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Breeding / Calving Issues
Calf size in an ET program
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<blockquote data-quote="WalnutCrest" data-source="post: 1160955" data-attributes="member: 21715"><p>Interesting.</p><p></p><p>I have discussed BW of ET calves with numerous people who have extensive experience with emrbyo work. To a man, they all told me that ET calves are bigger at birth than AI or natural service calves. I never thought to go look it up; they were so consistent in the tone and nature of their comments it never occurred to me to second guess them.</p><p></p><p>So, today I did look it up at your suggestion.</p><p></p><p>It appears that some research says there is no difference; some research says there is.</p><p></p><p>Here's one report (<a href="http://www.journalofdairyscience.org/article/S0022-0302(13" target="_blank">http://www.journalofdairyscience.org/ar ... 22-0302(13</a>)00748-0/pdf) showing a difference in Holstein -- AI vs. ET-fresh vs. ET-frozen -- birth weights of 41.7kg vs. 42.5kg vs. 45.3kg (respectively) and gestation lengths of 274.9 days, 275.0 days and 279.5 days, respectively.</p><p></p><p>It would appear that the BW differences might stem more from whether or not the embryos were frozen before implant, or transferred fresh.</p><p></p><p>If you have any research or personal experiences to share, I'd love to hear them.</p><p></p><p>Thanks.</p><p></p><p></p><p></p><p>Yes. I agree...</p><p></p><p>*****************************</p><p></p><p>My question still stands ... does anyone have any ideas/theories about whether or not there is an in-utero heterosis effect that would influence the size of the calf ... should you use recips of the same breed as the donor to moderate BW's ... or does it matter?</p></blockquote><p></p>
[QUOTE="WalnutCrest, post: 1160955, member: 21715"] Interesting. I have discussed BW of ET calves with numerous people who have extensive experience with emrbyo work. To a man, they all told me that ET calves are bigger at birth than AI or natural service calves. I never thought to go look it up; they were so consistent in the tone and nature of their comments it never occurred to me to second guess them. So, today I did look it up at your suggestion. It appears that some research says there is no difference; some research says there is. Here's one report ([url=http://www.journalofdairyscience.org/article/S0022-0302(13]http://www.journalofdairyscience.org/ar ... 22-0302(13[/url])00748-0/pdf) showing a difference in Holstein -- AI vs. ET-fresh vs. ET-frozen -- birth weights of 41.7kg vs. 42.5kg vs. 45.3kg (respectively) and gestation lengths of 274.9 days, 275.0 days and 279.5 days, respectively. It would appear that the BW differences might stem more from whether or not the embryos were frozen before implant, or transferred fresh. If you have any research or personal experiences to share, I'd love to hear them. Thanks. Yes. I agree... ***************************** My question still stands ... does anyone have any ideas/theories about whether or not there is an in-utero heterosis effect that would influence the size of the calf ... should you use recips of the same breed as the donor to moderate BW's ... or does it matter? [/QUOTE]
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