Nighttime Cooling Is an Effective Method for Improving Milk Production in Lactating Goats Exposed to Hot and Humid Environment.

Katsunori Sunagawa,Yasuhiro Kamata,Itsuki Nagamine,Noriko Niino,Kazuhide Kinjo,Yoshihiko Taniyama,Ayano Matayoshi

doi:10.5713/ajas.14.0890

Abstract

Heat production in ruminants follows a diurnal pattern over the course of a day peaking 3 hours following afternoon feeding and then gradually declining to its lowest point prior to morning feeding. In order to clarify the cooling period most effective in reducing decreases in feed intake and milk production, experiments were carried out based on the diurnal rhythm of heat production and heat dissipation. In experiment 1, the effects of hot environment on milk production were investigated. The animals were kept first in a thermoneutral environment (20.0°C, 80.0%) for 12 days, they were then transitioned to a hot environment (32°C, 80.0%) for 13 days before being returned to second thermoneutral environment for a further 12 days. In experiment 2, the effectiveness of daytime cooling or nighttime cooling for improving milk production in hot environment was compared. While ten lactating Japanese Saanen goats (aged 2 years, weighing 41.0 kg) during early lactation were used in experiment 1, ten lactating goats (aged 2 years, weighing 47.5 kg) during mid-lactation were used in experiment 2. The animals were fed 300 g of concentrated feed and excessive amounts of crushed alfalfa hay cubes twice daily. Water was given ad libitum. The animals were milked twice daily. When exposed to a hot environment, milk yield and composition decreased significantly (p<0.05). Milk yield in the hot environment did not change with daytime cooling, but tended to increase with nighttime cooling. Compared to the daytime cooling, milk components percentages in the nighttime cooling were not significantly different but the milk components yields in the nighttime cooling were significantly higher (p<0.05). The results indicate that nighttime cooling is more effective than daytime cooling in the reduction of milk production declines in lactating goats exposed to a hot environment.

Highlights

The goats were maintained in individual metabolic cages that allowed for the separate collection of urine and feces
Statistical analysis While feed intake, water intake, and milk yield were measured each day, in order to mitigate the carry over effects of the previous environment, only the values from the last 7 days of each of the environments were used in the statistical analysis
Sunagawa et al (2002) reported that both rectal temperature and heart rate in goats exposed to a hot environment increased with feeding the same as in thermoneutral conditions

Summary

Introduction

The animals spend more time feeding and standing than is normally observed while they are at rest during the night (Yamamoto et al, 1979). More body heat is produced during feeding and standing than resting or lying down. Because ruminal fermentation and nutrient absorption in the lower digestive tract take place following feeding, a great deal of body heat is produced during the day. The metabolic rate of diurnal animals is higher during the day Submitted Nov. 21, 2014; Revised Feb. 3, 2015; Accepted Feb. 13, 2015 than at night, and the amount of body heat produced during the day is higher than at night (Ando et al, 1997). The body temperature of ruminants is higher during the day than at night

Methods

Results

Conclusion