Using Distillers Grains In Heifer Development Diets
We used 316 crossbred heifers divided evenly into 2 groups, a treatment and control group. All heifers were treated alike except the diet for the treatment heifers included DDG. Because DDG have a high amount of UIP, treatment heifers had a much higher daily consumption of UIP compared to the control heifers. 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. In addition, blood samples were collected throughout the experiment so that we could determine when puberty occurred. Heifers were synchronized for estrus using two shots of prostaglandin (PGF, trade name Prostamate) 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. Forty-five days after the AI period, heifers were ultrasounded for pregnancy to determine if pregnancy occurred during the AI period.
The percent pubertal prior to PGF and age at puberty were not different between groups. Weight at puberty was different in favor of the DDG fed heifers. The weight difference was due to a 0.24 lb ADG difference in the second year. Time to estrus after the second PGF injection was 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. Overall pregnancy rate, using a total of 45 day breeding season, was not different between groups. These data clearly demonstrate that diets using DDG that may result in high by-pass protein (average UIP intake 253 grams/day, maximum UIP intake 351 grams/day in our experiment) does not have a negative effect on reproductive performance in replacement heifer development programs.
The DDG were supplemented at 0.57% of the heifer body weight on a dry matter basis. Heifer weights and average body weight was determined throughout the experiment. If the average weight of the heifers was 700 lb, they were fed 4 lb/head/day (4.5 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 17.5 lb/head/day. Of the 17.5 lb/hd/day intake, 4 lb/hd/da would be DDG. DDG at this level calculates to 23% ([4 lb/hd/da DDG/17.5 lb/hd/da intake] x 100 = 22.9%) of the diet on a dry matter basis. This amount of DDG is well within my recommendation for the inclusion of DDG in the diet, which is not feeding over 1/3 of the diet on a dry matter basis as DDG.
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 animal 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 eliminate the negative impact of fat on forage digestion in the rumen
Dr. Rick Rasby, Professor of Animal Science
Animal Science, University of Nebraska - Lincoln, Lincoln, NE