by Tamara Scully
Farmers who confine the milking herd and those who graze their herds often have differing perspectives on which environment provides the optimal level of cow comfort, has positive impacts on herd health and results in the best financial results for the dairy.
Anne-Marieke Smid, a University of British Columbia Ph.D. candidate, recently presented her study, “Dairy cattle preference for different types of outdoor access,” during the Dairy Cattle Welfare Council’s Student Showcase.
“Less than 20% of lactating dairy cows in the United States have access to pasture,” Smid said. “Most of them are housed indoors year-round. Is this actually a problem for the cows?”
In previous studies, dairy cows given free access to pasture 24 hours per day during the summer months were found to utilize pasture primarily during the overnight hours. From 8 a.m. to 4 p.m., less than 50% of cows chose pasture. But from 6 p.m. until 7 a.m., more than 50% – and a steady 90% between midnight and 5 a.m. – of the cows were out on pasture.
For some dairy farmers, access to land could prevent them from offering their cows pasture access, even if the cows would prefer to utilize that pasture. Competition between utilizing land for crop production or pasture, or concern about inclement weather, could also hinder a dairy farmer’s ability to provide pasture, even though cows do prefer time on pasture when given an option, she said.
Smid opted to study whether alternative outdoor access might be used in lieu of pasture. Her research focused on a confined dairy herd in a deep-bedded sand-free stall barn setting, at 100% capacity, with stalls replenished every other week.
“The indoor environment was pretty good,” she said, and most of the cows in the herd had never had any outdoor access.
In or Out?
Smid’s study divided the herd into eight groups of 12 cows, each observed for a two-week period. The first week consisted entirely of observing the cows in the free-stall housing, the time spent at the feed bunk with ad libitum access to TMR rations and the time spent perching in the stalls. Perching is a risk factor for lameness. Observation was via 24-hour video recording.
The first three nights allowed the cows to acclimate to their new groupings, and the cows were confined in the barn. The next two nights the cows were observed for baseline behavior while remaining in the barn continually, to allow comparison to the behaviors shown when later given access to the pasture and sand pack area.
The cows were then put on pasture for 24 hours, followed by 24 hours on the sand pack. This was done to familiarize the cows with these areas. After returning to the barn for the daytime hours, the herd was next given free choice access to the pasture, to the barn or to the outdoor sand pack between 8 p.m. and 8 a.m.
The pasture allowed 6,000 square feet of space per cow. The sand pack offered 130 square feet of space per cow if fully utilized.
When cows could only access the sand pack or the free stalls, but not pasture, 45% of the night was spent outside. When only pasture was made available as an option to the barn, 90% of the time was spent outdoors.
When the cows could freely access the pasture, sand pack or barn, the vast majority of the herd primarily chose the pasture. For over 90% of the night, cows chose to be outside, and only 1% of their time was spent on the sand pack.
“When both outdoor options were available, the cows showed a strong preference for pasture over the outdoor sand pack,” Smid said.
Once the gate was open on the nights offering outdoor access, the cows left the barn within 45 seconds, Smid said. Prior to opening the gate, most cows were lying and ruminating in their stalls.
Temperatures averaged 55º F during the study. There were a few rainy nights during the experiment, and the sand pack did have some drainage issues. They switched to woodchip bedding in future studies and saw no differences in cow choice despite better drainage with woodchips, Smid said.
Cows kept in the free-stall barn without any outdoor access spent longer amounts of time eating TMR during the nighttime hours than when the cows were provided with outdoor access. Cows given pasture access spent the least amount of time feeding indoors during the night, while cows with sand pack access spent an intermediate amount of time at the feed bunk overnight.
From 8 a.m. to 8 p.m., when the cows were always in the barn, there was no difference in time spent feeding no matter where the cows went at night.
“Nighttime access to the outdoors did not change time spent feeding indoors during the day,” Smid said.
The dry matter intake of cows was not studied. It is not known how much pasture was consumed or how much time the cows on pasture spent grazing.
Perching behaviors were significantly higher when the cows were confined to the free-stall barn 24 hours a day. When given sand pack access at night, time spent perching dropped by 50%. Pasture access led to an even greater decrease in perching behaviors.
“If you are outside, you cannot perch inside the barn. But when we just look at the daytime, when the cows cannot go outside, we still saw a decrease in time spent perching during the day for the pasture and the sand pack treatments,” Smid said. “That shows that there is actually a positive aspect of the nighttime pasture access that carries forward into the day when cows are confined to the free-stalls.”
Lameness was not studied, although increased time spent perching is a factor which predisposes to lameness.
Further study will be needed to understand which factors influence cows’ preference for pasture at night.
What is motivating cows to seek pasture? Will they continue to do so if they have to walk farther? Was it the pasture or the fresh air that compelled them?
“The free-stall and the outdoor areas differed in many aspects, so we don’t know really what drove the cows’ preference for pasture,” Smid said. “When they had both outdoor options, they showed a strong preference to pasture over the sand pack. But when allowed only access to the sand pack, cows still spent about half the night outside.”