[Jacob-list] Low birth weights

[Jacobflock at aol.com]

Fred Horak here.  In the December 1999 Journal of the JSC an article detailed 
records for 21 of 33 ewes and 5 of the 9 rams used for Fall 1998 breedings.  
The purpose was to test "ease of lambing", document parturition problems and 
test the "old wive's tale" that the "slant of the croup" was the reason for 
"ease of lambing".  The method and conclusions were reviewed by Texas A&M.

Some of the inputs into this Jacob parturition study include height, weight, 
length, head circumference, and four pelvic measurements for rams and ewes.  
Rams and ewes were about a grade 3; fingers across the backbone test.  The 
output consisted of detailed birth records of how each lamb was born, time 
from water to birth, birth to on its feet, feet to nursing, as well as lamb 
weight, height, length skull diameter and chest diameter.  Ewes were flushed 
and those in small pens were on about 1/3 pound of grain until after breding. 
 Ewes were then returned to pasture and moved back to grain at about eight 
weeks before lambing...increasing grain to about a pound until 
lambing...checking to see that all the ewes ate.

Measurements (weight, height, length, head and chest circumference, etc) were 
completed for 36 lambs; 6 singles and 30 multiples.  The average weight for 
the 36 lambs was 7.40 pounds with a standard deviation of .86; the singles 
averaged 8.26 pounds with a standard deviation of .56; the twins averaged 
7.21 pounds with a standard deviation of .79.  Ruth, a yearling ewe, had the 
lowest weight twins and among all 36 lambs studied, the lightest weight lamb. 
 Her twins were 5.75 (lightest weight lamb of 36 lambs) and 7.5 pounds.  

This year, we only bred 17 ewes.  They were all condition 4-5 at the start of 
breeding.  One ewe was horned in the spleen (completely punctured the spleen) 
and died.  The necropsy confirmed the punctured spleen, revealed she had 
triplets...and abdominal fat.  Abdominal fat reduces lamb size; fatter ewes 
generally have lighter lambs. The lambs born this year, I HAVEN'T RUN THE 
NUMBERS YET, I suspect are lighter weight.  The lighest, out of about 25 
lambs, are twins at 3 pounds 12oz and 4 pounds 10 oz; both viable.  One of 
the most probable causes of dystocia is pelvic fat (another is commercial 
muscling), however, we did not experience any dystocia, perhaps because of 
the ASSUMED lighter weight.  

Another cause of light birth weight is ewe diet.  Inadequate nutrition 
inhibits fetal growth not only at breeding (carnucles) but especially during 
the last six to eight weeks (foetal development).  If you had adequate forage 
(16% protein hay is often just a "story") and grain energy (corn is not a 
good source of protein but some shepherds just throw more corn thinking it's 
energy) and keep the ewes in "good"/not heavy weight, the lamb crop should 
reflect the diet.  

Soft hooves:  The hoof keratin material is soft at birth and hardens in a few 
days...it all takes time to dry out.  I think that hooves appear at about 60 
days...so they've been soaking for another 90 days before they get "air" 
dried and set up.  When I get my manicure, my nails get soaked and soften 
up...afterward they get hard. 

Fetal development: Gary Anderson (CA "party guy" for 2001) might have some 
input on fetal development and energy needs; splitting of the cell, genome 
activation, maternal recognition of pregnancy, start of the placenta, legs at 
4-5 weeks, nose and eyes at 7 weeks, hair, teeth, ...and why when it looks 
like it could pass for a lamb at 130 days does it wait 2 more weeks.  The 
"wive's tale" for when it will be born?  It will be born at the new moon, in 
the middle of the night, on the night you didn't bring the ewes in from the 
pasture...because it was cold, raining or snowing. 

That first "wives tale" about slope of croup and "ease of lambing"?  
Anatomically, the slope of the croup has virtually nothing to do with ease of 
lambing.  The pelvis and its slope has everything to do with motion and gait.
 
Fred