ARS | Publication request: REPRODUCTION AND MATERNAL PERFORMANCE OF TWO-YEAR-OLD TOPCROSS FEMALES BY TROPICALLY ADAPTED SIRE BREEDS IN TEMPERATE AND SUBTROPICAL REGIONS OF THE UNITED STATES

Submitted to: World Congress of Genetics Applied in Livestock Production
Publication Type: Proceedings
Publication Acceptance Date: March 1, 2006
Publication Date: August 1, 2006
Citation: Franke, D.E. and Cundiff, L.V. 2006. Reproduction and maternal performance of two-year-old topcross females by tropically adapted sire breeds in temperate and subtropical regions of the United States. Proceedings 8th World Congress of Genetics Applied in Livestock Production. CD-ROM Communication No. 32-6. Belo Horizonte, Brazil.

Interpretive Summary: 0utput per cow has been significantly greater for Bos indicus x Bos taurus than for Bos taurus x Bos taurus cows, especially in subtropical. However, concerns about meat quality, delayed puberty, and reduced reproduction rates have prompted introduction and evaluation of tropically adapted germplasm into the U.S. Semen from 20 Bonsmara (from S. Africa), 20 Romosinuano (from S. America), 22 Beefmaster, and 22 Brangus sires was used in matings (AI) to Angus and Composite MARC III (1/4 Angus, 1/4 Hereford, 1/4 Red Poll, and 1/4 Pinzgauer) females to produce F1 progeny in the spring of 2001 and 2002 at the U.S. Meat Animal Research Center (MARC), Clay Center, Nebraska (NE). At about 8 months of age, the females were divided into two groups representing each breed group about equally. Half (202) were transferred by truck to Louisiana State University (LSU) and half remained at MARC. Management of F1 females and their progeny was consistent with that generally practiced under commercial production systems in the respective locations (Louisiana, LA and Nebraska, NE). Sire breed of female x location was significant for calving ease score, percentage unassisted births and 205-day weaning weight. Heifer sire breed differences were significant for calf birth and 205-day weight. Location differences were significant for all traits. The difference in calving difficulty means between locations was greater for Bonsmara sired females than for Brangus and Beefmaster sired females. Calving difficulty expressed by Romosinuana sired females was similar at both locations. The percentage of unassisted births was greater in LA than NE for Brangus, Beefmaster, and Bonsmara sired females, however Romosinuana sired females had similar percentages of unassisted births in both locations. For 205-d weight, the difference between locations was similar for Brangus and Beefmaster sired females and of nearly twice the magnitude of that for Bonsmara and Romosinuana sired females. Heifers retained in NE had a 9.8% higher weaning rate than heifers transferred to LA. Birth weights of calves for Brangus, Beefmaster, and Bonsmara sired females were similar and greater than those for Romosinuana sired females. Birth weights for calves born in NE were 1.8 kg heavier than for calves born in LA.

Technical Abstract: Semen from 20 Bonsmara (from S. Africa), 20 Romosinuano (from S. America), 22 Beefmaster, and 22 Brangus sires was used in matings (AI) to Angus and Composite MARC III females to produce F1 progeny at the U.S. Meat Animal Research Center in Nebraska (NE). At about 8 months of age, half of the females in each breed group were transferred by truck to Louisiana (LA). Management was consistent with that generally practiced in the respective regions. Sire breed of female x location interaction was significant for calving ease score, percentage unassisted births and 205-day weaning weight. Heifer sire breed differences were significant for calf birth and 205-day weight. Location differences were significant for all traits. Percentage unassisted births were greater in LA than NE for Brangus, Beefmaster, and Bonsmara sired females, but similar at both locations for Romosinuana sired females. The 205-d weights were greater in NE than LA, but the difference between locations in Brangus and Beefmaster was nearly twice the magnitude of that in Bonsmara and Romosinuana. Birth weights for calves born in NE were 1.8 kg heavier than for calves born in LA.