PREPARTUM SUPPLEMENTATION WITH PROTEIN OR FAT AND PROTEIN FOR GRAZING COWS IN THREE SEASONS OF CALVING

Authors: Grings, Elaine; SHORT, R - RETIRED ARS; BLUMMEL, M - ARS PAST POST DOC; Macneil, Michael; BELLOWS, R - RETIRED ARS

Submitted to: Research Update for Fort Keogh Livestock and Range Research Laboratory
Publication Type: Popular Publication
Publication Acceptance Date: 10/1/2002
Publication Date: 1/15/2003
Citation: GRINGS, E.E., SHORT, R.E., BLUMMEL, M., MACNEIL, M.D., BELLOWS, R.A. PREPARTUM SUPPLEMENTATION WITH PROTEIN OR FAT AND PROTEIN FOR GRAZING COWS IN THREE SEASONS OF CALVING. RESEARCH UPDATE FOR FORT KEOGH LIVESTOCK AND RANGE RESEARCH LABORATORY. p. 46-47. 2003.

Interpretive Summary: Several reports have suggested that supplemention of beef cows with dietary fat either before or after calving can improve their reproductive performance. While some studies have shown positive responses to fat feeding, others have not. We believe some of the difference between experiments is due to the nutritional quality of diets fed between calving and breeding. Cows grazing rangelands exist under a dynamic environment where rapid changes in forage quality can occur. Time of calving and individual years can have significant impacts on the quality of diets for grazing cows both before and after calving. This varied forage quality may have some effect on the response to fat supplementation. Much of the research testing the effects of fat supplementation on reproduction has been conducted with first-calf heifers. These heifers are under greater nutritional stress than older cows because of the compounding need for nutrients for both growth and milk production. Therefore, young cows may be more sensitive to dietary fat levels than older cows. These results differ from previous studies where pregnancy rate was improved by including safflower seed in the diets of first-calf heifers. Differences in how cows respond to dietary fat may be related to cow age or diet nutrient concentrations both pre- and post-calving. This study showed that varying conditions associated with season of calving affect cow performance and response to supplementation. For most cows in this study, reproduction was not impaired and there may have been no need of additional fat to 'turn-on' reproductive signals.

Technical Abstract: Several reports have suggested that supplemention of beef cows with dietary fat either before or after calving can improve their reproductive performance. While some studies have shown positive responses to fat feeding, others have not. We believe some of the difference between experiments is due to the nutritional quality of diets fed between calving and breeding. Cows grazing rangelands exist under a dynamic environment where rapid changes in forage quality can occur. Time of calving and individual years can have significant impacts on the quality of diets for grazing cows both before and after calving. This varied forage quality may have some effect on the response to fat supplementation. Much of the research testing the effects of fat supplementation on reproduction has been conducted with first-calf heifers. These heifers are under greater nutritional stress than older cows because of the compounding need for nutrients for both growth and milk production. Therefore, young cows may be more sensitive to dietary fat levels than older cows. These results differ from previous studies where pregnancy rate was improved by including safflower seed in the diets of first-calf heifers. Differences in how cows respond to dietary fat may be related to cow age or diet nutrient concentrations both pre- and post-calving. This study showed that varying conditions associated with season of calving affect cow performance and response to supplementation. For most cows in this study, reproduction was not impaired and there may have been no need of additional fat to 'turn-on' reproductive signals.