The effect of long-term feed restriction and over-nutrition on body condition score, blood metabolites and hormonal profiles in ewes

Abstract

The trial was conducted to determine the effects of long-term feed restriction and overfeeding on blood metabolites and hormones and to examine the potential usefulness of these blood parameters and body condition score (BCS) on the assessment of the nutritional status of ewes. Four groups of mature, non-lactating and non-pregnant ewes with different initial BCS's were induced to change body condition by diet adjustments. Ewes with a BCS (0–5) of 1.25, 2 and 3 were fed 200% of the energy requirements for maintenance, so that the BCS increased to 4. Ewes with a BCS of 4 were fed 30% of the energy requirements for maintenance in order to decrease their BCS to 1.25. Blood samples were collected every time the mean BCS in a group matched half of a BCS unit. Serum or plasma concentrations of glucose, insulin, glucagon, non-esterified fatty acids, β-hydroxybutyrate, triglycerides, total lipids, albumin, globulins, total protein, urea, creatinine, triiodothyronine, thyroxine and insulin-like growth factor-I were recorded. Results demonstrated the general nutritional status of ewes could be monitored by a simple and non-expensive method such as the assessment of BCS on a regular basis. The direction and rate of BCS changes may offer the first and broad picture of the two main metabolic processes, namely anabolism or catabolism. Blood indicators could confirm and refine the first diagnosis, providing objective measures of the energy and protein status. Seventy-four weeks were required to obtain a decrease in BCS from 4 to 1.25, whereas the opposite increase in BCS was attained in 54 weeks. A 40% decrease in voluntary feed intake was recorded in ewes with over-nutrition at about week 44, with a BCS of 3.7–3.9. Hormone and metabolite concentrations during the chronology of changes in BCS clearly showed that ewes easily manage their body reserves between a BCS of 2 and 3.5. Evident metabolic welfare was observed between a BCS of 2.5 and 3. A BCS below 1.5 and above 3.5 must be avoided to prevent metabolic disturbances and to save the cost of excessive fattening in ewes. From the variables tested as metabolic predictors, plasma glucose and triiodothyronine concentrations and serum non-esterified fatty acids, albumin, urea and insulin concentrations proved to offer valuable diagnostic information for the interpretation of the nutritional status in ewes and could then be used to improve the nutritional management and prevent metabolic disorders.