COMMODITY: BEEF

TITLE: Reproductive and Maternal Performance of Crossbred Cows

CONTACT: Dr. Sid DeRouen, Animal Scienitist, Hill Farm Research Station (318) 927-2578

TAKE HOME MESSAGE: Pregnancy rates for first exposure Brangus- (BA) sired heifers were lower than F₁ Brahman x Hereford (BH), Angus- (A), Gelbvieh- (G), and Gelbray- (GB) sired heifers. Overall production efficiency (measurement of fertility, maternal ability, and cow weight) was lower for first-calf BA heifers. A higher success of rebreeding and maternal performance was achieved when first calving at 2½ years of age compared to first calving at 2 years of age. Pregnancy rates were similar among breed types for mature cows. Maternal performance and production efficiency for mature BH cows were superior to A-, BA-, and GB-sired cows, but were similar to G-sired females.

PROBLEM / TOPIC: Crossbreeding is widely recognized as a means for improving productivity through the exploitation of heterosis and combining desirable traits from different breeds. For the majority of producers, with cow herds of 100 animals or less, traditional crossbreeding systems may not be feasible. In this study, female productivity was evaluated for F₁ Brahman-British, straightbred-sired, and composite-sired females that varied in percent Brahman inheritance. In addition, British (Angus) and Continental (Gelbvieh) sire breeds were evaluated along with their Brahman derivative counterparts (Brangus and Gelbray) for production of replacement females.

ACTION: Total of 606 reproductive and 362 calving records were evaluated from 1994 to 1998. The mating scheme included exposing BH cows to A, BA, G, or GB sires to produce the crossbred females. In addition, contemporary BH weanling heifers were purchased to compare productivity. After weaning, heifers were developed on a forage-based diet. Heifers were exposed during a 60-day spring breeding season to first calve at either 2- or 2½-years of age. Cows were exposed during a 60-day spring breeding season. Calves were weaned in late September of each year at an average age of 210 days and non-pregnant females were culled from the study at this time.

IMPACT: Pregnancy rates for first exposure heifers were similar and acceptable when bred as yearlings. BA-sired heifers, however, had lower pregnancy rates (P < .05) than the other four breed types when exposed at 1½ year of age. This resulted in lower (P < .05) overall fertility for BA-sired heifers at first breeding. Rebreeding rates of first-calf heifers were similar (P = .18) among the five breed types. For age at first calving, rebreeding rates were 14% higher (P < .03) for 2½ year olds compared to 2 year olds. Rebreeding rates were similar by breed type for mature cows. Body weight of cows did not vary ( P = .26) among breed type; however, A-sired cows were 86 to 156 lb heavier than the other breed types. 205-day calf weaning weight for first-calf heifers were similar among breed types. Heifers calving at 2½ years had 25 lb heavier (P < .01) weaning weights compared to heifers calving at 2 years. Furthermore, production efficiency for 2½ year old heifers was greater (P < .01) compared to 2 year olds. Overall production efficiency was lower (P < .05) for first-calf BA-sired heifers compared to the other breed types (due mostly to poor fertility). Calf weaning weights for mature BH cows were heavier (P < .08) compared to A-, BA-, and GB-sired cows, but were similar to G-sired cows. Similar rankings were observed for mature cows among breed types for production efficiency.
 

COMMODITY: BEEF

TITLE: Replacement Heifer Development

CONTACT: Dr. Ron Del Vecchio, Beef Specialist, Cooperative Extension Service (225) 388-2219

TAKE HOME MESSAGE: Age at puberty is an important production trait. The significance of making sound management decisions when developing replacement heifers cannot be underestimated. Economically, reproduction is estimated to be approximately five time more important than growth performance and ten times more important than product quality (e.g., carcass quality). Furthermore, nothing has a greater impact on continued reproductive performance/success of the entire cow herd than proper development of the replacement heifer. A heifer managed to first calve 20 days earlier than the average of the herd can result in a $28.00 increase in the value of her calf.

PROBLEM / TOPIC: Historically, beef heifers were first bred as two-year-olds to calve for the first time at three years of age. As production systems intensified more producers now breed their heifers as yearlings to calve at two years of age. Heifers that start calving as two-year-olds and drop their first calf early in the season will produce more calves during their lifetime than those that first calve as three-year-olds or calve late in the season. Such practices can translate into increased efficiency of the cow herd and more pounds of weaned calf per cow. Two major challenges facing producers are: 1) to get yearling heifers cycling and ready to breed by the start of their first breeding season; and 2) to get these heifers bred early in their first breeding season i.e., preferably within the first 25 days of the breeding season.

ACTION: Heifer development programs involving numerous management schemes, such as the use of growth promoting implants and creep feeding to achieve desirable weight gains, social interactions (e.g., bull exposure), pelvic area measurements, disposition, breed type, etc. have been and are currently being studied at different phases of heifer development in an attempt to maximize reproductive efficiency. In order to maximize future lifetime productivity of these females it is imperative that cattle producers understand the effects and impact of these different management practices.

IMPACT: Proper management and development of replacement heifers can translate into a more profitable cattle operation. To produce the most pounds of weaned calf during their lifetime, heifers need to produce a calf every year starting as two-year-olds and should drop their calves early in the calving season. It is fairly clear that heifers calving for the first time as two-year-olds will produce more calves in their lifetime versus starting as three-year-olds. The importance of calving early in the calving season is just as critical. It has been estimated that a 20 day reduction in age of the calf across the cow herd at weaning is similar to a 10% reduction of the calf crop. More specifically, if a calf is 20 days younger at weaning, this means 20 days of lost growth. At 2 lbs per day that equals 40 lbs of lost calf weight. At a per lb sale price at weaning of approximately 70 cents that equals $28.00 lost per calf. Multiply that amount by 45 calves (approximate average herd size in Louisiana) the total amount lost by a 20 day reduction in age of the calf across the cow herd at weaning then becomes $1,260.00. Heifers that become pregnant early tend to be early calvers the rest of their lives and as you know this is an important, and often overlooked, aspect of beef cattle management.

Dr. Del Vecchio also used Selecting and Developing Replacement Heifers, LCES Pub #2739, available from your parish Cooperative Extension Office.

COMMODITY: BEEF

TITLE: Frame Size and Muscle Scoring of Market Calves

CONTACT: Mr. Paul Morris, County Agent, Sabine Parish (318) 256-3406

TAKE HOME MESSAGE: In order to plan for a marketing and breeding program every cattle producer should establish some goals. The primary goal of a market calf producer should be to produce medium to large frame, #1 muscle score steers that will grade USDA Choice at a 1200 lb finished weight with a yield grade of 3.0 or less. The heifers in this program will finish at 1000 lbs.

PROBLEM / TOPIC: Feeder calf prices are reported by the USDA and other reporting services based on calf frame size and muscle score. These reports are standardized so that prices can be compared on a nationwide basis. Furthermore, with this scoring system cattle can be described for sale with uniform categories. The feeder calf grading system also allows for a prediction of subsequent feedlot performance and the carcass characteristics of the cattle.

ACTION: It is important for cattle producers to develop the ability to determine the frame and muscle score of their calves. Evaluating the frame and muscle of a set of calves helps the producer estimate the value of his/her calves. It also helps a producer as he/she develops a breeding program to maximize income. Culling and selection decisions can be made if calves are consistently small framed or light muscled.

IMPACT: Cattle feeders express their desire to purchase groups of feeder cattle that fit into the medium and large frame categories with adequate muscling. They usually like a mixture of these cattle so they can maximize gain, efficiency, and grading qualities. In order for cattle producers to consistently produce calves that fit these specifications, breeding programs need to be developed to produce uniform calf crops. A set of uniform calves is worth more money than a set with a great deal of variation in frame size and muscling. Cow herds should be sized and typed into uniform groups so that bulls can be selected based on size and type to produce the desired size and type of calf. Matching bulls to cows for planned breeding systems and known genetic makeup improves the predictions of how the cattle will perform in the pasture before weaning, in backgrounding operations, in the feedlot, and in the packing plant. Beef consumers desire a more uniform, consistent product when they eat beef. As the beginning of the beef production system, cow-calf producers should utilize the tools available to produce calves that fit into the frame size and muscle scores needed for todays cattle industry.
 

Feeder calf frame and muscle scoring was developed by the USDA so there would be a standard terminology and description of cattle for market reporting. This standardized description also allows for a prediction of the feedlot performance and the carcass characteristics of the finished cattle.

The current USDA system is based on frame size and muscle thickness. There are three frame sizes and three muscle thicknesses in place for thrifty cattle. There is an inferior grade for unthrifty stock or for double muscled cattle. All cattle are graded based on a slightly thin fat cover. Age of the cattle should be considered when they are graded. Frame size is dependent on age since the skeleton grows as the animal gets older.

The frame scores are:

L-Large frame: These cattle are thrifty, tall and long bodied for their age. Steers would be expected to have 0.5 inches of fat over the 12'th rib at a weight greater than 1200 pounds. Heifers would be expected to have 0.5 inches fat at greater than 1000 pounds.

M-Medium frame: These cattle are thrifty and moderate in height and body length for their age. Steers would be expected to have 0.5 inches of fat at weights of 1000 - 1200 pounds. Heifers would be expected to have 0.5 inches of fat at 800-1000 lbs.

S-Small frame: These cattle are thrifty but are shorter in height and body length than medium frame cattle. Steers would be expected to have 0.5 inches of fat at weights less than 1000 pounds. Heifers would have 0.5 inches of fat at no larger than 850 lbs.

The muscle scores are:

No 1--These feeder cattle have a high proportion of beef breeding. They are full in the forearm and exhibit muscularity over the back and through the loin with moderate width between the legs.

No 2--These feeder cattle are narrower through the fore and hind quarters. The forearm is thin and the back and loin have a sunken appearance. The legs are set close together.

No 3--Feeder cattle in this grade have less thickness than the minimum requirements for No 2 grade cattle.

The combination of frame scores and muscle scores give nine possible combinations for feeder calf grades.

Several studies tell us that feedlots and packers like to purchase groups of cattle that fall into the medium and medium to large frame category. Most buyers prefer a mix of these cattle to ensure good growth and performance and to provide a high percentage of choice grade cattle.

When developing a breeding program to produce this type of slaughter animal, consideration must be given to the frame and muscle present in the cow herd and in the bulls to be used. The following chart may help you develop a program to produce the type of cattle preferred by the industry. When using this chart be aware that weights for given frame sizes are dependent on the muscle and thickness in the individual animal. Many of our cattle may be lighter muscled and therefore have a lighter weight at a given frame size.
 

BIF NUMERICAL  FRAME SCORE	USDA  FEEDER CALF FRAME SIZE	MATURE  BULL  WEIGHT	MATURE  COW  WEIGHT	STEER SLAUGHTER WEIGHT	HEIFER SLAUGHTER WEIGHT
2	small		955	850	700
3		1615	1030	950	800
4	medium	1750	1100	1050	900
5		1890	1175	1150	1000
6	large	2040	1250	1250	1100
7		2195	1320	1350	1200
8		2360	1395	1450	1300
9			1470	1550	1400

The ideal cow size is different for each producer. The cow herd has to be efficient on the available forage resources and under the management system in use. Breeding programs should be planned to produce the desired calf size. Care should be taken not to use bulls over 3 frame sizes larger than the cows. Using bulls that are a great deal larger can result in calving difficulties.

All producers should carefully evaluate changes in breeding programs. Uniformity in calf crops begins with a set of uniform size and type of cows. Breeding programs have to balance several traits in order to maintain cow herds that are efficient and profitable.
 
 

Revised:  April 3, 1999