In 2016, less than 20% of beef heifers calved at 22-26 months. Heifers averaged 31.5-months-of-age at the point of first calving, according to the ICBF.
As a result, this has led to the development of unproductive breeding cattle. According to Teagasc, there is scope to improve both the efficiency and the profitability of the suckler cow herd in Ireland – through improvements in reproductive performance.
In Ireland, reproductive efficiency is a major determinant of production and profitability for suckler cow farmers.
Age and timing of puberty play important roles in the heifer’s potential productive life within the herd; this is particularly important when heifers are bred to calve down at 24 months.
Cattle that calve at 24-months-of-age, and indeed within the first 21 days of the calving season, have greater longevity and profit per cow.
In addition, recent studies at Teagasc, Grange, have shown that for spring-calving, grass-based systems, delaying age at first calving from 24 to 36 months of age results in a decreased net margin per hectare by 50%.
Age at puberty in beef heifers is dependent on body weight and age; this varies between individual breeds . In general, puberty is earlier in breeds selected for milk production and in early-maturing animals compared to late-maturing breeds.
Speaking at this week’s National Beef Conference, Teagasc’s John Heslin outlined a two-year study carried out at the Grange Beef Research Farm.
This focused on the effect of breed type and post-weaning plane of nutrition on age of puberty and pregnancy rate in beef heifers.
The study involved a total 311 spring-born early (Angus) and late (Limousin) maturing breed heifers born to dams from either beef or dairy cows.
Two dietary nutrition levels were fed over the winter period. 69% DMD grass silage was fed ad-libitum along with 1.5kg of a barley-based concentrate per day, in order to achieve an average daily gain (ADG) of 0.5kg/day.
The second diet consisted of both grass silage and concentrates. This was fed ad-libitum in order to achieve an ADG of >1kg – a high intake (HI) diet.
Animals were turned out to pasture on April 7 in year one. They were let out to grass on April 15 in year two of the study. At pasture, they were rotationally grazed in six groups – balanced for breed type and winter dietary nutrition.
Heslin outlined that breeding (AI) commenced on the April 27 and 25 and finished on July 18 and 20 in years one and two of the study.
Results
According to Heslin, dam source had no effect on age at puberty, the number of heifers pubertal at the beginning of the breeding season or age at first AI.
“Pregnancy rate at six weeks and at 12 weeks was higher for dairy-bred animals compared to beef suckler-bred heifers,” he said.
Heifers sired by early-maturing breeds were younger at puberty and at first AI than those sired by late-maturing breeds.
Pregnancy rate at six weeks was higher for early-maturing than late maturing breeds; but there was no difference in pregnancy rate between the sire breeds at 12 weeks.
“Age at puberty was younger for the high-intake heifers than the other heifers. The HI diet increased the number of heifers pubertal at the beginning of the breeding season for late-maturing sired heifers but not early-maturing sired heifers.
“Age at first AI was younger for the HI diet group, but there was no difference in pregnancy rate at six or 12 weeks between the high-intake diet and the other group of heifers,” he concluded.