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Relationship between energy expenditure and heart rate in pregnant Boer x Spanish does with different litter size

R. Puchala, I. Tovar-Luna, A. L. Goetsch, and T. Sahlu

Journal of Animal Science 84(Supplement 1):27. 2006

Twenty-four Boer x Spanish does (3 yr of age, having kidded once previously and initial BW of 42.7 1.19 kg) were used to determine effects of litter size (LS) and stage of gestation (near day 80, 100, 120 and 140) on the relationship between energy expenditure (EE) and heart rate (HR). Six does were nonpregnant (0) and, based on ultrasound determination on day 45 of gestation, six had LS of 1, 2 and 3. However, only 10 of the pregnant does had the expected number of kids (three, four, and three with LS of 1, 2 and 3, respectively). Does were fed a diet of approximately 50% concentrate in accordance with assumed maintenance plus pregnancy energy requirements based on LS. EE determined by respiration calorimetry on d 80, 100, 120 and 140 of gestation with head-boxes was expressed relative to average BW within the 2-d measurement periods and HR was determined at the same time using Polar S610 HR monitors. There was an effect of animal within LS (P < 0.05), CV of 10.2, 11.2, 3.8, and 8.6% and maximum differences of 41.7, 16.6, 5.2, and 12.0 of means for LS 0, 1, 2, and 3, respectively). Time of the day affected (P < 0.05) EE, HR, and EE:HR; highest values 0900 and 1600 and lowest values between 0200 and 0700). CV for hourly values were 3.9, 2.1, and 2.4%, and maximum differences relative to means were 9.0, 4.1, and 4.8% for EE, HR and EE:HR, respectively. There was an interaction in EE:HR between LS and stage of gestation (P < 0.05). EE:HR decreased as gestation progressed (LS 1:7.29, 6.79, 6.14, and 5.53; LS 2:6.73, 6.42, 6.07, and 5.02; LS 3: 6.53, 6.07, 5.71, and 5.07 (kJ/kg BW0.75)/(beats/min) on d 80, 100, 120, and 140, respectively, whereas nonpregnant goats had stable EE:HR (8.04, 7.78, 7.78, and 7.74 (kJ/kg BW0.75)/(beats/min)). In conclusion, changing EE:HR in pregnant animals may preclude use of HR to predict EE. Magnitudes of difference in EE:HR among animals and time of the day suggest benefit from determinations for individual animals and over extended periods of time.


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