Energy requirements for pregnant dairy cows

Abstract

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.

Energy metabolism of pregnant zebu and crossbred zebu dairy cattle

“…uterus (k p ). The k p value obtained in the present study is also close to values obtained by [6,38,39]. There was no difference for the the efficiency of ME utilization data for pregnancy (k p ) in our work should be applied mostly to the development of the conceptus (growth of fetuses and fetal membranes), since the heat coming from the uterus itself was already considered in the measurement of NE m requirements using similar non-pregnant cows.…”

“…The [35] adopts an ME/DE ratio of 0.80 and points to the fact that this value can vary considerably depending on the level of consumption, animal age and type of food. Confirming this, the [16] mentions that the ME/DE ratio can vary from 0.80 to 0.86 according to characteristics of the diet [6] used a fixed value of 0.82 to obtain the ME intake by pregnant F1 Holstein x Gyr cows, without considering any possible variations on this efficiency due to pregnancy or different gestational ages.…”

“…5 ME m = metabolizable energy for maintenance [15]. 6 ME p = metabolizable energy for pregnancy (ME p = MEI-ME m ). 7 Fed HP = fed heat production determined in open-circuit calorimetry system.…”

“…Therefore, it should not be considered in the formulation of diets for dairy cows [5]. Recently, a study presented data for energy requirements of crossbred F1 Holstein x Gyr cows [6]. Although the study of [6] represents a major advance in the study of energy metabolism of pregnant cows used in tropical conditions, the slaughter methodology adopted has some limitation regarding energy efficiency and detail the energy partition by animals.…”

“…Recently, a study presented data for energy requirements of crossbred F1 Holstein x Gyr cows [6]. Although the study of [6] represents a major advance in the study of energy metabolism of pregnant cows used in tropical conditions, the slaughter methodology adopted has some limitation regarding energy efficiency and detail the energy partition by animals. In this work, using respirometry technology, we intend to describe the energy partition, energy requirements and efficiency of energy utilization by pregnant F1 Holstein x Gyr (F1 HxG) and Gyr cows at 180, 210 and 240 days of gestation.…”