title: A survey detailing the calving performance of primiparous 2-year-old beef heifers and outcomes of assisted calving.
abstract: OBJECTIVE
  To examine via a survey the management at calving of primiparous, 2-year-old beef heifers on selected beef cattle farms in New Zealand and to investigate the causes and outcomes of assisted calving of these heifers.
  
  
  METHODS
  An initial survey of beef cattle farmers identified that many beef breeding heifers were assisted at parturition in 2006. The outcome of assistance at parturition in the industry was not examined in that survey. A two-part questionnaire was sent to 204 respondents to the previous survey who had indicated a willingness to participate and had bred 15-month-old heifers in 2006. These respondents are unlikely to be a representative sample of all beef cattle farmers in New Zealand. A total of 127 responses were received to Part A, which encompassed mating and calving management and results and 107 responses were received to Part B, which addressed survival of calves and management of the replacement heifers.
  
  
  RESULTS
  A total of 6726 heifers were joined with bulls in the respondents' herds in 2006. The percentage of calves born to primiparous, 2-year-old heifers present at marking was 83 (95% CI = 80-86)% of heifers joined with a bull. Overall assistance percentage was 9.7 (95% CI = 7.6-11.9)%, and 30 (95% CI = 25-35)% of 376 calves assisted at birth for which fate was reported were stillborn. The predominant cause of assisted calving was feto-maternal disproportion, and 11 (95% CI = 7-16)% of assisted heifers had died by 4 weeks postpartum. The most common time to first graze heifers with the mature cow herd was between first calving and second mating. Eighty-five (95% CI = 58-100)% of heifers that calved at 2 years of age in 2006 calved again in 2007 and this was not affected by stage of integration into the mixed-aged cow herd. Failure to conceive at second mating was the predominant reason for heifer attrition: 3.8 (95% CI = 0-16)% were culled after being diagnosed non-pregnant and a further 2.3 (95% CI = 0-18)% were carried over as empty 3-year-old heifers.
  
  
  CONCLUSIONS
  The 85% retention of heifers as second-calving, 3-year-olds indicated that heifers were achieving adequate rebreeding rates after first calving. The survival of heifers and calves in the neonatal period could be increased by reducing the need for or improving the outcomes of assistance at parturition.
authors.affiliation: Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand. r.hickson@massey.ac.nz
authors.forename: R E
authors.initials: RE
authors.lastname: Hickson
authors.forename: W J
authors.initials: WJ
authors.lastname: Anderson
authors.forename: P R
authors.initials: PR
authors.lastname: Kenyon
authors.forename: N
authors.initials: N
authors.lastname: Lopez-Villalobos
authors.forename: S T
authors.initials: ST
authors.lastname: Morris
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000628:therapy*; D004420:Dystocia / Q000628:therapy / Q000662:veterinary*; D005260:Female; D036801:Parturition / Q000502:physiology*; D011247:Pregnancy; D016896:Treatment Outcome