The frequency of twinning has increased from 1.4% in 1983 to 2.4% in 19931 and from 3.4% in 1996 to 4.8% in 2004.2 Increased milk production has been reported as an important risk factor for the increased twinning rate.1,3 Lopez et al3 reported that the occurrence of multiple ovulations increased steadily from 0.0% (0/30) to 51.6% (31/60) for cows producing from < 30 to ≥ 50 kg (66 to 110 lb) of milk/d during the 14 days preceding estrus. It is well-known that milk production per cow is steadily increasing in the United States; thus, it is also expected that the occurrence of twin parturitions will continue to rise as milk production increases.4
Twinning is an undesirable condition in dairy cattle because of the detrimental effect on the dams' survival, milk production, and reproduction.5 Furthermore, there is no increase in the number of replacement heifers despite the increase in the total number of calves born because of increased stillbirth for twins, compared with singleton parturition.1,5 Gregory et al6 evaluated natural twinning in beef cattle and reported that birthing twins was associated with higher frequency of retained placenta, dystocia, and stillbirth and increased days from calving to conception. An economic analysis of naturally occurring twinning in dairy cattle estimated that a twin birth costs $108.00 US dollars more to the farmer than a single birth.7
The occurrence of stillbirth parturitions among cows that have singleton parturition is associated with decreased survival and increased calving-to-conception interval, independent of assistance at calving.8 Nielen et al5 reported that stillbirth incidence was 16% higher for twins than for singleton parturitions. Therefore, the negative affect of twin births on the dams' performance may be exacerbated by increased stillbirths.
The purpose of the study reported here was to evaluate the hypothesis that twin parturitions will decrease dams' survival and milk production and increase calving-to-conception interval and that at least 1 stillbirth twin calf will affect the dams' hazard of culling or death, milk production, and calving-to-conception interval.
Calving ease score
Mature equivalent milk for a 305-day lactation
Least square means
Dairy Comp 305, Valley Agricultural Software, Tulare, Calif.
JMP, SAS Institute Inc, Cary, NC.
MIXED, SAS Institute Inc, Cary, NC.
TPHREG, SAS Institute Inc, Cary, NC.
CONTRAST statement of TPHREG, SAS Institute Inc, Cary, NC.
MedCalc for Windows, version 220.127.116.11, MedCalc software, Mariakerke, Belgium.
Silva del Rio N, Stewart S & Rapnicki P, et al. An observational analysis of twin births, calf sex ratio, and calf mortality in Holstein dairy cattle. J Dairy Sci 2007;90:1255–1264.
Lopez H, Caraviello DZ & Setter LD, et al. Relationship between level of milk production and multiple ovulations in lactating dairy cows. J Dairy Sci 2005;88:2783–2793.
Nielen M, Schukken YH & Scholl DT, et al. Twinning in dairy cattle: a study of risk factors and effects. Theriogenology 1998;32:845–862.
Echternkamp SE, Gregory KE & Dickerson GE, et al. Twinning in cattle: III. Effect of twinning on dystocia, reproductive traits, calf survival, calf growth and cow productivity. J Anim Sci 1990;68:3133–3144.
Beerepoot GM, Dykhuizen AA & Nielen M, et al. The economics of naturally occurring twinning in dairy cattle. J Dairy Sci 1992;75:1044–1057.
Bicalho RC, Galvão KN & Cheong SH, et al. Effect of stillbirth on dam's survival and reproduction performance in Holstein dairy cows. J Dairy Sci 2007;90:2797–2803.
Ettema JF, Santos JEP. Impact of age at calving on lactation, reproduction, health, and income in first-parity Holstein on commercial farms. J Dairy Sci 2004;87:2730–2742.
Bendixen PH, Oltenacu PA, Andersson L. Case-referent study of cystic ovaries as a risk indicator for twin calvings in dairy cows. Theriogenology 1989;31:1059–1066.
Mangurkar BR, Hayes JF, Moxley JE. Effects of calving ease-calf survival on production and reproduction in Holsteins. J Dairy Sci 1984;67:1496–1509.
Fourichon C, Seegers H & Bareille N, et al. Effects of disease on milk production in the dairy cow: a review. Prev Vet Med 1999;41:1–35.
Srikandakumar A, Johnson EH. Effect of heat stress on milk production, rectal temperature, respiratory rates and blood chemistry in Holstein, Jersey and Australian milking zebu cows. Trop Anim Health Prod 2004;36:685–692.