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Paper-Lecture41 - Synchrony of nutrient supply to the rumen...

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Synchrony of nutrient supply to the rumen and dietary energy source and their effects on the growth and metabolism of lambs 1 J. M. Richardson, R. G. Wilkinson, and L. A. Sinclair 2 Animal Science Research Center, School of Agriculture, Harper Adams University College, Edgmond, Newport, Shropshire TF10 8NB United Kingdom ABSTRACT: The objective of the current series of experiments was to assess the effects of dietary syn- chrony of OM and N supply to the rumen, achieved by altering the sequence of feeding individual ingredients and in diets with different energy sources, on the metab- olism and performance of growing lambs. In Exp. 1, the in situ degradability coefficients of OM and N were determined for five feed ingredients and subsequently was used to formulate two diets, based either on barley or sugar beet pulp, to have a similar predicted nutrient content. Within each diet, specific ingredients were shifted between the 0900 and 1600 feeding to provide either a synchronous, intermediate, or asynchronous supply of OM and N to the rumen. In Exp. 2, these diets were fed at a restricted level to 48 growing lambs with an initial live weight of 25.1 ± 4.22 kg and a slaugh- ter weight of 41.4 ± 1.94 kg. There was no significant effect of dietary treatment on live weight gain or feed conversion efficiency. Lambs fed the synchronous diets deposited more kidney knob and channel fat than lambs on the asynchronous or intermediate diets ( P < 0.05), whereas lambs fed the barley-based diets deposited more carcass ( P < 0.05) and noncarcass ( P < 0.001) fat Key Words: Blood Plasma Ammonia, Energy Retention, Growth, Lambs, Microbial Protein 2003 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2003. 81:1332–1347 Introduction Current diet formulation systems for ruminants (AFRC, 1993; NRC, 1996) assume a 24-h time scale for calculating dietary supply of energy and protein. While this methodology may be convenient, some (Johnson, 1 The authors would like to acknowledge K. D. Sinclair, Scottish Agricultural Colleges, Aberdeen, for conducting the insulin analysis and D. Kyle, Rowett Research Institute, for conducting the purine derivative analysis. 2 Correspondence: phone: ++ 44 1952 815332; fax: ++ 44 1952 814783; E-mail: [email protected] Received May 10, 2002. Accepted December 23, 2002. 1332 than lambs on the sugar beet-based diets. Lambs fed the asynchronous diets retained less energy over the course of the experiment than lambs on the intermedi- ate or synchronous diets ( P < 0.05), and had a lower energy efficiency (0.079, 0.097, and 0.093 MJ retained/ MJ of intake, respectively, P < 0.05). Lambs fed the barley-based diets retained more energy than lambs on the sugar beet-based ( P < 0.001) and had a higher en- ergy balance (0.095 vs. 0.084 MJ retained/MJ intake, respectively; P < 0.01). Plasma ammonia concentrations mirrored ruminal ammonia concentrations on the bar- ley-based diets, but not sugar beet-based diets. In Exp.
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