By: Levi Trubenbach, Ph.D., Livestock Nutrition Center
As we approach the end of a summer season with relatively (historically, in some areas) dry conditions across much of our serviceable area, we have been receiving more calls than normal about supplemental feed for the cow herd. As always, our answer to the basic question, “What and how much should I be feeding my cows?” is straightforward – it depends.
Nutrient balance in a cow herd is an ever-moving target that seems to continuously wander around as forage conditions and production cycles change across the year. However, we focus on a science-based approach, quantifying both nutrient intake and requirements in real-time, to determine what and how much cows should be supplemented at any given time.
In a normal year, we typically think about supplemental feed being required at the first frost, when forage protein falls below an optimal threshold, at calving, as we approach a cow’s greatest nutrient requirements. However, this year’s dry conditions – and subsequently poor forage quality will soon lead to deficiencies in nutrient intake and body condition loss if not corrected.
Our method for quantifying forage quality (Figure 1) using a 1-5 scale helps us accurately estimate nutrient intakes.
In years with normal rainfall and temperatures, forage during August and September can often be described by, “3,” on the LNC Forage Quality Scale (FQS). For both fall- and spring-calving cows, a FQS of 3 is mostly sufficient during this season. For fall-calving herds, a FQS of less than 3 (approximately 7.5% CP, 45 Mcal NEm/cwt; Figure 2) will typically require significant supplementation during this period, as requirements due to calving increase with fetal development. Spring calvers may be able to manage adequate body condition during early fall on FQS of 2 (6.0% CP, 41 Mcal NEm/cwt; Figures 3 and 4), but if conditions worsen only slightly, nutritional intervention may be required.
Aside from supplemental feed, we have also been recommending early weaning as a strategy for managing dry conditions for a couple of reasons. First, removing calves can alleviate significant grazing pressure. Calves can consume 1.5% of their body weight in forage; additionally, dry cows eat less than lactating cows. For each pair, the total forage conserved by early weaning could be as high as 25-30% of projected intakes. Secondly, removing the demands associated with milk production takes significant pressure off the cow herd when the nutrient balance is being challenged. Not only does milk itself require significant nutrient contributions, but also the physiological processes associated with making that milk increase maintenance energy requirements in the cow by approximately 10%. Overall, early weaning can reduce daily energy requirements by up to 40%.
Because production systems and forage conditions vary so dramatically across our serviceable area, developing a generic recommendation for, “what and how much,” to feed is impossible. For support in developing an optimal drought strategy specific to your program, please contact a sales consultant at one of our LNC locations.