Álvaro García
Assessing the nutritional status of dairy cows is critical for ensuring their overall health and productivity. While both Body Condition Score (BCS) and Body Weight (BW) are commonly used metrics, BCS offers distinct advantages over BW alone. Unlike BW, which simply measures the total weight of the cow, BCS provides a more detailed evaluation of body fat distribution and muscle condition. By considering factors such as fat cover and muscle development in specific body areas like the tailhead, hooks, pins, and ribs, BCS offers a more thorough understanding of the cow’s body composition. This allows for the early detection of metabolic health issues such as ketosis, fatty liver syndrome, and negative energy balance. Furthermore, BCS is closely linked to reproductive performance in dairy cows. Recent advances in technology, such as the development of 3D cameras fitted with specific algorithms within computerized systems, have changed BCS assessment. These innovations offer increased precision with unmatched repeatability, providing dairy farmers with a powerful tool for optimizing herd health and performance.
Lactation dynamics
Cows that start the lactation with better BCS often exhibit improved lactation persistence compared to those with lower BCS. This can be attributed to various metabolic and hormonal changes that occur during the transition period from late gestation to early lactation. Figures 1 and 2 show the BCS and lactation performance measured with 3D cameras in a commercial herd characterized for excellent reproduction and lactation persistence. The BCS of the herd is very good, slightly skewed towards the upper end of the ideal (white band). Cows approaching the end of the lactation are mostly around 3.5 with some approaching the 4.0 score.
Energy balance plays a significant role in dairy cow reproductive performance. Cows often experience negative energy balance (NEB) in the early stages of lactation, which can delay the resumption of ovarian cyclicity and estrus activity. When cows transition into positive energy balance, usually around 60 days post-calving, it usually coincides with improved reproductive function, including increased expression of estrus behavior. The cow’s metabolism reacts to the change in BCS and not so much at the actual score. Cows at BCS 3.0 for example will show heat more readily if they are improving their condition (e.g. coming from 2.5) than if losing condition (e.g. coming from 3.5). In this farm example cows are reaching energy balance between 80- and 120-days post calving and not 60. If the farm has a voluntary waiting period (VWP) for first insemination set at 45 or even 60 days post calving it is likely most of the cows might not be in heat.
What does the research say?
A recent study out of Wageningen University in the Netherlands (Burgers et al., 2021) looked at the impact of different voluntary waiting periods (VWP) from calving to first insemination on various factors like body weight, body condition, milk yield, and lactation persistency. The study also pinpointed individual cow traits during early lactation that influenced milk yield and persistency across different VWP lengths. The study examined three VWP durations: 50, 125, or 200 days.
During the first 44 weeks of lactation, the VWP duration didn’t seem to affect fat-corrected milk yield for either first-time calvers (primiparous) or those who have calved multiple times (multiparous). However, while VWP length didn’t impact daily milk yield in primiparous cows, those with a 125-day VWP showed increased daily milk yield in multiparous cows. Interestingly, as cows approached the dry-off period in the last 6 weeks, those with a 125-day VWP exhibited lower milk yield compared to those with a 50-day VWP. This drop could potentially benefit their udder health during the dry period and after calving.
Moreover, cows with a 200-day VWP displayed better lactation persistency compared to those with a 50-day VWP. In addition, multiparous cows with a 200-day VWP showed higher body condition scores in the last 3 months before dry-off and the first 6 weeks of the subsequent lactation compared to those with 50 or 125 days VWP.
The study suggested that extending the VWP from 50 to 125 days didn’t seem to affect daily milk yield. For primiparous cows, extending the VWP to 200 days didn’t seem to impact their daily milk yield. However, for multiparous cows, a 200-day VWP led to reduced milk yield per day of calving interval but an increase in body condition during late lactation and the subsequent lactation.
The results of this experiment align with what can be observed in the milk production of the commercial dairy using 3D technology in this example (figure 2).
Body condition and lactation performance
Cows in this dairy showed a good performance early in the lactation, but what was even more striking was the sustained production as the lactation advanced (Figure 2).
During late gestation, cows undergo significant physiological changes to support the developing fetus and prepare for parturition. As a result, cows often experience negative energy balance (NEB) during this period, where energy intake from feed is insufficient to meet the demands of pregnancy and lactation. In cows with better BCS at calving, the presence of adequate body fat reserves serves as an energy buffer during the transition period. This allows them to better cope with the metabolic challenges of early lactation, such as NEB. Cows with higher BCS have greater energy reserves available for mobilization, which can help offset the energy deficit experienced during early lactation. Furthermore, cows with better BCS at calving tend to exhibit more stable hormone profiles during the transition period. Hormones such as insulin and insulin-like growth factor 1 (IGF-1) play crucial roles in regulating metabolism and energy partitioning in dairy cows. Elevated levels of these hormones have been associated with improved reproductive performance and metabolic health.
In contrast, cows with lower BCS at calving may experience more pronounced hormonal fluctuations and metabolic challenges during early lactation. This can negatively impact reproductive performance, milk production, and overall herd productivity. Therefore, maintaining optimal BCS at calving is essential for maximizing lactation persistency and reproductive success in dairy cows. Cows with higher body condition scores (BCS) at the onset of lactation generally have a greater amount of body fat reserves available to support their energy needs during early lactation. This surplus of body fat serves as an energy reservoir, allowing these cows to better cope with the increased energy demands associated with milk production without experiencing excessive fat mobilization or negative energy balance.
When cows calve with higher BCS, they enter lactation with a metabolic advantage. Additional body fat provides a readily available source of energy, reducing the reliance on liver glycogen and muscle protein for fuel. As a result, cows with higher BCS are less likely to experience disruptions in metabolic homeostasis, such as subclinical or clinical ketosis. Furthermore, cows with higher BCS tend to have improved lactation persistence, meaning they can sustain higher milk production levels over an extended period. This can be attributed to several factors:
- Energy Reserves: Cows with higher BCS possess sufficient energy reserves to sustain milk production during negative energy balance, preventing excessive fat mobilization and metabolic imbalances.
- Nutrient Partitioning: Cows with higher BCS efficiently direct nutrients toward milk synthesis rather than body maintenance, resulting in increased milk production and extended lactation curves.
- Hormonal Regulation: Cows with higher BCS possess larger adipose tissue reserves, impacting hormone signaling pathways crucial for lactation, metabolism, and reproductive function.
The utilization of BCS in dairy cow management offers invaluable insights into metabolic health, reproductive performance, and overall productivity. By embracing these innovative tools, such as 3D imaging technology, farmers can improve their herd management capabilities, drive sustainable productivity gains, and ensure the long-term success of their dairy operations. Extending the voluntary waiting period can significantly benefit cow health and longevity, as demonstrated by recent studies. Longer voluntary waiting period durations not only improve lactation persistency and reduce metabolic stress but also contribute to better BCS and reproductive outcomes.
© 2025 Dellait Knowledge Center. All Rights Reserved.
