22 January 2013

6 minute read

The Story so Far

Farmers in two of the traditional power house regions of dairying can take the credit for introducing the two dairy types that have dominated the New Zealand dairy industry for over 30 years.

First, in 1952, Waikato farmer Ron Sharp developed his version of the herringbone1, which was quickly adopted by farmers and by the mid-1980s more than 80 percent of all herds were milked using this type of dairy (Figure 1).

The second development came 17 years later, when in 1969 Merv Hicks, a Taranaki farmer, constructed the first rotary abreast dairy (more commonly known as the external rotary) in New Zealand2. In contrast, the adoption of the rotary has been slower, likely due to the durability of the herringbone, the early rotary’s higher capital and maintenance costs, and its lack of labour saving without automation (as a cups-off operator was required).

As the dairy industry has grown, investment in rotary dairies has accelerated, led mainly by operators of large herds. Between 1998 and 2008, 72 percent of new dairy installations were rotaries, up from 52 percent in the previous decade3. The average herd size for farms with rotaries is approximately 625, compared with 326 for herringbones⁴.

Figure 2 shows that for herds larger than 500 cows, the rotary becomes the dairy of choice. Today, 23.6 percent of herds are milked through rotaries; the most common are between 50 and 60 bails (Figure 3).

The remainder of herds are milked in swing-over herringbones. Other dairy types, such as double-up herringbones, a few remaining walk-throughs and the first handful of fully automated robotic milking systems are in use, but these make up fewer than 1.5 percent of all dairies.

Herringbone

Rotary

Milking Potential

The proportion of herds milked by dairy type from early 1960s through to 2012/13⁴

The herringbone and rotary dairy differ in design but how do they differ in their ability to milk cows?

The data presented in Figure 4 (pg 10) are from two sources: recent data manually entered by farmers on the Milksmart website (milksmart.co.nz) and electronic data obtained in the 2010/11 season from 80 high tech rotary dairies5,6. The number of cows milked per hour increases as the number of clusters increases (i.e. the larger the shed, the more cows per hour that can be milked). Looking at the Milksmart data, 40-aside herringbones and 40-bail rotaries, on average, achieved a similar number of cows milked per hour.

Accounting for the labour required to operate the dairy, the advantage of the larger dairies was reduced. The most labour efficient was the 60-bail rotary with automatic cluster removers (ACR) and, therefore, no cups-off operator.

The proportion of herds milked through herringbone or rotary dairies by herd size³

Economics

Modern rotary dairies are more efficient at milking cows but how do they compare as an investment? To answer this question, two scenarios were considered.

Scenario 1

This represented a farm with 450 cows building a new dairy. The analysis compared investment in a 40-aside herringbone operated by two people, with a 44-bail rotary including sufficient automation to be operated by a single operator (i.e. ACR, auto teat sprayer).

Both options had automatic drafting. Production and farm working expenses were calculated based on an analysis of the average 2010/11 Waikato farm7. Other assumptions included: milk price at $6.50/kg MS, twice daily milking, interest calculated at 7 percent, plant and machinery depreciated over 12.5 years, buildings and yards over 25 years.

Herd milking duration was calculated based on a 9 minute row or round and it was assumed that two operators were required for the herringbone and a single operator for the rotary. Labour to fetch herds and assist with other tasks associated with milking were the same for both farms.

Number of herds milked through herringbone and rotary dairies by dairy size⁴

The total labour saving was accounted for in the model using a rate of $25/hour, which included an accommodation allowance.

Scenario 2

This represented a 1000 cow dairy conversion with income and farm working expense data based on the average 2010/11 Canterbury-Marlborough farm7. Four options were considered: 40-aside herringbone, 50, 60 or 80-bail rotary.

It was assumed that two operators were required for the herringbone and the 80-bail rotary, and a single operator for the smaller 50 and 60-bail rotaries. All other assumptions were the same as for scenario one.

Pros and cons

Advantages and disadvantages of herringbone dairies⁸

Advantages

• Cheaper to build and maintain
• Highest cows per cluster per hour rate – cows exit and enter while other side is milking
• Cows are in full view of the milker while in the dairy
• Easier to drench
• Can increase capacity (by lengthening the pit if starting from a small dairy size)
• More sociable.

Disadvantages

• Requires a lot of walking and swivelling for milkers
• An efficient milking routine is important to achieve maximum throughput
• Installation of automatic cup removers (ACR) can be complicated; can complicate the milking routine; and may not offer any efficiency advantages
• Loading and unloading can be slow in large herringbones
• Slower milking cows can slow down the whole row if MaxT (milksmart.co.nz) is not used
• In-shed feeding system not as simple as for a rotary.

Advantages and disadvantages of rotary dairies⁸

Advantages

• Quick entry and exit times, if working well
• Cow flow less affected by cow/people interactions
• Usually a low milk line, so lower vacuum
• Little walking required of the milker
• Slower milking cows do not hold up more than one set of cups
• Platform speed can be varied with the stage of lactation and yield of the herd
• Automation often easier to install
• Generally brighter and airy working environment.

Disadvantages

• Expensive to build
• Difficult to expand
• Without automation, it requires at least two milkers
• Awkward for drenching
• Difficult for the milkers to see the cows for at least some of the milking
• Cows frequently milked out before they get to the cluster removal station (only an issue if no ACR)
• More moving parts than a herringbone, requiring more maintenance.

References

1. Agricultural innovation in the Waikato [Online]. Available at http://www. agheritage.co.nz/innovation
2. Eltham man turns milking around [Online]. Available at http://www. pukeariki.com/Research/TaranakiResearchCentre/TaranakiStories/ TaranakiStory/id/464/title/eltham-man-turns-milking-around.aspx
3. Cuthbert S. 2008. DairyNZ milking practices and technology use survey. Report prepared for DairyNZ, Hamilton, New Zealand. pp 40.
4. Data sourced from LIC, 8th October 2012.
5. Jago J., Edwards P., Burke J., and Scott S. 2011. Milking effectively in Rotary Dairies. Proceedings of the South Island Dairy Event (SIDE), 27-29 June, Lincoln University, 288-298 http://side.org.nz/Papers/2011/Milksmart%20 What%20makes%20a%20farm%20dairy%20efficient
6. Edwards P., Jago J. and Lopez-Villalobos N. 2012. Increasing the percentage of cows completing a second rotation improves throughput in rotary dairies. Animal Production Science. http://dx.doi.org/10.1071/AN12071
7. DairyNZ. 2012. DairyNZ Economic Farm Survey 2010-11 [Online]. Available at http://resources.dairynz.co.nz/DownloadResource.aspx?id=719
8. New Dairy Design [Online]. Available at http://www.milksmart.co.nz/ NewDairyShed

January 2013