Increased calf production in cattle selected for twin ovulations

• Published in: Journal of animal science Vol. 85; no. 12; pp. 3239 - 3248
• Main Authors: Echternkamp, S.E, Thallman, R.M, Cushman, R.A, Allan, M.F, Gregory, K.E
• Format: Journal Article
• Language: English
• Published: Savoy, IL American Society of Animal Science 01-12-2007; Am Soc Animal Sci; Oxford University Press
• Subjects: Animal productions; Animals; Animals, Newborn - growth & development; artificial selection; beef cattle; Biological and medical sciences; birth weight; Birth Weight - physiology; Breeding of animals; Cattle; Cattle - physiology; dystocia; Female; fetal death; fetal development; Fetal Development - physiology; fetal growth; Fundamental and applied biological sciences. Psychology; gestation period; Gestational Age; litter size; ovulation; Ovulation - physiology; Parity; parity (reproduction); Pregnancy; pregnancy complications; Pregnancy, Animal - physiology; Pregnancy, Multiple; Prenatal development; Reproduction - physiology; Seasons; Sex Ratio; Survival Analysis; Terrestrial animal productions; Twins; uterine crowding; uterine horns; uterus; Vertebrates; Weaning; weaning weight; Farming animal; Weaning; Calf; Ox; cattle; calf birth and weaning weight; Ovulation; Survival; Sex ratio; twins; Vertebrata; Fetal development; Meat animals; Mammalia; Production; Livestock; Birth weight; Artiodactyla; Ungulata
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas.2007-0210

The effects of increasing fetal numbers and their distribution between the left and right uterine horns on calf survival, calf BW at birth and weaning, gestation length, dystocia, and calf sex ratio were evaluated for single (n = 1,587), twin (n = 2,440), and triplet calves (n = 147) born to primiparous and multiparous females in the Twinner population at the US Meat Animal Research Center between 1994 and 2004. Cattle were distributed equally between the spring and fall breeding seasons. Fetal number and distribution in utero were determined by real-time ultrasonography at 40 to 70 d postbreeding. For cows and heifers combined, number of calves per parturition increased from 1.34 in 1994 to 1.56 in 2004. Gestation length was 6.8 d shorter (P < 0.01) for twins compared with singles (277.5 ± 0.2 vs. 284.3 ± 0.2 d) and 12.7 d shorter for triplets (271.6 ± 0.8 d). Survival and BW of individual calves at birth decreased (P < 0.01) but total calf BW per dam increased (P < 0.01) as fetal number increased from single to triplet births. Twins resulting from bilateral twin ovulations had increased (P < 0.01) survival and BW at birth, a longer (P < 0.01) gestation length, and less (P < 0.01) dystocia than twins resulting from unilateral twin ovulations. Calf survival and BW at birth were 97.2 ± 0.3% and 48.0 ± 0.1 kg for singles, 92.0 ± 0.4% and 39.0 ± 0.2 kg for bilateral twins, 83.2 ± 0.4% and 36.7 ± 0.2 kg for unilateral twins, 73.8 ± 1.4% and 30.6 ± 0.7 kg for bilateral triplets, and 51.9 ± 3.2% and 31.7 ± 1.6 kg for unilateral triplets. Birth weight of single calves increased by 0.51 kg/d for each additional day of gestation length vs. 0.38 kg/d for individual twins. Calf BW at birth increased (P < 0.01) with age of dam from 2 to 4 yr. Twin and triplet births had a greater (P < 0.01) incidence of dystocia than single births. The ratio of male:female calves (0.52:0.48) at birth was not affected by type of birth. Postnatal calf survival was similar for all 3 types of birth. Total progeny BW at weaning for single, twin, and triplet births was 217.7 ± 2.5, 328.3 ± 3.2, and 378.4 ± 15.0 kg, respectively (P < 0.01). Although most bovine females have the uterine capacity to gestate twin calves, decreased survival and BW of unilateral twins and of all triplets indicate that their growth and development may have been compromised by uterine crowding.