In commercial suckler beef systems, the cow’s key output is the weaned calf. The weight of the calf (and therefore its value) at weaning is affected by several factors such as the calf’s genetics for growth, the management of the cow and calf and the mother’s genetics for milk production. It is well known that cows with greater milk production will tend to rear heavier calves to weaning, with research suggesting that these calves will also go on to be heavier at slaughter(1). However when breeding for milk – it is the optimum not the maximum that should be aimed for. Increased milk yields will lead to greater calf growth, but excessive milk production can have several detrimental effects such as increased cow maintenance costs and loss of condition during lactation (leading to problems such as loss of fertility).
Estimated Breeding Values (EBVs) use performance and pedigree information to indicate the genetic merit of animals for specific production traits. The 200 Day Milk EBV in an indicator of the genetics for milk production in a particular breeding line, with higher EBVs implying greater milk production. The calculation of the 200 Day Milk EBV is one of the more complicated equations in breeding evaluations – it is based on the maternal component of calf growth to 200 days (milk). Although complex in its calculation, the key question is a simple one – does estimating milk production from calf weights work?
Several trials have been run in the past to investigate the effectiveness of Milk EBVs in beef cattle, with one of the most recent being a study conducted in New Zealand by Morris and Colleagues (2). In this trial, 20 Aberdeen Angus heifers were selected for high milk EBVs, and 16 were selected for low Milk EBVs. The heifers were monitored as they produced their first two calves, with milk production information being collected using a weigh-suck-weigh method (a method in which calves are kept away from the mother for a period, weighed, allowed to suck, and weighed again). Table 1 shows the milk yield in kg from the High Milk EBV and Low Milk EBV heifers.
Table 1: Milk Production Data extracted from work by Morris et al., (2010), comparing milk production from heifers selected for high Milk EBVs and low Milk EBVs.
As can be seen in Table 1, heifers selected for High Milk EBVs on average consistently outperformed heifers selected for Low Milk EBVs (excluding 150th day of lactation at first parity).
Further evidence of the effectiveness of the 200 Day Milk EBV concept is observed from US research conducted by Diaz and colleagues in 1992 (3). In this work, Polled Hereford bulls were selected for high or low genetic merit for milk, and the crossbred daughters were subsequently milked by machine to determine yields. Crossbred heifers sired by bulls with high genetic merit for milk production were found to produce more milk, and led the authors to conclude…
“Milk expected progeny differences of sires do predict differences in actual milk production of their daughters. Thus, milk expected progeny differences can be used as a selection criterion to change milk production as a breeding objective in improvement programs in beef herds. “
The information produced by both these trials demonstrate the viability of determining breeding merit for maternal milk production from calf weaning weights. This tells us that selecting bulls for breeding female replacements using the 200 Day Milk EBV, in bulls with high accuracy values for this trait, will allow genetic gain in both commercial and pedigree beef herds.
Take Home Messages
- Milk is extremely important, however it is the optimum not the maximum that should be aimed for
- 200 Day Milk EBVs and their equivalents provide robust indicators of the milk producing genetics of an individual.
- Selection of bulls for replacement heifer breeding using 200 Day Milk EBVs is likely to have a positive effect on sucker beef productivity.
1. Minogue, D., Cromie, A., McGee, M., Minchin, W. and McHugh, N. (2013). The relationship between milk yield and predicted transmitting ability for maternal weaning weight across four cow breed types. In: Proceedings of the Agricultural Research Forum, Tullamore, Co. Offaly, 12th March
2. Morris, S. T., Garrick, D. J., Lopez-Villalobos, N., Kenyon, P. R., Burke, J. L., & Blair, H. T. (2010). Growth, feed intake and maternal performance of Angus heifers selected for high or low growth and milk production. Animal Production Science, 50(6), 349-353.
3. Diaz, C., Notter, D. R., & Beal, W. E. (1992). Relationship between milk expected progeny differences of polled Hereford sires and actual milk production of their crossbred daughters. Journal of animal science, 70(2), 396-402.