Annual energy intake and the metabolic and reproductive performance of beef cows differing in body size and milk potential

Abstract

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 (M 075 ) (mean daily intakes equivalent to 705 and 820 kj/kg M°' 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.

Effects of nursing frequency and parity on the productive, metabolic and reproductive parameters of beef cows

“…Also, Sinclair et al (1998) suggested that mechanisms controlling the anabolic processes governing maternal growth are antagonistic towards the mechanisms controlling reproduction. These authors found that the catabolism of lean tissue rather than fat tissue during the early post-partum period impaired reproductive performance in young cows.…”

Effects of Parity Order on Performance, Metabolic, and Hormonal Parameters of Grazing Beef Cows During Pre-calving and Lactation Periods

“…However, in the current experiment, multiparous cows displayed higher βHB only during the rst week postpartum, and no parity effect on NEFA concentrations. For Bos taurus beef cows, Sinclair et al [10] found higher βHB postpartum for primiparous than nulliparous during the rst postpartum weeks, consistent with increased βHB for primiparous at days 7 and 21. Based on the contrasting results of NEFA and βHB between studies, it seems that energy status parameters are impacted differently between parity in dairy and beef cows since they differ in milk production potential.…”

“…Increased SUN can also be related to the mobilization of amino acids for gluconeogenesis, so the deamination process is responsible for the enhanced blood urea (a by-product of protein catabolism). For young cows, Sinclair et al [10] suggested a preference for catabolism of lean tissue rather than fat tissue during the early postpartum period, although some studies did not nd a difference in SUN between parities [31,36]. Also, a likely explanation that supports these outcomes is that as multiparous cows calved with better BCS, they had more adipose tissue to support milk production, so they had to mobilize less protein to support gluconeogenesis.…”

“…Metabolic pro le evaluation is a tool widely used in ruminant nutrition as metabolic cues that relate nutrition to physiology [6]. It helps to accurately indicate the effects of a diet [7,8] or supplementation on animal metabolism, as well as understand homeorhetic states such as gestation and lactation [9][10][11] in which changes in metabolism occur to establish a new physiological state.…”

Effects of parity order on performance, metabolic, and hormonal parameters of grazing beef cows during pre-calving and lactation periods

“…However, in the current experiment, multiparous cows displayed higher βHB only during the first week postpartum, and no parity effect on NEFA concentrations. For Bos taurus beef cows, Sinclair et al [ 10 ] found higher βHB postpartum for primiparous than nulliparous during the first postpartum weeks, consistent with increased βHB for primiparous at days 7 and 21. Based on the contrasting results of NEFA and βHB between studies, it seems that energy status parameters are impacted differently between parity in dairy and beef cows since they differ in milk production potential.…”