caa a22 4500 388059710 CHVBK 20180307125117.0 cr unu---uuuuu 161130e199806 xx s 000 0 eng 10.1017/S135772980000922X doi S135772980000922X pii (NATIONALLICENCE)cambridge-10.1017/S135772980000922X Annual energy intake and the metabolic and reproductive performance of beef cows differing in body size and milk potential [Elektronische Daten] The metabolic status and reproductive performance of four pure breeds of beef cow (small size and low milk potential, Aberdeen Angus; small size and high milk potential, Welsh Black; large size and low milk potential, Charolais; and large size and high milk potential, Simmental) were monitored during their first two parities. Heifers from each breed were allocated to one of two levels of annual energy intake relative to metabolic body weight (M075) (mean daily intakes equivalent to 705 and 820 kj/kg M0·75) in a factorial design. In the 1st year 64 heifers (eight per treatment) which had calved as a consequence of first or second service were selected for the experiment. In the 2nd year 40 of these animals (five per treatment) which held to first or second service remained on experiment. Animals were housed all year round and given diets designed to represent energy intakes while grazing during the summer and conserved feeding during the winter. Pregnancy was established in late July of each year using a combination of oestrous synchronization and artificial insemination. Blood samples were collected at monthly intervals from weaning in November until calving in May; three times weekly from calving until oestrous synchronization (11 weeks later); and fortnightly thereafter until weaning. For the annual levels of dietary energy intake offered, two breeds (Welsh Black and Charolais) exhibited relatively high growth rates and had the longest post-partum anovulatory periods; and Charolais cows also had the poorest conception rates of all breeds. Relatively lean cows at calving (body condition score < 2·5 units) were sensitive, in terms of the duration of the anovulatory period, to live-weight loss during the early post-partum period, particularly when blood glucose levels were low, whereas relatively fat cows at calving (body condition score > 2·5 units) were not. The data suggest: (i) that mechanisms controlling the anabolic processes governing maternal growth are antagonistic towards those that control reproduction; and (ii) the catabolism of lean tissue rather than fat tissue during the early post-partum period is also antagonistic towards the mechanisms that govern reproductive function in cows. Copyright © British Society of Animal Science 1998 beef cows nationallicence energy intake nationallicence genotypes nationallicence metabolites nationallicence reproduction nationallicence Sinclair K. D. Scottish Agricultural College, Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen AB21 9YA Yildiz S. Scottish Agricultural College, Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen AB21 9YA Quintans G. Scottish Agricultural College, Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen AB21 9YA Gebbie F. E. Scottish Agricultural College, Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen AB21 9YA Broadbent P. J. Scottish Agricultural College, Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen AB21 9YA Animal Science Cambridge University Press 66/3(1998-06), 657-666 1357-7298 66:3<657 1998 66 ASC https://doi.org/10.1017/S135772980000922X text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S135772980000922X text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Sinclair K. D. Scottish Agricultural College, Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen AB21 9YA NATIONALLICENCE 700 1- Yildiz S. Scottish Agricultural College, Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen AB21 9YA NATIONALLICENCE 700 1- Quintans G. Scottish Agricultural College, Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen AB21 9YA NATIONALLICENCE 700 1- Gebbie F. E. Scottish Agricultural College, Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen AB21 9YA NATIONALLICENCE 700 1- Broadbent P. J. Scottish Agricultural College, Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen AB21 9YA NATIONALLICENCE 773 0- Animal Science Cambridge University Press 66/3(1998-06), 657-666 1357-7298 66:3<657 1998 66 ASC CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence SWISSBIB 388059710 BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge