The effects of induced abortion on the feedlot performance of beef heifers fed urea and cottonseed meal, with and without hay

There were three objectives in this study. The first objective was to determine the effects of abortion on the performance of medium grade, yearling heifers showing some evidence of beef breeding. Secondly, the effects of adding good quality alfalfa hay to feeder cattle rations were to be identified. A third objective of this study was to determine the relative effects of using a high level urea supplement in comparison to cottonseed meal (GSM). One hundred and seventy two medium grade, possibly pregnant, yearling heifers showing evidence of beef breeding were involved in a three-year study at the Greeneville Tobacco Experiment Station. The heifers were pregnancy checked before being placed on feed, and those determined to be pregnant were intramuscularly injected with ICQ milligrams of diethylstilbestrol (DES) in an attempt to cause abortion. In 1967, half of the heifers determined to be non pregnant were given 100 mg of DES in order to identify the effects of this one time, intramuscular injection. The heifers were lotted into light and heavy weight groups. Each treatment contained two lots of from six to eight heifers per lot each of the three years. One lot contained heavy heifers; the other lot contained light heifers. Pregnant heifers were uniformly distributed throughout all subclasses. There were two general phases of feeding each year. During the first phase, the heifers were given corn silage ad libitum with five pounds of ground ear com and one pound of protein supplement for an average of 113 days. Following the high silage phase was the concentrate phase, during which each heifer consumed a maximum amount of ground ear corn and either one pound of urea supplement or 1.26 pounds of CSM. The concentrate period lasted an average of 58 days. There was a highly significant (P ± .01) difference in the total average daily gain of the open heifers (1.65 pounds per day) as compared to those determined to be pregnant (1.54 pounds per day), for the three years studied. Heifers fed hay gained at a significantly faster rate (P plusmn; .05) than heifers not fed hay; 1.64 versus 1.55 pounds per day, respectively. Results of the cottonseed meal (CSM) treatments versus urea treatments showed that rate of gain for heifers fed urea were very highly significantly lower than for the CSM fed groups during the silage feeding phase. However, gains made during the concentrate feeding phase were such that the total average daily gains were different only at the 10 percent level of probability in favor of CSM. Total average daily gains for light heifers (1.65 pounds per day) were highly significantly (P plusmn; .01) different from total average daily gains for heavy heifers (1.54 pounds per day).