Effect of four different reflective barriers on black-globe temperatures in calf hutches and on calf ADG

Abstract Text: Polyethylene hutches are a popular method of housing dairy calves from birth to 60 or more days of age, although these hutches get hot when in full sun. Shading the hutches and yard has been effective, but shade increases concerns about increased pathogens and moisture from the lack of sunlight. This study characterized the relative differences in the ability of four different types of radiant barriers to reduce black globe (BG) temperature within these hutches during hot weather and reports the results from some field trials. Treatments for the BG trials included three different types of covers (two types of reflective laminates (Cadpak P and Cadpak ESD) and an aluminized 3.0 mil white LDPE), and a reflective paint (LO/MIT-1).  The reflective covers were 1.8 x 3 m finished size, and covered the top and sides of the hutch down to .15 m above the ground, leaving the front and back exposed.  The LO/MIT-1 paint covered the entire sides and roof of the hutch.  Two 24- h trials one week apart were conducted during relatively hot and clear days in early August. Black globe temperatures were recorded at 20 – min intervals in duplicate using blackened table tennis balls mounted 0.3 m above the floor in the center of each hutch.  Ambient temperature (shade) during the hottest 2 - h period for both trials averaged 39.9, while the uncovered control averaged 41.1°C and LO/MIT-1 39.9 °C, both of which were significantly higher (ANOVA followed by LSD, P<0.01) than the Cadpak P (38.9); Cadpak ESD (38.6); and aluminized LDPE  (38.7 °C).  Twelve to 24 of the covers were field-tested on three collaborating dairy farms in the Panhandle region of Texas from June to September, 2013.  Despite having a relatively cool summer, the farms reported increased ADG ranging from 0.018 to 0.045 kg per day.  A statistical analysis was not possible because the calves in each treatment were weighed as a group on the farms (n = 3). Both the Cadpak P and Cadpak ESD were starting to delaminate at the end of the trails. The reflective covers evaluated in this study can be expected to improve calf comfort and most likely gain, but additional field testing is needed to refine the design and determine cost effectiveness of the covers. 

Keywords: calf, hutch heat stress