Planning for a Prolonged, Dry Spring

Dr. John Arthington
UF/IFAS Range Cattle Research & Education Center

I keep hearing about the dry winter and spring we are expected to experience in the coming months. Have you heard this too? If this is true, and it is already looking like it is, then we are potentially headed for a very difficult start to the new production year.

Our previous winter (2009/2010) will be remembered for the excessive and prolonged cold-events that we experienced. We have all been concerned about reduced pregnancy rates in our herds as a result of that difficult winter. Fortunately, most of the reports I have received (our Station herd included) have found pregnancy rates reduced, but not as much as we might have originally expected. I fear, however, that although we were fortunate to get most of our cows pregnant, many became pregnant late in our breeding season. These cows will calve late this year and thus will have fewer days to become pregnant during the current breeding season. Therefore, this is the time for us to be focused on reducing the period of post-partum anestrus in the cowherd to be certain that the majority of late-calving cows have an opportunity to become pregnant in the current season and produce a calf next year.

By the time you read this, it will be early January. I hope, but sincerely doubt, that our dry conditions have changed by that time. I am preparing this document, however, to provide some management options for us to consider when dealing with the current drought - both now and over the coming months. These options are based on a couple expectations, which encompass most production systems in Florida. Thus, I assume that at this time we are now calving or just finishing calving and we are getting ready to begin the breeding season. Under this scenario, it is our foremost goal to make sure our cows are returning to estrus. A prolonged period of anestrus can be particularly damaging to overall pregnancy rates, especially in this year’s late-calving cows. The two most influential factors impacting post-partum anestrus in beef cows are, 1) nutritional status, and 2) calf presence.

Most herd managers have an understanding of the average amount of supplemental winter nutrition required in their production systems. Feed costs account for as much as 70% of the total costs associated with producing a calf. It is not surprising, therefore, that management considerations that optimize the efficacy and efficiency of winter supplement utilization are critical to overall performance and cost of a beef production system. To start, consider which supplemental feeds are appropriate. Are needs related to deficits in energy or protein? Typically the answer is both; however, energy deficits almost always make up the majority of need as measured by the total pounds of supplement purchased. Nevertheless, producers should always attempt to satisfy the protein requirement before energy is provided. Cows are unable to fully utilize supplemental energy if protein in the diet is inadequate. An example of this concept is apparent with the use of citrus pulp as a supplemental energy source for Florida beef cows. Citrus pulp is high in energy, but low in protein. Some producers have attempted to utilize significant amounts of citrus pulp in an attempt to overcome winter forage shortages. Without the addition of supplemental protein, this supplementation strategy has proved self-defeating. Research has shown that voluntary forage intake and utilization are increased when citrus pulp-supplemented cows are also provided a source of additional supplemental protein.

Depending on the location in the state and local pasture conditions, we usually know approximately how much and for how long we will need to provide supplemental feed to our cows. In this current winter it will be particularly important to maximize our supplementation investment early in the calving season. This is not a time to accept shortcuts – particularly in a dry year with late calving cows. We want to maximize the front-end investment in supplemental feed to make sure our cows are not losing too much body weight after they calve. Lactating cows in a decreasing plane of nutrition will almost certainly have extended periods of post-partum anestrus. We can combat this by making certain that adequate nutrition is offered at this critical time. This isn’t always as easy as it may sound. A moderate frame beef cow, losing 1 lb of body weight daily will need over 6 weeks to show a visual reduction of 1 body condition score. We may have already caused a prolonged period of anestrus by the time that we visually recognize that we have a problem. This year, we should place particular emphasis on supplemental nutrition early in the calving season. If the dry winter extends into the late spring, after the breeding season (May/June), which is a likely possibility, then we might be able focus our supplemental nutrition savings at that time. Yes, the cows will likely begin losing weight as we await the early summer rains, but this weight loss will not impact post-partum anestrous or the ability for cows to become pregnant.

The second factor that influences post-partum anestrus is calf presence. Research has shown that the physical presence of the calf will lengthen cow post-partum anestrus. Therefore, management practices that temporarily or permanently separate cow and calf pairs will help to induce estrus in post-partum anestrous cows – even in many cows that are experiencing anestrus due to a lack of body condition. This is typically achieved by a single, temporary 48-hour calf withdrawal period. However, our research has recently shown that multiple 48-hour calf withdrawal periods can be more effective than a single occurrence, particularly in thin, first-calf heifers. Temporary calf withdrawals can be achieved by separating calves from cows and confining them in a secure area for a period of 48 hours. A source of good quality, fresh hay and clean water should be available to calves during this time.

Along the same consideration, this winter may be an excellent time to try early-calf weaning. We have been advocating early weaning in young or low-body condition cows for a number of years. Calves can be successfully weaned from their cow at any time after about 70 days of age. The removal of the calf creates a physiological response in the cow that initiates cyclicity, even when the cow is in less than optimal body condition. In addition, early permanent weaning has advantages over temporary weaning in that once lactation ceases, the cow’s voluntary forage intake will reduce by about 25% allowing forage resources to extend further during times of limited availability. Once early weaned, there are several options for managing the calf, including; 1) sell at the time of early-weaning, 2) graze on dormant perennial pasture with free-choice access to a complete grain-based mixture containing 18 to 20% crude protein, or 3) graze on winter ryegrass with supplement (16 to 18% crude protein) provided at approximately 1% of body weight. Many Florida producers have begun using early weaning management systems in their cowherds, especially young cows, with considerable success.

In summary, the extreme cold winter that we experienced last year has resulted in many of our cows breeding late and thus calving later in the current season. This winter it will be particularly important that we focus on getting our cowherd re-bred as soon after calving as possible. This can be assisted by focusing on reducing the period of post-partum anestrus. Two options that should be considered include; 1) optimizing supplemental energy and protein nutrition early in the calving season, and 2) utilizing temporary (48-hour withdrawal) or permanent (early-weaning) cow/calf separation systems.