(Producer Questions prior to 2009)
I weaned calves from their dams. How long should I keep them apart to dry the cow up and be able to manage the cows and their calves together?
We have weaned calves for 4 days, 8 days, and 12 days then turned the calves and dams back together. Calves weaned at 4 days, 8 days, and 12 days all mothered-up and began suckling their dams. We measured milk production and all cows that had their calves at 4 days, 8 days, and 12 days produced milk after the calves were returned.
Milk composition didn't change much depending on whether cows had their calves weaned for 4 or 8 days, but when calves were weaned for 12 days, milk composition was slightly different indicating that the cows that had their calves weaned for 12 days were beginning to dry up.
So the answer to your question is that I think you will need to have calves weaned for at least 30 days to "dry" the cow up then cows and their calves could be co-mingled.
We are planning to put weaned calves (500-550 lbs) on irrigated grass. Dry hay, salt, and mineral will be available free choice. Do we need to supplement them with any other feeds?
The question you asked is a good one. We don't have data on spring-born calves grazing irrigated pastures in the fall after they are weaned. You didn't indicate what the pasture mix consists of. If there is alfalfa in the mix, then manage the calves so that bloat is not a problem. Also, grass tetany can occur in the fall, so if you are in a grass tetany prone area, supplement the calves with a mineral mix that includes magnesium oxide (MgO). You can get this at the local feed supply store. Follow label directions. Provide salt.
We do have data on calves grazing meadow and the calves were in that 500 lb range. Our meadows are mostly cool-season grasses. I would point you toward research by Lardy that was done at Gundmundsen and is reported in the 1998 Beef Report: Escape Protein Supplementation and Weaning Effects on Calves Grazing Meadow Regrowth (PDF 53KB). In this research study, they supplemented calves on meadow regrowth and calves gained 1.94 lb. per day. The important thing here is the type of supplement. The supplement they used was a high by-pass supplement and fed 2.0 lb/head daily.
So..... Looks to me, it depends on what kind of gain you want to achieve. Without supplementation, you might expect an ADG of 1.5 to 1.75 lb, with supplementation ADG would be close to 2.0 lb. The supplement needs to be higher in by-pass protein compared to degradable protein. A cube or pellet that is high in distillers grains would work because distillers are high in by-pass protein. Looks like about 2 lb per head per day of a pellet that is about 75% distillers grains. The nice thing about using grain co-products is that we don't see the negative effects on forage digestion that we see with grains. If you decide to use a supplement that has distillers, you will need to have a mineral that is high in calcium because distillers are high in phosphorus.
If you supplement with hay, the hay will be substituted for the grass and the result will be reduced ADG. I think it will be difficult to get the calves to eat hay once they are on the pasture. I would recommend filling the calves up on grass hay before turning them out especially if calves are going to be weaned, then dry-lotted for a period of time, then turned out. If they are going from the dam directly to pasture and the pastures are similar, then filling them up with hay is probably not needed.
If you decide to supplement the calves, offering the calves the supplement 3 times a week, two weeks before they are weaned and still on the dam, will make the transition smoother.