Invited Review: Increasing Milk Yield and Negative Energy Balance: A Gordian Knot for Dairy Cows?

Abstract

The continued increase in milk production during the last century has not been accompanied by an adequate dry matter intake (DMI) by cows, which therefore experience a negative energy balance (NEB). NEB is low and of minor importance at low milk yield (MY), such as for the nutrition of one calf, and under these circumstances is considered “natural”. MY and low DMI around parturition are correlated and are the reason for the genetic correlation between increasing MY and increasing NEB up to 2000 MJ or more for 2–3 months postpartum in high-genetic-merit dairy cows. The extension and duration of NEB in high-producing cows cannot be judged as “natural” and are compensated by the mobilization of nutrients, particularly of fat. The released non-esterified fatty acids (NEFAs) overwhelm the metabolic capacity of the cow and lead to the ectopic deposition of NEFAs as triglycerides (TGs) in the liver. The subsequent lipidosis and the concomitant hampered liver functions cause subclinical and clinical ketosis, both of which are associated with “production diseases”, including oxidative and endoplasmatic stress, inflammation and immunosuppression. These metabolic alterations are regulated by homeorhesis, with the priority of the physiological function of milk production. The prioritization of one function, namely, milk yield, possibly results in restrictions in other physiological (health) functions under conditions of limited resources (NEB). The hormonal framework for this metabolic environment is the high concentration of growth hormone (GH), the low concentration of insulin in connection with GH-dependent insulin resistance and the low concentration of IGF-1, the so-called GH-IGF-1 axis. The fine tuning of the GH-IGF-1 axis is uncoupled because the expression of the growth hormone receptor (GHR-1A) in the liver is reduced with increasing MY. The uncoupled GH-IGF-1 axis is a serious impairment for the GH-dependent stimulation of gluconeogenesis in the liver with continued increased lipolysis in fat tissue. It facilitates the pathogenesis of lipidosis with ketosis and, secondarily, “production diseases”. Unfortunately, MY is still increasing at inadequate DMI with increasing NEB and elevated NEFA and beta–hydroxybutyric acid concentrations under conditions of low glucose, thereby adding health risks. The high incidences of diseases and of early culling and mortality in dairy cows are well documented and cause severe economic problems with a waste of resources and a challenge to the environment. Moreover, the growing public concerns about such production conditions in agriculture can no longer be ignored.

The Complex Interplay of Insulin Resistance and Metabolic Inflammation in Transition Dairy Cows

“…This situation is particularly pronounced in high-yielding cows, which are unable to sufficiently increase their DMI to meet the energy demands of milk production in the immediate postpartum period [ 30 ]. This NEB results in the mobilization of body reserves, particularly fat [ 31 ]. Under the situation of the high yield, the reduced-DMI-caused NEB is the cause.…”

“…The latter further contributes to impaired insulin sensitivity, resulting in IR and the initiation of inflammatory responses [ 15 ]. The inefficient hepatic processing of these NEFAs leads to lipidosis, commonly known as fatty liver, and the production of ketone bodies, indicative of ketosis [ 31 ]. In the study of Arshad and Santos, as the concentration of hepatic triacylglycerol increased, there was an increase in milk yield and energy-corrected milk (ECM), but this came at the expense of body reserves, as indicated by exacerbated losses of body weight and a more negative body energy change [ 34 ].…”

“…Unlike in beef cattle where NEB may be considered natural, continuous selection for higher milk production in dairy cows has exacerbated NEB, leading to significant energy deficits. However, since the measurement of DMI is difficult and the corresponding data for genetic selection are not sufficiently available, the energy balance (indicator) itself is not typically considered a direct trait for genetic selection in dairy cattle breeding programs [ 31 ].…”

Effect of high NEFA concentration on lipid metabolism disorders in hepatocytes based on lipidomics

“…The released NEFA can be utilized for energy production and fat synthesis ( Adewuyi et al, 2005 ). However, the hepatic uptake of NEFA during NEB exceeds its oxidative capacity, resulting in hepatic lipid accumulation and the development of fatty liver ( Roberts et al, 1981 ; Reynolds et al, 2003 ; Martens, 2023 ).…”

The effect of oral administration of zeolite on the energy metabolism and reproductive health of Romanian spotted breed in advanced gestation and post partum period

“…Energy availability, or more specifically a lack of available energy, frequently limits milk or milk component synthesis, reduce reproductive performance, and prevents body condition replacement in cows. When NEB is severe and persists for long time, it also alters global gene expression and immune responses in the uterus of postpartum dairy cows ( Holger., 2023 ).…”