So far this week you've been looking at the care of companion animals. And today, we'll start to focus on farm animals, or production animals as we sometimes call them. These farm animals are kept as part of a farm business, and therefore economics plays a large part in their management. Today we're going to have a look at dairy cattle. The number of dairy farms in the UK has decreased significantly in recent years due to the difficult economic climate, although the number of cattle has actually remained fairly stable at just under 2 million. Therefore the farms that have survived have done so by increasing the herd size and also increasing milk yields. The average UK dairy farm has around 125 cows, yielding roughly 7,000 liters of milk per year. Here at Lang Hill Dairy Farm on the outskirts of Edinboro, we're well above average with 220 Holstein Friesian cows yielding around 9,000 liters of milk per year. If you're struggling to visualize 9,000 liters of milk, this is what it would look like. Two main housing systems for dairy cattle are straw yards and cubicle sheds. Cubicle sheds like we have here at Lang Hill are very popular because they tend to be easier to manage, but it's really important that the cubicles are comfortable, and therefore they must be well designed and the correct size. And ideally there should be 10% more cubicles than there are cows. And these cubicles are really well designed because they allow the cows to lie in a really natural position. And they're fitted with mattresses to make them really comfortable. And we put a dusting of sawdust on the top, which helps us to keep them clean. Poor cubicle design can encourage cows to stand with their back feet in the slurry passage, which can predispose them to lameness, which can be quite a problem in some farms. Cows are ruminant animals, and they naturally spend a lot of time lying down chewing the cud. And quite a good indication of how successful a cubicle shed is, is just by looking at how many cows are lying down, looking content at any one time. The purpose of a dairy farm is obviously to produce milk to sell. And in order to produce milk, these cows need to have calves. And ideally, we want them to have a calf every year. The number of days between consecutive calvings is called the calving interval, and most dairy farmers would like the cows to work to a 365 day cycle. Now, within that 365 day calving interval, we'd milk the cows for 305 days, and then we'd give her a holiday for 60 days, called the dry period. Now, in the dry period, we stop milking her and we give her time to recover and put on a bit of body weight and for her udder to repair and regenerate for the next lactation. Our cows calve in these straw yards so that we can be on hand, and supervise them, and give them the help if they need to at calving time. When a cow calves, for the first few days she produces a special milk called colostrum. This is a highly nutritious milk packed full of immunity providing antibodies. It's absolutely vital that the calves get a good feed of colostrum as soon as possible after birth because they're born with no natural immunity. From day four after calving, the milk returns to a more normal composition, and that's when we're able to start selling it. A cow's milk yield will gradually increase up until about six weeks after calving, and that's what we call her peak yield. That's when she'll be producing her maximum amount per day. At Lang Hill, the cows here produce about 45 to 50 liters per day at peak yield. Here at Lang Hill we have a herring bone parlor which can milk 28 cows at a time, 14 cows on either side. Traditionally, dairy cows are milked twice a day, and the milking times at Lang Hill are 5 AM and 3 PM. The modern milking process is very automated, with some farms now even having robotic milking systems where the cows go and milk themselves up to four times per day. Each cow wears a transponder round her neck, which allows them to be automatically identified as they enter the parlor. In the milking parlor, we have to pay great attention to hygiene, both from a cow health and milk quality point of view. As the cows enter the parlor, they are identified by their electronic collar, and then they receive their ration of concentrates. We then prepare the udder by spraying the teats with a disinfectant, and then wiping them clean with an individual paper towel per cow. At this stage, we also check that the milk looks normal. And if anything abnormal is noticed, such as clots in the milk, this would indicate that there would be an udder infection called mastitis, and that cow would be milked into a separate tank. We attach the clusters and the cow starts to milk, and then when the cluster comes off automatically when the milk flow drops below a set level. And we then disinfect the teats again to make sure they are not at risk of infection immediately after milking, when the teat canal is still open. The milk leaves the parlor and is cooled as quickly as possible to 4 degrees C in the bulk tank. And each week, a milk sample is taken from the tank and is analyzed to check the compositional and hygienic quality of the milk. The hygienic quality of the milk is monitored by a BactoScan test, which counts the number of bacteria in the milk sample, and a somatic cell count test, which gives us an indication of the cow's udder health. Compositional quality of the milk is expressed as butter fat percent and protein percent. The amount of money we're paid for our milk is dependent on the volume of milk we sell, and also on the results of these tests, so it's really important that we have really high quality milk. This is the lactation curve, and as we've previously mentioned, cows are encouraged to work to a 365 day cycle. We would milk the cow for 305 days, followed by a 60 day dry period, and her peak daily yield would occur around six weeks after calving. However, with the gestation length of cattle being around 282 days, in order to achieve a 365 day calving interval, cows need to be pregnant again by 83 days. This coincides with early lactation, which is a tough time for these cattle, because that is when their bodies are already working hard to produce high yields of milk. And it can be a difficult time for them to get pregnant again. And therefore, cow fertility is one of the main challenges facing dairy farmers and their vets. Dairy cattle lead really busy lives and they're expected to meet lots of targets and deadlines. The main challenges facing dairy cattle are fertility, mastitis, and lameness. And therefore there's plenty of interesting work for farm vets to do to help ensure that the farmer has a healthy, high yielding, profitable herd of dairy cattle.