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Title: The effects of exercise on the lactational performance of cattle
Author: Matthewman, Richard W.
ISNI:       0000 0001 3621 3989
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1989
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The aim of this work was to investigate the effect of exercise (walking a specified distance for a fixed number of days) on the lactational performance of pregnant cows and to investigate the effect of diet on the lactational response to exercise. The results of the reseach are particularly applicable to the effects of exercise on the lactational performance of cows which are used as draught animals in tropical countries. A literature review was carried out of the role of cows as draught animals in tropical farming systems, of the metabolites used for muscular activity and lactation, factors which affect the supply of these metabolites and the effect of exercise on lactational performance, body weight change and food intake. Three experiments were done to investigate the effect of exercise on milk yield, milk constituent yield (g/d), milk constituent content < g/kg milk), body weight change, blood metabolite concentrations and the voluntary intake of barley straw. The effect of five different diets on the response of the above variables to exercise was also investigated. The experiments were carried out at the Easter Howgate Farm six miles south west of Edinburgh using in each instance twelve pregnant, lactating crossbred Hereford x Friesian cows in their second or subsequent lactations. The animals were exercised in the Peritland Hills for three five day periods each separated by two non-walking days. They walked approximately 8.8 kilometres each day and climbed a vertical distance of approximately 480 metres a day. This exercise was calculated to be equivalent to an energy expenditure of approximately 12MJ per day or a quarter of the maintenance energy requirement of the animals. It was found that the exercise carried out caused a milk yield reduction of between 7 and 14 percent depending on diet. Milk yields declined on walking days and recovered to almost non-walking levels on the intervening non-walking days. Milk fat content increased as milk yield declined, with the result that the daily yield of milk fat was not affected by exercise. Milk protein content and lactose content were not markedly affected by exercise, with the result that the daily yields of these two milk constituents declined approximately in proportion to the decline in milk yield. When animals walked, their rate of weight gain was not as great as when they were not walking. Animals on some diets lost body weight when they walked. After walking animals on all diets increased weight faster than prior to the walking period and in most cases achieved the expected weights (based on extrapolations from the first non-walking period weight gains) by the end of the experiment. It appeared that exercise may have caused changes in gut-fill which influenced body weight. Measurements of the concentrations of blood metabolites showed increases in the concentrations of (3-OH butyrate and free fatty acids and decreases in the concentrations of glucose, magnesium and inorganic phosphorus. The response of blood metabolites to exercise was influenced by diet and some adaptation to exercise was observed over the three week walking period. These changes were indicative of energy deficits when the animals exercised and in some cases were similar to the changes in blood metabolites observed by other authors in fasting animals The intake of barley straw offered ad libitum and supplemented with one of three diets was not affected by exercise. No measurements were made of the products of digestion, but it appeared that diets which might be expected to sustain high rates of fermentation and high levels of propionate production supported lactational performance during exercise better than diets which were designed to supply larger quantities of rumen undegradable protein and starch. It was calculated that cows offered some diets were in energy deficit when they walked and concurrent weight losses were observed. In other groups however, although cows were in negative energy balance, positive weight gains were measured. Gut-fill changes, increased weight of concepta and changes in fat to lean tissue ratio might explain these observations. No adverse effects of exercise were observed in the animals and all animals subsequently calved successfully. It was concluded that the levels of energy expenditure experienced by the cows in the present experiments would have no long-term adverse effects on the lactational performance of the animals and that while milk yields would suffer in the short term, if working periods were separated by two or more non-working days, milk yields would recover to near pre-work levels. The consequences of heavier work, greater daily levels of energy expenditure, work sustained for longer periods of time without intervening nonworking days, work carried out at different stages of lactation and work carried out by animals fed tropical diets is worthy of further investigation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Zoology