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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #122246
Title: PREPARTUM SUPPLEMENTATION WITH PROTEIN OR FAT AND PROTEIN FOR GRAZING COWS IN THREE SEASONS OF CALVING

Author
item Grings, Elaine
item Short, Robert
item BLUMMEL, M - ICRISAT
item Macneil, Michael
item BELLOWS, R - RETIRED ARS

Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2001
Publication Date: 6/1/2001
Citation: GRINGS, E.E., SHORT, R., BLUMMEL, M., MACNEIL, M.D., BELLOWS, R.A. PREPARTUM SUPPLEMENTATION WITH PROTEIN OR FAT AND PROTEIN FOR GRAZING COWS IN THREE SEASONS OF CALVING. WESTERN SECTION OF ANIMAL SCIENCE PROCEEDINGS. 2001. v. 52. p. 501-504.

Interpretive Summary: It has been suggested that the feeding fat to cows in late pregnancy or early lactation can improve reproductive performance, but there has been variation in response depending on the nutritive quality of diets fed between calving and breeding. Cattle grazing Northern Great Plains rangelands exist under a dynamic environment where rapid changes in forage quality can occur. Therefore, time of calving has an impact on the quality of postcalving diets for grazing cows. Young cows tend to be under greater nutritional stress than older cows because of the need for nutrients for both growth and milk production and may be more sensitive to fat supplementation than older cows. The objectives of this study were to evaluate fat supplementation in late pregnancy for cows calving in different seasons. Additionally, we wished to determine whether these responses differed in cows of different ages. A 2-yr study was conducted using both 3-yr-old and 5-yr-old and older cows from each of 3 seasons of calving. Cows grazed native rangeland and were supplemented with either a combination of safflower seed and meal (high fat) or safflower meal and barley (low fat). In most subgroups of cattle, reproduction was not impaired. However, reproduction was low in 3-yr-old cows calving in April and feeding a high fat supplement during the late pregnancy did not improve this. These cows were under some degree of nutritional stress as evidenced by low condition scores at calving. These results differ from previous studies at this location where pregnancy rates were improved in 2-yr-old heifers fed corn silage and hay based diets with or without added fat. Differences in response may be related to cow age or diet nutrient concentrations both pre- and postcalving.

Technical Abstract: A 2-yr study was conducted to evaluate prepartum supplementation of cows (n = 177) grazing rangeland with a combination of safflower seed and meal (high fat, HF: 21.7% CP, 14.8% ether extract, EE) compared to safflower meal and barley (low fat, LF: 22.5% CP, 2.6% EE) on cow performance. Interactions with calving date and cow age (CA) were also evaluated. Each year, 30 cows (15 three-yr-olds and 15 five-yr-olds or older) from each of three seasons of calving (SC; February, April, or June) were assigned to supplementation type (ST). Cows were assigned to one of two pastures per SC and supplements were group fed for 49 d. Cows were then moved to drylot and fed sudangrass hay plus supplements until calving (average = 22 d). While effects of SC and CA were pronounced for performance measures, effects of ST were limited and were only found in interactions. Changes in BW during the prepartum grazing period were affected by SC (P < 0.01), a year by CA interaction (P < 0.05), and an interaction among SC, ST, year, and CA (P < 0.05). In the April calving group, proportion of 3-yr-olds exhibiting estrous cycles at the beginning of breeding was 0.46 compared with 0.92 in the older cows, but there was no effect of CA in the February or June groups (SC by CA interaction, P < 0.05). Pregnancy rates exhibited a SC by ST by CA interaction (P < 0.05). Three-year-old cows calving in February and 5- yr-old cows calving in April receiving HF had greater pregnancy rates than cows fed LF; the opposite effect was found for 3-yr-olds calving in April. There was no effect of ST on pregnancy rates of cows calving in June. Varying conditions associated with SC affected cow performance and response to supplementation.