Research has indicated it takes the net revenue from approximately 6 calves to cover the development and production costs of each replacement heifer. In addition, any cow that misses a single calving is not likely to recover the lost revenue of that missed calf. Therefore, longevity of a beef female is very important to the sustainability and profitability of any beef operation. Considering the importance of longevity, an important question is as follows: Why are females culled from a beef herd? According to the 2008 NAHMS survey the greatest percentage of cows culled from the herd were for pregnancy status (33.0%); other reasons for culling included age or bad teeth (32.1%), economic reasons (14.6%), other reproductive problems (3.9%), producing poor calves (3.6%), temperament (3.6%), injury (2.9%), udder problems (2.7%), bad eyes (1.8%), and other problems (1.8%). Furthermore, 15.6% of animals culled were less than 5 years of age and 31.8% were 5 to 9 years of age. These females that are culled from a herd prior to producing 6 calves increase the developmental cost of other heifers and do not contribute to the profitability and sustainability of the farm.
To achieve maximum life-time productivity heifers need to calve by 24 months of age, and heifers that lose a pregnancy or conceive late in the breeding season are likely to not have enough time to rebreed during a defined breeding season. In addition, heifers that calve early with their first calf have a longer post-partum interval and are more likely to breed back as two year olds and continue to calve early in the calving season. This is important to overall profitability since age of calf at weaning is the single largest factor that affects weaning weight.
In a recent collaborative study between SDSU and the USDA- Meat Animal Research Center (MARC), longevity data were collected on 2,195 heifers from producers in South Dakota, and longevity and weaning weight data were collected on 16,549 heifers at the USDA-MARC. Data was limited to heifers that conceived during their 1st breeding season. 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 1st or later period was 5.1 ± 0.1 and 3.9 ± 0.1 yr, respectively. Average longevity for USDA-MARC heifers that calved in the 1st, 2nd, and later period was 8.2 ± 0.3, 7.6 ± 0.5, and 7.2 ± 0.1 yr, respectively. Calving period also influenced weaning weight of the 1st, 2nd, 3rd, 4th, and 5th calf born from these heifers. In addition, calving period influenced total pounds weaned and average weaning weight, with heifers that calved during the 1st period having increased weaning weights, total pounds weaned, and average weaning weight compared to heifers calving in the 2nd period or later, and heifers calving during the 2nd period had increased weaning weight, total pounds weaned, and average weaning weight compared to heifers calving later.
Therefore, 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. So when we think about increasing longevity in our beef cattle, we need to begin with management decisions that impact our replacement heifers. If we get them developed correctly they will continue to be productive for several years.
Source: Dr. George Perry