Breeding from ewe lambs –an opportunity to increase flock profitability
The cost of a replacement ewe joining the flock at 18 months is equivalent to 25% of the value of lamb carcass output that she produces in her lifetime. One option to cut replacement cost is to join ewe lambs to lamb at one year, with the aim to increase lifetime productivity, Dr. Tim Keady outlines
- Use of the ‘ram effect’ compacted the mating and thus lambing season resulting in 62% and 84% of lambing occurring within 2 and 3 weeks respectively.
- Lambing ewes to produce their first litter at 1 year of age had no effect on performance when lambing at 2 years of age.
- Compared to the ≥75% Suffolk ewes, Belclare ewes reared 0.37 and 0.29 more lambs when lambing at 1 and 2 years respectively. This increase in productivity is equivalent to approximately €40 per ewe lamb joined
Replacements are a major cost in mid-season prime lamb production systems. The cost of a replacement ewe at joining the flock at approximately 18 months of age is equivalent to 25% of the value of lamb carcass output that she will produce during her lifetime. One option for reducing replacement costs is to join ewe lambs to lamb at one year of age with the objective of increasing lifetime productivity.
Ewe lamb mating management
The “ram effect” can be used to induce ewes (ewe lambs or adult ewes) to start cycling provided they are sufficiently close to the time of onset of normal cyclicity but have not entered their breeding season. In practice the ram effect can be employed to ensure that all ewes in the flock are at the stage of exhibiting overt oestrus during the first 17 days of the joining period. For the “ram effect” to work the ewes should have not been in contact (either sight or smell) with rams for the previous month.
The “ram effect” is summarised in Table 1. Fertile rams should be introduced to the flock 14 days after the rams used to induce the ‘ram effect’ were introduced; the peak mating times will be 4 and 9 days later. The reason the rams are introduced at day 14 is to allow for any short cycles and to pick up any individuals that were already cyclic at the time of ram introduction.
At Athenry when the “ram effect” was used all ewe lambs were raddled during the joining period. Also the lambing season was compact with 62 and 84% lambing within 2 and 3 weeks, respectively. This clearly illustrates that the “ram effect” synchronised lambing. When using the “ram effect” to synchronise the mating season it is essential to have an adequate number of rams for mating (1 experience ram per about 30 ewes). It is essential to have adequate facilities - especially lambing pens (1 pen per 6 ewes) and labour- to cope with the flock during the lambing season.
Management during pregnancy
Nutrition during pregnancy needs to meet the requirements for pregnancy and facilitate body weight gain to meet mature body weight. At Athenry ewe lambs received high feed value grass silage (75% DMD) ad libitum supplemented with concentrate (250 g/day) from early January to 6 weeks prior to lambing. During the last 6 weeks of pregnancy ewes carrying singles, twins and triplets received 18, 26 and 33 kg concentrate respectively.
Effect of ewe genotype on ewe lamb performance
The effect of ewe genotype on performance is presented in Table 2. Relative to Suffolk (≥ 75% Suffolk) ewe lambs Belclare ewes had larger litters (+ 0.39 lambs) and reared 0.37 more lambs per ewe joined. Ewe genotype did not affect lamb mortality.
Effect of weight at joining
The effect of weight at joining on the probability of a ewe rearing at least one lamb when lambing at 1 year of age is presented in Figure 1. The data presented in Figure 1 reflect differences due to ewe and lamb mortality, litter size and ewe barrenness. Regardless of ewe genotype, as weight at joining increased the probability of rearing at least one lamb improved. To have a 0.9 probability (90% chance) of rearing at least one lamb Belclare, Suffolk x Belclare and ≥75% Suffolk ewe lambs would need to be 48.5, 51.2 and 60.0 kg at joining respectively. Thus Belclare, Suffolk x Belclare and ≥75% Suffolk ewe lambs would need to be 63%, 64% and 72% of mature body when joining at 8 months of age to have a 90% probability of rearing at least one lamb when lambing at 1 year of age.