regolith
Well-known member
http://www.stuff.co.nz/waikato-times/fa ... ig-savings
Wondered if the US dairy people had any comment on this. Obviously as NZ dairy cows are seasonal calving and AI in most herds is only for 3 - 4 weeks (meaning heifers retained were conceived on the first chance at breeding, rarely the second) the national herd should be genetically as fertile as it's possible to select for. Yet there's been a lot of talk over the last few years about declining fertility; I've heard enough anecdotal evidence and theory/opinion to have absolutely no idea why or even if its true that fertility is declining. My heifers still come back from my grazier's 95 - 100% pregnant each year although the same grazier has other groups of heifers that every year have high open rates.
Talking about early embryo loss... I ran some numbers past my vet a few years ago and he agreed that measured against his data my herd had a higher than acceptable early embryo loss, although overall their in-calf rates are better than average. Part of the problem is that if the pregnancy is lost early enough the cow returns to heat on schedule and no-one knew she'd ever conceived. The ones I know about are the ones lost late enough to cause a delayed or missed cycle - from measuring returns to mated versus un-mated heats I know my cows have a consistent 5% loss between three weeks and six weeks, every year, measured the same loss in other herds I'd managed. Six week conception rate thus ranges from about 50% - 60% (usually 58 - 60 in recent years). I can't imagine anyone getting 40% and still being in business.
What sort of impact do you think early losses are having on fertility in your herds?
The breeding company monitors their technicians' 3-wk non-return rate by recording the matings/returns of cows most likely to conceive - calved longer than six weeks, no calving problems, in the right age band &c - and I think every technician has to have over 70% non-return rate on that group of cows to keep their job, mine last year calculated at 73%. So that's bringing in a new set of factors again related to fertility, if we know that those other cows dragging the average down were late calvers or had retained membranes/assisted calvings.
Wondered if the US dairy people had any comment on this. Obviously as NZ dairy cows are seasonal calving and AI in most herds is only for 3 - 4 weeks (meaning heifers retained were conceived on the first chance at breeding, rarely the second) the national herd should be genetically as fertile as it's possible to select for. Yet there's been a lot of talk over the last few years about declining fertility; I've heard enough anecdotal evidence and theory/opinion to have absolutely no idea why or even if its true that fertility is declining. My heifers still come back from my grazier's 95 - 100% pregnant each year although the same grazier has other groups of heifers that every year have high open rates.
Talking about early embryo loss... I ran some numbers past my vet a few years ago and he agreed that measured against his data my herd had a higher than acceptable early embryo loss, although overall their in-calf rates are better than average. Part of the problem is that if the pregnancy is lost early enough the cow returns to heat on schedule and no-one knew she'd ever conceived. The ones I know about are the ones lost late enough to cause a delayed or missed cycle - from measuring returns to mated versus un-mated heats I know my cows have a consistent 5% loss between three weeks and six weeks, every year, measured the same loss in other herds I'd managed. Six week conception rate thus ranges from about 50% - 60% (usually 58 - 60 in recent years). I can't imagine anyone getting 40% and still being in business.
What sort of impact do you think early losses are having on fertility in your herds?
The breeding company monitors their technicians' 3-wk non-return rate by recording the matings/returns of cows most likely to conceive - calved longer than six weeks, no calving problems, in the right age band &c - and I think every technician has to have over 70% non-return rate on that group of cows to keep their job, mine last year calculated at 73%. So that's bringing in a new set of factors again related to fertility, if we know that those other cows dragging the average down were late calvers or had retained membranes/assisted calvings.
