Cows have the capacity to gestate twin calves, but not without decreased survival and body weight due to uterine crowding, researchers at USDA's Meat Animal Research Center (MARC) conclude.

The effects of increasing fetal numbers (twins and triplets) and their distribution between the left and right uterine horns were evaluated for calf survival, calf body weight at birth and weaning, gestation length, dystocia and calf sex ratio. Unilateral gestation refers to development in the same uterine horn; bilateral refers to separate uterine horns.

From 1994 to 2004, 1,587 single-born calves, 2,440 twins and 147 triplets born to first-calf heifers and cows in the Twinner population at MARC were studied. Cattle were equally distributed between the spring and fall breeding seasons.

Fetal number and distribution in utero were determined by real-time ultrasonography at 40-70 days post breeding. Results found:

  • From 1994 to 2004, the number of calves per calving increased from 1.34 to 1.56.

  • Gestation length was 6.8 days shorter for twins compared with singles (277.5 ± 0.2 vs. 284.3 ± 0.2 days), and 12.7 days shorter for triplets (271.6 ± 0.8 days).

  • As fetal numbers increased, survival and birth weight of individual calves decreased, but total calf body weight produced per cow increased.

  • Twins resulting from bilateral twin ovulations had increased survival and body weight at birth, longer gestation length and less dystocia than twins resulting from unilateral twin ovulations.

  • Calf survivability and body weight: Singles: 97.2% ± 0.3% and 105.2 ± 0.2 lbs. Bilateral twins: 92.0 ± 0.4% and 85.9 ± 0.4 lbs. Unilateral twins: 83.2 ± 0.4% and 80.9 ± 0.4 lbs. Bilateral triplets: 73.8 ± 1.4% and 67.5 ± 1.5 lbs. Unilateral triplets: 51.9 ± 3.2% and 69.9 ± 3.5 lbs.

  • Birth weight of single calves increased by 1.12 lbs./day for each additional day of gestation vs. 0.84 lbs./day for individual twins.

  • Calf body weight increased with the age of dam from 2 to 4 years old.

  • Twins and triplets had a greater incidence of dystocia than single births.

  • Ratio of male:female calves (0.52:0.48) was not affected by type of birth. Postnatal calf survival was similar for all three types of birth.

  • Total progeny bodyweight at weaning by type of birth was: single (479.9 ± 5.5 lbs.), twin (723.7 ± 7.1 lbs.) and triplet (834.2 ± 33.1 lbs.).

Researchers conclude that the production of twin births has the propensity to increase reproductive efficiency in beef cattle by 20-30%. However, a portion of the potential gain from twinning is compromised by reduced calf survival at birth, lighter bodyweight of twin progeny at birth and weaning, and an increased incidence of dystocia associated with abnormal presentation of twin fetuses within the birth canal. Continued selection for the increased frequency of twin ovulations and births has increased the frequency of triplet ovulations and births, but triplet births provide little additional production benefits compared with twin births.
S.E. Echternkamp, et al, 2007.
Journal of Animal Science, 85:3239.

The bacterial species that commonly causes leptospirosis in cattle has lost much of its ability to survive in water. This change, say Agricultural Research Service (ARS) scientists in Iowa and Australia, affects the ability of Leptospira borgpetersenii serovar Hardjo to spread through the environment.

Leptospirosis is among the most widespread of zoonotic diseases, which are infections transmitted naturally from domestic or wild animals to people. Broadly distributed in wildlife and persistent in livestock, each serovar appears to be adapted to a particular species in which it causes problems with pregnancy and fertility, but usually doesn't cause severe disease.

L. borgpetersenii is one of two leptospiral species associated with most cases of bovine leptospirosis worldwide, and is responsible for most cases in North American cattle. The other species is L. interrogans. Research results indicate L. borgpetersenii is now spread mainly through close contact with infected animals, while L. interrogans is still able to spread easily through contaminated water.

The findings are a result of genomic sequencing studies of L. borgpetersenii conducted at the National Animal Disease Center in Ames, IA and Monash University in Melbourne, Australia. In the report, researchers explain that the L. borgpetersenii genome is decaying. Its defective genes impair the bacterium's ability to sense changes in the environment and survive outside of a mammalian host. L. borgpetersenii is evolving toward dependence on a strict host-to-host transmission cycle.
Agricultural Research, August 2007

Dried distiller's grains (DDGs) improved artificial insemination (AI) conception and pregnancy rates compared to a control supplement, University of Nebraska researchers discover.

A two-year study conducted at two locations with 316 crossbred heifers was conducted to determine if supplementing beef heifers with excess undegradable intake protein (UIP) during development affected growth or reproduction. Heifers were blocked by age, or sire and age, and randomly assigned to the following treatments:

  • Control — Supplement (dried corn gluten feed, whole corn germ, urea) fed at 0.78% of body weight (dry matter basis).

  • DDGs — Fed at 0.59% of bodyweight (dry matter basis).

Heifers received prairie hay in amounts sufficient for ad libitum intake and supplements were formulated to be equivalent in energy and crude protein content, but differ in protein degradability.

Control UIP averaged 90 grams daily (0.20 lbs.). DDG UIP averaged 267 grams daily (0.59 lbs.).

Heifers were synchronized with two injections of prostaglandin, 14 days apart. Estrus was detected and heifers were artificially inseminated for five days and placed with bulls 10 days later. The following are results of the treatments:

  • Initial age, body weight and body condition score (BCS) did not differ between treatments.

  • Final body weight, average daily gain and BCS were also not affected by supplementation.

  • Proportions of pubertal heifers did not differ at the beginning of the 14-day sampling intervals, or before synchronization.

  • Estrus synchronization rate, time of estrus and overall pregnancy rate were not affected by treatment.

  • A greater proportion of DDG heifers (75%) conceived to AI than control heifers (52.9%), resulting in greater pregnancy rates for DDG heifers (57% vs. 40.1%).

  • Body weight or BCS at pregnancy diagnosis did not differ.

The authors concluded that supplementing beef heifers with DDGs during development did not affect age at puberty, but improved AI conception and pregnancy rate compared to an isocaloric control supplement.
Martin, et al, 2007. Journal of Animal Science, 85:2298