Selection and Management of Beef Replacement Heifers (Part II) Source: University of Arkansas Division of Agriculture Preweaning Considerations Good management of the replacement heifer actually begins before birth. When producing replacement females, cows should be bred to produce offspring with a high level of maternal merit. The cow should be in good body condition at calving, which will result in a thrifty calf and increase the level of colostrum produced. This will improve general thrift of the heifer calf throughout its early life. The suckling heifer should receive adequate nutrition to maintain a body condition score of 5 to
6, which will result in an adequate weaning weight. Excess fat deposition negatively impacts udder development. Consequently, fat heifers have reduced milk production later in life, and this condition should be avoided. Overconditioning preweaned heifers usually comes from creep feeding. Before weaning, heifers should be vaccinated for blackleg (7-way), IBR-BVD, PI3, brucellosis (4 to 12 months of age), leptospirosis and any other diseases your local veterinarian determines necessary. Internal and external parasite control is also important. Selection of Heifers at Weaning At weaning, evaluate each heifer for weight, height, body capacity, structural soundness, health (thriftiness) and other important production traits. Rank the heifers on traits such as 205-day adjusted weaning weight and frame score. If a heifer is structurally unsound, then eliminate her from consideration. Select those heifers with above average 205-day adjusted weights. Take into consideration that heifers that are overly fat at weaning may be uneconomical
as mothers. Select against extreme muscling patterns and frame sizes (large and small). Do not keep heifers that were twinned with a bull. These heifers, also known as freemartins, are usually sterile. Performance records are helpful in determining growth and reproductive potential and in identifying the calves from above average producing cows. It is desired to select heifers from dams that have shown a history of producing a heavy weaning weight calf every 365 days. The old rule of thumb to select the largest and oldest heifers because they will usually reach puberty earliest is still true. It also indicates that these heifers were conceived early in the breeding season, which gives some indication of dam fertility. Managing Heifers During the Weaning Process Weaning is a time of stress, and it is a time when heifer calves can fall behind in their development. A good weaning program can overcome the weight loss and nutritional stress of weaning. To offset the reduction in nutrient intake from depressed intake during weaning, feed supplements should contain a higher concentration of nutrients. Heifers fed good quality hay (11 percent protein and 56 percent TDN, dry
matter basis) will require a supplement ranging from 14 to 16 percent crude protein on a dry matter basis (12 to 14 percent crude protein, as-fed basis) to gain approximately 1 pound per day over a two-week weaning period (Table 2). Weaning or receiving rations can be blended on the farm, custom blended by local feed mills or purchased as commercial weaning rations. Follow the recommended guidelines when feeding weaning rations, in particular, formulated supplements blended on the farm or custom blended. These generally have very little roughage and must be limit fed to prevent digestive disorders. Medicated feed additives are beneficial in weaning rations for stressed calves. Ionophores such as Bovatec (lasalosid) and Rumensin (monensin) help control coccidiosis and improve feed efficiency. Antibiotics such as chlortetracycline or chlortetracycline plus sulfamethazine also help maintain weight gain during periods of respiratory disease challenge associated with shipping fever. If mixing feeds on the farm, medicated feed additives can be either purchased as a concentrated pre-mix or some can simply be added by purchasing mineral mixes containing the desired medicated feed additive. Bovatec, Rumensin and chlortetracycline are commonly available in complete minerals. The example supplements in the table below were formulated with feedstuffs readily available in Arkansas. These supplements were formulated for conditions of free access to good quality hay plus 5 lbs per head per day of supplemental feed over a two-week weaning period. If the calves have not been creep fed, placing hay in the feed bunk with the feed may help adapt the heifers to the feed bunk more quickly. Under conditions of minimal weaning stress, such as fenceline weaning, supplementation may not be necessary if the calves are weaned on good quality pastures.
Table 2. Examples of weaning or receiving rations. aExample 3 would require either ground corn or loose hulls to adequately mix the limestone and mineral.
bDry molasses can be used to enhance palatability. Liquid molasses has the added benefit of reducing feed dustiness.
cThe mineral level used in these examples assumes a 4 oz intake. Most mineral mixes contain the maximum level of selenium that can be added to provide 3 mg per head per day; so follow the intake/mixing guidelines when adding minerals.
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