Many are either in the midst or soon to be in the middle of spring calving. Hopefully your cows have been well prepared for the changes that face cows entering lactation. While it can sometimes be a mindless exercise in repeating the same things year after year, there are a couple of changes that may have taken place within your herd that has crept up on you over the years and negatively impacted reproductive performance and overall profitability. Two of these factors are;
1. Mature cow size
2. Milk production
Both of these factors can dramatically impact nutrient requirements and they could easily have happened without you realizing it through genetic selection.
Before we get to either cow size or milk production, let’s first touch on the impact that simply moving from gestation to lactation has on nutrient requirements. This dramatic change in physiological state of the cow is the driver for many cow-calf operations to shift their calving further into the spring. Calving on green pastures provides much higher nutrition more closely aligned with increased cow requirements associated with milk production. Many have fought through calving earlier when forages are dormant and much of the diet has to be delivered to the cow-herd. This can cost you a fortune when compared to simply supplementing spring pastures with key nutrients rather than trying to deliver huge energy supplies in the form of high quality forages, silage or grains.
So, what do we mean when we say that nutrient requirements go up from late stage gestating cows to once they have calved and are producing milk? Let’s take a 1,400 pound cow with average milk (20 pounds peak milk per day). During the last 3 months of gestation she requires approximately 14.4 pounds of TDN which moves to 17.6 pounds in early lactation. This is an increase of 23% for her energy needs, primarily driven by lactation demands. This may seem dramatic enough but when we look at protein, the increase is even more pronounced. During gestation this same cow requires 2.15 pounds of crude protein, but in early lactation her requirements increase to 3 pounds of protein. A whopping 40% increase in protein requirements! And we haven’t even gotten to the two other longer-term factors that more than likely have impacted nutritional needs by your cow herd.
Mature Cows’ Nutrient Needs
Let’s first look at what larger cows mean for nutrient needs as shown in Table 1. There is overwhelming evidence that average mature cow weights have been increasing for a number of years. When milk is held constant and cows can increase their intake, they have the ability to compensate for the additional requirements needed for both energy, i.e. TDN and crude protein (CP) by eating more. A very decent quality forage with minimum values of 58% TDN and 10% CP (Table 1) could support cows that vary in weight from 1,200 to 1,600 pounds. If cows are short on the energy side they can offset the shortfall with mobilizing body condition for a period of time to help maintain milk production.
The effects of larger mature cow weight in a beef herd has its most significant impact on total feed requirements of the herd (intake) as opposed to the quality of feed that is needed. You’ll simply need more acres to compensate for larger cows. If you are restricted to only low quality forages, that now becomes a problem and additional supplementation will be required. If hay quality is adequate to meet nutrient requirements, then moving from a 1,200 pound cow herd to 1,600 pound cows will require nearly 25 more tons of feed for a 100 cow herd fed for 90 days after calving.
Just to put that in perspective, 5.4 pounds of additional forage valued at 5 cents per pound is 27 cents more per day per cow. That’s over $24 per cow for a 90 day feeding period. So, think back to what you were putting up for hay and how much pasture you needed 10 or 20 years ago compared to today for similar cow numbers. It’s probably safe to say that what you provide today has increased.
Probably a more concerning factor affecting nutrient requirements of beef cow herds after calving is where your genetics program and selection have taken milk production (Table 2). Increasing milk production generally will result in significant increases in both energy but even more importantly in crude protein requirements. For example, if you are meeting protein requirements for a 1,400 pound cow with low milk output and consuming 27.9 pounds of dry matter, you would need roughly an 8% CP forage (Table 2). If you feed that same forage to cows that are producing on the high end or 30 pounds of milk at peak and let the intake rise to the 33 pounds as indicated, you will still be short roughly 1 full pound of CP. The same can be said for energy where a 55% TDN forage will meet low milk requirements but consumed at 33 pounds you would still be short over 2 pounds of TDN to achieve the high milk requirements. What this means is that higher quality diets must be fed to ensure nutritional needs are met for high milking beef cows. They simply cannot adjust their intakes high enough to compensate for lower quality diets that can meet lower milk needs. So, with milk comes a higher quality diet along with increasing intake.
These examples are meant for you to look at the impact of:
1) What moving from gestational requirements to lactation can mean
2) How larger cow size affects intake/quantity of forage
3) How increasing milk genetics have over a longer term, likely impacted your herd’s nutritional needs
These may have happened in steps that from year to year were not very noticeable and even undetectable. But when you look at a span of 10, 20 or even 30 years, what does your herd look like today? How are you feeding them today? Are you managing them to spring pastures to help with providing increased energy and protein for early lactation? Are you saving your better forages to meet late gestation and lactation needs? Are you focusing on a complete protein supplement to make sure you get all that you can from the forage base that is already paid for as well as meeting the increasing protein requirements due to advancing milk genetics?
These are some things to think about as you’re staying up late during calving and reasoning through why nutritional demands may be higher today compared to yesterday.
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