CALF Rearing Your 2010 Herd
| Rearing Your 2010 Herd |
Rearing Your 2010 Herd - An A to Z of Heifer Rearing Rearing dairy heifers efficiently has the potential to improve farm profit by over £11,000 per 100 cows. It was recognised that an integrated approach in terms of research development and technology transfer was necessary in order to make progress. Thus, the Agri-Food and Biosciences Institute (AFBI), the College of Agriculture, Food and Rural Enterprise (CAFRE), DARD, AgriSearch and John Thompson and Sons formed a partnership to integrate the results from research programmes, an extensive survey of NI dairy farmers and on-farm trials into a new rearing regime to improve the sustainability of dairying. This A to Z of heifer rearing in 11 articles provides new information across a range of key areas on which to base systems for rearing young stock which will maximise performance of replacements entering the dairy herd in 2010 and beyond. Parts 1 to 4 and 11 are in the calf section of the web site while Parts 5 to 11 are in the dairy section. Part 1. Calf health Dairy farmers know the value of colostrum for the young calf and the need to achieve adequate intakes early in life. Yet local research has shown that in many instances, calves have received inadequate levels of colostrum and that calf mortality, and health problems in general, represent a significant economic and welfare cost to the Northern Ireland cattle industry.
Insufficient intake of colostral antibodies in the first six hours of birth is the main cause of calf health problems in the pre-weaning period. Calves that do not receive adequate antibodies through colostrum are twice as likely to die as those calves receiving adequate colostrum. Recent research has found that calves fed 4 litres of colostrum compared with 2 litres within one hour of birth had reduced veterinary costs and increased milk output during their first and second lactations. Calves that are fed colostrum either by stomach tube or by bottle within the first hours of life, compared with calves that are left to suckle the mother, are almost 3 times more likely to have adequate immunity to fight off neonatal diseases. Primarily this is a result of variation in the time taken by calves to suckle successfully. Slowness to suckle successfully can be pronounced in dairy calves, with the average calf from a dairy cow taking over 4 hours to suckle. Particular types of antibodies in colostrum attach to the lining of the intestine in the calf preventing pathogens from causing disease. Consequently, it is recommended that, wherever possible, colostrum should be fed for the first 3-4 days of the calf’s life making full use of this protective function of colostrum as well as its high nutritive value. Using the Zinc Sulphate Turbidity test (ZST), carried out on a blood sample taken within 1 week of birth, AFBI Hillsborough investigated the immune status of 150 bull calves, sourced from 12 commercial dairy farms. Overall, 19% of calves (Figure 1) had inadequate immune status (ZST levels less than 20 grams per litre), although there was very significant variation between farms. Over 70% of the calves purchased from one farm had ZST levels less than 20 grams per litre whereas at the other extreme some farms had no calves with ZST levels less than 20 grams per litre. The importance of immune status has been highlighted by data produced by AFBI Veterinary Sciences Division, where 37% of calves submitted for post mortem had no detectable colostrum immunity and 60% of the dead calves had inadequate cover, with ZST values less than 10 grams per litre. The immune status of calves can have long-term effects on growth. Data from AFBI Hillsborough has shown that calves with ZST levels less than 20 grams per litre had 7% lower liveweight gains from birth to 9 months relative to those with ZST levels greater than 20 grams per litre. Thus at 9 months of age, cattle which had ZST levels less than 20 grams per litre were 23 kg lighter than those with adequate ZST levels.
Main messages Emphasis on colostrum management during the first 6-hours of life is crucial. Wherever possible, stomach tube or bottle feed calves with colostrum (10% of calf weight) within 6 hours of birth and continue feeding colostrum for 3-4 days.
Part 2. Main diseases affecting calves It is well known that disease in early life will affect the thrive and growth of calves but results of AFBI research indicate that it can also affect milk yield and fat and protein content when these calves reach the milking parlour.
Calf scour The survey indicated that calf scour remains a major issue on farms, with 38% of producers in Northern Ireland indicating it is a significant problem within their calf rearing system. To minimise the risk of nutritional scour it is important that feeding times each day do not vary and that recommendations regarding the mixing of milk replacers are followed rigidly. Non nutritional calf scours can be caused by a number of pathogens. The results of tests on calf faecal samples sent to the AFBI Veterinary Sciences Division in the last few months indicate that the main pathogens linked with severe calf scour in calves are cryptosporidia and rotavirus. Neither of these are treatable with antibiotics, but the antibodies present within colostrum do control their effects. Pathogens are often picked up from the surrounding environment, thus lack of cleanliness in the calving area and in the calf rearing accommodation are major risk factors. Dry bedding, disinfecting utensils after each use and minimising the time period the calf is in the calving pen, all reduce the risk of infection. Pneumonia AFBI Hillsborough data indicates that calves with a case of pneumonia in early life experienced a significant reduction in growth right through to weaning (-0.57 kg perweek compared with calves with no cases). In addition, there was some evidence that a case of pneumonia in early life had significant long-term effects. Calves that had suffered from pneumonia in the pre-weaning stage tended to have lower milk fat production in first lactation compared with calves clear of pneumonia. Pneumonia at a later stage in development, from post-weaning to 1 year of age, also had detrimental long-term effects (Table 1). Outbreaks of pneumonia occur more frequently when calves are housed in poorly designed, poorly ventilated houses, with high stocking rates and where young calves are housed in the same airspace as older cattle. Table 1. Milk production of first lactation heifers with or without pneumonia during the rearing stage (AFBI Hillsborough)
Effective colostrum management is the key tool in preventing many calf diseases. However, vaccination of cows in order to boost colostrum quality, coupled with early life vaccination of the calf against a number of pathogens, can help when required. Vaccinating cows prior to calving can help protect the calf against a number of common pathogens such as Rotavirus, Coronavirus, E Coli K99 and Salmonella. Unfortunately there is no vaccine currently available for Cryptosporidia. Vaccinations that are given early in the calf’s life can help protect the calf against pneumonia related pathogens such as Bovine Respiratory Syncytial Virus (BRSV), Parainfluenza type 3 (PI3), Infectious Bovine Rhinotracheitis (IBR) and Bovine Viral Diarrhoea (BVD). A vaccination programme should be designed in consultation with your veterinary surgeon. Survey data from farms across Northern Ireland indicates that 15% of producers currently vaccinate their cows to provide better immunity to calves against scours (only effective where calves receive adequate colostrum). Twenty-one percent of producers vaccinate their calves against pneumonia agents. The survey also indicated there is some uncertainty amongst producers on the specific details of their current vaccination programmes. Main messages Emphasis on colostrum management during the first 6-hours of life is crucial. Wherever possible, stomach tube or bottle feed calves with colostrum (10% of calf weight) within 6 hours of birth and continue feeding colostrum for 3-4 days. Vaccinations can be an effective method of boosting a calf’s ability to combat many disease causing pathogens. In designing the most appropriate vaccination programme, seek advice from your local veterinary practitioner. Part 3. Calf Feeding Systems Traditionally the main method of feeding calves has been twice daily bucket feeding. However, now with the increased need to reduce labour on dairy farms a number of other systems are increasingly being adopted.
Once a day feeding system Research over a number of years has shown that calves can be fed successfully on once daily feeding systems. General recommendations for once per day individual bucket feeding systems are as follows:
Group feeding cafeteria Research with beef calves at AFBI Hillsborough has examined the relative performance of a low labour calf feeding system based on a group feeder designed to feed 30 calves. Calves on the cafeteria, fed once daily, had slightly lower liveweight gains relative to those on a standard system (calves individually bucket fed twice per day). At 9 months of age, calves reared on the cafeteria weighed 11 kg less than those on the conventional bucket feeding system. Research is on-going to investigate reasons for poorer growth rates with the cafeteria system. Automatic Feeders There is growing interest in the use of computerised automated milk feeders that control nutrient input on an individual calf basis, with 3% of dairy farmers in Northern Ireland using these feeders. These types of feeders have been used at AFBI Hillsborough for 9 years and have been found to rear calves with similar levels of performance to individually housed bucket fed calves The high initial capital cost of purchase of automatic feeders and ongoing maintenance costs must be considered carefully before choosing this approach. Labour requirements From experience of different calf feeding systems practiced at AFBI Hillsborough, the time required to feed 50 calves per week using a range of feeding systems has been estimated (Table 5). In this exercise, once per day feeding systems (bucket and cafeteria) started when calves reached 2 weeks of age and calves on all systems were assumed to be weaned at 6 weeks. The time required for veterinary treatment or bedding is not included. Table 5. Estimated time required daily to feed 50 calves with different milk feeding systems (from 2 weeks to weaning at 6 weeks)
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Part 4. Milk Feeding and Weaning Whole Milk Versus Milk Replacer For Calves The detailed survey carried out across Northern Ireland farms indicates that most dairy producers (77%) reared their calves on predominately whole milk with only 23% using predominately milk replacer. Whilst it is recognised that to minimise waste, discard milk needs to be used for calf rearing, it appears that a significant amount of saleable milk may also be used. There are significant cost implications – £14/calf if all milk fed is saleable. Opinion on feeding discard milk is mixed. As expected, numerous studies have demonstrated higher levels of bacteria and/or antibiotic residues in waste milk. There are concerns that feeding mastitic milk may increase the risk of scours and some research has shown that calves fed infected milk had mastitis as fresh calvers, caused by the same genotype of bacteria. However, most of the common organisms that cause mastitis are found all over the body, so even a calf suckling from it’s mother is likely to ingest potentially mastitis-causing organisms. Feeding whole milk increases the risk of Johnes transmission. For this reason, herds infected with Johnes should not pool colostrum or feed milk from infected cows to calves. Where large numbers of calves are being fed whole milk, on-farm pasteurisation should be considered to reduce the bacterial loading of waste milk. As for antibiotic milk, it has been highlighted that most cows have had dry cow therapy, and colostrum therefore contains antibiotics. Consequently, it is difficult to argue against the use of whole milk solely on this basis. However, the variation in quality of whole milk should be recognised. Within farms, the whole milk fed to calves can vary from 2.9-5.0% butterfat and 3.0-5.0% protein. In view of (a) possible disease transmission (b) inconsistent quality, discard milk should be fed, wherever possible, to bull calves only. Feeding level and protein content of milk replacer Over the last 20 years recommendations for the pre-weaned calf (up to 8 weeks of age) have been to offer 500-600 g per calf per day of a milk replacer (approximately 1.1 lb per day) containing 20-23% crude protein, together with access to ad libitum concentrates and water. The aim has been to achieve growth rates from 450 to 600 grammes per day. Recently, research from North America has questioned the approach of restricted milk feeding and proposed that higher feeding levels should be adopted in a bid to accelerate growth (up to 1 kg per day) in the pre-weaning period. These higher growth rates can theoretically be achieved by feeding 900 to 1200 g of high protein (up to 30%) milk replacer. To evaluate the merits of such feeding systems, which have significant cost implications, a series of collaborative studies have been undertaken at AFBI Hillsborough and Teagasc, Grange to compare the performance of dairy-bred calves offered milk replacer containing 23% or 30% crude protein at two feeding levels (600 grammes per day or 1200 grammes per day). Relative to calves offered 600 g milk replacer per day, calves offered 1200 g milk replacer per day grew significantly faster during the milk feeding period (birth to 8 weeks) (Table 1). However, differences in live weight and body size recorded at weaning for calves on the higher level of milk replacer had disappeared by 6 months and there were no beneficial effects on milk production during the first or second lactation. Increasing the protein content of the milk replacer above 23% had no short or long-term effects on performance.
Table 1. Performance of Holstein calves offered 600 or 1200 g milk replacer per day containing 23% or 30% crude protein (AFBI Hillsborough)
Weaning On average, calf rearing systems in Northern Ireland wean calves at 8 weeks of age, although there is considerable variation with over 20% of producers surveyed delaying weaning to between 9 and 12 weeks Previous research has shown that, provided calves are at least 5 weeks of age, concentrate intake is the key factor on which to base when to wean. Concentrate intake is very important in preparing the calf for a solid food diet as the fermentation of the ingredients promotes rumen development. As a general rule, the calf should be consuming approximately 0.7 kg concentrate/head/day to minimise a post-weaning check on growth. A recent study at AFBI Hillsborough found no difference in the performance of calves weaned on age at 8 weeks, compared with those weaned as soon as concentrate intake went above 0.5 kg per day, with calves totally off milk when concentrate intake was above 1.5 kg per day. Average weaning age for the latter group was 6 weeks. Provided the rumen has developed sufficiently prior to removal of milk feeding, there is limited evidence to indicate any difference between abrupt weaning and gradual reduction in milk intake. However, if feeding high levels of milk, studies have shown gradual weaning over a 7-10 day period can prevent the associated slump in growth the week after weaning, compared with abrupt weaning. The recent survey of Northern Ireland heifer rearing enterprises has shown that on farms where concentrate is offered as soon as the calf enters the calf rearing accommodation, rather than later (11 days plus), heifers are served earlier resulting in a lower age at calving. For every day delay in offering calves concentrate, the associated age at first calving increased by 4 days. Part 11. Summing up the different aspects of research and development when put into practice. Typical performing herd with 100 cows with 30 replacements • Calf feeding and management o Reducing calf mortality to 3% equates to £400 per annum. o Increasing reliance on milk replacer and optimum weaning age: estimated at £12 per calf i.e. £360 per annum. • Smoothing the transition into lactation o Introducing heifers in groups to main milking herd: estimated at 1-2 litres additional milk in early lactation. Longer-term effects currently being determined. • Managing heifers to calve at 24 months o Additional cows milked: moving from 28 months to 24 months of age increases profit by £3,300 per annum. • Targeting live weight of 540-580 kg o Compared with 600 kg+ heifers, feed costs reduced by £130/heifer equating to cost saving of £3,900 per annum. o Reproductive performance improved (30 days shorter calving interval) Reduced lameness also observed. Overall, assumed 4 months additional herd life in milking herd increasing output, net of variable costs, by £2,140 per annum. Overall financial impact of over £10,000 or over 1 pence per litre on all milk produced. |
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Figure 1. Immune status of spring-born Holstein and beef x Holstein bull calves sourced from dairy farms in Northern Ireland (AFBI Hillsborough)