FRUITFUL FINDINGS ON FERTILITY

Transcription

1 Vet Times The website for the veterinary profession FRUITFUL FINDINGS ON FERTILITY Author : Phil Christopher Categories : Vets Date : February 2, 2009 Phil Christopher reports on two meetings where speakers findings suggest veterinary help can boost dairy herd profitability with metritis management methods HELPING dairy-farming clients improve herd fertility presents a major opportunity for veterinary surgeons. In a 578-participant survey, nine out of 10 dairy farmers said they wanted to reduce their herd calving interval, on average by a target of 19 days1. In farmers own estimations, the financial gain arising from this was expected to be 57 per cow per year, and worth 9,345 per year in the average 163-cow herd taking part. However, some may be underestimating quite how much money is at stake. At a CPD seminar for practising vets in Hereford on dairy cow fertility with specific reference to postpartum metritis, Chris Hudson (senior farm animal clinician at the University of Bristol s farm animal veterinary practice) presented a new model of the losses arising from longer calving intervals (or, indeed, the gains available from shorter ones)2. It takes into account all the relevant gains and losses (see Table 1) and, sure enough, using today s milk and feed prices, it comes up with a loss of 2.36 per cow for each day of extended calving interval, in a range of 365 to 395 days. At the seminar, which was held at the Belmont Lodge Hotel, Dr Hudson pointed out that the national average calving interval from National Milk Records data was 425 days, which suggested 1 / 13

2 that up to half of all UK dairy farms were above this, many by a large margin. When he ran the model again, at calving intervals in the 400s, the losses increased markedly (see Table 2). So, as Table 3 shows, a practitioner who helps a 150-cow client to reduce calving intervals from a notuncommon 455 days to the current national average (425) can put 25,000 on to the farm s bottom-line profit. For herds at higher calving intervals than this, the incentive is clearly greater still. National average The opportunity for practices is that 40 per cent of farmers said they would welcome more proactive involvement from their veterinarian in pursuit of better fertility. A further 50 per cent said this was already happening, while the remaining 10 per cent viewed this as unnecessary. Among farmers who have made successful changes, the most commonly reported were a greater involvement of their veterinarian and/or nutritionist, better dry cow nutrition and more cattle observation. One area of farm animal practice where a major impact on fertility could be made is the early diagnosis of metritis. At the Pfizer International Metritis Consensus Conference in Paris, Martin Sheldon from the RVC said this disease was important for a number of reasons3. Animals with metritis are often systemically ill; there is reduced milk production and they are in pain, so their welfare is compromised, Professor Sheldon said. In addition to these immediate problems, metritis often leads to longer-term infections, including endometritis, pyometra and subclinical endometritis. All these conditions are associated with the infertility of delayed conception. Indeed, the financial cost of uterine disease is of a similar order to that of mastitis, yet the latter condition dominates the minds of farmers and vets. To address this issue, the symposium involved a group of European cattle practitioners and researchers with a special interest in bovine fertility. One aspect covered was the under-diagnosis of metritis. Sylvie Chastant-Maillard, assistant professor at the National Veterinary School of Alfort, France, said farmers observations revealed an incidence of puerperal metritis in about two per cent of calvings4. However, if a systematic medical examination is carried out post-partum, including measurement of rectal temperature, the incidence increases to 10 per cent, she said5. This discrepancy can be explained by a lack of symptoms, added Dr Chastant- Maillard, with only 24 to 33 per cent of cases showing vaginal discharge, for example6. Particularly in large herds, sick cows can easily be lost in the crowd, according to Mark Burnell7, a UK participant in the symposium. In large herds, there is an increasing tendency to reduce the amount of skilled labour and perhaps replace it with inexperienced staff essentially employed to carry out milking, he said. 2 / 13

3 Mr Burnell advocated identifying recently calved cows, ideally in a separate group, or otherwise by distinct individual marking using tail tapes or marker paint, for example. Upon such cows, he reported that some UK farms had initiated USA-style fresh cow programmes, under which every cow was examined daily for the first 10 days post-calving, with a rectal temperature above 39.5 C being a key indicator of potential problems. However, he was also cautious about temperatures that may be high at the beginning of the disease process, but then fall to sub-normal. Therefore, a normal temperature may be found in a cow midway between the high and low points, so additional evidence is needed to confirm a metritis diagnosis. Skilled farmers and stockmen can be trained to do vaginal examinations. In addition, monitoring milk yields each day is essential because cows with puerperal metritis are likely to either not come into milk fully, or drop in yield significantly as the disease develops. A number of factors are associated with metritis incidence, including twin calves, dystocia, stillbirth, retained foetal membranes (RFM) and milk fever. Among these, a paper from Wolfgang Heuwieser from the Free University of Berlin addressed the sometimes contentious issues of uterine washouts and the question of whether to remove RFM. Traditionally, the treatment of choice for retained foetal membranes and grade-two [puerperal] clinical metritis has been the infusion of antibiotics into the uterus, he said. Attempts are usually made to manually remove the foetal membranes. However, the efficacy of local antibiotic treatment and manual removal is controversial. A large-scale trial at the Free University of Berlin found that local antibiotic treatment or manual removal of RFM (or a combination of both) did not affect clinical efficacy or reproductive performance, compared to exclusive systemic treatment with ceftiofur in cows with fever. Systemic treatment alone, based on elevated rectal temperature, was effective and reduced the use of antibiotics compared to therapies that included intra-uterine antibiotics, said Professor Heuwieser. He said three factors in particular had led to the traditional approach being questioned: inhibition of uterine defence mechanisms by either manual manipulation and/or the irritant effect of drugs (such as oxytetracycline); negative interactions between antibiotics and the uterine environment; and questionable efficacy of locally administered antibiotics. Prof Heuwieser added that the milk withdrawal time of this approach clearly imposed a significant financial downside on clients. In contrast, of course, the ceftiofur licence requires a zero milk 3 / 13

4 withdrawal period. Infectious agents The Hereford meeting, where Dr Hudson was speaking, also heard from University College Dublin s Erin Williams. Dr Williams spoke about the findings of her research into the prevalence of infectious agents in the uterus post-calving, and their likely effects on cow fertility8. She said that since 2001, the National Disease Information Service had identified a 57 per cent rise in the number of cattle with uterine disease that required veterinary intervention. In Dr Williams study, 82 freshly calved cows were monitored closely for a month. Cows with high bacterial numbers in the uterus, identified by weekly uterine swabbing, showed slower growth of ovarian follicles and had smaller corpora lutea than herdmates with low bacterial counts. Among the bacteria identified, Dr Williams said Escherichia coli was by far the most prevalent. She explained that, at a cellular level, E coli was known to produce a toxin called lipo-polysaccharide (LPS), which is found in the uterine and follicular fluids of infected cows, in direct proportion to the bacterial load. Therefore, stage two of her research investigated whether LPS acted locally to affect the physiological function of uterine or ovarian cells. The short answer is yes in both cases, she said. In the uterus, the presence of LPS increases total prostaglandin production and disrupts the delicate ratios between different ones. The impact is a prolonged or disrupted oestrus cycle. Then, in the ovary, one effect of LPS is to reduce oestrodiol production, with a detrimental impact on ovulation. To gauge these effects in practice, Dr Williams ran an intervention study in which Holstein- Friesian heifers had LPS infused into the uterus. This treatment resulted in a longer time to reach follicular dominance and markedly reduced ovulation. Veterinarians can have a marked impact on a dairy herd s profitability by helping farmers and their staff manage fertility at an individual cow and herd level. While different farms require different priorities, the following factors are must do for clients. Gear late-lactation feeding to preventing cows from being over-fat at drying off. The condition score should be between three and 3.5. Dry-period nutrition should keep cows full of low-nutrient density, high-fibre and highly palatable feed. Never let dry cows go hungry or thirsty. The transition from dry cow to milking diet should be managed carefully under the supervision of a skilled animal nutritionist. 4 / 13

5 Identify newly calved cows clearly for at least 10 days postcalving, and monitor health and demeanour closely every day. Ideally, take rectal temperatures during milking once a day and seek veterinary advice for any that exceed 39.5 C or look off-colour. Monitor for vaginal discharge, rumen fill and feeding behaviour. Never let freshly calved cows go hungry or thirsty. On a fresh cow scorecard, keep a record of each day s observations and treatments for every freshly calved cow under surveillance. Veterinarians, farmers and staff should review scorecards regularly. Papers presented at the Paris symposium have been published in a 100-page book called 21 Recommendations Against Metritis. For Veterinary Times readers, 50 copies are available free of charge, on a first-come, firstserved basis. The document is available by writing to Phil Christopher, Box 123, 3 Bellstone, Shrewsbury, SY1 1HU. References 1. Data on file (2007). Pfizer-sponsored survey of Dairy Farmer readers. 2. Hudson C (2008). Interview with the author at CPD seminar for practising vets: dairy cow fertility with specific reference to post-partum metritis, organised by Pfizer Animal Health. 3. Sheldon M (2008). Foreword to Post-partum Metritis Consensus Conference, Paris. In Chastant-Maillard et al (eds), 21 Recommendations Against Metritis, Pfizer Animal Health. 4. Bareille N and Fourichon C (2006). Facteurs de risque des affections postpartum, Point Vet 37: Bareille N et al (2003). Effects of health disorders on feed intake and milk production in dairy cows, Livestock Production Science 83: 53-62; and Drillich M et al (2001). Evaluation of a systemic antibiotic treatment of toxin puerperal metritis in dairy cows, Journal of Dairy Science 84(9): 2,010-2, Zhou C et al (2001). Multilocation trial of ceftiofur for treatment of postpartum cows with fever, Journal of the American Veterinary Medicine Association 219(6): Burnell M (2008). The diagnosis of metritis in dairy cows. In Chastant-Maillard et al (eds), 21 Recommendations Against Metritis, Pfizer Animal Health. 8. Williams E (2008). Interview with the author at CPD seminar for practising vets: dairy cow fertility with specific reference to post-partum metritis, organised by Pfizer Animal Health. 5 / 13

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7 Speakers Chris Hudson. 7 / 13

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9 Erin Williams. 9 / 13

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11 Table 1. Calculating the cost of a 365-day to 395-day extended calving interval 11 / 13

12 Table 2. Losses arising from extended calving intervals in 30-day steps from days to days 12 / 13

13 Table 3. Losses arising from extended calving interval (CI) and gains available from improvement 13 / 13 Powered by TCPDF (