Transition of cows from late gestation to early lactation is challenging for both animals and dairy farmers. The period at the end of the dry period and the beginning of lactation in dairy cows is commonly known as the transition period. Traditionally, transition period was considered as the 3 weeks before calving and the 3 weeks following calving. However, with the increasing understanding about cow’s physiological and metabolic changes, this period has been recognized as the 60 days before calving and the 30 days following calving. The transition refers to dairy cows going from a near maintenance state in late gestation, rapidly changes to a state of increased metabolic and nutrient demands at the onset of lactation. This period is extremely important in determining future health, milk production, and reproductive success of the dairy cow. It has been suggested that up to 80% of metabolic disorders or production diseases experienced by dairy cows during the transition period. Managing the transition phase is important because cows are stressed due to fast growing fetus and advanced pregnancy. Reduction in feed intake and low immunity make them vulnerable to metabolic and infectious diseases – mastitis, metritis and have poor hoof strength. The period is considered as most critical because of the long-term health and productive consequences. The root cause of transition cow challenges is complex and in most of the cases multifactorial.
Energy requirement and negative Energy Balance:
The transition period of dairy cow is characterized by a sharp decline in dry matter intake and the negative consequences in dairy cow’s health and productivity after parturition. During the transition period, nutrient requirements increase to support foetal growth and milk production. The energy requirements of a recently calved cow are so significant that most dairy cows do not initially eat enough to meet the requirement. The gap in the energy requirement along with increasing milk production results in negative energy balance. To cop-up with the requirement cows mobilize energy from body reserves, mostly from the body fat stores. In extreme cases, degradation of muscles and bone may take place. The more time a fresh cow spends in a negative energy balance, the higher the probability she will have a health challenge. Hence, management of reduction in the amount of time the cow spends in a negative energy balance is of utmost importance.
Metabolic and Physiological changes:
Due to mismatch in the required calories and the energies generated from dietary intake during transition period, cows most often mobilize energy from stored body fat. Decrease in dry matter intake around the time of calving may be one of the main problems with metabolic homeostasis in dairy cows. The blood Ca concentration starts decreasing in the 1 to 2 days before calving and reaches its lowest point within 48 hours of parturition.
The prevalence of clinical hypocalcaemia has decreased in the last few years. However, subclinical hypocalcaemia remains a significant problem affecting over half of multiparous high yielding cows. Subclinical hypocalcaemia is mostly associated with impaired postpartum health and with decreased milk yield.
Excessive lipolysis and increasing levels of non-esterified fatty acids (NEFA) takes place blood during this span. It is often associated with the accumulation of triglycerides in liver cells and impairment of liver function resulting in an elevated ketone production and predispose animals to ketosis. Along with increased NEFA concentration, there is subsequent accumulation of beta-hydroxybutyric acid (BHBA) in the blood. These changes are considered normal as a part of adaptive process in high yielding cows; involves an orchestrated series of changes in metabolism that allow an animal to adapt to the challenges of the altered state. However, when a cow fails to adapt to these metabolic challenges, several metabolic and infectious disorders took place and affect the productive and reproductive efficiency.
Pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α are mainly released by macrophages located at different organs like liver, brain, and adipose tissue. The fat mobilization associated with the reduction in DMI during the period is considered responsible for the release of these pro-inflammatory cytokines into the bloodstream. Besides high growth hormone (GH) concentration, animals in negative energy balance shows insulin resistance and reduced glucose uptake by peripheral tissues.
All metabolic processes are interconnected with each other. If there is a failure of one metabolic process, it will impact on the efficiency of others. Such effect may persist beyond the transition period; can be a major risk factor for subsequent productive and reproductive performance.
Immune Status:
One of the major negative impacts of poor transition cow management is immune-suppression. Immune status of animals decreases in and around parturition due to interaction of several factors. In peri-partum period, both humeral and cell mediated immunity get depressed due to the increased cortisol concentration. The week prior to and immediately after parturition, leucocyte proliferation is higher but antibody production ability in response to mitogen (non-specific stimulants of immune cells) is decreased. The serum concentration of components of immune system such as immunoglobulin and complement factor also decreases at the time of parturition in dairy cow. Thus, the depressed immune system of the cow around calving, associated with the dramatic changes in circulating metabolites is hypothesized the basis of the high disease incidence postpartum and the subsequent low performance. On the other hand, negative energy balance due to reduction in DMI during transition period leads to suppressed immune function that may promote uterine diseases and other metabolic diseases.
Diseases and Disorders during Transition period:
Maladaptation to the physiological or metabolic changes may result in excessive fat mobilization, dysregulation of inflammation, immunosuppression, and, ultimately, metabolic or infectious disease in the postpartum period. Diseases that result from disruption in homeostasis of rumen function, calcium and bone metabolism; energy metabolism, protein metabolism and immune function. These conditions are often inter-related, leads to:
- Hypocalcaemia and downer’s cow syndrome
- Hypomagnesaemia
- Ruminal Acidosis
- Ketosis and fatty liver
- Udder oedema / Mastitis
- Abomasal displacement
- Retained placenta
- Metritis
- Poor fertility and
- Poor production
- Other clinical and subclinical conditions
In adult dairy cattle, 80% of disease costs occur in the first four weeks after calving. This is also a peak period for involuntary culls and deaths.
Management of Transition period:
The prime objectives of transition cow management are:
- To increase dry matter intake and energy supply
- Prevention or control of Ruminal Disruption
- Prevention of Macro and Micro mineral deficiencies
- Minimizing Lipid Mobilisation disorders
- Management of Stress and to optimize Immune functions Dr
An integrated approach to managing transition cows is needed if these challenges are to be dealt with effectively. Therefore, an integrated transition diet should comprise of energy and protein supplement, macro-minerals and DCAD, micro-minerals, rumen modifiers and buffers and other immunity enhancement additives. If these challenges are addressed during the transition period, a successful lactation and health status of the animals can be established.
The management practices for transition cows must be focused on maximizing dry matter intake and modulating stress and inflammation. To maximize dry matter intake, diet composition especially fibre and energy concentrations is one of the most critical factors. Other cow comfort parameters like control of heat stress, stocking density, bedding management etc. are essential to minimize stress during the transition period.
Benefits of Yeast Extract (Aspergillus Oryzae) in the management of Transition Cows:
Yeast extract is a natural product which is rich in proteins, amino acids, enzymes, nucleotides and a variety of minerals. Its application as animal feed additive is proven and supported by many research publications; however, their full potential has not been realized yet. In dairy cows, supplementation of yeast extract has been found to be very useful to prevent ruminal.
Disturbances, increase in dry matter intake, utilization of fibre and other nutrients and thereby improves overall improvement in body conditions. Aspergillus oryzae (AO) extract is considered as a precision prebiotic that enhances digestibility by amplifying the nutrient supply for maximum performance. Aspergillus oryzae extract contains wide variety of polysaccharide and amylase enzymes, which increases rumen function by enhancing fibre digestion and reducing the transient post-prandial drop in ruminal pH. The combined effect of such additive help cows to adapt from high roughage diets to higher concentrate diets especially in the transition cows. An increase in feed digestibility due to the prebiotic would lead to an increase in nutrient absorption. The increase in rumen fermentation and VFA production improve overall energy supply and metabolic profiles. It helps in reduction in rumen lactic acid concentration. by stimulating lactic acid utilizing bacteria and thus minimize nutritional stress due to subacute acidosis. The extra energy made available to the cow support for a healthy transition. Evidence suggests that supplementation of yeast extracts provide a substantial benefit to transition cow during immune challenge through improving availability of energy. Besides, the prebiotic AO supplement decreases the number of cytokines and other inflammatory metabolites and thereby reduce levels of stress and boost immune function.
Conclusion:
The transition period constitutes a turning point in the productive cycle of the cow as it encompasses a number of changes on the cow which are in physiological transit from one lactation to the subsequent lactation and hence it requires proper management for successful dairy farming. General management practices of transition cows include control of hypocalcaemia (milk fever) and feeding of propylene glycol or glycerol as an energy source. Such strategies have some benefits in addressing a particular problem, however transition cow challenges are complex and multifactorial that needs integrated nutritional strategies.
An integrated transition diet should comprise of energy and protein supplement, macro-minerals and DCAD, micro-minerals, rumen modifiers and buffers and other immunity enhancement additives. To meet specific objectives in support of the transition cow, adequate nutrient supplementation and specific additives to be provided that support and enhances rumen function, nutrient absorption and immune functions. Recently, several fungal and yeast cultures or extract as feed additives have demonstrated significant beneficial effect in improvement of health, productivity and combating stress in dairy cows. Aspergillus oryzae is considered as a precision prebiotic that improves rumen function, enhances digestibility, improvement in overall energy supply and metabolic profiles and enhances immune functions.
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