Gestation length correlations (goats)

[SheepGirl]

View the sheep version of this thread here: http://www.backyardherds.com/threads/gestation-length-correlations.30719/

Is there a correlation between number of days bred and the age of the dam, the birth type, birth weights, or sex of the kids?

According to Virginia State University:

While the placenta experiences the most rapid growth between 90 to 110 days, fetal growth increases exponentially during the last trimester of pregnancy. Gestation length in the goat is approximately 150 days, but is affected by breed and sex of kids, and tends to increase with age, and decrease with litter size.

According to Bunda College of Agriculture:

Effect of breed of sire on gestation length

The average gestation length of dams sired by Saanen bucks was not different from that of dams sired by local bucks (Table 1). Although previous data on gestation length of Malawi local goats are not available, that of Saanen has been reported to be 150 days (Peaker, 1978). This seems to indicate that the sire of the litter has no effect on gestation length. Overall gestation length was 147.17±2.58 days and agrees with reports by Wilson (1957) on the Mubende goat in Uganda (146 1/2 days).

Effect of age of dam and season of kidding on gestation length

Although dams that kidded in the wet season and were younger had shorter gestation lengths than the others, the observed differences were not statistically significant. However, results reported by Asdell (1929) seem to have shown significant age and seasonal differences.

Effect of litter size and sex of kid on gestation length

Gestation length in dams kidding single kids (147.14±2.86 days) was about the same as in dams kidding multiple kids (147.09±3.05 days). Similarly, the gestation length in those kidding male kids (146.94±2.7 days) were the same as those kidding female kids (147.34±2.98 days). The results therefore agree with Asdell (1929) that gestation length is not affected by litter size and sex of kid.

According to Small Ruminant Research:

The mean gestation period [in Boer Goats] is quoted as being 148.2+/-3.7 days, with multiple births having no significant effect on gestation length.

According to Journal of Agricultural Science:

Data on 1468 pregnancies and 2356 newborn goat kids of six genetic groups under intensive management were utilized to determine some genetic and non-genetic factors affecting gestation length, and to assess the relationship between gestation length and survival of kids to 25 days of age. The study revealed significant (P < 0·01) effect of breed of dam, litter weight, breeding season and parity on gestation length. Number of kids born and sex of kids were not a significant source of variation affecting this trait. Granadina goats had the shortest gestation (149·0±0·31 days), whereas Toggenburg (151·7±0·28 days) and Alpine (151·4±0·46 days) had the longest. Litter weight and gestation period were related curvilinearly in summer and linearly in autumn. Gestation of goats bred in summer was 1 day longer (P < 0·01) than those mated in the autumn. There was a progressive reduction of gestation length as parity increased (151·3±0·24, 150·6±0·17 and 149·9±0·39 days for 1, 2·6 and > 7 kiddings, respectively). The mean survival rate of kids gestated < 148 days and 148–;152 days were 78±2 and 87±1, respectively, and these were significantly lower (P < 0·05) than the survival rate of kids gestated 152–156 days and > 156 days (94±1 and 95±2). In conclusion, prolonged gestation (152–160 days) in goats was beneficial because it resulted in heavier litters at birth and higher viability of neonatal kids.

I would love to see your personal results in your herd, if you have breeding and kidding dates. Birth weights are a great addition as well! Here is a sample of my own data, from my flock of sheep.

If you could make something similar to this except for goats, we could organize the data and have our own "study" and see how well it matches up to the findings in the quotes above.

 

[Southern by choice]

I have all our breeding dates, kidding dates, weights etc...
How bout I send it to you and you do the work!

 

[Pearce Pastures]

It would be interesting to study. I have heard the complete opposite when it came to dam age. The first fresheners tend to go longer than subsequent. It isn't something I read in research, just word of mouth.