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Previous issues of the BEEF Cattle letter
Issue # 671
January 27, 2010
Winter Environment and Nutrition - Rory Lewandowski, Extension Educator, Athens County, Buckeye Hills EERA
Cold temperatures, wind chill, snow, freezing rain, and mud are all terms that come up at some point in describing our winter weather here in Ohio. The cattleman needs to pay attention to the terms because they play a role in determining the nutrient requirement of cattle. Specifically these conditions increase the energy requirement of cattle, can reduce the efficiency of utilization of dietary energy, can decrease voluntary intake, and can change cattle behavior.
As temperature falls below a critical level, the cow must increase energy intake to maintain body temperature and basic body maintenance functions. Cattle have a comfort zone of 59 to 77 degrees F. that is considered optimum for body maintenance, animal performance and health. At temperatures lower than the comfort zone, that is, below 59 degrees F, the animal can make use of a thickening hair coat and heat from normal tissue metabolism and rumen fermentation to conserve body heat without any increase in energy intake requirements. This is known as the thermoneutral zone. The lower boundary of this zone is referred to as the lower critical temperature (LCT). Below the LCT, animal metabolism must increase to provide adequate heat to maintain body temperature. This can be accomplished through increased energy intake. The general rule of thumb is that energy intake must increase by 1% for each degree of cold below the LCT. The LCT is usually described by the coat description of cattle as in the following table:
Lower Critical Temperatures for Beef Cattle
|Coat Description||Degrees F|
|Summer (or wet)||59|
Note that once the coat is wet, regardless of how heavy it is, the lower critical temperature increases to 59 degrees F. Dry, cold weather is easier on cattle than cool wet weather. Wind speed produces wind chill and can further increase energy requirements for cattle when those values are below the LCT. The following chart provides wind chill values at various wind speeds when combined with a range of ambient temperatures:
Temp., Degrees F
At this point, let's take a look at some examples of how winter temperatures can affect energy requirements. Consider a 1200 lb cow in late gestation with a 10 degree air temperature and a 10 mph wind on a dry day. The cow has a moderately heavy winter coat, providing a LCT of 20 degrees F. The wind chill value is -1 degrees F. According to NRC nutrient requirement tables, this cow requires a TDN concentration of about 56% in her diet or 13 lbs of TDN per day within the thermoneutral zone. Providing a 56% TDN hay with an intake between 1.9 to 2.0 percent of the body weight in dry matter will meet this energy requirement in terms of pounds of TDN required. The -1 degree wind chill temperature is 21 degrees below the LCT of the thermoneutral zone. Following our general thumb rule, energy intake must increase by 21%. This cow must consume an additional 2.6 lbs of TDN (15.6 lbs total) to maintain body temperature. This additional energy requirement can be met in two ways. Either the intake of the current feedstuff must increase so more total energy is consumed, or a feedstuff with a higher nutrient density can be provided.
Hay with a TDN value of 56% is low quality forage. To get an intake of 15.6 lbs of TDN from this forage the cow will need to consume this hay at about 2.4% of her body weight. Is this realistic? If total dry matter intake is to remain at about the same number of pounds, the energy concentration of her diet must increase to a TDN level of about 66.5%. Another way of meeting this need is to add about 2.5 lbs of shelled corn with a TDN value of 88% to the ration. This, along with a hay intake of about 2% of body weight of the 56% TDN hay, will provide the added energy that is needed.
Now, what happens if the air temperature is 35 degrees F with a freezing rain and no wind? The insulating ability of the coat is lost because of the rain and the CLT is 59 degrees F. The cow requires a 24% increase in energy intake to maintain body temperature. As in the first example, this additional energy requirement will have to be met through either an increased intake of whatever feedstuff is being provided or through the addition of some higher energy density feedstuff, such as shelled corn.
In real life, practical terms there are very few beef farmers that are constantly monitoring the weather, thinking about lower critical temperature and adjusting the ration for daily weather fluctuations. Those increased energy requirements that adverse winter weather brings are handled in a number of ways including: providing forage that has more than the minimum required nutrient density. This forage could be stockpiled grass, hay, or a combination of the two. The key is that it is more than just the minimum nutrient density. In a free-choice situation, the cow is likely consuming more than the minimum pounds needed to meet nutrient needs. The cow is able to self-regulate to some extent, her nutrient needs with regard to weather conditions. Cows in a pasture situation may also change their behavior instead of changing intake. For example, they may seek shelter on the side of a wind break to avoid the full effect of a wind chill.
In the event of a predicted longer-term adverse winter weather condition, for example, a week or longer spell of temperatures in the 5 to 10 degree range, the cattleman may want to provide some higher energy in the ration. This is most important when low quality forages are being provided, because the nutrient density is low and they provide limited potential for increased intake. This is another example of why the cattleman should use forage testing to know the nutrient level of hay that is being fed.
A final winter condition that beef cattle managers must be aware of is mud. As in the case with rain, mud reduces the insulating ability of the hair coat, leading to a need for increased energy. In addition, there is research that suggests that mud may decrease feed intake in the 15% and up to 30% range. In an Oklahoma Panhandle Research and Extension Center beef cattle research update from January of 2007, there is a table that lists mud at 4-8 inches deep as decreasing intake by 15% and mud at 12-24 inches deep decreasing intake by 30%. Thus the worst situation for cattle is cold stress combined with mud.
Winter provides challenges for both the beef cow and the cattle manager. Understanding the effects of winter weather conditions upon cattle nutrient requirements combined with the knowledge of the nutrient content of the feedstuffs being provided to the cow herd can help the manager to better care for the cows, and maintain potential profitability.
Crossbreeding - Its Cool Again! (Part 2) - Dr. Scott P. Greiner, Extension Animal Scientist, VA Tech
Part 1 of this series dealt with the fundamental principles of crossbreeding. The primary advantages of crossbreeding beef cattle are heterosis (hybrid vigor) and breed complimentarity. The power of crossbreeding results from the advantages of the crossbred cow, due to her advantages in fertility, weaning weights, and longevity. In fact, 60% of the advantage of crossbreeding is realized through the crossbred cow. In addition, individual heterosis exhibited in the calf results in increased livability coupled with an increase in growth rate. Breed complimentarity provides the opportunity to capture the strengths of various breeds, and enables selection of individual animal within those breeds for specific purposes. The key element to the success of any crossbreeding program lies in its application. This article will focus on the design and management of crossbreeding systems, with specific attention on the application for small and modest-sized herds.
The success of a crossbreeding program will depend on its simplicity and ease of management. There are several factors and challenges that need to be considered when evaluating choice of crossbreeding system, including:
The design of any crossbreeding program should take advantage of both heterosis and breed complimentarity. The goal of a crossbreeding program should be to 1) optimize heterosis in both the calf crop and most importantly in the cow herd heterosis), 2) utilize breeds and genetics that fit the feed resources, management, and marketing system of the operation, and 3) is easy to apply and manage, and is sustainable over time.
Two-Breed Rotational Cross: The two-breed rotational cross or criss-cross is a relatively simple and popular form of crossbreeding. In this system, two breeds are mated and the resulting female offspring are kept as replacements and mated to one of the breeds. In following generations, females are bred to the opposite breed of their sire. For example, with an Angus and Simmental were two-breed rotation, cows sired by Angus bulls would be mated to Simmental bulls and cows sired by Simmental bulls would be mated to Angus bulls. For their entire lives, females would be mated to the bull breed opposite their sire. This system would require a minimum of two breeding pastures (if only natural service is used), one for each breed of sire- and cows need to be identified by breed of sire. A critical component for this system is that the two breeds utilized must be reasonably compatible in biological type. Both breeds must be suitable as both sire and dam breeds. The two breeds utilized in this system should be similar in mature size, and individual bulls selected to avoid large differences in birth weight, milk production, and cow size/nutritional requirements from one generation to the next (addressed in Part 3 of this series). Breed of choice when mating first-calf heifers is warranted, as calving ease needs to be a primary consideration. An advantage to this system is the use of the crossbred cow, with pounds of calf weaned per cow exposed increased approximately 15% compared to the average of the breeds used in the cross. Over several generations, 67% of the maximum amount of heterosis is realized. Additionally, there are a large number of heifers from which replacements may be selected.
The addition of a third breed as a terminal sire to a two breed rotational cross system can further enhance the system. In this rota-terminal system, approximately 50% of the cowherd is mated to the terminal sire breed (different breed than used in the two-breed rotation) with the resulting offspring all marketed (no replacement females retained from resulting mating). The other 50% of the cowherd operates as a two-breed rotation as outlined above. The two-breed rotation functions to produce all replacement females for the herd. Terminal sire breeds should be selected for calving ease, growth rate and carcass merit. Selection emphasis should concentrate on maternal performance, appropriate mature size, and longevity for the two breeds used to produce replacements. These selection criteria may simplify bull selection, and enhance the opportunity to specifically match genetics for their intended purpose. Older (> 4-5 years) and poorer producing cows are the best candidates for mating to the terminal sire. Younger cows should be genetically superior due to selection and should be used to produce the replacement females. The rota-terminal system has been shown to increase pounds of calf weaned per cow exposed by approximately 20%. Maximum heterosis is realized in the calves sired by the terminal breed, and advantages in maternal heterosis are realized as all females are crossbred. The rota-terminal system requires more management in that a minimum of three breeding pastures are required (assuming all natural service). Additionally, less selection may be practiced on potential replacements, as a larger percentage of the eligible heifers must be retained to maintain herd size. The rota-terminal system is difficult to apply herds with less than 100 cows.
Rotating Breeds of Sire: Rotating the breed of sire every three to four years may be a feasible crossbreeding option for producers who have small, single-sire herds. With this type of system two sire breeds are used in rotation by replacing sire breeds every three to four years. A greater number of breeds may be utilized over an extended period of time. In single sire herds, bulls may need to be replaced more frequently to avoid father-daughter matings. This system is relatively simple yet maintains an acceptable level of heterosis. Pounds of calf weaned per cow exposed is increased 10-15%, dependent upon the number of sire breeds used.
Utilizing Hybrid Bulls: The use of hybrid or composite bulls is another strategy to incorporate crossbreeding. Properly designed and selected composite bulls blend the strengths of the breeds utilized to form the composite. Advances in statistical methodology allow for direct comparison of EPDs published for composite bulls with EPDs published for purebred bulls of the same breed. In other words, we have the same selection tools at hand to properly select composites just as we do purebreds. One of the challenges with the use of purebreds in a crossbreeding scheme is the fluctuation in breed percentage of the cow herd resulting from females sired by different breeds (particularly early in a crossbreeding program). Composite bulls offer the opportunity to avoid this, while potentially reaching a desired breed mix in fewer generations. For example, assume the goal is to achieve a herd with 75% British and 25% Continental genetics. Starting with a straightbred British cow herd, achieving the desired 75:25 breed mix would require two generations with purebred bulls, and only one generation with half-blood composite bulls. Research has established that variation composite populations is not greater than that found in purebred populations. Additionally, heterosis realized through the use of composites is retained in future generations when the same composite is used over time.
A major challenge to making a crossbreeding program work is keeping the system going over time, i.e. keeping the system well-planned and systematic without sacrificing optimum levels of heterosis and breed complimentarity. Purchasing of replacement females and the incorporation of an AI program are two means to assist with these challenges and have particular application for small herds.
Purchasing Replacement Females: The simplest, most manageable crossbreeding system utilizes purchased crossbred females mated to a third terminal sire breed. All calves are marketed in the system. Optimum heterosis can be realized in the cow, as well as the calf crop. There are several advantages to this system, especially for small cow herds. First of all, management becomes simplified as heifers no longer need to be grown, developed, and bred. Bred females may be acquired, which have been confirmed pregnant to highly proven bulls for calving ease and other economically important traits. Secondly, bull selection is simplified since these terminal sires will be not be mated to heifers, and maternal traits are not of interest. Sire selection can focus specifically on acceptable calving ease, and optimum growth and carcass merit. Additionally, only one breed of sire needs to be maintained. Remember that the health program, as well as the genetic package are both acquired from the heifer supplier. Of utmost interest is the economics of raising vs. purchasing replacement heifers. For many producers, purchasing females may be cost effective, especially when the contribution of the heifers to genetic progress of the herd is considered.
Use of Artificial Insemination: The use of artificial insemination may make the application of these described crossbreeding systems more feasible provided the expertise, labor, and facilities are available to make effective use of AI. The use of AI can significantly reduce the number of breeding pastures necessary for rotational cross or rota-terminal systems. Additionally, the use of AI may significantly reduce the number of bulls (and breeds) required for natural service. As an example, in a rota-terminal system the top 50% of the cows could be mated AI for the production of replacement females. Cows that did not conceive AI as well as the other 50% of the cows could be mated naturally to the terminal sire. This would reduce the number of breeding pastures required from three to one or two (depending on cow numbers). Additionally, in any system heifers could be bred AI to calving ease sires. Another major advantage to the use of AI is genetic improvement, as semen from top bulls in any breed could be utilized.
Improved productivity and efficiency is realized in commercial herds not only through a crossbreeding program, but also through sire selection. A well-implemented crossbreeding program does not diminish the importance of sire selection. In fact, appropriate sire selection is the key to making the system sustainable. In Part 3, we will examine more closely the importance of sire selection, and describe tools to use to make both across and within-breed selections.
Weekly Roberts Agricultural Commodity Market Report - Mike Roberts, Commodity Marketing Agent, Virginia Tech
Politics may soon come in to play in the commodity markets. Pressure from President Obama's bank plan could lead to reduced participation by the large hedge funds in the commodity markets if implemented. These funds typically take long positions. Is that good or bad? I don't know. Is that politics? Yes.
LIVE CATTLE futures on the Chicago Mercantile Exchange (CME) ended down on Monday. FEB'10LC futures closed down $0.425/cwt at $86.200/cwt but $1.150/cwt higher than two weeks ago. The APR'10LC contract finished at $90.175/cwt; off $0.375/cwt but $0.950/cwt higher than last report. Friday's USDA Cattle on Feed report was considered somewhat bullish even though supplies were at a 7-year low and an 11-year low for December and offset by better-than-expected marketings. On-feed supplies were put at about 11 mi head (98% of last year); placements at 1.5 mi head (94% of last year); and marketings at 1.7 mi head (104% of last year). Cash cattle prices were higher than expected. Packers still in the black were supportive. However, this was not enough to overcome higher feed prices, higher than expected marketings, and higher than expected placements. According to several floor sources placements should have been down another 0.5-1.0 %. Maybe prices will ameliorate for producers in a few months when these cattle clear the pipeline? Cash cattle were $0.50-1.00 higher in Texas on Friday with USDA putting the 5-area average on Monday at $84.91/cwt. USDA on Friday put the choice boxed beef cutout at $143.21/cwt; off $0.67/cwt but $1.11/cwt higher than week before last. According to HedgersEdge.com, average packer margins were raised $11.25 from last report to a positive $37.35/head based on the average buy of $84.73/cwt vs. the average breakeven of $87.52/cwt. Wait to price feed inputs. Relief is just around the corner.
FEEDER CATTLE at the CME finished lower on Monday with deferreds near even. JAN'10FC futures closed at $96.525/cwt; down $0.575/cwt but $0.250/cwt higher than week before last. MAR'10FC futures finished at $98.775/cwt; off $0.825/cwt but $2.375/cwt higher than two weeks ago. The MAY'10FC contract was off $0.650/cwt at $100.550/cwt but$ 2.225 cents over last report. Live cattle selling influenced feeder futures. In addition, the January and March price skid tripped sell orders resting below the market. Profit taking and deferred month's premiums to the CME feeder cattle index also pressured prices. Friday's USDA Cattle on Feed report and lower corn prices were supportive. Cash feeders in Oklahoma City were steady to $2/cwt higher on good demand. The CME feeder cattle index for January 21 was placed at $97.22/lb; down $0.20/lb but $2.32/lb higher than last report. Good feed and feeder prices are just over the horizon.
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