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Pre-calving


Post calving ‘Type 2’ ketosis ‘Type 1’ ketosis


Target group relative to calving -7 to -1 days


+1 to +15 days +25 to +45 days


Selecting the cohort of animals to test Choice of animals is crucial because reference ranges change for animals at different stages of the production cycle and at different times of the year. This is especially true for beta carotene and vitamin E status which can be very poor at the tail end of winter before turnout in maize fed herds. Choice of animals is very important when diagnosing or monitoring a herd for types 1 and 2 ketosis.


FEED INTAKE AND REPRODUCTION IN CATTLE Sartori, R.; Guardieiro, M.M.; Mollo, M.R.; Surjus, R.S. Department of Animal Science, ESALQ, University of São Paulo (USP), Av. Pádua Dias, 11, Piracicaba, SP, Brazil 13418-900. robertosartori@ usp.br The importance of nutrition for animal reproduction has been known


to producers and researchers for a long time. However, contemporary studies have brought new perspectives and further details of this relationship, allowing fine-tuning of diet formulation in order to increase production and reproduction in ruminants. Nevertheless, especially in high-producing dairy cows, there are still serious multifactorial fertility problems, with a heavy nutritional involvement. High feed intake, for example, affects reproductive physiology in several manners; by increasing the metabolism of steroid hormones, or by affecting the response of cells to other hormones. These changes result in increased size and number of ovarian structures; however, the changes also reduce circulating steroids, potentially compromising oocyte and embryo quality. High circulating insulin due to long-term high feed intake may also contribute to reduction in oocyte quality. Although changes in feed intake affect ovarian function in Bos taurus and Bos indicus cattle, it seems that overfeeding may more profoundly affect oocyte/embryo quality in Bos taurus than Bos indicus cows and heifers. Thus, this article presents and discusses results of some relevant studies on these subjects, especially those related to the influence of feed intake on reproduction.


SUPPLEMENTAL ANTIOXIDANTS TO IMPROVE REPRODUCTION IN DAIRY CATTLE – WHY, WHEN AND HOW EFFECTIVE ARE THEY? Peter J. Hansen Department of Animal Sciences, University of Florida, Gainesville FL 32611-0910, USA The transition dairy cow is potentially at risk from oxidative stress because of decreased feed consumption, neutrophil activation associated with parturition, inflammation in the uterus in the early postpartum period, and a large increase in oxygen consumption caused by lactation. Accordingly, provision of antioxidants during this time might


Biochemical substrate NEFA


BHB + NEFA BHB +/- NEFA


No. animals to sample 12


12 12


be expected to improve health and performance of the lactating cow. There have been two approaches for increasing antioxidant status of the transition dairy cow. The first has been to provide metal cofactors of enzymes that facilitate electron donation to reactive oxygen species. Most efforts have focused on selenium and copper because there are deficiencies in amounts of these metals in many soils. The second approach has been to increase availability of antioxidant molecules that directly react with reactive oxygen species and cause their elimination. The most important of these free-radical scavenging molecules for dairy cattle nutrition have been vitamin E and β-carotene. These have been fed as supplements or provided through injection. There are also commercial products that combine vitamin E with selenium. The most consistent benefit to antioxidant supplementation for


dairy cow reproduction is a reduction in retained placenta. This is an important effect of antioxidants because occurrence of retained placenta is associated with subsequent endometritis, metritis, and reduced fertility. In contrast to the effects of antioxidants on reducing the incidence of retained placenta, benefits of antioxidant supplementation on uterine health, resumption of cyclicity, and fertility have been highly variable. Some of this variation probably reflects differences in chemical structure, route, and dosage of the antioxidant tested. It is likely, however, that much of the variation in effectiveness of antioxidant treatments reflects variation in the antioxidant status of un- supplemented cows. Depending on diet and physiological and immune status, innate antioxidant defences of the cow are probably sufficient in many cases to protect cells involved in reproductive processes from the oxidizing actions of reactive oxygen species. In those cows, additional antioxidants are not required. One way to improve the efficacy of antioxidant supplementation for the dairy cow is to assess which cows are at risk for oxidative stress and whether the incidence of these cows in the herd is sufficiently high to warrant intervention with supplemental antioxidants. Analysis of feed composition to determine levels of vitamins and minerals involved in antioxidant defence can be one tool for assessing risk for oxidative stress. It is also likely that blood metabolites can be used to assess the oxidative status of individual cows and groups of cows. To date, there are insufficient data to establish benchmark values of key metabolites that predict cow response to antioxidant supplementation.


We are grateful to the organisers of the Nottingham Feed Conference for permission to publish these abstracts from the conference. Further abstracts will appear in the next issue. Full papers will be published in:


Recent Advances in Animal Nutrition – 2012 Nottingham University Press www.nup.com


FEED COMPOUNDER OCTOBER 2012 PAGE 25


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