14 Sept 2015
John Dawson
Job Title
Figure 1. More than 90% of cows pictured are lying down, meaning they have adequate space and are relaxed and comfortable.
Interest in keeping dairy cows indoors comes from developments in animal genetics, health and nutrition, which have contributed to a cow’s milk output increasing by 80 litres a year in the past two decades. High-quality pasture alone does not provide balanced diets for maximum feed efficiency as cows’ stomachs cannot fully digest and make best use of the nitrogen in grass. There is also a limit to the amount of grass a cow can graze, which limits its milk yield to below its genetic potential. Continuous housing presents an opportunity to utilise a cow’s use of feed, increase intake and realise a cow’s full potential for producing milk, but it can affect the fertility performance of the cow.
Many dairy buildings are relatively old and cow size has increased progressively over time. Consequently, cubicles, feeding passages, lighting and ventilation in older buildings may have become incapable of maintaining the adequate cow health and welfare required for optimum reproductive performance.
Continuous housing of cows requires skilled cow management, especially from a nutritional perspective where diets can be tailored to meet requirements for a good oestrus – vital to get the cow in calf.
As a result, continuous housing is often practised with larger herds where economies of scale justify greater investment in expert labour and specialist advice, as well as higher capital expenditure on buildings and equipment. Larger herds also allow cows to be grouped so their needs can be more easily met and stress on the animals is minimised.
However, many continuous housing herds are being housed in adapted buildings with all of the shortcomings these provide.
Fertility is governed by the combination of oestrus detection rates coupled with conception rate. Oestrus detection in housing is influenced heavily by the comfort of the housing. Uncomfortable cubicles reduce cow lying times, tiring the cow and reducing oestrus demonstration. Inadequate passage space frightens the cow. Inadequate feeding area reduces intakes and strength of oestrus signs. Slippery floor surfaces prevent the cow demonstrating oestrus. Poor lighting and cow management reduces demonstration of oestrus.
Cubicle size and design is crucial, particularly with the increased size of dairy cows, and many cubicles are no longer of sufficient size or adequate design. Cows find these cubicles so uncomfortable they will spend considerably more time standing up or choosing to lie in dirty passageways, which seriously affects fertility.
Recommendations for cubicle size and design obviously vary according to breed requirements, but, in general, cubicles should be a minimum of 2.36m long by 1.17m wide for Holstein-Friesian cattle, with a preferable size of 2.43m × 1.22m for larger cattle.
Newer types of cubicle division allow flexible sharing of forward and side lunge and lying space. Cubicle bases need to be clean, dry and have a cushioned surface with good grip. This allows the cows to lie down and stand without difficulty and to be able to ruminate properly while lying. The hierarchy of the herd affects stress levels and reproduction. Subordinate cows are frightened to lie next to a dominant cow, therefore there should be an absolute minimum number of cubicles as there are cows in the herd and, ideally, 10% more cubicles than cows.
Having sufficient feeding space for the number of cows in the herd has implications for reproduction, as insufficient feed will compromise hormonal production. Where not enough space is available at feed barriers, particularly with total mixed ration feeding, the shyest cows and heifers, those far down the herd hierarchy and any lame or otherwise ill cows may not be able to feed sufficiently or have the opportunity to eat the most freshly mixed and dispensed feed. Fresh, good-quality feed needs to be accessible at all times, requiring pushing up of the feed – which can easily be done with the use of a robot. In most situations, dairy cattle should have at least 0.6m of feeding space at feeding barriers per cow.
Competition for feeding space has direct implications in terms of poor fertility, as those cows pushed out at feeding time are likely to suffer from health problems linked to poor nutrition and subsequent lowered immune defences. They are likely to spend more time standing and putting unnecessary pressure on their feet, thereby reducing their voracity to demonstrate oestrus.
Non-slip floor surfaces are vital for reproduction efficiency. Cows will not demonstrate oestrus on slippery floors. If they are unsure of their footing they are very reluctant to even walk on the surface. They will be frightened to stand and demonstrate oestrus. Activity meter readings will be affected as the cow fails to increase movement.
Rubber floor coverings are increasingly used in dairy cattle housing. Their use needs to be carefully assessed as the durability of rubber flooring is not known and it may be difficult to scrape the passageway. Rubber flooring is relatively new and research is ongoing to measure its value. While it is apparent standing and walking on rubber is generally more comfortable for cows because it reduces the traumatic impact on the cow’s foot, there may be implications for hoof growth and wear that mean foot trimming may be required more often.
Studies have proven that on some types of rubber flooring, wet or badly scraped rubber can be particularly slippery. It is apparent the design and type of the rubber used in the flooring defines its properties in this respect, so some types of rubber flooring may be better than others. A well-recognised advantage of good rubber-floored passageways is the increased bulling activity.
Cows, as all living organisms, need water. Restricted water intake and stale water supply indirectly affects reproduction due to the health and production consequence. Dairy cattle should never be denied access to good-quality drinking water. Recommendations for space allowances are a minimum of 10cm of trough space per cow for all cows at all times, particularly when waiting to be milked or after milking.
Floor areas around troughs should be particularly well-designed and maintained to limit slippage and foot damage. Troughs should be cleaned regularly. Self-tipping water troughs are of particular benefit – ensuring easy cleaning and reducing the build-up of harmful contamination, which can affect fertility directly.
Correct light intensity and duration have a very positive effect on the health, fertility, welfare and productivity of dairy cattle. One of the best-known phenomena of light is the part it plays in the control of hormone levels in dairy cattle. It has a positive impact on milk yield, which can increase by 15%. Uniform lighting in livestock housing improves fertility, with a positive influence on oestrus, and good lighting makes it easier to spot. Greater levels of activity are recorded where there are more hours of daylight and where the period of light has been extended artificially. The calving interval can also be reduced by using the correct lighting regime and light levels. Signs of disease can also be detected at an earlier stage.
Dairy cattle cannot distinguish between high-pressure sodium and metal halide, so only the intensity and duration of the light are important. Research has shown the minimum light level should be 150 lux. A lighting regime of 16 hours of light at a minimum of 150 lux, followed by eight hours of darkness (maximum five lux) will produce the positive benefits. Using the lighting to increase the day length affects melatonin production. Light inhibits melatonin production and darkness accelerates it. Longer periods of light mean less sleep hormone and healthier, more active cows. The aforementioned lighting regime simulates long summer days, the days when the cow is naturally most active, resulting in higher oestrus behaviour and fertility.
Walkways are often neglected as potentially restricting reproductive performance, but they are a crucial element. Cows need adequate space to walk freely without intimidation by superior cows and enough space for the demonstration of oestrus without impeding other herd mates. Bottlenecks and sharp turns from the feeding and housing area to the parlour can be restrictive and detrimental. Narrow passageways allow bullying of the more submissive cows by the dominant herd members. If passageways are narrow, it can mean the more submissive herd members find it difficult to avoid dominant cows. This increases the risk of foot trauma, and slips and falls.
Narrow passageways also require more frequent scraping to avoid the problems of slurry pooling, while falls across the width of passageways should be avoided. Feeding passageways should be four to five metres wide, to allow for two cows to pass side-by-side behind a feeding cow. With particularly large breeds or types of cow, more space should be allowed. Cubicle passageways should be between three metres and 4.5 metres wide, which allows space for two cows to pass should a third cow be partially stood in a cubicle.
Cow comfort has been identified as a prime focus for improving reproductive performance in the dairy herd. All aspects of the cow’s life on the farm – most particularly when housed – play a vital role in controlling potential fertility performance. Even issues such as providing adequate ventilation and controlling heat stress in herds have an influence on cow reproduction.
Housing requires good cow management and the stockman’s skills. The cows should be moved through the buildings quietly and in a non-hurried fashion. Driving them can cause slipping and damage. Cows should be in groups so management tasks such as TB testing and milking are performed in minimal time, allowing the cow maximum feeding time and maximum time for oestrus to be demonstrated and observed. Enough time needs to be set aside for the stockman to observe oestrus. Cows demonstrate oestrus best during quiet periods of the day.
Observation requires the housing arrangement to offer free access to the cow with plenty of room for mounting and unobstructed sight of the cow so the stockman can accurately identify the cow bulling.
The environment has a large impact on fertility, but fertility has a large effect on the environment.
Dairy cows are estimated to contribute about 20% of total UK atmospheric methane emissions and 25% of total UK ammonia emissions. Fertility has a major effect on the number of heifer replacements required to maintain herd size for a given milk quota or number of cows.
The proportion of total gas emissions produced by herd replacements is up to 27% of methane and 15% of ammonia with commercially common fertility levels. Restoring fertility to 1995 levels is predicted to reduce methane emissions by 10% to 11% and ammonia emissions by about 9%. Further improvements in fertility could reduce methane emissions by up to 24% and ammonia emissions by about 17%. Improving housing conditions, increasing cow comfort and its reproductive benefits will get more cows in calf quicker, reducing heifer replacement levels and emissions.
