Herd & Individual Performance
My herd is achieving high production with high profitability yet it has a low BW, why?
Milk production and profitability is a combination of environment and genotype.
Environment includes feeding and management. It is likely your herd is fed to high levels on quality feed and well managed. The statistical models to calculate BW (the genotype component) remove the environmental component via contemporary groups and permanent environmental effects so that environment does not influence the BW.
Other reasons for the low BW include that your cows are sired by bulls that do not have a large number of progeny records, relatives of animals in your herd performed poorly when managed in another herd in New Zealand or your herd is genetically heavy.
To see how BW should be used click here
What is a contemporary group?
A contemporary group is a group of cows who are tested:
- in the same herd (e.g. same farm location and herd number)
- on the same test day (e.g. using AM + PM, AM only, PM only, OAD)
- belonging to the same age group - 2 year old, 3 year old, 4 year old, or 5-7 year old
- with the same season of calving - spring or autumn
For liveweight, body condition score or Traits Other than Production (TOP), a contemporary group is a group of animals who are:
- in the same herd or mob (e.g. same farm location and herd number)
- weighed/assessed on the same day
- belonging to the same age group - 2 year old, 3 year old, 4 year old, or 5-7 year old
- with the same season of calving - spring or autumn
Note: For TOP, only 2 year old records are used.
Contemporary grouping allows us to compare animals on an even footing by removing the environmental, age or season of calving effect of an animals performance.
Otherwise, animals who are fed to higher levels, are tested on a day with more favourable weather conditions, under a different calving regime or are at a higher stage of production potential (e.g. animals 5-7 year old) will seem better than they actually are e.g. their breeding values, BW, production values or PW would not be a true reflection of their breeding or production potential.
- Full Desciption of Contemporary Groups View PDF (12 kb)
- New Zealand Standard - Dairy Herd Testing
Some of my highest milk solids producers have low BW, how can this be?
The definition of BW is “animals whose progeny will be the most efficient converters of feed into farmer profit.”
BW mainly relates to the expected ability of animal to produce profitable progeny. How a cow performs is a combination of her permanent environmental effect which consists of how well she was reared and the random sample of genes she received from her parents. For instance, those higher producers may have inadvertently had a better growth pattern and environment, and received a collection of more favourable genes from her parents. The calculation of BW removes this permanent environmental effect from the calculation, and places greater weighting on how well related individuals have performed.
In addition, BW does not include solely milksolids production and places moderate emphasis on live weight, fertility, somatic cell count and survival. Those highest producers’ maybe genetically larger animals for which they are penalised because of higher growing and maintenance costs or they are from families with lower fertility. PW and LW reflect an individual’s performance as they include the permanent environmental effect, but PW and LW still include estimates for traits such as live weight, fertility, somatic cell count and survival.
My oldest cows that produce to high levels and get in calf every year have low BW and PW, why?
There may be a number of reasons for this. Firstly, they may not have produced progeny that have performed well. Remember that BW mainly relates to the expected ability of animal to produce profitable progeny, and does not include the permanent environmental effect.
Secondly, an animal that has reached an advanced age has not been given a positive value for survival. Until she exits the herd, survival is based on the survival of her relatives. Currently, the system does not give her a bonus for her longevity.
Thirdly, every year we have genetic progress of approximately 10 BW. So this cow is a result of parents who were, say eight-years-older, than a two-year-old animal in the herd. Therefore, this two-year old may have a sire that has eight years of genetic advancement (approximately 80 BW units) compared to your 10 year old animals. In saying all this, if these older cows have been producing progeny that outperform animals in their age group and still has a low BW then we would like to know about it so we can investigate.
Isn't production - 5% breeding and 95% feeding?
The old saying of “5% breeding, 95% feeding” is simply not true. We know that, on average, 30% of the differences in milk production between animals of the same age, breed, season of calving and herd is due to differences in genetic merit and 70% of the difference is due to environmental effects. These environmental effects include feeding and management. Animal evaluations remove the environmental effects so that you can compare animals on an equal genetic basis.
How do we know that cow BWs and PWs are a good representation of what is actually happening in a herd?
Divide your herd into three groups by their PW, and then by their BW: top third, middle third and bottom third. Then examine the production from those groups of cows (as a group), and the income they are generating. The difference between the profitabilities of the three groups will usually be very apparent.
If you are a MINDA user, your LIC representative can arrange for you to receive a report on your herd called Age Group Performance Profile, which does this analysis for you.
Why do you include so many traits in BW, surely this is limiting genetic gains in key traits such as fat and protein production?
Our current breeding objective is “animals whose progeny will be the most efficient converters of feed into farmer profit”. We know that all the current traits in BW contribute economically to this overall objective. For instance, cows with poor fertility limit days in milk, herd life and replacement rates. All these affect farmer profit.
Therefore, fertility has to be included in BW. If you don’t include key economic traits in your breeding objective, these traits can quickly become faults and have a large economic impact. Our overriding reason for any including any trait in BW is that it has an economic impact on the overall objective (BW).
Why are type traits not included in BW, surely udder, capacity and farmer opinion traits are important?
Type traits or TOP traits are included indirectly in BW. Owner opinion, milking speed, leg conformation, dairy conformation and udder overall are all included as predictor traits in the residual survival trait as they are known to influence how long a cow survives in the herd. So, cows that have higher rankings for these type traits do receive a small bonus in their BW.
Who decides which traits are included in BW?
The worldwide customers of our dairy products, the national market place and the economic environment together dictate which traits are (or become) economically important. All traits in BW have an economic importance.
Ultimately, the NZAEL Board of Directors makes the final decision to include a particular trait. Their decision depends on research undertaken by the Standing Advisory Committee in regards to how the trait can be measured, its economic importance, and availability of technology to estimate the trait.
How does the animal evaluation system cater for the fact that not all farmers have the same objectives?
The animal evaluation system identifies bulls and cows that have a high merit for profit - a common objective for farmers - while collecting data on other traits that farmers can use to meet their other objectives.
The current system currently provides genetic information on 26 different traits: milkfat, protein, milk, liveweight, fertility, somatic cell score, residual survival, longevity, calving difficulty, body condition score, adaptability to milking, shed temperament, milking speed, overall opinion, stature, capacity, rump angle, rump width, legs, udder support, fore udder, rear udder, front teats, rear teats, udder overall and dairy conformation. Farmers can use this information to suit their own objectives and weight traits for their own importance.
How often do the Economic Values change?
Economic values are reviewed annually and updated, if required, in February. Click here to view the latest economic values.
Why do you penalise cows for high live weight in BW?
We know that if we didn’t include live weight in BW then cows would get larger as we know there is positive correlation between fat, milk and protein production. Larger animals require more feed to grow to their mature live weight potential, and have higher maintenance energy costs.
If two herd mates have identical milk production but one is say, 100 kg heavier than the other, then the heavier cow requires more feed to maintain herself and requires more feed overall. This heavier cow produces less milksolids per kg of liveweight. If the whole herd consisted of heavier cows, fewer cows can be carried on the farm which results in less milksolids production per hectare. If the heavier cow produces more milksolids than the lighter cow (which is generally the case), the heavier cow will gain more positive economic values for milkfat and protein, but this may not offset the economic penalty for high liveweight.
The current negative economic value for liveweight has not resulted in animals getting smaller over time. In fact, there have been small increases in liveweight. The current weighting of traits has resulted in cows that produce more milksolids per kg of live weight.
For more about the live weight breeding value and its economic value click here
Why do milk, liveweight and somatic cell have negative economic values?
Because, all other things being equal, the higher volume cow, or the heavier cow, or the high SCC cow, is less profitable.
Why does milk have a negative economic value?
Milk volume has a negative economic value because of the processors levy and the feed required to produce milk volume and lactose.
Most of New Zealand’s milk production is exported in solid form as butter, cheese, milk powder and other manufactured dairy products. For these products, the liquid must be removed and this has a cost. Other costs related to milk volume are involved in refrigerating and transporting milk from the farm for processing. This is reflected in a volume charge that is used to calculate the price per kg of milk solids by all milk processors. Milk volume and the associated lactose also require significant feed intake to produce.
For more about the milk breeding value and its economic value click here
Won't negative economic values for some traits (liveweight and volume) cause cows to get smaller with less milk volume and capacity?
All our evidence suggests that this is not the case. Liveweight has shown a slight increase over time and milk volume and capacity have continued to increase. Both volume and liveweight are positively genetically correlated with milkfat and protein yield.
Therefore, both liveweight and volume tend to increase with genetic improvement of cattle. Negative economic values for liveweight and volume merely constrain genetic increases in volume and liveweight to avoid economically wasteful genetic change. Over time we are breeding an animal that produces more milksolids per kg of liveweight.
How can the animal evaluation system take liveweight into consideration when not all cows are weighed?
Liveweight recording has been practised for over 20 years for inspector scored liveweights for two-year old heifers, and for over 15 years for scale-recorded weights for mixed age cows. Progeny tested bulls have a high proportion of liveweight recorded daughters. For example, 76% of the production recorded daughters of the progeny test bulls born in 2004 had at least one liveweight record. On average, these bulls had 62 liveweight recorded daughters. This enables the genetic merit for liveweight of these bulls to be estimated with a high degree of precision.
For overseas origin bulls without daughters with liveweight records in New Zealand we are reliant on overseas information to estimate liveweight breeding values for these bulls. This estimate has a low reliability, and consequently may change once their daughters are raised and weighed in New Zealand conditions.
As with any traits, more data enables more accurate breeding values. The production worth of individuals in your herd will be more accurate if actual liveweight information is available, and this will also contribute to the accuracy of liveweight breeding values for bulls.
Why does protein currently have such a high economic value compared to fat when I thought they are now similar in value?
Over the past 10 years, protein has had a higher farm gate return than fat. The current economic value model is based on a 10 year rolling historical average, and the higher returns for fat in the past few years take a while to shift this long term average. We are investigating whether this rolling average should be shifted to a shorter period to make the value more dynamic and reflective of current conditions.
For a summary of current economic values click here
Why was "2000-born cows" chosen as the base cow?
A genetic base is chosen arbitrarily. The choice of the base group affects the size and the sign (+ve or -ve) of the evaluation and not the ranking of the animals. The genetic base is chosen to be practically relevant e.g. cows that you are familiar with, and is regularly updated over time. For instance, there are plans to update the base cow to a 2005-born cow in 2015. The base cow always has individual breeding values of zero and a BW of zero.
Why was "5,000kg DM" chosen as the reference unit of feed?
Like the base cow, the reference unit of feed is purely an arbitrary figure, and was chosen because it was the approximate amount of feed a cow consumed when BW was introduced (1996).
The reference unit of feed could equally be 1,000kg DM or 1kg DM. Unfortunately, if we chose 1kg DM then BW values would be very low as all BW would have to be divided by 4,500. For instance, a BW of 100 ($100 net income per 4,500kg DM) would become 0.022 ($0.022 per 1kg DM).
Does a negative BW mean that a cow will make no profit?
No. A negative BW simply means that a cow’s progeny are expected to earn less net income than a base cow if mated to a 0 BW animal.
Systems and Structures
Who pays for animal evaluation?
Approximately 10% of the cost of running the animal evaluation system is paid directly by AB companies (including LIC, CRV Ambreed) for evaluations of their bulls; about a further 36% is funded by DairyNZ; and the remaining 54% is paid by LIC’s MINDA service for the operation of the cow indexes. This is why LIC charges other companies or individuals for cow information if they are not using the MINDA service.
What sort of quality control is NZAEL subjected to, to ensure our Animal Evaluation system is up to international standards?
New Zealand Animal Evaluation Limited (NZAEL) currently manages the National Breeding Objective on behalf of DairyNZ. DairyNZ is an incorporated society that co-ordinates and funds dairy industry activities that are financially beneficial to New Zealand dairy farmers.
NZAEL reviews the national breeding objective annually, and recommends the statement of goal, the list of traits to be evaluated, and the assignment of relative importance to each of the traits. The review includes a report to DairyNZ on the input data used for the economic model, and on compliance with the established procedures.
NZAEL also monitors breeding value estimation (carried out as part of the national genetic evaluation system) to ensure that it meets the standards required by Interbull for participants in international genetic evaluations. Interbull conducts validation checks before incorporating data from a new national genetic evaluation - New Zealand’s data has been accepted at every Interbull international evaluation since being included in 1996.
Other audits are commissioned from time to time as required, including scientific peer reviews by national and international experts. Additions and modifications (for example, calving difficulty BV, cow fertility BV, and re-definition of the longevity BV) are usually submitted for peer review.
Why was the animal evaluation system developed to provide across-breed comparisons, rather than within-breed comparisons?
Because across-breed comparisons were needed, and because it could be done!
Currently, the highest proportion of cows are crossbreds. Farmers with mixed breed herds and/or crossbred cows in their herd needed to be able to make economic comparisons between cows across breed, and not just within breeds.
Why do LIC provide the cow indexes?
A little bit of history is probably required here. Cow and bull indexes originated from the forerunners of LIC, when it was part of the New Zealand Dairy Board (NZDB). These successive organisations set up the database, collected data, performed the research and development, and eventually developed, with dairy industry support, the first indexes of an animal evaluation system.
When LIC became a farmer-owned co-op in 2002, LIC voluntarily passed the responsibility for the bull BW to DairyNZ (formerly Dairy InSight). And so the indexes for bulls are dairy industry indexes, available to all in the dairy industry. At the same time, it was agreed that information about cows would continue to be provided by commercial dairy service providers, and not by DairyNZ. Any service provider can provide cow indexes, but the cow BW, PW and LW are indexes provided by LIC at its own cost. This is why LIC charges other companies or individuals for cow information if they are not using the MINDA service. BWs, PWs and LWs are available through LIC’s MINDA service. However, if you’re not using the MINDA service you can still obtain the cow indexes. If your herd test or herd records provider wishes to supply the cow BW, PW and LW indexes to you, they can obtain them from LIC for a fee.
What is the RAS List?
The RAS list is the abbreviation for the Ranking of Active Sires across and within breeds which are produced after each animal evaluation run. Always use the latest RAS List, click here to view.
To be eligible for inclusion on a RAS list, a bull must have commercial quantities of semen available, nominated by their marketer, have a BW reliability of more than 75% and have daughters in at least 10 herds.
Why do stock agents, bankers and farm owners place so much emphasis on BW when pricing animals, loaning money and employing new sharemilkers?
BW has probably been a function of its own success in this area. They use it because it is easy, a common unit of currency and, in some cases, and indication of how much effort has gone into animal recording.
We all know that BW is not the be all and end all, and that other functional traits are important such as udder and capacity. These traits are included in BW but only in a small way. It is about us educating that there is more to an animal than her BW. Nevertheless, BW exists as common breeding objective across the industry.
How well is the Animal Evaluation system working?
We can determine this from genetic trend graphs over time. These remove the environmental (feeding and management) from a cow’s performance. The rate of genetic change from 2001 to 2010 is shown below:
BW +$9.3/yr Milkfat +0.98kg/yr Protein +1.14kg/yr Milk +21 litres/yr Liveweight +0.09kg/yr Fertility +0.07%/yr Somatic Cell -0.02 SCS or -700 SCC/yr Residual Survival -2.4 days/yr
To see the impact of genetic evaluation and animal selection on individual breeding values over time for different breeds, visit breeding values