Seasonal variations in physiological and behavioural parameters in a bachelor group of stallion ponies (Equus caballus)
Authors: Morel M. C. G. Davies , McBride S. D. , Chiam R. S. , McKay A. , Ely E. 
Published: August 2009

Animals living in temperate climates are continually adapting to seasonal demands of reproduction and survival. Whilst it is well documented that ruminants show seasonal changes in both reproductive and non-reproductive physiological and behavioural characteristics (reduction of metabolic rate and appetite during the winter with respective increases during spring and summer), this information has not been fully established in the non-ruminating ungulate species of Equidae. This may be important information from a practical management perspective since groups of equids are increasingly being kept in natural conditions for the purposes of conservation grazing.

The aim of this study, therefore, was to document the behavioural and physiological adaptive changes made by ponies during a 12-month period and to relate these to changes in forage availability and environment. Five mature pony stallions were kept in west Wales (4°5′W, 52°25′N) and monitored for 12 months. A range of physiological (testis size, body weight, condition score (CS), hoof growth, moult (M), pelage fibre length, depth and density) and behavioural measurements (foraging and non-foraging activities) were recorded along with monthly forage analysis (crude protein (CP), water-soluble carbohydrates (WSC)), dry matter (DM)) and environmental conditions (day length and minimum ambient temperature). All physiological measurements were significantly (P<0·001 to P<0·05, r2=0·16 to 0·69) related to day length and all except testis size, body weight and M were significantly related to minimum temperature, CS (P<0·001; r2=0·583), hoof growth (P<0·001; r2=0·457), pelage fibre length (P<0·001; r2=0·61), pelage fibre depth (P<0·001; r2=0·489) and pelage density (P<0·05; r2=0·192). Fewer significant relationships were observed in relation to forage characteristics; significances only obtained between CP and CS (P<0·001; r2=0·854), fibre length (P<0·01; r2=0·625) and pelage fibre depth (P<0·01; r2=0·624); between DM and CS (P<0·05; r2=0·352) and pelage fibre depth (P<0·05; r2=0·343); between WSC and pelage fibre depth (P<0·01; r2=0·55) and pelage fibre depth (P<0·05; r2=0·34). Behaviour results showed a significant relationship between time spent alert and day-length (P<0·05; r2=0·35) and between minimum ambient temperature and time spent eating (P<0·05; r2=0·37), locomotory behaviour (P<0·01; r2=0·53) and passive interaction (P=0·001; r2=0·63). A significant relationship was also reported between eating and CP (P<0·01; r2=0·53) as well as DM (P=0·01; r2=0·43). The ponies in this study demonstrated a series of adaptive changes during winter concomitant with energy conservation, however, forage availability and intake also decreased indicating lower energy input. Despite energy conserving adaptations it is unlikely that nutrient intake was adequate to account for the limited winter decline in CS and weight. In conclusion, it was considered that: (a) ponies demonstrated physiological and behavioural adaptation in response to environmental demands, (b) during winter ponies demonstrated behaviours indicative of a cost benefit analysis of expending energy in the pursuit of poor quality forage, (c) despite energy conserving adaptations, intake is unlikely to have been adequate to maintain the CS observed, and (d) reduction in metabolic rate and increased food conversion efficiency may be additional adaptations made during times of environmental challenge.