Pregnancies in Sheeps and Cows

February 2012 PREGNANCY DIAGNOSIS The main benefit of early pregnancy diagnosis is to know as soon as possible if a mated cow is not pregnant, so that she can be re-bred with the minimum delay. Reducing the time to reinsemination will improve the overall reproductive performance of the dairy herd. The economic benefits of pregnancy diagnosis depend on several factors; the time after insemination when pregnancy diagnosis is performed, the accuracy of the pregnancy diagnosis method, the efficiency of heat detection, and the steps that are then taken when cows are diagnosed not pregnant. METHODS OF PREGNANCY DIAGNOSIS A wide variety of methods have been used, and each has its own advantages and disadvantages would be low in the non-pregnant cow. A single sample taken around 24 days after service will accurately identify non-pregnant cows with around 95% accuracy if progesterone levels are low. However although a high progesterone level at this stage suggests that the cow is pregnant, a single test is only about 85% accurate… Therefore a second later pregnancy check to confirm pregnancy should be routine. ¾ Transrectal examination The two methods of rectal examination (rectal palpation and ultrasound) both detect the same structures – foetus, fluid and foetal membranes. Pregnancy diagnosis can be rapidly and accurately diagnosed with ultrasound from around 28 days after insemination under most on-farm conditions (a couple of weeks earlier than with rectal palpation). ¾ Non-return to oestrus Failure to return to heat is commonly used as a cheap and simple method of pregnancy diagnosis. It is usually the first method (in terms of time after service) used by the stockperson to pick up non-pregnant cows, and integrates well with a good heat detection strategy (as the same methods are used). However the percentage of ovulating cows observed in oestrus can be lower than 50%, and so the non-return rate usually overestimates conception rates (especially if heat detection is poor). It is worth bearing in mind that about 6% of pregnant cows will show signs of oestrus… Although detecting non-return to oestrus is a useful part of fertility management, additional methods are required. ¾ Plasma and/or concentrations milk progesterone In the pregnant cow, blood and milk progesterone concentrations remain high between days 21-24 after ovulation, when they The additional benefits of ultrasound examination are; – the ability to assess the viability of the embryo, identification of cows carrying twins, detection of ovarian and uterine problems, and determination of foetal sex. In the majority of farms scheduled pregnancy diagnosis remains a key factor in improving reproductive performance. CORRECT PROTEIN NUTRITION IN LATE PREGNANCY IN EWES We have long known about the importance of energy in ewes in late pregnancy, and the harmful effects that a shortage of energy can have on lamb birthweights, lamb survival and milk production. However recent work from SAC and others has highlighted the importance of protein nutrition in late pregnancy. Like all things, balance is the key to protein nutrition in late pregnancy, and sheep need a balance of rumen degradable protein (ERDP) and bypass protein (DUP). ERDP is important for the rumen microbes to work efficiently and produce protein, and supply can be limiting with diets based on poor quality hay or straw. In our last analyses of sheep results, approximately 6% of the group average urea-N results were low in DHHPS sheep blood tests indicating that the diets were short of ERDP. The recent SAC work has also highlighted the importance of bypass protein (DUP), which is necessary to meet any shortfall in late pregnancy when the rumen is working at full capacity. In SAC trials, increasing protein supplementation by roughly 20% above current recommendations resulted in: • Around 10% heavier lambs at birth • Around 30% increase in milk production • Over 60% reduction in worm burden • Almost 90% reduction in worm egg output Any additional protein supplementation needs to be discussed in conjunction with your feed advisor – grass silage systems will obviously need less than straw-based diets for example. Get your forages analysed first. This will not only potentially save on feed costs, but enable you to work out how much supplementation is needed. The SAC work looked at feeding twin-bearing Greyface or Mule ewes 200 grams of soya per head per day for the last 3-4 weeks of pregnancy (the rule of thumb used was 100 grams of soya per day per lamb carried), and then increasing this to 400 grams per head per day in early lactation to maintain the benefits (especially for worm control). One of the key findings was the reduction in worm burdens and egg outputs. As twin-bearing ewes excrete more eggs than singles, one recommendation is to separate off the twinbearing ewes in late pregnancy and target only these ewes for protein supplementation. So we need to look beyond the crude protein content of the cake (which is crude – as it says!), and feed diets in late pregnancy that are correctly balanced for ERDP and DUP. A properly balanced ration is key. Blood testing is the quickest and cheapest way of checking on the diet in late pregnancy, and measuring urea/urea-N will assess whether ERDP requirements are being met. Detailed analysis of the concentrate will show whether enough DUP is being supplied prior to lambing.