Calving replacement heifers for the suckler herd at two years of age
Dr Norman Weatherup, Beef Technologist, Greenmount Campus
Introduction
The current relatively high price for cull cows makes this an opportune time to assess cow performance and cull out the under-achievers. Many suckler farmers are rearing their own replacements to avoid purchasing heifers with a Holstein background, unknown genetics and undefined health status. Replacement heifers must calve down for the first time at either two or three years of age if a consistent, single calving period is to be maintained.
Advantages of calving at two years of age
- Fewer resources are invested in the heifers and a much faster return is obtained from the investment.
- Generation interval is reduced so genetic progress is more rapid.
- There are fewer groups of stock on the farm which reduces requirements for grazing paddocks, silage and housing by approximately 15 percent.
Why aren’t all heifers calved at two years old?
Although the majority of replacement heifers are calved at two years of age in the major beef producing areas of the world there is often considerable resistance on the part of the local industry to implement this practice. Often the decision is based on a bad experience with an “accidental” pregnancy in a poorly developed heifer.
What are the key principles to calving a two year old heifer?
- Suckler cows should be mated with performance recorded bulls with carcase and maternal traits placing them in the top 25 percent of their breed.
- Calving records must be used to identify the heifer calves of the most fertile cows in the herd.
- These heifers should be managed to achieve at least 50 percent of their mature weight at the start of the breeding season. However, more heifers will be cycling if they have reached 65 oercent of their mature weight. The aim at CAFRE is to have heifers at 380-420 KG at bulling.
- AI sires in the top 25 percent of the breed for calving ease, low birth weight and short gestation length should be selected to minimise calving difficulty and maximise rebreeding success.
- Heifers may be synchronised using a CIDR programme so that the labour requirements for heat detection and supervision of calving is minimised. Heifers should be programmed to calve down two weeks before the main herd to allow extra attention to be devoted to them.
How has it worked at Greenmount?
So far, forty one heifers have calved into the Greenmount Hill Farm herd at two years of age and a comparison of two versus three year old calving is shown in Table 1. (Heifers had been calved at three years of age previously).
Table 1. Calving information for two- and three-year-old heifers.
| 2 years | 3 years | |
|---|---|---|
| Animals requiring veterinary assistance at first calving (%) | 12* | 0 |
| First calf birth weight (KG) | 42.1 | 42.1 |
| Animals requiring veterinary assistance at second calving (%) | 0 | 0 |
| Second calf birth weight (KG) | 42.9 | 44.4 |
| Calving interval (days) from first to second calf | 363 | 379 |
*In the first year of mating two different bulls were used through Ai on the 15 month old heifers One bull with EBVs which indicated very easy calving and one bull with average calving ease EBVs. Veterinary assistance was required to calve four progeny of the bull with average calving ease EBVs. Typically selecting bulls with easier calving traits will reduce veterinary and labour costs by £22 per heifer.
Financial benefit
While some additional management effort and expense is required to achieve two year old calving, costings must be compared on a whole herd basis. To achieve 100 calves born and bringing in 20 heifers per year calving at three years of age means that there will be 12 percent more stock on the farm on average, 7 percent higher feed costs and 15 percent more land required. Calving heifers at three years of age increases the cost of EVERY calf born by £44 (costing the additional land required at £250/ha).
Summary
- It is possible to successfully calve suckler heifers at two years of age.
- Calving replacement heifers at two rather than three years of age reduces the cost of EVERY calf born by at least £44/head.
- Adequate growth rate during the first winter and correct sire selection are keys to success.
- Two year old heifers can produce their second calf at three years of age with equal or better rebreeding success than three year old heifers.
