Abstract:
The objective of the study was to evaluate the effect of environmental modifications by evaporative cooling system compared with conventional system on feed utilization, productive performance and some physiological parameters in early lactation of cross-bred Friesian heifers. Twently, cross-bred Friesian heifers were divided into two groups of 10 animals each. One group was kept in evaporative cooling system (EVAP). Another group was kept in the open conventional housing system (NEVAP). Animals received feed in the form of total mixed ration (TMR) throughout the experiment. Temperature of both housing, feed intake and milk production were recorded daily from postpartum to 10 wk of postpartum. DMI and DMI%BW were significant different when compared between groups (P<0.05). Cows in EVAP produced significantly more milk than cows in NEVAP (P<0.01). No significant differences were found on body weight and milk composition between groups (P>0.05). Average temperature in EVAP was lower than temperature in NEVAP. Average ambient temperature in both housing was only 3C difference. During the day, RH in EVAP was higher than in NEVAP. RR and RT in VEVAP were significantly difference between EVAP and NEVAP (p<0.01). THI in NEVAP was higher when compared to NEVAP. All animals in this experiment were in the situation of heat stress at different level of severity. It can be concluded that cows in EVAP were in the mild stress condition while cows in NEVAP were in the medium stress condition. Water intake and water intake/DMI were significant difference (P<0.05) between EVAP and NEVAP. The nutrient digestibilities (DM, NDF and ADF) were slightly higher in EVAP group but no significant difference was found (P>-0.05). There were no significant differences (P>0.05) in milk allantoin and VFA concentrations. However, cow in EVAP trend to have these values higher than cow in VEVAP. There were no significant differences (P<0.05) in eating and ruminating times. In addition, total chewing and resting times were highly significant difference when comparing EVAP and NEVAP (P<0.01). It can be concluded from the current study that the EVAP has the potential to decrease the exposure to and alleviate the symptoms of heat stress in lactating dairy cow under the conditions found in Thailand. As a result, DMI, DMI%BW, MY, 4% FCM were found to be higher in cows raising in NEVAP. There was also the tendency of improvement of the efficiency nutrient utilization.
