Performance of lactating dairy cattle housed in a four-row freestall barn equipped with three different cooling systems

Ninety-three multiparous Holstein cows averaging 130 days in milk (DIM) were utilized to evaluate three cooling treatments installed in separate pens of a four-row freestall barn in northeast Kansas during the summer of 1999. Treatments were: 1) a double row of 36-inch fans spaced at 24-ft intervals over the freestalls; 2) a single row of 36-inch fans spaced at 24-ft intervals over the freestalls and over the cow feed line; and 3) a double row of 36-inch fans spaced at 24-ft intervals over the freestalls and a single row over the feed line. Each pen was equipped with identical sprinkler systems over the cow feed line. The 85-day study evaluated milk production, body condition score, respiration rate, and feed intake of cows cooled with the systems. Cows cooled with fans over the freestalls and feed line produced more (P< .05) milk (98.8 vs 93.9 lb/cow/day) than those cooled with fans only over the freestalls. Milk production was similar for cows cooled with fans over the freestalls and feed line, and doubling the number of fans over the freestalls had no apparent advantage. Cows in all treatments consumed similar amounts of feed, and those cooled only by fans over the freestalls tended to gain more body condition than cows in the other two treatments. Estimated increase in net income realized from using these cooling systems ranged from $3,500-6,100/year/pen.; Dairy Day, 1999, Kansas State University, Manhattan, KS, 1999;

1 Department of Biological and Agricultural Engineering.

Summary
One hundred fifty-nine Holstein cows (66 primiparous and 93 multiparous) were assigned to each of three different cooling systems installed in two-row freestall barns on a northeast Kansas dairy. One barn was equipped with a row of five 48-inch fans mounted every 40 ft over the freestalls and a row of 10 36-inch fans mounted every 20 ft over the cow feed line. Another barn was equipped with five 48-inch fans mounted over the freestalls. Both of these barns were also equipped with identical sprinkler systems mounted over the feed line. The third barn was equipped with a row of five 48-inch fans mounted over the freestalls. In addition to the sprinklers over the feed line, additional sprinklers were mounted on the back alley of the third barn. Data were collected for an 85day period to evaluate the three systems under heat stress during the summer of 1999. Cows cooled with these three systems produced similar amounts of milk and consumed nearly equal amounts of feed. Summer heat stress generally reduces milk production 20%, if cooling systems are not installed. Based on this estimated loss, these systems returned over $10,000/pen/year above ownership and operational cost. These results indicated that effective cooling in a two-row freestall barn includes a sprinkler system on the feed line and properly sized and spaced fans over the freestalls.

Introduction
Properly designed, two-row, freestall barns can provide maximum natural ventilation because of the reduced building width compared to four-and six-row barns. Increased natural air flow can help keep cows cooler during the summer. However, cows will still experience heat stress, so other measures generally are applied in these facilities. The purpose of this study was to evaluate the use of fans and additional sprinkler area upon the performance of dairy cattle.

Procedures
One hundred fifty-nine Holstein cows were blocked by lactation number, milk production, and days in milk (DIM) and assigned to each of three cooling treatments. A commercial dairy in northeast Kansas constructed three identical two-row freestall barns. The barns were similar in dimensions (Table 1) and equipment. Each barn contained a single pen with 100 freestalls and 108 cows. One barn (F+S) was equipped with a row of fans (five 48-inch-diameter circulations fans with 1 horsepower motors) over the freestalls and another row of fans (10 36-inch-diameter circulation fans with 0.5 horsepower motors) over the cow feed line. Fans were angled down at 30E. Fans over the stalls produced an estimated air flow of 1,000 cfm/stall, and those mounted over the cow feed line produced an estimated air flow of 900 cfm/headlock. Barns two (S) and three (S+) were equipped with a row of fans (five 48-inch-diameter circulations fans with 1 horsepower motors) over the freestalls that were angled as above. Treatments F+S and S both had a similar sprinkler system installed on the feed line. The sprinkling system consisted of 2.5 gal/hr nozzles spaced every 78 inches on center mounted at a height of 8 ft on the feed line. Sprinklers were on a 15-minute cycle, with 3 minutes on and 12 minutes off. They were activated when the temperature was above 75EF. The designed application rate was 0.04 inches/sq ft of surface area, which consisted of 12-sq ft/headlock or 24-inch feeding space. Total application rate was 25 gal/cycle. Treatment S+ had a similar sprinkler system to that of F+S and S, except that an additional line was installed on the rear alley of the barn. Sprinkler nozzles were spaced 156 inches on center and the total application rate was 35 gal/cycle. The system was activated as described above.
Fans for all treatments were activated both day and night when the temperature was above 70EF. When wind speed was greater than 15 mph, fans in all barns were switched off manually.
Amounts fed and refused for each pen were recorded daily for each pen. Cows were fed twice daily for 105% of ad libitum intake. Intake data were collected on a pen basis and included the treatment cows plus an additional 55 cows that were not part of the study. Cows were milked 2×, and daily milk production was measured for a 24-hr period every 2 weeks. Animals eligible for rbST were injected on 14-day intervals throughout the study. Respiration rates were measured four times during the study in periods of heat stress. Rates were estimated in the morning and again in the afternoon from 50 cows/pen.

Results and Discussion
Milk production and days in milk did not differ among treatments at the beginning of the study (Table 2). Average milk production was similar during the trial as well as intake. Firstlactation cows (Table 3) had lower milk production at the start and during the trial than older cows. However, neither heifers nor cows differed in treatment response. Respiration rates (Figure 1) were similar and increased 16 to 18% from morning to afternoon.
The economic analysis (Table 4) demonstrates that cooling systems are both economical and effective. Based on the assumptions presented, net income after expenses was $10,000 to $12,000/pen/year. This could amount to $100 to $120 per cow/year. These cooling systems are important to the profitability of Kansas dairies.

Conclusions
These results indicated that an effective cooling system for a two-row freestall barn would include fans over the freestalls and a sprinkler line over the feed line. Installing additional fans or sprinkler area did not increase milk production in this study.   dimensions, width (40 ft), length (220 ft), sidewall height (12 ft), and roof slope (2/12); and configuration, 1 pen with 100 stalls per pen and 110 headlocks per pen. 2 F+S = one row of fans over the feed line and one row of fans over the freestalls; S = one row of fans over the freestalls; and S+ = one row of fans over freestalls and additional sprinkler lines. .04 1 F+S = one row of fans over feed line and one row of fans over freestalls; S = one row of fans over freestalls; S+ = one row of fans over freestalls and additional sprinkler lines. SEM = standard error of mean. .07 1 F+S = one row of fans over feed line and one row of fans over freestalls; S = one row of fans over freestalls; S+ = one row of fans over freestalls and additional sprinkler lines. SEM = standard error of mean. Net income due to cooling system ($/yr/pen) $11,232 $12,153 $10,607 Net income per stall due to cooling ($/stall/yr) $112 $122 $106 Additional income per day due to heat abatement (per stall) 1.12 1.22 1.06 1 F+S = one row of fans over feed line and one row of fans over freestalls; S = one row of fans over freestalls; S+ = one row of fans over freestalls and additional sprinkler lines.

Assumptions:
-100 cows or stalls per pen -Calculations over a 85 days of heat stress -Milk price = $13/cwt -Rural water cost = $1.60/1000 gal -20% reduction in milk production with no cooling -5% loss in milk production per month due to increasing days in milk -Feed cost = $135/ton of dry matter -Estimated life of fan is 7 years, and that for sprinkler system is 5 years