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The NM$ index has new weights

The CDCB health traits will be added to the Lifetime Net Merit (NM$) formula starting in August. They will be combined into a health trait sub-index called HTH$, which will not be published separately.

You can find the relative value (%) for the traits in HTH$ in Table 1. DA, MAST, and METR represent over 80% of the index, due mainly to the higher costs and heritabilities associated with those traits.

Table 1. HTH$ sub-index relative values

TRAITABBREVRELATIVE VALUE in HTH$
MastitisMAST32.9
MetritisMETR26.5
Displaced abomasumDA23.3
Retained placentaRETP10.3
KetosisKETO4.7
Milk feverMFEV2.3

HTH$ Correlations

The correlations between HTH$ and the other traits in the NM$ formula are in Table 2. HTH$ is moderately to highly correlated with the health traits that were already included in the formula (PL, DPR, SCS, HCR, CCR, and LIV).  The heritability of HTH$ is low (0.01) as are many of the health traits.

Table 2. Genetic correlations between HTH$ and other NM$ traits

TraitMilkFatProtPLDPRSCSHCRCCRLIVCA$UdderF&LBWC
HTH$0.030.080.040.560.42−0.440.180.360.550.33−0.010.02−0.26

The new NM$ Index

A comparison of the 2017 and 2018 NM$ formulas is in Table 3 below.  The addition of HTH$ to NM$ results in slightly less weight on some of the traits already in the formula. In addition to new health traits in the index, NM$ now puts slightly more emphasis on the yield traits. SCS emphasis decreases because indirect correlated health costs are now allocated directly to HTH$.

The Fat to Protein ratio shifts to favor fat more, as the price paid for Fat is increasing and the price paid for Protein is decreasing (see Table 4 below).

Emphasis on SCS decreases since MAST is now directly included through the HTH$ index. PL emphasis also decreases slightly because later lactations are less valuable now that replacement heifer prices are lower.

Table 3. Net Merit $ Relative Values

Trait2017 NM$2018 NM$
Milk-0.7-0.7
Fat23.726.8
Protein18.316.9
PL13.412.1
SCS-6.5-4.0
DPR6.76.7
HCR1.41.4
CCR1.61.6
CA$4.84.8
LIV7.47.3
HTH$-2.3
UDC7.47.4
FLC2.72.7
BWC-5.9-5.3

NM$ 2017 versus NM$ 2018

An illustration to compare the index weights on production, health and conformation of Net Merit $ 2017 versus Net Merit $ 2018

Table 4. Component prices used to calculate Net Merit

YearFat ($/lb)Protein ($/lb)F:P ratio
20172.611.871.4
20162.312.101.1
20152.302.241.0
20142.383.390.7

Genetic Progress

Table 5 shows the expected genetic progress per trait for the 2017 and 2018 NM$ formulas.

The new 2018 formula will result in more progress for Fat, Protein, and FLC, and less progress for PL, DPR, CA$, and HCR.

The correlation between the 2017 and 2018 NM$ indexes are very high. For current industry genomic Holstein bulls the correlation is 0.998, and for current active, proven Holstein bulls, the correlation is 0.999.

Of the current top 100 NM$ genomic bulls, 88 remain in the top 100 NM$ using the 2018 formula.

Of the current top 100 NM$ active, proven bulls, 95 remain in the top 100 with the new formula.

Table 5. Expected genetic progress from NM$

Trait2017 NM$ (PTA change per year)2018 NM$ (PTA change per year)
Milk104104
Fat5.55.9
Protein3.73.8
PL0.540.51
SCS-0.02-0.02
DPR0.180.16
CA$3.53.4
HCR0.210.20
CCR0.420.42
LIV0.380.38
HTH$0.90.9
BWC-0.08-0.08
UDC0.050.05
FLC0.020.03

Customize your genetic plan

Ever-changing industry indexes serve as a reminder that your own farm’s customized genetic plan is as important as ever. When you set your emphasis on the production, health, and conformation traits that matter to your own bottom line – and stick to the plan you set – you’ll continue to maximize the progress you make in the direction of your own farm’s goals – even when other indexes change.

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Gestation length added as new trait

The Council on Dairy Cattle Breeding (CDCB) is adding gestation length as a new trait to be released with August 2017 proofs.

Gestation length can be most useful as a genetic tool for herds that implement seasonal calving. These herds will have the option of choosing service sires with shorter gestations for cows that didn’t settle to the first breeding.

Gestation length can also be a useful predictor of a cow’s calving date, which allows for more efficient management of close-up and maternity pen moves.

As of now, gestation length will not be included in TPI or the Net Merit index.

As new traits like gestation length are released, it’s important to keep your farm’s current situation and future goals front of mind. Work with your trusted Alta advisor to review your customized genetic plan. Only incorporate new traits like gestation length into your plan when they aid your farm’s goals and bottom line.

Learn more information about the research, heritability, and correlations behind gestation length, as presented by Wright, Van Raden and Hutchison at the 2017 ADSA meetings.

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Cow livability added to the NM$ formula

Starting in April 2017, the CDCB will include Cow livability into the Net Merit $ formula.

Cow livability (LIV) was introduced as a new trait in August 2016. It measures a cow’s ability to stay alive on the farm, and has a high (0.70) correlation with Productive Life (PL). The difference between LIV and PL is that PL measures a cow’s ability to be productive on the farm. It does not distinguish between death and culling as the reason for leaving the herd.

Cows that die on the farm are a great expense. In fact, based on cull prices, farmers could earn $1,200 less profit for each cow that dies on farm and cannot be sold for beef.

LIV is also correlated to DPR by 0.45 and to SCS by -0.25.

Net Merit changes

Net Merit (NM$) is an estimate of a cow’s lifetime profit to the farm. CDCB updated the formula for April 2017 proofs. It now includes new traits and revisions of traits using current incomes and expenses.

New changes include:

  • LIV is now part of the NM$ formula
  • Economic values are updated and current
  • Body weight composite (BWC) will replace Body size composite (BSC)

Relative values for most other traits included in the formula decreased slightly. The 2017 NM$ formula correlates by 0.989 to the previous NM$ from 2014. The table below shows the differences in the relative value of trait weights between the NM$ formula in 2014 and 2017.

TRAIT2014 NM$ TRAIT WEIGHT2017 NM$ TRAIT WEIGHT
Fat2223.7
Protein2018.3
Milk-1-0.7
Productive life1913.4
Cow livability7.4
Somatic cell score-7-6.5
Daughter pregnancy rate76.7
Calving ability $54.8
Cow conception rate11.6
Heifer conception rate21.4
Udder87.4
Feet & legs32.7
Body size composite-5
Body weight composite-5.9

The relative value of weight on PL decreases now that LIV is part of the NM$ formula. This adjustment will not hinder genetic progress for PL. Instead, it will increase the progress for LIV.

Body weight replaces body size

Since BWC is more closely related to the actual body weight of the cow than BSC, this change results in less selection against stature, body depth, and dairy form.

Finally, to account for updated milk component prices, the new NM$ formula increases emphasis on fat while decreasing emphasis on protein slightly.

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