Abstract

Abstract. Calving records from the Animal Breeding Center of Iran collected from January 1993 to December 2007 and comprising 1 163 594 Holstein calving events from 2 552 herds were used to evaluate reported perinatal calf mortality, 305-d milk yield, 305-d fat yield of milk and 305-d fat percentage of milk in single- and twin-births. A logistic regression model was constructed to analyze calf mortality between singletons and twins. Also statistical analyses of 305-d milk yield, 305-d fat yield of milk and 305-d fat percentage of milk were performed using the general linear models procedure. Greater odds of calf mortality existed for calves born from primiparous cows than from multiparous cows (P<0.001) and for calves born as twins than singletons. The odds of calf mortality increased over years from 4.2 % in calving year Y1 (1993–1997) to 5.1 % in calving year Y3 (2003–2007) (odds ratio [OR] = 1.14; P<0.001). The odds of calf mortality was greater after twin births, with 16.7 % of the twin calving events reporting calves as dead compared to 5.2 % for singleton births (OR=5.62; P<0.001). For same-sex twin pairs, the odds of calf mortality was greater (P<0.01; OR=1.72) for male than for female twin pairs. Also, twin-calved cows had greater 305-d milk production, fat yield and fat percentage of milk than single-calved cows (P<0.05). In general, development of practical management strategies to cope with the negative effects associated with twinning on dairies is critical, especially if the trend toward increased twinning in the dairy cattle population continues.

Highlights

  • Ovaries of cattle contain two different pools of follicles, the non-growing pool and the growing pool

  • Information for individual calving events, including herd, cow identification, service sire identification, cow’s sire identification, calving date, dry date, parity, multiple births, calf gender, calf mortality, 305-d milk yield, fat yield of milk, fat percentage of milk and calving difficulty were included in the data set

  • The overall incidence of perinatal calf mortality was 7.6% it varied among herds from 1.2% to 15.7 %

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Summary

Introduction

Ovaries of cattle contain two different pools of follicles, the non-growing pool and the growing pool. If luteolysis occurs during the growth phase of dominant follicles, final maturation and ovulation occurs. Initiation of an induced or naturally occurring ovulatory stimulus causes release of a single oocyte from the dominant follicle at ovulation. If the subsequent events from fertilization to parturition occur normally, the pregnancy will result in birth of one calf. Two follicles are selected to continue growth from among the group of growing follicles in a follicular wave resulting in a phenomenon termed codominance. If the appropriate stimulus for ovulation occurs naturally or is induced when codominant follicles are present, two oocytes, one from each follicle, will be released. If the subsequent events from fertilization to parturition occur normally for both oocytes, twins will result (RYAN and BOLAND 1991)

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