Institute of Mountain Stockbreeding and Agriculture, BG - 5600 Troyan, Bulgaria
ALEKSIEV, Y., 2008. Effect of shearing on some physiological responses in lactating sheep kept indoor. Bulg. J. Agric. Sci., 14: 417-423
The effect of early spring shearing on dynamics of some physiological responses was studied in six lactating Tsigai ewes kept in barn. Rectal temperature, pulse rate and respiratory frequency were recorded for 5 days before and 15 days after shearing twice daily in the morning (07.00 h) and in the afternoon (14.00 h). Rectal temperatures were lower in the morning both in unshorn and shorn sheep compared to the values recorded in the afternoon but the difference was significant (P<0.05) only in shorn ewes. Rectal temperature in unshorn sheep averaged 39.0°C in the morning and 39.2°C in the afternoon. Shearing resulted in a significant decrease in rectal temperature of 0.73 °C in the morning (P<0.01), and of 0.41°C in the afternoon (P<0.05) compared to pre-shearing levels. Heart rate in the morning prior to shearing was 82.8 ± 0.4 beats.min-1 and an average increase of approximately 10 beats.min-1 was recorded after shearing. In the afternoon, similar mean values of 102.9 ± 0.4 and 103.3 ± 0.5 beats.min-1 respectively were recorded in unshorn and shorn ewes. A transient elevation of 25 beats.min-1 accompanied by shivering was noted only in the first morning after shearing but subsequently they both disappeared indicating a downward shift in the lower critical temperature Prior to shearing, respiratory frequency averaged 36.6 ± 3.1 breaths.min-1 in the morning and 55.9 ± 5.8 breaths.min-1 in the afternoon. Shearing brought about a considerable drop in respiratory activity, which reached significantly lower mean values of 16.6 ± 0.9 breaths.min-1 in the morning (P<0.01) and 20.6 ± 1.5 breaths.min–1 in the afternoon (P<0.001). Regardless of the substantial enhancement of ambient temperatures during the daytime, respiratory activity remained almost unchanged. The results suggest that adaptation in shorn sheep was realized mainly through the activation of energy saving mechanisms which played an essential role in supporting the thermal homeostasis under cold stress induced by shearing.