Linking first lactation survival to milk yield and components and lactation persistency in Tunisian Holstein cows
<p>Genetic parameters were estimated for first lactation survival defined as a binary trait (alive or dead to second calving) and the curve shape traits of milk yield, fat and protein percentages using information from 25 981 primiparous Tunisian Holsteins. For each trait, shape cur...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-04-01
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| Series: | Archives Animal Breeding |
| Online Access: | https://www.arch-anim-breed.net/62/153/2019/aab-62-153-2019.pdf |
| Summary: | <p>Genetic parameters were estimated for first lactation
survival defined as a binary trait (alive or dead to second calving) and the curve
shape traits of milk yield, fat and protein percentages using information
from 25 981 primiparous Tunisian Holsteins. For each trait, shape curves
(i.e. peak lactation, persistency), level of production adjusted to 305 days in
milk (DIMs) for total milk yield (TMY), and average fat (TF %) and protein (TP %)
percentages were defined. Variance components were estimated with a
linear random regression model under three bivariate animal models.
Production traits were modelled by fixed herd <span class="inline-formula">×</span> test-day (TD)
interaction effects, fixed classes of 25 DIMs <span class="inline-formula">×</span> age of
calving <span class="inline-formula">×</span> season of calving interaction effects, fixed classes of
pregnancy, random environment effects and random additive genetic effects.
Survival was modelled by fixed herd <span class="inline-formula">×</span> year of calving interaction
effects and age of calving <span class="inline-formula">×</span> season of calving interaction effects,
random permanent environment effects, and random additive genetic effects.
Heritability (<span class="inline-formula"><i>h</i><sup>2</sup></span>) estimates were 0.03 (<span class="inline-formula">±0.01</span>) for survival and
0.23 (<span class="inline-formula">±0.01</span>), 0.31 (<span class="inline-formula">±0.01</span>) and 0.31 (<span class="inline-formula">±0.01</span>) for TMY,
TF % and TP %, respectively. Genetic correlations between survival and
TMY, TF % and TP % were 0.26 (<span class="inline-formula">±0.08</span>), <span class="inline-formula">−0.24</span> (<span class="inline-formula">±0.06</span>) and
<span class="inline-formula">−0.13</span> (<span class="inline-formula">±0.06</span>), respectively. Genetic correlations between survival
and persistency for fat and protein percentages were <span class="inline-formula">−0.35</span> (<span class="inline-formula">±0.09</span>)
and <span class="inline-formula">−0.19</span> (<span class="inline-formula">±0.09</span>), respectively. Cows that had higher persistencies
for fat and protein percentages were more likely not to survive.</p> |
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| ISSN: | 0003-9438 2363-9822 |