Research in Veterinary Science
The effects of short term dietary restriction on haematological
responses and leukocyte gene expression of anovulatory and
ovulatory beef heifers
The study objective was to characterise the impact of negative energy balance (NEB) on immune-stress
responsiveness in beef heifers. A short term (18-day) dietary restriction model was used. Dietary restriction
(0.4 maintenance (Mn) energy requirements) induced abrupt onset of anoestrus in nine heifers
(Restricted Anovulatory; RA) while nineteen heifers maintained oestrous cyclicity (Restricted Ovulatory;
RO). In addition a control (C) group of 12 heifers received a higher level of feeding (1.2 Mn).
Haematological related biomarkers of husbandry stress, leukocyte gene expression of seven cytokine genes
and five immunological biomarkers were investigated. After 18 days of differential feeding of the heifers
alterations in eosinophil and monocyte numbers and altered expression of CXCL8, IL2 and TNFα could
be attributed to diet restriction. More specifically, changes in these five variables were found in heifers
that became anovulatory (RA) and are therefore considered to be more sensitive biomarkers to an energy
deficit.