One of the interesting aspects of attending professional meetings is the opportunity to hear a presentation that challenges standard practices and production systems. One such presentation discussed research at Colorado State University on the potential of a single-calf system.
A single calf production system breeds replacement heifers to calve as 2-year-olds, calves are weaned around 100 days of age. The 2-year-old cows are then placed on a high concentrate diet with the goal of marketing these animals before they reach 30 months of age. In this study reported by Arce et al. (2015) heifers calved at 24 months of age and their calves were early weaned at 106 days of age. The heifers were fed a high concentrate diet for 88 days after weaning and were approximately 30 months of age at harvest. The researchers evaluated the lean maturity skeletal maturity, overall maturity score, marbling score, and Warner Bratzler shear force of the resulting carcasses. Overall maturity scores were based on scores for lean and skeletal maturity, with A, B, and C maturity groups equivalent to scores of 100, 200, and 300, respectively.
The carcasses were divided into two groups; < 300 or ≥ 300 maturity scores. In this study, 64% of the carcasses were classified as < 300. There were no differences for lean maturity (170 vs 169), marbling score (470 vs 485) or shear force (4.87 vs 4.98) between the two maturity score groups. However, bone maturity (248 vs 342) and overall maturity (220 vs 301) were lower for carcasses classified as < 300. The differences in skeletal maturity (ossification) did not affect either marbling scores or shear force values.
Based on this preliminary experiment using 53 animals, this single calf system can produce beef that has acceptable quality. However, there are several critical questions to consider before adopting this production system, such as producing sufficient numbers of replacement heifers, management options for the young weaned calves, and expected returns for the slaughter heifer.
For instance, let’s assume that 200 two-year old heifers was the target herd size each year. If the breeding season pregnancy rate was 85%, then 236 heifers (200 animals ÷ 85% pregnancy rate = 236 animals) would be needed to enter the replacement pool. Using sexed semen to produce heifer calves is one option, however this will not produce 100% heifer calves. According to published research, pregnancy rates using sexed semen averaged 52% and 90% of the resulting calves will be the desired sex. Using those values, 110 heifers would be produced, (236 x 52% = 122; 122 x 90% = 110 heifers). Assuming an 85% pregnancy rate amongst the 114 heifers bred by the clean-up bulls will produce 48 more heifer calves, resulting in a grand total of 158 heifer calves. Even if every heifer calf was retained, additional replacements would need to come from outside the system to maintain the desired herd size.
Early weaning calves at about 100 days of age concerns many producers. These calves would weigh 200 to 300 pounds at weaning. Are there facilities on the farm/ranch to care for these calves or should they be sold upon weaning? Feed bunks and waterers must be designed that allows younger (smaller) calves to reach feed and water. Nutrient requirements for these calves are higher than normal weaned calves. Energy density of the diet would be the same for early versus normal weaned calves; however, the protein content of the diet is higher for the smaller calves (Table 1). Developing a good health program with the local veterinarian is key for reducing morbidity and mortality.
Table 1. Nutrient requirements for calves.
|Dry Matter Intake (lb)||TDN
|NEm (Mcal/lb)||NEg (Mcal/lb)||CP
|300 lb calf|
|ADG = 2.0 lb/d||8.6||68||0.70||0.42||16.2|
|ADG = 2.5 lb/d||8.6||73||0.78||0.50||18.7|
|ADG = 3.0 lb/d||8.3||80||0.88||0.58||22.0|
|400 lb calf|
|ADG = 2.0 lb/d||10.7||68||0.70||0.42||14.1|
|ADG = 2.5 lb/d||10.7||73||0.78||0.50||16.1|
|ADG = 3.0 lb/d||10.4||80||0.88||0.58||18.7|
|500 lb calf|
|ADG = 2.0 lb/d||12.6||68||0.70||0.42||12.9|
|ADG = 2.5 lb/d||12.6||73||0.78||0.50||14.6|
|ADG = 3.0 lb/d||12.2||80||0.88||0.58||16.8|
|600 lb calf|
|ADG = 2.0 lb/d||14.4||68||0.70||0.42||12.1|
|ADG = 2.5 lb/d||14.4||73||0.78||0.50||13.5|
|ADG = 3.0 lb/d||14.0||80||0.88||0.58||15.4|
|Estimated finished weight at 1,200 lb
Source: Nutrient Requirements for Beef Cattle, 2000
A final critical factor would be avoiding discounts because of carcass maturity. In this study, 64% were either A or B maturity and therefore eligible for USDA Prime, Choice, or Select quality grades. Thirty-six percent of the heifers were classified as C maturity. These could be considered cow beef and valued significantly less than their contemporaries that scored an A or B maturity. Minimizing the number of C carcasses and the associated discounts would be critical in the financial success of this system.