Should You Be Considering Pasture for Dairy Heifers?
Dr. Ronald L. Boman
USU Extension Dairy Specialist
High voltage portable electric fences make it possible to move dairy heifers on pasture frequently. We have learned a lot about how to make irrigated pasture productive and how to maintain forage quality in recent years. The process is called �Management Intensive (Rotational) Grazing� (MIG).
This past grazing season at USU we grazed bred Holstein heifers on perennial ryegrass pastures that also contained some white clover and birdsfoot trefoil. The pasture was seeded in a field that was previously in alfalfa. The pasture was sprinkle irrigated every 7 to 10 days as needed and fertilized four different times with 55 units of N/acre. The pasture was divided into one acre paddocks using portable electric fences with drinking water available in each paddock. Heifers were moved to new paddocks daily. They grazed one day behind lactating cows and all of their feed came from pasture. In other words, the cows grazed the choicest growth in each paddock one day before the heifers had access to graze the same paddocks.
Daily Liveweight Gain of 1.75 lbs/day
We used 17 bred heifers that were on pasture for 118 days. Initial body weight averaged 1084 lbs and final weight averaged 1291 lbs for an average daily gain of 1.75 lbs/day. Remember that these heifers were bottom grazers following the top-grazing lactating cows. Bear in mind too that these heifers still had plenty of available forage even though it had been picked over by the lactating cows. Carrying capacity for these intensively managed pastures was 2.75 head of 1200 lb animals per acre.
On a nearby private grazing farm, open Holstein heifers grazed perennial ryegrass pasture during the 1996 grazing season. Heifers were individually weighed four times during the grazing season (see Table 1). Average daily gains during the first 46-days on pasture were a very acceptable 1.76 lbs/day. There was plenty of forage available during this period. The second 77-day period spanned the hotter part of the year. This was the first full year of grazing for this particular grazier and he admits that he didn�t sprinkle often enough and didn�t fertilize adequately. During the last period (55-days) average daily gains were 1.50 lbs/day. Carrying capacity per acre was 2.45 head of 1000 lb animals/acre for the grazing season.
Table 1. Dairy Heifers Grazing Perennial Ryegrass (125 head)
Management Intensive Grazing Components
1. Electric Fencing - to divide paddocks.
2. Drinking Water - available within each paddock.
3. Irrigation - available on demand. Sprinkling is preferred to flooding.
4. Fertilization - four applications of 50-60 lbs of N/acre. White clover reduces the need for N Fertilizer.
5. Vegetative Growth - keep grazing height at 6" to 8".
6. Move Heifers - every 24 to 48 hours to a fresh paddock.
7. Grass Species - this article is about perennial ryegrass which establishes quickly (you can graze 60-days after germination) and responds well to fertilization and frequent grazing. Holland-type varieties are more cold tolerant and winter hardy than New Zealand varieties. Orchard grass and meadow brome should also fit well into an MIG system.
If you have questions about this article, contact your local county Extension agent or Dr. Ron Boman at USU (435-797-2163, Fax: 435-797-2118 or firstname.lastname@example.org).