Effect of temperature and humidity on gestation length

1
Effect of temperature and humidity on gestation
length H.D. Norman, J.R. Wright, and J.B.
Cole Animal Improvement Programs Laboratory,
Agricultural Research Service, USDA, Beltsville,
MD 20705-2350
Abstr. M38

• INTRODUCTION
• High temperature and humidity have been shown to
  affect production traits but their effects on
  other traits has not been examined.
• More accurate prediction of gestation length (GL)
  could aid herd managers in assuring that
  appropriate nutrition and health actions are
  given to pregnant cows at the optimal time.

• DATA METHODS (cont.)
• Edits
• Inseminations initiating gestation must have been
  after February 1998 and subsequent calving
  parturition must have been before January 2006
• Holstein with gt86 breed purity based on AIPL
  crossbred database
• Matings to identified AI sires only
• 10 sample selected for analysis (477,068
  conceptions)
• Model
• GL calf conception year
• (4 heifer groups, 8 cow groups)
• calf conception herd-year (absorbed)
• calf conception month (Jan., Feb., etc.)
• calf parturition code (8 groups based
• on multiple birth status and gender)
• age within parity at conception
• (5 heifer groups, 17 cow groups)
• lactation length (7 groups)
• milk yield (5 groups)
• THI (16 groups)
• residual (random)

• RESULTS (cont.)
• Adding THI to the model including conception
  month increased prediction of GL only slightly.
• Only small differences between were found between
  various THI measures.
• THI measured at days 5 and 6 were slightly more
  effective than other single-day measures.
• THI mean of 7 days or 14 days was more useful in
  helping to predict GL than single-day measures.
• Solutions by THI group for model including all
  effects, conception month, and THI at 6 days
  prior to calving

• RESULTS (cont.)
• Adding THI to the model including conception
  month increased prediction of GL only slightly.
• Only small differences were found between various
  THI measures.
• THI measured at days 5 and 6 were slightly more
  effective than other single-day measures.
• THI mean of 7 days or 14 days was more useful in
  helping to predict GL than single-day measures.
• Solutions by THI group for model including all
  effects, conception month, and THI at 6 days
  prior to calving

• RESULTS
• Frequency of records by THI level
• Relationship of THI with GL

• OBJECTIVES
• Determine if monthly differences in GL are caused
  by temperature and humidity.
• Determine how various measures of temperature and
  humidity account for differences in GL.

• DATA METHODS
• Lactation, reproductive, and dystocia records
  from the national dairy database at AIPL as
  supplied by dairy records processing centers,
  breed associations, and the National Association
  of Animal Breeders.
• Meteorological data from 238 weather stations
  supplied via subscription to the Southern
  Regional Climate Center, Louisiana State
  University.
• Meteorological data matched to herd ZIP code by
  choosing closest weather station based on
  distance between latitude/longitude of center of
  ZIP codes using Haversine formula to approximate
  distance.
• Trait definition
• Temperature-Humidity Index (THI)
• (1.8T 32) (0.55 0.0055H) (1.8T 28)
• where T temperature in Celsius and H
  relative humidity expressed as a percentage.

Model Model effect(s) R2 effect(s) R2 A .1071 A,M
,T7 .1143 A,M .1125 A,M,T8 .1141 A,T6 .1097 A,M,T9
.1140 A,M,T0 .1139 A,M,T10 .1139 A,M,T1 .1140 A,M
,T11 .1139 A,M,T2 .1140 A,M,T12 .1139 A,M,T3 .1142
A,M,T13 .1138 A,M,T4 .1143 A,M,T0-6 .1154 A,M,T5
.1145 A,M,T0-13 .1164 A,M,T6 .1145

• CONCLUSIONS
• THI is useful in predicting GL but has limited
  value when conception month is included in the
  model.
• Effectiveness of THI in predicting GL is greater
  at higher temperatures.

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