Effects of IQs on performance and somatic cell counts in dairy cattle

Milk yield is the most important factor in determining the profitability of dairy farms. Thus, the dairy community continuously seeks strategies aimed at improving productivity through the im-plementation of strategies that are environmentally friendly, focus on animal welfare and meet the consumer demands for high-quality products in terms of health and safety. Over the last decade milk yield per cow has increased by 11 % and the modern high producing dairy cow is able to produce more than 10,000 kg of milk. This improvement has been achieved through genetic selection, optimization of management practices, improved animal welfare and techno-logical advances. Nonetheless, despite these major improvements, dairy cows will experience certain challenges throughout their productive cycle that can impair their health and productivity.
 

   
^{Figure 1: Schematic representation showing the energy (Mcal/day) provided by the feed (black dotted line), energy required for milk production and maintenance (green dotted line) and body energy stores (orange dotted line) throughout the cow productive cycle.}
   
 

The transition period typically defined as the timeframe between three weeks before to three weeks after parturition is characterized by a series of physiological changes that allow the cow to shift from a gestating state, to support the onset of milk synthesis (Figure 1). During this period, which is the most challenging for dairy cows, dry matter intake (DMI) is significantly reduced, the energy requirements of the animal exceed the dietary energy intake and cows will enter a state of negative energy balance (Figure 1). Furthermore, post-parturient cows will experience varying degrees of local and systemic inflammation due to damage of the birth canal, uterine and mammary gland tissue remodeling, infectious and metabolic diseases, and changes in the rumen environment, among others.

All these physiological changes experienced by cows during the transition period disrupt the partition of nutrients which are mainly directed towards maintenance and the immune system in detriment of milk production, health and fertility. Thus, how cows’ transition from gestation to lactation is critical in determining the future health, productivity and reproductive success of dairy cows.

Nutritional strategies aimed at mitigating the negative impact of reduced DMI typically rely in in-creasing the energy density of the diet. Nevertheless, the elevated content of highly fermentable carbohydrates of these rations along with lower amounts of fiber can lead to detrimental changes in the rumen environment, microflora, and mucosa of the digestive tract. Because feed accounts for up to half of all the production costs on dairy farms, strategies aimed at improving the nutrient utilization are critical. Dietary energy and nutrients are prioritized for processes that are essential for survival of the animal. Once those demands are met the remaining nutrients are directed towards other activities such as growth, milk production, reproduction, among others (Figure 2).

In this sense, Sangrovit^® a plant-based product derived from Macleaya cordata, has been exten-sively used as a feed additive in food-producing animals. The active ingredients are isoquinoline alkaloids (IQ). Sangrovit^® promotes feed intake and supports digestibility of nutrients. Consequently, more dietary nutrients and energy are available for productive processes hence supporting per-formance and contributing to overall health (more energy for expendable process).
 

   
^{Figure 2: Partitioning of metabolic fuels based on priority. While energy and nutrients are prioritized for processes that are critical for survival and maintenance (essential), secondary uses of nutrients are directed towards reducible process and expendable process such as milk production, reproduction and fat storage (Adapted from Wade and Jones 2004, Am J Physiol Regul Integr Comp Physiol 287:R1277-96)}
   

A summary of research and field trials that evaluated the effects of IQ supplementation on milk yield in lactating dairy cows is presented in figure 3. Data collected from more than 5,600 cows included in 13 trials conducted in 9 countries were summarized to evaluate the effects of IQ supplementation on milk production of dairy cows. Analysis revealed that on average milk yield was improved in 84.6 % of the trials, and overall, IQ supplemented cows yielded 2.4 % more milk relative to control cows.
 

   
^{Figure 3: Summarized data showing the percent (%) difference in milk yield relative to control in dairy cows supplemented with IQ. Dark green bars represent data from field trials and light green bars re-present research trials. The right column shows the average milk yield for cows in the control and IQ- supplemented cows.}
 

A similar analysis was performed to evaluate the effects of supplementing dairy cows with IQ on somatic cell counts (SCC). For this evaluation data from more than 7397 cows from 15 research and filed trials performed in 10 countries were compiled. Overall, SCC were reduced by 20.5 % in IQ-supplemented cows relative to controls. Additionally, SCC were reduced in cows treated with Sangrovit^® in 93.3 % of the trials.
 

   
^{Figure 4: Summarized data showing the percent (%) difference in somatic cell counts (SCC) relative to control in dairy cows supplemented with IQ. Dark green bars represent data from field trials and light green bars represent research trials. The right column shows the SCC for cows in the control and IQ- supplemented cows.}
 

   
^{Figure 5: Summarized data across different production and SCC levels showing the percent (%) difference
in milk yield and SCC relative to control.}
 

Furthermore, the effects of Sangrovit^® on milk production and SCC were evaluated across different milk production and SCC levels. Milk yield analysis revealed that in dairy farms with production levels between 30 to 39 L/cow/day had the greatest response to IQ supplementation with an overall improvement of 3.7 % in milk production. Additionally, the greatest response in terms of SCC reduction was observed for dairy farms with SCC levels above 200 x 103.
 

• Milk yield per cow has significantly increased over the last 2-3 decades.
• Strategies to optimize DMI and nutrient utilization are essential to cope with the cows’ increased demands.
• The beneficial effects of IQ supplementation on milk yield and SCC can be attributed to a more efficient utilization of dietary nutrients and energy by dairy cows.
• Overall, IQ supplementation improved milk yield by 2.4 % and reduced SCC by 20.5 % relative to controls.