The Cow-Calf Manager

Livestock Update, February 2005

John B. Hall, Extension Animal Scientist, Beef, Virginia Tech

Deja vu All Over Again
With poor hay quality and tough winter weather, the winter of 2004-2005 looks a lot like last year. In the immortal words of Yogi Berra, "It's deja vu all over again". The same problems that resulted in more open cows in fall 2004 have reared their ugly heads again.

Poor hay
Last year's first cutting hay was just as poor in quality as the year before. Much of the 1st cutting hay sampled and tested this year is deficient in energy for cows in late gestation (2-3 months before calving) and early lactation. In addition, fiber levels in these hays are high enough to prevent cows from consuming extra energy by eating more hay. Producers should test their hay to design supplementation programs or assume 1st cutting hay needs supplementation.

Bad winter weather?
Overall the winter hasn't been too bad right? December was warm, but very wet. Wet cattle need to start to expend energy to keep warm at much higher air temperatures than dry cattle. Table. 1 shows the lower critical temperature (the temperature below which a cow will use extra energy to keep warm) for cattle based on coat type. Notice that in our wet December, it had to be very warm (<50°to 60°) for cattle not to need extra energy.

January has been cold and windy, but drier. There have been multiple nights when wind chills have been from 0° to -15°, especially in the western mountains. So in both December and January cows needed more energy to keep warm and maintain body condition.

Table 1. Lower Critical Temperature (LCT) for cattle depends on coat condition.

Coat Description	Lower Critical Temperature (°F)
Summer or wet	59°
Fall	45°
Winter	32°
Heavy winter	18°

From Marsten et al., 1998

Research from Kansas and Iowa indicates that maintenance energy requirements of the cow increase by 1% for each degree below the LCT (Table 2). For wet cows, the rule of thumb is 2% of every degree below LCT. So energy requirements of cows in January are normally 10 to 20% above what is expected. These past few weeks with cold temperatures and high winds, energy requirements were 25% above expected. Unless producers compensated by feeding more energy in the form of grain or by-products, cows lost body condition.

Table 2. Percentage of Increased Energy Needed per Degree of Temperature Below Lower Critical Temperature.

	Cow Weight (lbs)
	1,000	1,100	1,200	1,300
Coat type	Percentage increase in energy req. per degree below LCT
Summer or wet	2.0	2.0	1.9	1.9
Fall	1.4	1.3	1.3	1.3
Winter	1.1	1.0	1.0	1.0
Heavy winter	0.7	0.7	0.6	0.6

From Ames, Kansas State University

Poor body condition puts breaks on reproductive system
Losing body condition in late gestation has a negative effect on calf vigor and cow reproduction. Cows in poor body condition will be delayed in the resumption of estrous cycles after calving. The beef cow's body has built in "sensors" that relay information about cow body condition and nutrient supply to the centers of the cows brain that control reproduction. Although all the sensors and messengers are not fully understood, research from several states indicates that energy availability is the critical factor. Energy availability includes cow body fat stores as well as energy in the diet.

Cows in low body condition score (< 5) may be 90 to 120 days post-calving before they have their first heat. Cows in extremely poor condition (BCS < 3) may not resume estrous cycles until calves are weaned or they gain 100 to 150 lbs. As a result of poor body condition at calving or breeding, pregnancy rates for cows with BCS < 5 will be lower than cows in good condition (Table 3). All beef producers should body condition score their cows immediately. For information on body condition scoring cows see VCE Publication 400-795. Producers can use the herd's cow body condition scores to plan management strategies.

Now is the time to get cows back into shape, before calving. Increasing body condition before calving is much better for the cow and calf than trying to increase body condition after calving. After calving, the cow's system is geared towards milk production, so extra energy results in extra milk but little increase in body condition.

Table 3. Effect of Body Condition Score at Calving on Cumulative Pregnancy Rates

		Day of the Breeding Season
	BCS	20 d	40 d	60 d
Mature Cows (Richards et al., 1986)		Cumulative % Pregnant
	¾ 4	41	67	84
	„ 5	51	79	91
First Calf heifers (Spitzer et al., 1995)		Cumulative % Pregnant
	4	27	43	56
	5	35	65	80
	6	47	90	96

Feeding cows now
So how does this change how producers should feed cows? In normal January and February conditions, cows will need an additional 3 to 4 lbs of hay OR 2 to 2.5 lbs of grain. For all practical purposes, cows fed free choice amounts of good quality hay will compensate on their own. However, if limited amounts of hay are fed or hay is of poor quality (like this year!) then 2 to 2.5 lbs of grain or by-products should be fed per cow. Cows that do not receive extra energy will lose 0.5 to 1 lb per day.

In extremely cold or wet conditions, cows will need to eat 7 to 8 more pounds of hay OR 4 to 5 lbs of grain. In most cases, cows will not be able to eat another 8 lbs of hay per day unless hay is very good quality. In these extreme weather cases, cows should be fed the additional grain or by-products during the period of cold stress. Cows that are not fed additional energy can lose 1.5 to 2 lbs per day during extreme conditions.

Fescue and orchardgrass hays produced in Mid-Atlantic are rarely deficient in protein. However, this year may be the exception. Hay made in late June or July may not contain enough protein. Care should be taken to test hays for protein before supplementing protein. Overfeeding protein is expensive and can cause cows to lose weight (ie. The Atkins diet for cows).

There are many good sources of energy available in the Mid-Atlantic States corn and barley are the best and cheapest grains available. By-products such as corn gluten feed, soy hulls, wheat mids, and brewer's grains provide energy and protein. Often these by-products are the best choices since they provide both nutrients and are relatively in expensive. Soybean meal is the most common protein supplement.

Pay now or pay later
So, body condition score your cows now and change your feeding program if needed. With all the hay we have this year, many producers are reluctant to spend money on supplements. However, failure to employ management strategies to increase energy intake and body condition before calving will result in weak calves this spring and too many open cows this fall.

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