title: Effect of energy restriction and re-alimentation in Belgian Blue double-muscled beef cows on digestibility and metabolites.
abstract: Four groups of five non-lactating and non-pregnant Belgian Blue double-muscled (BBDM) cows were used to investigate the effect of energy level (E) on digestion, and blood and urine metabolites. The energy levels of the groups, applied indoors during a 140-day restriction period, were 100%, 90%, 80% or 70% of their energy requirements (E100, E90, E80, E70) respectively. Afterwards, animals grazed on the same swards for 203 days (re-alimentation period). Balance trials were conducted at the end of the restriction period (BT1) and at the end of the re-alimentation period (BT2). Blood was sampled at the end of these trials. Diets consisted of maize silage and straw (80/20 on a dry matter basis) and a mineral-vitamin premix, fed at the appropriate E during BT1, or maize silage and a mineral-vitamin premix, fed at 125% of the maintenance requirements, during BT2. Significant increases of the digestibility coefficients were found during BT1 when E decreased, resulting in a better net energy capture of 7% for E70 compared with E100 (p < 0.05). Slightly, but non-significantly higher digestibility coefficients were observed for decreasing E during BT2. Plasma concentrations of glucose and creatinine did not differ between treatments during BT1, while differences were found for triacylglycerols and alpha-amino nitrogen. A tendency for a linear increase was observed for non-esterified fatty acids with decreasing E. Differences in blood metabolite concentrations disappeared in BT2. Urinary creatinine excretion was not affected by E, while body nitrogen loss increased linearly with energy restriction in BT1. No differences were found during BT2, suggesting that non-lactating and non-pregnant BBDM cows are able to adapt to a cyclic change of body weight and body reserves. These data show that restricted cows mobilized body fat as well as body protein. It is concluded that the qualitative aspects of metabolism during energy restriction are comparable in double-muscled cows with those in non-double-muscled animals, although the magnitude of the effects may be different.
authors.affiliation: Department Animal Nutrition and Husbandry, Agricultural Research Centre, Melle, Belgium. leo.fiems@ilvo.vlaanderen.be
authors.forename: L O
authors.initials: LO
authors.lastname: Fiems
authors.forename: J M
authors.initials: JM
authors.lastname: Vanacker
authors.forename: J L
authors.initials: JL
authors.lastname: De Boever
authors.forename: W
authors.initials: W
authors.lastname: van Caelenbergh
authors.forename: J M
authors.initials: JM
authors.lastname: Aerts
authors.forename: D L
authors.initials: DL
authors.lastname: De Brabander
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D031204:Caloric Restriction / Q000662:veterinary*; D002417:Cattle / Q000097:blood / Q000378:metabolism*; D004063:Digestion / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D009584:Nitrogen / Q000378:metabolism; D009751:Nutritional Requirements; D011247:Pregnancy
chemical_list: D005230:Fatty Acids, Nonesterified; D009584:Nitrogen