleaning feeding equipment vary widely on NI dairy farms. When questioned about frequency of cleaning milk feeding equipment only 38.1% of 66 farmers indicated that they clean equipment after every feed, with just under 40% of those farmers using a disinfectant as part of the cleaning process (Picture 1). Those farmers cleaning milk feeding equipment after every feed were twice as likely to be within acceptable TVC hygiene targets, and where disinfectant was used as part of the cleaning process, they were nearly 30% more likely to be within acceptable targets for coliforms. This highlights that taking the time to regularly clean equipment pays off in terms of reducing the risk of disease-causing bacterial contamination.

Table 1. Proportion of feed and feed equipment samples where Total viable counts (TVC) were too high and Coliforms and E.coli were detected

Sample type TVC1 too high (%) TCC2 detected (%) E.coli detected (%)
Drinking water 91.2 94.0 89.8
Milk/Milk Replacer 52.1 59.3 14.9
Concentrate Feed 75.9 30.4 5.8
Feeding Equipment 51.8 32.8 8.4
Bedding 22.6 70.4
(9.6% too high)
(3.0% too high)

1Total viable count (TVC) gives an indication of overall bacterial level
2Total coliform count (TCC). Coliforms are linked to faecal contamination

Target a dry and draught-free environment for improved live weight gain

The key requirements for successful calf housing are to provide a clean, dry and well-ventilated environment with complete absence of draughts, particularly at calf height. Young calves are susceptible to the environment and potential growth and use of energy can be negatively impacted by temperatures below the lower critical temperature (less than 10°C in the first weeks of life) and damp conditions (relative humidity of more than 80%), which are commonly experienced on NI dairy farms.

A variety of environmental factors were recorded on the 66 Optihouse farms, with results reported in Table 2. As can be seen, average temperature was 9.5°C, and more importantly calves were spending more than 50% of their time in temperatures below 10°C at a relative humidity of more than 80%, this resulting in a cold and damp environment. When calf performance data from the Optihouse farms was modelled, it was found that calves in these conditions were losing out on approximately 70g/day of potential growth. One way to combat low temperatures is to use deep straw bedding as this allows calves to nest and create a microenvironment. However, it is of key importance that straw is dry, as analysis of data indicated that calves housed in pens where straw bedding is more than 70% dry matter stand to gain 70g/day more than those in damp bedding.

Table 2. Summary of calf house environment factors on the Optihouse project farms1

Environmental Factor Target range Average Maximum Minimum
Average temperature (°C) 10-15°C 9.5 14.3 2.7
% time temperature ≤10°C   57.1 96.6 9.1
Average relative humidity (%) <80% 82.1 92.6 70.7
% time relative humidity ≥80%   64.4 98.7 18.3
Average bedding dry matter (%) >70% 70.2 86.8 35.5

1Based on 66 dairy farms across Northern Ireland

Coming soon – Building guides and an online house design application

These results highlight factors than can cause failure to deliver expected growth from specific milk feeding levels, and they can be mitigated through housing design and management practices. One of the outcomes of the Optihouse project is the production of housing booklets for development new builds and modifications to existing builds. Published by AgriSearch, these booklets aim to give simple and effective guidance to design a calf-focused rearing environment. In addition to this, a soon to be released housing design application will allow the user to design a calf house according to their specific requirements and examine how their choices will impact the rearing environment.

Take home messages

Providing fresh clean drinking water in clean drinkers is an essential part of the calf diet as it encourages concentrate intake and is vital for rumen development. Minimising pathogen load through implementation of appropriate hygiene practices is key to lowering the risk of disease transmission – simple practices such as cleaning feeding equipment after every milk feed can double your likelihood of being within target hygiene levels. Young calves depend on a dry, well manged environment to make the most of nutrients – improving ventilation and drainage alongside providing dry deep bedding will allow calves to create a warm microenvironment and will improve growth from feed.

The results from the Optihouse project stress the fact that much opportunity exists to improve hygiene and environmental management on farms, they also clearly show that putting the time and effort into such improvements will contribute positively to calf health and performance.  

Notes to editors: 

AFBI’s Vision is “Scientific excellence delivering impactful and sustainable outcomes for society, economy and the natural environment”.

AFBI’s Purpose is “To deliver trusted, independent research, statutory and surveillance science and expert advice that addresses local and global challenges, informs government policy and industry decision making, and underpins a sustainable agri-food industry and the natural and marine environments”.

AFBI’s core areas:

  • Leading improvements in the agri-food industry to enhance its sustainability.
  • Protecting animal, plant and human health.
  • Enhancing the natural and marine environment.

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