Aspects of reproduction in New Zealand dairy herds 1. Gestation length

Kl, Macmillan; Rj, Curnow

doi:10.1080/00480169.1976.34332

Cited by 19 publications

(13 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Many abnormal GLs may arise through errors in the recording of insemination or calving dates. These errors are more prevalent with natural mating than with AI (Macmillan & Curnow 1976). Abortions, premature births and prolonged gestations, along with recording inaccuracies, will all affect calculated GLs (Macmillan & Curnow 1976) and increase differences between predicted and observed calving patterns.…”

Section: Introductionmentioning

confidence: 95%

“…The use of uncorrected GL data which may not have a normal distribution can bias means and inflate the measure of variation, thereby contributing to unjustified conclusions from statistical analyses (Macmillan & Curnow 1976) and reducing the accuracy or precision in predicting a herd's calving pattern from its conception data. Many abnormal GLs may arise through errors in the recording of insemination or calving dates.…”

Section: Introductionmentioning

confidence: 97%

“…Requests for predicted calving patterns to allow for planning and management have been common. Previous work suggested that cows conceiving to natural mating (i.e., after being served by a herd sire) had a shorter gestation length (GL) than those conceiving to AI (282 ± 4.6 versus 281.2 ± 4.5 days; mean ± SD; Macmillan & Curnow 1976). The mean GL and its variation needed to be determined before predicted calving patterns could be generated for herds using CBPs.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Predicting calving curves for herds using controlled breeding programs

Davis¹,

Anderson²,

Kl³

2003

New Zealand Journal of Agricultural Research

View full text Add to dashboard Cite

A database of gestation lengths (GLs) was generated over 2 years in three large dairy herds which had used controlled breeding programs (CBPs). This was compared with a database comprising a single calving season of 124 seasonally calving dairy herds using conventional artificial insemination programs (CAIs). Multiphase regression was used to derive two corrected databases by excluding outlying values of gestation length. The mean gestation length derived from the CBP database was slightly shorter than that of the CAI database (280.80 days, n = 775 versus 281.87 days, n = 1986; P < 0.001), but the two databases had similar variances (SD = 4.21 and 4.12 days, for CBP and CAI respectively; P = 0.36). The results from the multilevel analysis showed a mean difference in gestation length of 0.94 (SE 0.50) days; (P = 0.06) between CAI and CBP. The mean gestation length and its SD from the CBP data were used to predict calving curves in herds using CBPs which could be compared with observed calving data. The observed and predicted calving patterns generated for two farms were not significantly different (P = 0.37 and 0.31).The accuracy of the predictions was critically dependent on the completeness and accuracy of conception data and details for cows induced to calve prematurely.

show abstract

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Predicting calving curves for herds using controlled breeding programs

Davis¹,

Anderson²,

Kl³

2003

New Zealand Journal of Agricultural Research

View full text Add to dashboard Cite

show abstract

“…Macmillan & Curnow (1976), from data on over 90 000 pregancies in New Zealand dairy cattle, found that the factors intluencing gestation length included mating system (natural mating v. artificial insemination), district, year, dam age, twin v. single births, calf sex, calf's sire, and breed of sire. Between-herd differences accounted for less than 4% of the total variation in gestation length.…”

Section: 3mentioning

confidence: 99%

“…Everitt & Jury (1972) found that environmental effects were an important source of variation for some characteristics at calving. The effects of 12 factors on gest:::tion periods in New Zealand dairy cattle have been reported by Macmillan & Curnow (1976) .…”

Section: Introduction To Partmentioning

confidence: 99%