Energy requirements of gestating dairy cows
The NRC [6] determined the energy prerequisites for gestation based on findings by Bell et al. [3], while Ferrell et al. [1] evaluated the efficiency of metabolizable energy utilization by the embryo. Bell et al. [3] proposed that the energy demand for gestation gains significance after 190 days, exhibiting a linear rise up to 279 days. These requirements for gestation were obtained using Bos taurus breeds.
Therefore, when evaluating the needs of animals from different breeds, such as the crossbreed of Bos taurus × Bos indicus (Holstein × Gyr), there is no concrete evidence that energy demands for gestation are the same.
The Brazilian dairy industry is composed of approximately 70% Holstein × Gyr animals [9, 10], and this crossbreed exhibits higher milk production than the Gyr breed itself.
In a meta-analysis, Oliveira [11] found lower maintenance requirements and lower efficiency for milk production in Bos taurus × Bos indicus breeds compared to Bos taurus breeds. However, as far as we know, there is no quantitative data available regarding the nutrient requirements of Holstein × Gyr cows during gestation. Additionally, no studies have been found concerning weight gain requirements for Holstein × Gyr cows.
Estimation of energy requirements for gestating cows
In order to assess the impacts of various gestational periods, both pregnant and non-pregnant animals were slaughtered at intervals of 140, 200, 240, and 270 days following the onset of gestation.
The energy requirements for maintenance exhibited differences between pregnant and non-pregnant cows, thereby giving rise to the formulation of two distinct equations.
The efficiency of metabolizable energy utilization for maintenance of non-pregnant cows was 62.4%.
In summary, the net energy and metabolizable energy requirements for maintenance vary between pregnant and non-pregnant cows. Furthermore, researchers from the aforementioned study consider that the proposed nonlinear equations for estimating net energy requirements for gestation are more suitable than the current NRC equation and should be recommended for Holstein × Gyr cows.
Source: Journal Plos One
You may also like to read: “Dairy Cattle Nutrition during the Transition Period.”
Bibliographical References:
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11. Oliveira AS. Meta-analysis of feeding trials to estimate energy requirements of dairy cows under tropical condition. Anim Feed Sci Technol. 2015;210: 94–103.