This article appears in the May 2009 issue of Western DairyBusiness
By Ron Goble
RENO, Nev. – Stocking density on dairies of all sizes has been researched and scientists determine that a crowded corral or freestall barn is not a good thing for herd health or the bottom line. Rick Grant, researcher with the W.H. Miner Agricultural Research Institute in Chazy, NY, painted the big picture for attendees at the large herd Western Dairy Management Conference recently in Reno.
“According to the “Stall Use Index” from University of California, Davis, as stocking rates (SR) increase, resting time decreases,” Grant said.
He shared the following basic concepts on stocking rates:
• Overstocking reduces cow’s ability to practice natural behaviors.
• Overstocking improves economic returns on facility investments.
• Social, group dynamics and facilities influence response to stocking rate.
Grant noted some basic behavioral needs:
• 5 to 5.5 hours per day eating.
• 12 to 14 hours per day lying (resting).
• 2 to 3 hours per day standing and walking in alleys where grooming, agonistic, estrous activities take place.
• 0.5-hours per day drinking.
• 20.5 to 21.5 hours per total needed.
• 2.5 to 3.5 hours “milking” = 24 hours per day.
Grant explained that some of the common ways of disturbing time budget on-farm included mixing of primi- and multiparous cows and leaving them for an excessive amount of time in holding pens or the parlor. That relates to too much time away from resources.
More than an hour per day in headlocks – especially where fresh cows are concerned.– and uncomfortable stalls impact performance.
Overcrowding will make the negative response worse, he said. Grant reported on the response to stocking rates with primi- versus multiparous cows. He found there were numerous natural behavioral differences such as heifers taking smaller bites, eating more slowly, and spending more time feeding. Heifers that are typically less dominant are more easily displaced from the manger area and avoid stalls previously occupied by more dominant cows.
Researchers observed what he termed “neophobia – fear of a new environment.”
“As stocking density increases we see greater aggression and displacements. Time of eating shifted and fewer meals were noted. Eating rate increased and cows showed a greater potential for sorting. The most noted effect was on subordinate cows.
“Within limits, cows can adjust feeding behavior in response to variable stocking rates,” Grant said. “Cows can eat faster, although they ruminate less. Overstocked cows also may experience greater somatic cell counts due to greater teat-end exposure and immune suppression.”
SCC at 100% SR was 135,000 compared to 236,000 SCC at 142 SR.
Grant noted that milk quality is affected as stocking rates increase. Milk fat levels are depressed as stocking rate increases. At 100% SR milk fat was 3.84% compared to 3.67% at 142% SR.
In studies cited by Grant, 100% vs 130% stocking rate of stalls and headlocks, 4-row barn (Batchelder, 2000) showed rumination decreased by 25% at 130% stocking rate, resulting in 2 hours per day less rumination time.
Another research study (Hill et al., 2006) showed ruminating times and lying times for cows housed at 100%, 113%, 131%, and 142% stocking rate of stalls and headlocks in a 4-row barn.
Cows spent the following hours per day at each different stocking rates strictly ruminating: 8.5 hours per day at 100%, 8.5 hours at 113%, 8.1 hours at 131%, and 7.5 hours per day at 142%.
Researchers recorded the time cows would ruminate lying at: 6.6 hours per day at 100%, 6.5 hours at 113%, 6.1 hours at 131%, and 5.7 hours per day at 142%.
After the midnight hour…
Activity from midnight to 4 a.m. in research by Hill et al., 2009, showed a significant difference in cows resting, feeding and standing in the alley during the early morning hours. At 100% SR 71.1% resting, 11.8% feeding and 3.9% standing in alley. At 113% SR those figures were 70% resting, 12.6% feeding and 5.4% standing in alley. At 131% SR the figures were 63.7% resting, 14.6% feeding and 8.7% standing in alley. At the highest SR of 142% the numbers were 58.7% resting, 15.4% feeding and 12.6% standing.
Grant summarized research showing there is a positive relationship between stall availability, resting, and milk yield. Miner Institute data showed a significant relationship between resting and milk yield. Dairy producers can look for about 3.7 lb/day more milk for each extra hour of rest.
Stocking rates and repro
In their look at stocking rates and reproduction, Grant reported the following:
University of Wisconsin data from 153 farms used to identify factors affecting reproduction demonstrated that when bunk space in breeding pens was decreased from 24 to 12 inches, the percent of cows pregnant by 150 DIM decreased from 70% to 35%.
Grant reported that cows display territoriality in use of freestalls and social rank determines a cow’s location. Stalls nearest the feed alley are preferred (Gaworski et al., 2003), but subordinate cows avoid freestalls previously occupied by dominant cows.
Overcrowded conditions (from subordinate perspective) may exist even at lower stocking densities, Grant explained.
In summary, Grant concluded that changes in these behaviors: altered feeding behavior, greater aggression/displacements at feed bunk, reduced resting time, increased idle standing in alleys, decreased rumination, and subordinate cows (i.e. primiparous and lame cows) were most affected by high stocking density.
Such changes and behaviors caused by high stocking rates may result in the following performance (economic) losses: less milk yield, lower milk fat, greater SCC, greater health disorders, reduced fertility and lower average dairy gain.
Physical and social environments are additive, Grant pointed out. Heat stress and overcrowding contribute to reduced rumination, increased sorting, increased feeding rate and increased standing time. All of which can lead to acidosis, low percentage of fat and lameness.
Grant concluded that optimal stocking density could be:
• Close-up and fresh cows: ≤80% of bunk space (30 inches per cow) and may be a function of stall availability.
For lactating cows he suggested, not to exceed 115% to 120% of stalls in a 4-row barn. For mixed heifer and older cows optimum would be 100%. In a 6-row barn: 100% of stalls.
He stressed that dairymen need to ensure good access to feed, water and stalls.
■ To contact Rick Grant at the William H. Miner Agricultural Research Institute, Chazy, NY, call 518-846-7121, Ext. 116, or e-mail: grant@ whminer.com. For additional information you may visit their wibsite: www.whminer.org.