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Azevedo, Rafael Alves de; Genetics, Alta; Zambrano, J. A.; Teixeira, Alex de Matos; Bittar, Carla Maris Machado; Antunes, Lívia Carolina Magalhães Silva; Santos, J.E.P.; Rotta, Polyana Pizzi; Meneses, Rodrigo Melo; Coelho, Sandra Gesteira; Rehagro,; Famev,; Ufu,; Esaql,; Usp,; Fazu,; Ufv,

doi:10.26626/978-85-5953-053-7.2019b0001

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“…Calf body weight (35 kg) was obtained according to average weight of Holstein × Gyr calves from Silva et al [40] and Azevedo et al [41]. The NRC [6] uses a linear regression equation to estimate NE preg considering days of pregnancy and calf body weight, and the fetus accounts for approximately 80% of uterine dry weight [3].…”

Section: Net and Metabolizable Energy Requirements For Pregnancymentioning

confidence: 99%

Energy requirements for pregnant dairy cows

et al. 2020

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This study aimed to estimate energy requirements of pregnant Holstein × Gyr cows. Different planes of nutrition were established by two feeding regimens: ad libitum or maintenance. Sixty-two nonlactating cows with average body weight of 480 ± 10.1 kg and an age of 5 ± 0.5 years were used. Cows were divided into three groups: pregnant (n = 44), non-pregnant (n = 12), and baseline reference (n = 6). The 56 pregnant and non-pregnant cows were randomly allocated into a feeding regimen: ad libitum or maintenance. To evaluate the effects of days of pregnancy, pregnant and non-pregnant animals were slaughtered at 140, 200, 240, and 270 days of pregnancy. Energy requirements for maintenance differed between pregnant and non-pregnant cows, thus two equations were developed. Net energy and metabolizable energy requirements for maintenance of non-pregnant cows were 82 kcal/kg empty body weight 0.75 /day and 132 kcal/kg empty body weight 0.75 /day, respectively. The efficiency of use of metabolizable energy for maintenance of non-pregnant cows was 62.4%. Net energy and metabolizable energy for maintenance of pregnant cows were 86 kcal/kg empty body weight 0.75 /day and 137 kcal/kg empty body weight 0.75 /day, respectively. Efficiency of use of metabolizable energy for maintenance of pregnant cows was 62.5%. The efficiency of use of metabolizable energy for gain was 41.9%. The efficiency of use of metabolizable energy for pregnancy was 14.1%. Furthermore, net energy requirement for pregnancy was different from zero from day 70 of pregnancy onwards. In conclusion, net energy and metabolizable energy requirements for maintenance of non-pregnant cows are different from pregnant cows. Furthermore, we believe that the proposed non-linear equations to estimate net energy requirements for pregnancy are more adequate than current NRC equation, and should be recommended for Holstein × Gyr cows.

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Section: Net and Metabolizable Energy Requirements For Pregnancymentioning

confidence: 99%