Optimising the health and performance of dairy cows through improved copper nutrition
McCaughern, J.H (2020) Optimising the health and performance of dairy cows through improved copper nutrition. Doctoral thesis, Harper Adams University.
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Abstract
The dietary supply of copper (Cu) as an essential trace element has implications for dairy cow performance, health and fertility. Despite being the most widely reported mineral deficiency, there is evidence to suggest an over-supplementation of the element on farm,consequently 38% of Holstein-Friesian cull cow liver that enters the food chain contains toxic liver Cu concentrations.Suggested reasons for this over-supplementation include suppressing the effects of the Cu absorption antagonists sulfur and molybdenum, and a perception from those within the industry that in the absence of clinical toxicity, there are no harmful sub-clinical consequences of elevated hepatic Cu concentrations. Recent evidence however of an increasing Cu status in lactating Holstein-Friesian cows as a result of replacing grass silage with maize silage in the diet, advocates the potential of other nutritional factors to alter Cu absorption. The objective of these studies was to determine dietary factors other than concentrations of Cu antagonists that may have increased hepatic Cu concentration on farm,and determine the long-term consequences of Cu over-supplementation on Holstein-Friesian heifer performance, health, and fertility.Results in study one identify the potential of increased dietary starch concentration and/or decreased ruminal pH to increase the Cu status of lactating Holstein-Friesian cows, and may indicate a lack of understanding within the industry regarding Cu availability in total mixed rations. Despite a marginal growth rate increase in study two, feeding Holstein Friesian heifers Cu in excess of requirement during the growing phase decreased fertility, modulated the immune response, and compromised early lactation performance when continued beyond parturition in study three.In conclusion, increasing dietary starch concentration and/or reducing rumen pH increases hepatic Cu reserves, and the long-term feeding of Cu above requirement during the rearing phase and early lactation may compromise growing heifer fertility, as well as lactation performance.
| Item Type: | Thesis (Doctoral) |
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| Divisions: | Animal Production, Welfare and Veterinary Sciences (to 31.07.20) |
| Depositing User: | Ms Kath Osborn |
| Date Deposited: | 05 Mar 2021 10:40 |
| Last Modified: | 05 Mar 2021 10:40 |
| URI: | https://hau.repository.guildhe.ac.uk/id/eprint/17656 |
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