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United States Department of Agriculture

Agricultural Research Service

Research Project: STRATEGIES TO IMPROVE HEIFER SELECTION AND HEIFER DEVELOPMENT

Location: Nutrition and Environmental Management Research

Title: Heifer calving date positively influences calf weaning weights through six parturitions

Authors
item Cushman, Robert
item Kill, Lauren -
item Funston, Richard -
item Mousel, Eric -
item Perry, George -

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 29, 2013
Publication Date: September 1, 2013
Citation: Cushman, R.A., Kill, L.K., Funston, R.N., Mousel, E.M., Perry, G.A. 2013. Heifer calving date positively influences calf weaning weights through six parturitions. Journal of Animal Science 91(9):4486-4491.

Interpretive Summary: According to the 2007-08 NAHMS survey, the greatest percentage of cows culled from the herd were for pregnancy status (33.0%). Furthermore, 15.6% of animals culled were less than 5 years of age. Females that are culled from a herd prior to producing 3 to 5 calves decrease the profitability and sustainability of the operation. Calves born earlier in the calving season will also be older and heavier at weaning. Longevity data were collected on 2,195 heifers from producers in South Dakota Integrated Resource Management groups. Longevity and weaning weight data were collected on 16,549 individual heifers at the U.S. Meat Animal Research Center. Data were limited to heifers that conceived during their first breeding season. Heifers were grouped into 21-day calving groups. Heifers were determined to have left the herd when they were diagnosed not pregnant at the end of the breeding season. Heifers that left the herd for reasons other than reproductive failure were censored from the data. Heifers that calved with their first calf during the first 21-day period of the calving season had increased longevity compared to heifers that calved in the second 21-day period, or later. Average longevity for South Dakota heifers that calved in the first or later period was 5.1 and 3.9 years, respectively. Average longevity for USMARC heifers that calved in the first, second, or third period was 8.2, 7.6, and 7.2 years, respectively. Calving period as a heifer influenced unadjusted weaning weight of the first six calves. Estimated post-partum interval to conception as a 2-year-old was greater for females that calved in the first period as heifers but did not differ between heifer calving periods in subsequent seasons. In summary, heifers that calved early in the calving season with their first calf had increased longevity and pounds weaned compared to heifers that calved later in the calving season. By breeding more replacement heifers than are required, cow-calf producers can choose those that conceived earliest at pregnancy diagnosis and increase the proportion of heifers that wean enough calves to pay for their development costs. In addition, the increased weaning weights during the first six seasons will increase the profit margin for the operation.

Technical Abstract: Longevity and lifetime productivity are important factors influencing profitability for the cow-calf producer. Heifers that conceive earlier in the breeding season will calve earlier in the calving season and have a longer interval to rebreeding. Calves born earlier in the calving season will also be older and heavier at weaning. Longevity data were collected on 2,195 heifers from producers in South Dakota Integrated Resource Management groups. Longevity and weaning weight data were collected on 16,549 individual heifers at the U.S. Meat Animal Research Center (USMARC). Data were limited to heifers that conceived during their first breeding season. Heifers were grouped into 21-d calving periods. Heifers were determined to have left the herd when they were diagnosed not pregnant at the end of the breeding season. Heifers that left the herd for reasons other than reproductive failure were censored from the data. Heifers that calved with their first calf during the first 21-d period of the calving season had increased (P < 0.01) longevity compared to heifers that calved in the second 21-d period, or later. Average longevity for South Dakota heifers that calved in the first or later period was 5.1 ± 0.1 and 3.9 ± 0.1 yr, respectively. Average longevity for USMARC heifers that calved in the first, second, or third period was 8.2 ± 0.3, 7.6 ± 0.5, and 7.2 ± 0.1 yr, respectively. Calving period as a heifer influenced (P < 0.01) unadjusted weaning BW of the first six calves. Estimated post-partum interval to conception as a 2-year-old was greater for females that calved in the first period as heifers but did not differ between heifer calving periods in subsequent calving seasons. In summary, heifers that calved early in the calving season with their first calf had increased longevity and pounds weaned compared to heifers that calved later in the calving season.

Last Modified: 7/24/2014
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