Table III.

Reproductive Values for Guinea Pigs^a

First ovulation	4–5 weeks
First ejaculation	8–10 weeks
Breeding onset: male	600–700 gm (3–4 months)
Breeding onset: female	350–450gm (2–3 months)
Cycle length	15–17 days
Implantation	6–7 days postovulation
Gestation period	59–72 days
Postpartum estrus	60–80% fertile
Litter size	2–5
Litter interval	96 days
Weaning age	180gm (14–28 days)
Breeding life	18 months to 4 years (4–5 litters)
Young production	0.7–1.3/sow/month
Preweanling mortality	5–15%
Milk compositionb	3.9% fat, 8.1% protein, 3.0% lactose
Milk yield (maximum)c	45–65 ml/kg body weight/day

^aPhoenix (1970), Ediger (1976), Sisk (1976), Peplow et al. (1974), Laird (1974), and Festing (1976b).

^bNelson era/. (1951).

^cDavisei£z/. (1979).