Linda Benedict, Franke, Donald E., Williams, Dian A. | 3/31/2005 1:19:26 AM
Dian A. Williams and Donald E. Franke
Commercial cow-calf production is the primary beef cattle enterprise in Louisiana. The state has about 550,000 beef cows in 15,000 herds located in all parishes but Orleans. The primary product marketed from these herds is the weaned calf. At least 80 percent of the cow-calf herds in Louisiana use crossbred cows of one kind or another, and most of these crossbred cows have some Brahman inheritance.
Many producers prefer Brahman first-cross (F1) cows to produce calves for market because of their relatively high fertility, maternal ability and longevity in Louisiana’s subtropical environment. This advantage is mostly due to hybrid vigor, or heterosis. A disadvantage of using Brahman F1 cows is that they do not reproduce themselves, and replacements for culled cows must be purchased or produced in auxiliary herds. One alternative is to use a rotational crossbreeding system. The advantage is that replacement females are produced within the system, and a reasonable amount of heterosis is maintained.
Producers have asked whether they should embark on a rotational crossbreeding system and whether this system would compete with the production of calves from Brahman F1 cows. To answer these questions, a study was conducted to compare production of weaned calves from Brahman F1 cows and from rotational crossbred cows that included Brahman breeding.
Two-, three- and four-breed rotational crossbreeding systems involving Angus, Brahman, Charolais and Hereford breeds were being studied at the LSU AgCenter’s Ben Hur Farm in Baton Rouge. They were compared to straightbred Angus, Brahman, Charolais and Hereford cows producing straightbred calves, but not to Brahman F1 cows. In the fourth generation of the rotational crossbreeding study, the Angus, Brahman, Charolais and Hereford cows were mated to produce Brahman F1 calves. Brahman F1 heifers from these matings were retained for comparison to rotational crossbred heifers produced at the same time for generation 5.
Sires from unrelated breeds, Simmental and Gelbvieh, were mated to the Brahman F1 females and to half the rotational crossbred cows in generation 5. The remaining half of the rotational crossbred cows were mated to Angus, Brahman, Charolais or Hereford bulls, as determined by their breed composition, to continue the rotational crossbreeding systems. Straightbred Angus, Brahman, Charolais and Hereford cows were mated to produce Brahman F1 calves for comparison to the calves from the Brahman F1 cows and to the calves produced from rotational crossbreeding.
Breed composition of rotational crossbred cows varied at the start of generation 5. Two-breed rotation cows were 2/3 Brahman and either 1/3 Angus, 1/3 Charolais or 1/3 Hereford. Three-breed rotation cows were: 4/7 Charolais, 2/7 Brahman, 1/7 Angus; 4/7 Angus, 2/7 Brahman, 1/7 Hereford; or 4/7 Charolais, 2/7 Brahman,1/7 Hereford. Thus, two-breed rotation cows were 66 percent Brahman, whereas three-breed rotation cows were 28.6 percent Brahman. F1 cows were 50 percent Brahman.
A total of 1,180 calves were weaned in generation 5. Overall average birth weight was 83 pounds, and weaning weight adjusted to 205 days was 558 pounds (Figure 1). Terminal (T) is used to describe the mating of Simmental and Gelbvieh sires to Brahman F1 cows (T x F1), two-breed rotation cows (T2BR) and to three-breed rotation cows (T3BR).
Brahman F1 calves, Gelbvieh- and Simmental-sired calves from Brahman F1 cows, and Gelbvieh- and Simmental-sired calves from three-breed rotation cows were heavier at birth than calves from other mating systems. In these mating systems individual calves that weighed more than 100 pounds at birth often required assistance at birth, resulting in increased labor requirements and often a loss of the calf.
The differences shown in the bar chart (Figure 1) suggest that cows with 50 percent or more Brahman breeding apparently have more maternal ability than cows with predominant Angus, Charolais or Hereford breeding. Two-breed rotation calves were slightly heavier than three-breed rotation calves.
In rotation systems, heifers sired by each breed are retained as replacements. Study results suggest that rotational heifers sired by Brahman bulls are comparable to Brahman F1 cows when mated to the same breed of sire more so than rotational heifers sired by Angus, Charolais or Hereford bulls. The advantage of replacement heifers being produced within the rotation system may be offset by the maternal ability of Brahman F1 cows. Another advantage of the terminal sire x Brahman F1 cows appears to be more uniformity among calves produced for market. If one breed of sire is used on the Brahman F1 cows, all the calves have the same breed composition. In complete rotation systems where all sire breeds are represented, greater variation among calves can be expected.
Dian A. Williams, former Graduate Student, and Donald E. Franke, Professor, Department of Animal Science, LSU AgCenter, Baton Rouge, La.
(This article was published in the winter 2001 issue of the Louisiana Agriculture Magazine)