Effects of grazing vs. confinement on first lactation performance of dairy replacement heifers
Farms that put their bred heifers out to a properly managed grazing system before they calve vs. confining them in barns, find that the exercise not only stimulates their appetite, it also prepares them physically for the stress of milk production. This preparation for their first lactation protects the health of the animal by improving calving ease, reducing postpartum metabolic problems such as sub-clinical Ketosis and Metritis. This improved health pays benefits during their first lactation.
From 2000 through 2002 there were two studies done through the University of Minnesota that compared Rotational Grazing and Confinement raised dairy replacements.
The first study completed by Professor Hue Chester-Jones was an extensive three year study to look at the economics of the two raising regimes as well as the growing characteristics of the animals in the two systems. His results showed that both systems allowed the animals to attain the desired growth needed to reach maturity, and that grazing an animal was a more economical method than keeping them in confinement. The second study was completed by Laura Torbert, a Graduate Student of Chester-Jones. She looked at a health comparison of the animals in the two systems. In her study there were 21 animals in each of the regimes and the study ended shortly after calving. In the study by Torbert, there were significant health benefits for grazing the animals prior to calving vs. confining them. Torbert’s study had some interesting results; it was proposed that a similar study should be completed on commercial farms.
The Cornell Study
In the Minnesota study the comparison of 21 animals in each regime made for a small statistical pool, in addition the animals were housed in a research farm under non commercial management, and did not have full lactation results. The Cornell study, which began in April 2005, was designed to improve on those issues:
25 animals in each regime on 2 farms making a total of 50 animals under each regime.
The animals were taken from two large commercial herds which had a sufficient number of animals bred in the window required for the study and each group of heifers came back to be housed and managed together on the home farm.
The study will collect the final results in February of 2007 to capture any differences between the two regimes.
The project leader established contact and breeding records were reviewed to select 50 recently bred heifers from each farm. 25 randomly selected heifers will be designated the “MIG” group and 25 will be designated the “confinement” group. All animals will be weighed and a body condition score will be determined for each animal. The animals will be put in their designated raising regime. The project leader and/or SWCD cooperators will visit both the groups throughout the grazing season. A 6-month grazing season is expected. At the completion of the grazing season both groups at both farms will be again weighed and a body condition assigned. The MIG groups and the confinement groups will then be housed in the normal manner for the participating farms. With the help of Dr Stone and John Conway, the animals will be assigned a special code on the host farms computer system. Both farms use Dairy One’s Dairy Comp 305 software. The protocol for compiling health information will be synchronized on both farms. At freshening, calving ease will be noted and any calving difficulties will be entered. The production and any metabolic problems will be compiled.
In April of 2005 the animals were selected from these two farms: Pine Hollow Dairy in Cayuga Co. and Bergen Farms of Schuyler Co. The 50 animals from each farm were weighed and sent to their regime within two days of each other. The grazing season was a challenging one in 2005 due to the lack of rain. The Schuyler animals had to be removed from the grazing system 30 days ahead of schedule, and a portion of the Cayuga animals came off a week early due to the lack of pasture growth. The expected result of the shortening of the grazing period was that since the animals from the two regimes spent more time together under the confinement regime there would be less of a difference between them. This was not the case. There was a significant difference between the healths of the animals under the two regimes on both farms. The following are the results and the discussion:
The 39 lbs gained for the Bergen heifers on pasture was the result of the dry growing conditions and also a lack of experience of the contract grazer. It was feared that the poor weight gain and also the shortened grazing season might show up in a decrease of health compared to the confined animals from Bergen’s. Pine Hollow heffiers gained a total of 211 lbs while on pasture. Even though there was a vast difference in weight gained between the two grazing systems, both groups health benefited from the grazing.
The heifers on both farms were selected to freshen in the period between November of 2005 and January of 2006. The calving ease was determined by the difficulty the heifer experienced delivering her calf. A score of 1 meant that there was no difficulty, 2 some assistance was necessary, and 3 meant there was exceptional difficulty. The difference between the two farms can be explained by the somewhat subjective nature of scoring. These are the calving ease results for the two farms.
Bergen Confinement- 1.60
Bergen Grazed 1.25
Pine Hollow Confinement 1.75
Pine Hollow Grazed 1.60
Both farms had similar protocol for the monitoring of health of the newly fresh animals. On both farms there was a recent fresh group separate from the other cows; each animal had her temperature taken every day and if there was a temperature of 102 degrees or higher for two consecutive days, an antibiotic treatment was initiated. The usual cause of an elevated temperature is metritis, which is a vaginal infection connected to calving. Bill Stone, DVM, with Cornell PRO-Dairy, and also a collaborator on this study, commented on the results. He stated that metritis is often an indicator of sub-clinical Ketosis or an energy imbalance. The cause of the imbalance in this case can be explained by looking at the results of Torbert’s study. On the research farm they were able to monitor dry matter intake (DMI) for each animal 2 weeks before they freshened.
Number of animals requiring antibiotic treatment
Bergen Confinement 12
Bergen Grazed 6
Pine Hollow Confinement 12
Pine Hollow Grazed 0
Impacts and Contributions/Outcomes
In Torbert’s study her three regimes: Continuous grazed (C), rotationally grazed (R), and confinement (F).Showed that the animals that had been in a grazing regime were consuming more throughout the two weeks prior to freshening, and 17 lbs DMI the day of calving. The Confinement animals dropped to 12 lbs DMI. This difference in consumption would explain the higher incidence of sub clinical ketosis and the resulting metritis.
Milk Production Results
At the time of the last data collection the information was incomplete but the variations between the two groups showed little to no difference. This information will be collected on the final data collection as well as: is the animal still in the herd, Date to first breeding, and other relevant information.
In both the Torbert study and the Cornell study there was significant improvement to the postpartum health of the animals in the grazing regime. In order to identify the cause of these benefits we can look at the differences between the regimes. Grazing encourages more exercise which benefits the circulatory system and muscle development. The clean air is an improvement over the confinement air which has increased ammonia. The increased appetite that continues even after being taken off the pasture is likely the main contributor to the lack of metabolic problems at postpartum.
There are benefits other than health for grazing replacements:
Many dairy’s CAFO plans would benefit from moving animals away from the home farm for the 200 days of grazing each year.
The opportunity to contract graze replacements would be a good use of smaller dairy farms that have gone out of the dairy business.
Grazing is an economical way to raise replacements.
Grazing is an environmentally beneficial method of raising livestock.
Animal Nutritionist w/ Cornell Pro-Dairy
Ithaca, NY 14850
Dairy System Specialist
Ithaca, NY 14850