An Observational Analysis of Twin Births, Calf Sex Ratio, and Calf Mortality in Holstein Dairy Cattle

Abstract

A data set of Holstein calving records from January 1996 to September 2004 comprising 4,103 herds with 2,304,278 calving events representing 1,164,233 cows and 96,069 twin births was extracted from Minnesota Dairy Herd Improvement Association archives to assess reported twinning trends and calf mortality across time. Overall, the reported twinning rate was 4.2%, and twinning increased with parity [1.2% for nulliparous vs. 5.8% for multiparous cows; odds ratio (OR) = 4.9], and with time (3.4% in 1996 to 4.8% in 2004), with a parity by time interaction. Independent of parity, the greatest twinning rate was observed when conception occurred from August to October compared with other seasons (OR = 1.2). Calf mortality was greater after twin births, with 28.2% of twin calving events reporting one or both calves as dead, compared with 7.2% for singleton births (OR = 6.5). Calf mortality for primiparous and multiparous cows was 5.0% after a single birth and 25.5% after twin births, whereas for nulliparous heifers, mortality was 10.4% for singletons and 38.0% for twins (OR = 3.4). Calf sex ratio (male, M; female, F) was 53.3% M and 46.7% F for singleton calves, and 30.1% MM, 43.6% MF, and 26.3% FF for twin calves. Although specific factors cannot be implicated, the increase in twinning across time suggests a concurrent change in one or more causative factors associated with twinning during the 9-yr study period.

Factors associated with selling price of cattle at livestock marts

“…The proportion of cows that received assistance at calving, 18.0%, across dairy and beef cows, is within the ranges reported by Mee (2008) from studies reviewed across nine countries on dairy cows and heifers. The average twinning rate varied across maturity categories from 2% to 4%, which is similar to (inter)national estimates (Dematawewa and Berger, 1997;Silva del Rio et al, 2007;Mee et al, 2008). The overall sex ratio in this study across all maturity categories, with the exception of cows was 50.4% males, 49.6% females.…”

Holsteins Favor Heifers, Not Bulls: Biased Milk Production Programmed during Pregnancy as a Function of Fetal Sex

“…Importantly, uniformly biased milk production in favor of daughters across maternal conditions does not support the Trivers-Willard hypothesis [9], or other hypotheses positing facultative sex-biased allocation of resources as a function of maternal condition [10]. Dairy cows have a male-biased birth ratio; in the absence of sex-specific artificial insemination, between 50-54% of calves born are male [49,82]. The mediating effect of maternal condition on birth-sex ratio has been inconsistent [83] as has been the directionality of birth sex-ratio bias.…”

“…With the widespread availability of sexedselected semen for use in artificial breeding programs, dairy managers have the option of achieving approximately 90% female pregnancies rather than a natural rate near 47% [49]. There are many factors for managers to consider when evaluating the profitability of sexed semen use, including decreased conception rate [57] and increased semen cost.…”

Bio-economic model to evaluate twinning rate using sexed embryo transfer in dairy herds

“…The incidence of twin births is on average 4% to 5% in dairy herds and is strongly affected by age and parity of the dam (Silva del Río et al, 2007). Increased frequency of twinning would increase the potential for obtaining more progeny from a genetically superior female, thereby allowing those females to play a larger role in a selection program (Cady and Van Vleck, 1978).…”