Keep Heifer Development Cost Affordable
The more economical the replacement heifer program the greater the profit potential of the cow/calf enterprise as long as reproductive performance of the heifers is not compromised. Distillers grains have been affordable this year and at times was priced at 60% the price of corn. There has not been a lot of data generated investigating the use of corn stalk residue and dormant winter range and the impact of using these feed resources as part of a heifer development program. Using by-products in the heifer development program and management strategies using crop residue and dormant winter range has the potential to impact costs.
Distillers grains are a good source of energy, protein, and phosphorus. In addition, research trials already conducted indicate that distillers grains are higher in energy than corn. Research also indicates there are no negative interactions on forage digestion when distillers grain are included in high forage diets.
We designed an experiment to examine the use of dry distillers grains (DDG) in a heifer development program on reproductive performance. All heifers were treated alike except the diet for the treatment heifers included DDG. Minerals and vitamins were balanced in each diet. The remainder of the diets were grass hay that ranged between 8.4% and 11.0% crude protein and about 54% TDN.
Heifers used in this experiment were born in the spring and weaned in the fall of the year. Heifers were weighted throughout the trial and diets adjusted so as to achieve similar average daily gains.
Heifers were synchronized for estrus using two shots of prostaglandin given 14 days apart. For five days after the last shot of prostaglandin, the number of heifers responding to synchronization and the time (hours after the 2nd PGF shot) heat occurred were recorded and heifers that exhibited heat during the 5-day time frame were AI'ed using the same bull. We waited 10 days then turned in a clean-up bulls for a breeding season of 45 days total. The percent pubertal prior to PGF and age at puberty were not different between groups.
The AI conception rate, those heifers detected in heat after the second PGF injection and AI'ed, was significantly greater in the DDG fed heifers. This corresponded to a greater AI pregnancy rate in the DDG fed group. The DDG were supplemented at 0.57% of the heifer body weight on a dry matter basis. As an example, if the average weight of the heifers was 600 lb, they were fed 3.4 lb/head/day (3.8 lb/hd/da if the distillers were 90% dry matter) of DDG on a dry matter basis. If heifers are consuming 2.5% of their body weight on a dry matter basis daily, there total dry matter intake would be about 15 lb/head/day. Of the 15 lb/hd/day intake, 3.4 lb/hd/da would be DDG. DDG at this level calculates to 23% ([3.4 lb/hd/da DDG/15 lb/hd/da intake] x 100 = 22.7%) of the diet on a dry matter basis.
As with any diet that is developed using DDG, because DDG are high in phosphorus, it is important to make sure the calcium to phosphorus ratio is within the range for growing cattle. In addition, make sure there is plenty of bunk space or eating space so that each heifer gets their fair share. Make sure that the ration is mixed uniformly to avoid any complication with sulfur in the DDG. Finally, total fat in the diet should not exceed 5% to 5.5% to eliminate the negative impact of fat on forage digestion in the rumen. The full report on this research can be found in the 2007 Nebraska Beef Cattle Production "Utilization of Dried Distillers Grains for Developing Beef Heifers" article.
Not developing heifers in a dry lot has always been appealing to producers because they don't have to fight the mud in the winter. In addition, input cost have steadily increased over the last few years, especially harvested feed costs. In most areas of the country, there is an abundance of crop residue and in some areas, dormant native range available for winter grazing. Producers do a good job of using these feedstuffs in cow management feeding strategies. To get heifers developed to an acceptable target weight prior to first breeding, they have to achieve a minimal daily gain. Crop residue or winter range by itself will not provide the needed gain. A supplementation strategy for replacement heifers using these feed resources will need to be implemented.
Research conducted at the University of Nebraska compared performance of heifers developed in a dry lot (DL) compared to ones that grazed corn stalk residue (CR) for 145 days and supplemented 1 lb/hd/da of a 28% protein cube on a dry matter basis as part of their development program. Although there was a statistical difference in AI conception rate (64% DL, 54% CR), there was no difference in yearling pregnancy rate or pregnancy rate for their second breeding season. In a second experiment, heifer were developed using winter range and/or corn stalk residue and supplemented 1 lb/hd/da of a 28% protein cube on a dry matter basis as part of their development program. There was no difference in yearling pregnancy rate between the two groups and pregnancy rates as 2-yr-olds were not statistically different either. In the third experiment, the protocol was much like experiment 2, but the supplementation rate was between 1 to 2 lb/hd/day of the protein supplement (29% crude protein) dry matter basis. There was no difference in AI conception rate, yearling pregnancy rate, or pregnancy rate as 2-yr-olds. In all experiments (1, 2 and 3), there was no difference in calf birth weight or weaning weights. Although, experiments 2 and 3 should not be compared, an observation would be that when supplementation rate was increased (experiment 3) heifer gain increased, yearling pregnancy rates were not much different, but pregnancy rate for the 2-yr-olds were numerically greater in experiment 3 compared to experiment 2 especially for heifers that grazed corn stalk residue. Which might lead one to think that a supplementation rate closer to 2 lb/hd/da should be considered. At 1 lb/hd/da, the diet is deficient in protein (mainly degraded intake protein) for heifers consuming corn stalk residue or dormant winter range. Cost difference favored developing on residue compared to the dry lot.
It would be nice to think that all harvested forages could be eliminated, this is likely not possible because of snow and ice in some states, so you will need to have some harvested forages on reserve.
Dr. Rick Rasby, Professor of Animal Science
Animal Science, University of Nebraska - Lincoln, Lincoln, NE