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Animal Science Abstract

The effects of synchronizing the rate of dietary energy and nitrogen supply to the rumen on milk production and metabolism of ewes offered grass silage based diets

M. W. Witt^1,A, L. A. Sinclair¹, R. G. Wilkinson¹ and P. J. Buttery²

^APresent address: Trident Feeds, PO Box 11, Oundle Road, Peterborough PE2 9QX, UK

¹Animal Science Research Centre, School of Agriculture, Harper Adams University College, Edgmond, NewportTF10 8NB, UK
²University of Nottingham, Division of Nutritional Biochemistry, School of Biological Sciences, Sutton Bonington Campus, Loughborough LE12 5RD, UK

Abstract

Twenty-four multiparous ewes were used to test the hypothesis that synchronizing the hourly rate of release of energy and nitrogen in the rumen would optimize milk production. Three diets were formulated using the in situ degradability of the food ingredients, to differ in their rate of organic matter (OM) and nitrogen (N) release in the rumen. All diets contained 400 g grass silage per kg dry matter (DM) and were predicted to have a similar content of metabolizable energy (11·8 MJ/kg DM), metabolizable protein (102 g/kg DM), neutral-detergent fibre (365 g/kg DM) and daily ratio of N : OM supply to the rumen but differ in their hourly pattern of nutrient release to be either synchronous (S), asynchronous (A) or intermediate (I). The diets were offered ad libitum as a complete feed in a 3 × 3 Latin-square design consisting of three periods each of 28 days duration. Synchronizing the hourly supply of energy and N to the rumen did not significantly alter milk or milk fat yield (g/d), milk protein content (g/kg), DM intake (kg/day), total time spent eating or the number of meals per day. However, compared with ewes offered diets I or A, those offered diet S had a lower milk fat content (g/kg; P < 0·05) whilst protein yield (g/day) tended to be increased (P = 0·05). Animals offered the synchronous diet (S) had lower plasma urea concentrations throughout the day and significantly higher beta-hydroxybutyrate concentrations at 14:00 and 18:00 h than those offered diets I or A. In conclusion, synchronizing dietary energy and N supply to the rumen did not have a major effect on milk production in ewes.

Keywords: energy consumption, ewes, nitrogen, rumen, synchronization

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