Carbenicillin

Abstract

Sand and granite fines were compared as bedding in free stalls for lactating cows. Eighteen stalls were randomly bedded with sand or granite fines. Lactating cows [100 to 160; 31 to 90 d in milk (DIM)] had access to these stalls plus 142 other stalls bedded with sand. Experimental stalls were observed on 6 d (4 times/d) during the 27-d study. Using a logistic procedure, experimental stalls bedded with sand were 2.8 times more likely to be used than those bedded with granite fines (P

(Key Words: Cow Preference, Bacterial Counts, Bedding Materials.)

Introduction

The type of bedding material used for free stalls is one of many factors that can increase milk production, decrease mastitis, and increase cow comfort by allowing the cow to more easily enter, exit, lie, stand, rise, and rest in the stalls. Cows preferred sand equipped with a rubber free-stall base compared with a waterbed (Bernard et al., 1999). Sand bedding is a comfortable cushion that forms to the body of the cow and contains low OM, thus reducing bacteria that cause environmental mastitis (Brouk, 2000). However, adding sand to the stalls at least weekly is necessary to maintain stall acceptance and cow cleanliness and to decrease the presence of environmental bacteria that cause mastitis when cows lie on the sand (Hogan and Smith, 1987). With sand bedding, large quantities of sand, approximately 12 to 25 kg/d per stall, are raked out of the stall and incorporated into manure when cows leave the stalls (Bernard et al., 2002). Sand then causes excessive wear on pumping equipment and settles in the storage pond. Therefore, most dairy farmers either use sand in free stalls, if they have a system based on daily hauling of manure (Bickert and Ashley, 1991), or use other materials, if the manure handling system cannot handle sand (Brouk, 2000; Bey et al., 2002). A new bedding material, such as granite fines (a by-product of crushing syenite granite rock), may not only decrease the amount of material incorporated into the waste management system, but could also reduce bacteria in bedding materials and subsequent mastitis. In addition, the price of granite fines is one-half that of sand. Therefore, the objectives of this study were to determine cow preference, bacterial counts, and economics of using sand or granite fines as bedding material.

Materials and Methods

Free-Stall Housing. This study was conducted at the Ark-Tenn Dairy Research and Development Facility near Center Ridge, AR between November 26 and December 22, 2001. The freestall dairy barn dimensions were 38.1-m wide × 229-m long containing 1000 free stalls. The free-stall barn was divided into five pens, and cows were rotated every 21 d to the next pen based on lactation stage [210 DIM].

Free-stall design was a widespan loop with brisket board and neck rail. The free stall dimensions (1.17-m width, 2.40-m length, 1.75-m rear curb to brisket board, 0.16-m height above alley, and 1.02-m neck rail height) allowed adequate room for the cows to enter and exit the stall easily and to rest comfortably. The free-stall barn was naturally ventilated with open sides, was connected to the pre-milk holding area and milking parlor by a covered walkway, and was equipped with fans and foggers over the feeding area. On d 1, 5, 8, 13, 20, and 24, the temperature and relative humidity were measured with two wireless thermo-hygrometers (Radio Shack®, Ft. Worth, TX) set on posts approximately 2 m above the ground at the end of both sides of the pen that was used for the study; one central wireless thermo-hygrometer was outside the barn.

Preference and Physical Characteristics. Eighteen free stalls equipped with rubber free-stall bases (SAND TRAP(TM); Topper Inc., Monticello, IA) on one side of a row of 20 free stalls near the feed alley were identified and assigned to receive one of two bedding materials, river sand (Lentz Company, Morrilton, AR) or granite fines. The granite fines were a by-product of crushing syenite granite rock (Donna Fill, Inc., Little Rock, AR). The 18 free stalls used were divided into six sets, excluding both stalls at each end of the row. Each set of three free stalls was assigned randomly to sand or granite fines.

On d 0, all stalls were excavated to a depth 15.3 cm. All stalls were equipped with a rubber free-stall base (SAND TRAP(TM)). Then, the sand or granite fines were added to a depth of 15.3 cm. Materials were added 5.1 cm above the free-stall base so that they were slightly deeper in the front of the stall (an approximate 2% slope from front to back). Purchase prices, excluding transportation, for materials were $4.00 for sand and $2.00 for granite fines/907 kg. On d 1 of the study, 545 kg of sand and 636 kg of granite fines were needed to fill each stall. On this farm, workers raked the stalls to scrape feces and wet or dirty bedding materials from the stalls when cows went to the milking parlor three times daily (0600, 1200, and 2100 h). The alley containing feces was also cleaned approximately every 3 h via a water flush. Fresh bedding materials were added on d 5, 13, and 24 after cow observations, and these amounts were recorded.

During the experiment, approximately 130 lactating dairy cows (31 to 90 DIM) were housed in the pen that contained 160 stalls. Stalls not in the study were bedded with sand. Stall usage was observed beginning 3 h post-milking in the morning at approximately 0900 h on d 1, 5, 8, 13, 20, and 24. Five observations were made each day at 30-min intervals. The first observation time was for use of the 160 stalls. If cows did not occupy the stalls, data were recorded on whether they were in the area adjacent to the water troughs or were in the alley and whether they were standing or lying in those areas. The other four observations were made only in the 18 experimental stalls. At each observation time, the presence or absence of cows in each stall was recorded. If a cow was present in the stall, whether she was lying on her left or right side, or standing either partially or entirely in the stall, and her activity (chewing or at rest) were recorded.

Stall cleanliness was scored on d 1, 5, 8, 13, 20, and 24 from 1200 until 1330 h before the stalls were raked and while the cows were being milked. A score of 1 was assigned when >80% of the surface was dirty or wet, 2 when 60 to 80% of the surface was dirty or wet, 3 when 40 to 60% of the surface was dirty or wet, 4 when 20 to 40% of the surface was dirty or wet, and 5 when the surface was dry and clean. Temperature of the bedding material at the front and back part of each stall was measured by digital infrared thermometer (Raynger ST®; Santa Cruz, CA) on the same day and time as stall cleanliness was scored.

On d 24 before new material was added, the middle stall of each type of bedding material was measured for hardness at five sites: front left, front right, center, back left, and back right of the stall. Stall hardness was measured with a DICKEY-john Soil Compaction Tester® (DICKEY-john Corp., Auburn, IL) with a 7.5-cm diameter disk at a pressure of 2 kg/cm^sup 2^.

Bacterial Counts. Bacteria that contribute to environmental mastitis (Gram-negative bacteria, coliforms, Streptococci spp., and Klebsiella spp.) were measured by sampling the sand or granite fines prior to being added to the stalls (d 13 of study and d 0 for bacterial counts) and on d 14, 20, and 24. The bedding material in the back one-third of the middle stall of each set of three stalls was sampled using paper cups that would hold 142 g (Dixie; Fort James, Norwalk, CT) and plastic gloves. The back one-third of the middle stall was visually divided into three rows. Each row had three sites, left, central, and right. A sample size of one-half of the cup or approximately 71 g was taken from each of these sites. A sterile stomacher bag was used to composite these nine samples per stall. Bags were mixed by hand before being put in an insulated ice chest with ice packs for delivery to the microbiology laboratory.

Upon arrival at the laboratory, 20 g of the bedding sample were removed and analyzed for DM by drying in an oven at 100°C for 24 h. Ten grams were removed and mixed with 20 mL of deionized water and analyzed for pH with a pH meter (Denver Instrument Co., Denver, CO), and 10 g (ambient weight) were removed and mixed with 20 mL of deionized water for 3 h to allow absorption of water. Then, excess water was poured from the sample (wet weight). The wet sample was weighed again, and absorbency was calculated by the equation: absorbency = [(wet weight - ambient weight) × 100]/ambient weight (Zehner et al., 1986).

Bacterial populations were evaluated by weighing 10 g of bedding sample into 90 mL of sterile PBS at pH 7.2 in double sterile stomacher bags before mixing with a Stomacher® Model 400 (Seward, London, UK) at low speed for 1 min. A serial dilution of 1:10 was made with 1 mL of solution into 9 mL of sterile PBS per tube. Each dilution, starting at 1 × 10^sup 3^ to 1 × 10^sup 7^, was plated on the surface of the appropriate medium. MacConkey agar (Remel, Lenexa, KS) was used to identify Gram-negative bacteria and coliforms. Edward's modifer agar (Oxiod LTD, Basingstoke, Hampshire, UK) with 50 mg/L sterile bovine blood was the medium for Streptococci spp. identification. MacConkey agar for MacConkey-inositol-carbenicillin with 10 mg/L of myo-inosital and 75 mg/L of carbenicillin (Sigma Chemical Co., St. Louis, MO) was the medium for Klebsiella spp. Bacteria were counted after being incubated for 24 h at 37°C and recorded as cfu/g of fresh weight of bedding material. Plates with 30 to 300 colonies were used to calculate cfu/g, and the numbers were converted to logarithms for statistical analysis.

Statistical Analyses. Free-stall usage was analyzed by the logistic procedure (SAS®; SAS Inst., Inc., Cary, NC). The model included type of bedding material and day. Cow activity in the entire pen, percentage of experimental free-stall usage, and percentage of cow activity in the experimental stalls were analyzed by the frequency procedure. The bacterial counts, DM, pH, absorbency, temperature, and stall cleanliness score were analyzed with PROC MIXED (SAS). The model included bedding material, day, and the material × day interaction; repeated statement with stall was the subject. The amount of replacement bedding material added to stalls and the hardness of the two bedding materials were analyzed by the GLM procedure of SAS with a completely randomized design. The model included type of bedding materials. Least squares means were reported.

Results and Discussion

Preference for and Physical Characteristics of Bedding Materials. In the pen, there was an animal per free stall ratio of 0.81. Increasing the animal per free stall ratio above 1.5 has reduced average resting time and changed cow behavior (Friend et al., 1977). The current study did not approach that rate. The areas occupied and cow behaviors are summarized in Table 1. At 3 h after milking and feeding, >70% of cows were using stalls. The percentage of cows observed lying in stalls measured 3 h after milking was similar to the results of Overton et al. (2002), who found that when cows were milked at 0400, 1200, and 1900 h, the percentage of cows lying was greatest (86%) at 0600 h (2 h after milking).

In the experimental area, stalls bedded with sand were occupied more (79% of times observed) than those bedded with granite fines (63%; P

Our results were similar to the results of Overton et al. (2002) in that cow comfort index [calculated by (cows lying/cows in stall) × 100%; Gracia et al., 1998] for stalls bedded with sand was 89.5%. Based on this index, sand was more comfortable than granite fines (72.8% cow comfort index). More comfortable stalls generally mean softer bedding and adequate space for rising and lying down (Bergsten, 2003).

The odds ratio from the logistic procedure indicated that a cow was 2.77 times more likely to prefer stalls bedded with sand to those bedded with granite fines. Cow behaviors of lying (P

In this study, the percentage of cows standing partially in the stalls was greater than that of cows standing entirely in the stalls for both beddings, possibly because of the presence of the neck rail or the amount of stall area. The neck rail was fixed at the desired position, 165 cm from the alley side of the curb and at least 100 cm above the stall bed (Bickert, 2000; Roenfeldt, 2003; Tucker and Weary, 2003). Tucker and Weary (2003) reported that neck rail placement did not affect how much time cows spent lying, but it did affect the type of standing performed in the stall. Cows spent more time standing partially in the stalls when the neck rail was closer to the curb (165 cm), and less time standing entirely in the stalls. The neck rail forces cows to back up when rising and stops cows from moving too far forward in the stall (Bickert, 2000). Moreover, Tucker et al. (2004) reported that the stall length and width could affect how cows stand in stalls. They reported that cows spent more time standing partially in the stall when stalls were shorter (length: 2.29 vs 2.74 m) and narrower (width: 1.12 vs 1.32 m).

On d 24, the hardness (P0.05; Table 2) were not different and were high (dry and clean) throughout the study. The DM, pH, and absorbency of bedding materials (Table 2) did not differ (P>0.05). Because both bedding materials were inorganic, sand and granite fines did not absorb moisture. Similar to the research of Zdanowicz et al. (2004), DM of sand did not change as time passed because sand allows drainage of urine and other fluids (Schoonmaker, 2002). The temperatures at the front (P

Although materials were added only on d 5, 13, and 24, these amounts were expressed on a perstall, per-day basis. The weight of sand or granite fines added to maintain each stall was approximately 22 kg/d and did not differ because of bedding type. This result was greater than the results of Bernard et al. (2002) and Thoreson et al. (2000), where sand usage was 7.3 to 12.7 kg/d. The maintenance cost per stall for the material for 27 d was $2.62 for sand and $1.32 for granite fines or $0.096/d for sand and $0.049/d for granite fines. Transportation costs, on a per-kilometer basis, should be similar for both the sand and granite fines. However, the required transportation distance for each material could significantly influence the on-farm price.

Bacterial Counts in Bedding Materials. Interactions between bedding material and day of sampling (Figure 2) were found for Gram-negative bacteria (P0.10). Prior to new bedding materials being added to the stalls, granite fines were free of Gram-negative bacteria, but sand was not, similar to the results of Bernard et al. (2002). However, Streptococci spp. (cfu/g) were similar between sand and granite fines. After being in the stalls for 1 d, Gram-negative and Streptococci spp. bacterial counts in sand and granite fines were greater than those at d 0, and counts did not differ because of type of bedding material. Compared with stalls with sand, Gram-negative and Streptococci spp. bacterial counts in granite fines were greater on d 7 and 11 after the addition of bedding material to the stalls. Streptococci spp. counts in both bedding types were >6 log^sub 10^ cfu/g; however, counts of coliforms and Klebsiella spp. were

A general guideline is that coliform populations >6 log^sub 10^ cfu/g of bedding are likely to contribute to a coliform mastitis problem (Hogan and Smith, 1987; Bey et al., 2002). No similar guideline has been established for the environmental Streptococci spp. It is believed that an increase in Streptococci spp. may cause an increase in mastitis (Zehner et al., 1986). These data showed that sand tended to maintain lesser bacterial counts, possibly because the sand was softer and it was easier to rake the feces out of the stalls.

Implications

Odds ratios showed cows preferred the stalls bedded with sand 2.8 times more than the stalls bedded with granite fines. Cows lay in stalls bedded with sand more than in stalls bedded with granite fines. No differences were found in the cleanliness of stalls or the amount of bedding material added. However, the stalls bedded with sand had lesser counts for Gram-negative and Streptococci spp. bacteria than the stalls bedded with granite fines. Possibly the granite fines were packed after use, resulting in a harder surface and making it more difficult to rake feces out of stalls bedded with granite fines. Therefore, stalls bedded with sand offered more comfort because of a softer surface and it had lesser bacterial counts. The cost of materials added to maintain each stall without the cost of shipping was $0.096 for sand and $0.049 for granite fines.

Acknowledgments

The authors thank Ferrell Gray with Donna Fill, Inc., Little Rock, AR, for supporting material for this study. The assistance of Jerold Brock, Larry Anglea, and Jeff Buck at the Ark-Tenn Dairy Research and Development Facility in Center Ridge, AR, is gratefully appreciated for use of facility and cows.

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R. PANIVIVAT*, E. B. KECLEY*,1, PAS, D. W. KELLOGG*, PAS, J. A. PENNINGTON[dagger], K. VANDEVENDER[dagger], D. H. HELLWIG[double dagger], PAS, T. J. WISTUBA§, and S. L. KRUMPELMAN*

* Department of Animal Science, University of Arkansas, Fayetteville 72701; [dagger] University of Arkansas Cooperative Extension Service, Little Rock 72203; [double dagger] Berea College, Berea, KY 40404; and § Morehead State University, Morehead, KY 40351

1 To whom correspondence should be addressed: ekegley@uark.edu

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