In addition to using traditional cooling methods, have you ever given thought to how your cows’ diets could play a role in tackling heat? Recent research suggests certain nutritional strategies can actually help lessen the effects of heat stress.
Depending on a cow’s production level, she can start experiencing heat stress at a temperature humidity index (THI) of 65 to 68. As milk production climbs, cows become more sensitive to heat.
Increased heat thermal load can cause decreased milk production, changes in feed efficiency and animal health, and inhibit reproductive success – negatives that can stick with an animal for several months down the road even after heat has dissipated. Factored together, these consequences can greatly affect profitability. Milk production losses between 10 and 35 percent are common and may cost a dairy $1.60 to $5.60 per cow per day. Who can afford such an economic blow?
Bust through heat issues with nutritional help
Research on nutritional supplements has revealed that carbohydrate-based feed additives help herds maintain milk production throughout the year, regardless of weather conditions.
Digestion increases heat load, and a cow’s feed intake typically drops. Yet, it’s during this crucial type of stress that energy requirements increase as she attempts to cool herself. A decline in dry matter intake, coupled with an increase in energy demand, can quickly depress milk production.
Nutritional supplements can address energy needs by efficiently delivering glucose and energy to cows when intakes are challenged. Transition and lactating cows benefit by maintaining feed intake and producing more milk, even during times of heat stress.
Supporting cows from transition through mid-lactation
Research from the University of Missouri and the Purina Animal Nutrition Center showed that feeding carbohydrate-based feed supplements before and during a period of acute cyclical heat stress increased milk production, raised dry matter intake, improved feed efficiency and lowered postpartum plasma non-esterified fatty acid (NEFA) levels.
A research trial analyzed the effects of carbohydrate-based feed supplements on improving transition cow milk and component yield during summer months. Forty-four second-lactation (multiparous) and 18 first-lactation (primiparous) Holstein cows were randomly assigned to dietary treatments of control or supplement from day 28 pre-calving to day 30 post-calving. During this time, cows experienced environmental THI readings greater than 68 for 91.1 percent of the time and were cooled by thermostat-controlled fans only.
Multiparous cows that received the supplement produced an average of 6.5 pounds more milk per cow per day and showed an average 3.5-pound increase in dry matter intake through 60 days postpartum. Supplement-fed cows also exhibited 15 percent lower NEFA concentrations than control cows. When an animal with a negative energy balance mobilizes body fat, it circulates in the blood in the form of NEFA. A lower NEFA level can help prevent fatty liver and ketosis challenges and possibly result in greater energy. Additionally, plasma beta-hydroxybutyrate levels were reduced by several mg/dL.
In a University of Missouri study, control cows were fed 100 grams of sucrose (straight sugar product) and treatment cows received 100 grams of supplement as part of the TMR in two daily allotments for a total of 39 days (21 days in thermoneutral conditions in a freestall facility, six days in temperature-controlled environmental chambers with no heat stress and 12 days in the chambers under known amounts of heat strain).
The experiment included 24 animals for each treatment: 19 multiparous and 5 primiparous. The subjects were high-producing cows in a post-peak period of about 110 days in milk (DIM) at the experiment’s start. Animals were assigned to treatments in blocks based on DIM, production level, somatic cell count and body condition score to even out cow quality between the two groups.
Animals faced 12 days under an elevated thermal mode, with cycles that mimicked conditions typical of a summer day – ranging from a low of 74.8ºF up to 86.4ºF and a THI of 69.3 to 75.5.
Animal performance was measured in the form of milk production, dry matter intake and milk components. Studying a cow’s physiology through rectal and skin temperatures and respiratory rates helps reveal her internal response to heat load and were essential measurements within the study as well. Since losses in production are not always driven by drops in dry matter intake – metabolism changes can also have an impact – researchers measured energy metabolites such as plasma glucose, plasma hydroxybutyrate and NEFA. Insulin and cortisol hormones along with body condition scores were also recorded.
The degree of difference between controls and supplement-fed cows grew over time, and after 12 days, there was a significant gap in relation to dry matter intake and milk yield. Supplement-fed cows produced around 3.6 pounds more milk per cow per day, and dry matter intake also went up by 3.5 pounds per cow per day, on average. Milk fat percentage was lower in cows receiving supplement, but no difference in milk fat yield was detected.
Help cows make more milk during summer heat
The research clearly demonstrates that this nutritional supplement may help curb the effects of heat stress and boost productivity by improving milk yield and dry matter intake in transition, early- and mid-lactation cows. The data also pinpoints that to fully optimize the economic benefits of feeding this supplement and to address large seasonal performance fluxes, producers should start feeding it early in the season to pre-fresh cows 21 to 28 days before calving through approximately 150 days in milk – cows are most responsive to the supplement during this time frame.
Because it is a key ingredient for transition cows, feeding it to those calving during periods of heat stress is especially important. Cows approaching peak lactation during summer seasons also profit significantly. Even a 5-pound milk increase per day makes a notable difference throughout a cow’s lactation. And higher peak milk enables the whole lactation curve to shift higher, resulting in more milk overall.
