Sorting dairy cows by stage of lactation may improve farm profitability by supporting the peak production of high-producing cows and lowering feed costs for low-producing cows. Understanding your farm’s feed costs in addition to your cows’ response to pen moves and diet changes is key to capitalizing on this strategy.
The overall goal of grouping cows by stage of lactation is to reduce variation in metabolic requirements within each group. Thus, diets can be formulated more accurately to meet the cows’ nutritional needs. For high-production or early lactation cows, we need to provide enough nutrients to overcome a negative energy balance and maximize cows’ production potential.
Conversely, when excess nutrients are provided to low-production cows, they do not contribute to additional milk or components. Rather, those nutrients are either lost to the environment in the urine and feces or accumulated as adipose tissue in cows that are no longer growing. By adding a low-production or late-lactation group, a farm can avoid overfeeding nutrients, reduce the risk of excess body condition, and potentially reduce feed costs. Lowering feed costs in the late-lactation group may significantly impact the bottom line, especially as we consider income over feed costs (IOFC).
Potential impacts
Overall, research has shown that grouping cows this way can result in economic advantages, but the extent of the benefits is determined by the milk production responses due to pen moves and diet changes as well as milk price and feed costs.
Managing different rations and cow groups can be challenging for several reasons:
- Training: Feeders must be capable of mixing different rations.
- Labor: It takes extra time to feed more than one ration.
- Scheduling: Feeding and milking times must be coordinated to ensure cows return to fresh feed.
- Facilities: The barn design needs to allow more than one group of lactating cows.
- Potential milk production losses: Cows may drop in milk production when switching pens, particularly when moving to a late-lactation/low-production group.
Use your records to evaluate the effect of pen movements on milk production. Using monthly Dairy Herd Information (DHI) data and pen movement records over time, you can compare production responses when cows stay in the same pen versus moving them to a different pen.
I analyzed monthly DHI data from a 750-cow dairy from May to September 2023 to evaluate milk production responses when moving cows with and without a diet change. On this farm, cows in Pens 2, 3, 4, and 5 are fed a high-cow diet. Cows in Pen 5 are confirmed pregnant. Cows in Pen 6 are fed a low-cow diet.
I averaged milk production by pen and observed that, when cows moved from Pens 2, 3, and 4 to Pen 5 without a diet change, milk production decreased by 1.6 pounds. When cows moved from Pen 5 to Pen 6 with a diet change, milk production fell by 12.2 pounds. For the cows that stayed in Pens 5 and 6, milk production dropped 4.8 and 6 pounds, respectively (Figure 1).
These results indicate that, on this farm, pen movement is not a factor that substantially reduces cow performance; milk responses are consistent with advancing days in milk (DIM). The more drastic drop in milk production was due to diet change.
Effects on income
Figure 2 shows milk production with advancing DIM for the high- and low-cow groups using individual cow data from five months of DHI testing. Clearly, cows fed a high-cow diet had greater milk production compared to cows fed a low-cow diet. For example, at 250 DIM, cows fed the high-cow diet produced an average of 95.4 pounds of milk whereas cows fed the low-cow diet produced 73.6 pounds of milk. This big difference is due in part to moving the lower performers to the low-cow group.
The logical follow-up question is this: How does the loss in milk production due to diet change affect the bottom line, specifically IOFC?
A recent publication addresses this question. Alex Bach in Spain found that grouping and feeding cows based on their level of production most likely results in improved IOFC even when milk production is penalized. Benefits of grouping to improve IOFC occur when the savings in dietary cost are greater than the losses in milk production and components. Moreover, IOFC advantages are sensitive to milk price and feed cost. When milk prices are low relative to feed cost, or when feed cost is high relative to milk prices, grouping cows according to their level of production substantially improves IOFC.
Using the example shown in Figure 1, we can see the increasing economic advantage of grouping cows as the milk price falls — even when average per-cow milk production dropped by 12.2 pounds as cows moved to the low-cow diet (Table 1).
How much cheaper does the low-cow diet have to be relative to the high-cow diet to improve IOFC? Using the same farm data, if the high-cow diet costs $6.80 per cow per day and the milk price is $15 per hundredweight, the low-cow diet must cost less than $4.96 (73% of the cost of the high-cow diet) to see a positive difference for IOFC. If the milk price is $20 per hundredweight, the low-cow diet must cost less than $4.42 (65% of the high-cow diet) to see a positive difference in IOFC.
Now let’s say the cost of the high-cow diet rises to $9.18 per cow per day (a 35% increase). If the milk price is $15 per hundredweight, the low-cow diet needs to cost less than $7.34 (80% of the cost of the high-cow diet) to see a positive difference in IOFC. If the milk price is $20 per hundredweight, the low-cow diet must cost less than $6.79 (74% of the high-cow diet) to see a positive difference in IOFC. This demonstrates that grouping strategies are more beneficial when feed prices climb relative to milk price.
Look at your dairy
These results are farm-dependent, so farm-specific conditions and needs must be considered when determining grouping strategies. Stocking density, DIM, primiparous versus multiparous grouping, cow comfort, and barn layout also can affect IOFC.
Grouping cows according to their production level is a strategy that can improve IOFC, especially when the milk price is low and feed costs are high. Work with your nutritionist to analyze your farm’s data and conditions. Use that information to determine the best strategy to support milk production and control costs on your dairy.
AUGUST 2024 issue:
