ฉันรักการแปลABSTRACT: The objective of this study was to
validate the use of exogenous gonadotropin (PG600)
treatment for stimulating estrus in noncyclic gilts and
to compare lifetime productivity of gilts recorded as
having natural (NAT) versus PG600-induced (PG600)
first estrus in a commercial setting. Prepubertal
Camborough gilts (n = 4,489) were delivered to a gilt
development unit (GDU) with the goal of delivering
known cyclic breeding-eligible females to the sow
farm (SF). A boar exposure area (BEAR) was designed
to facilitate stimulation and detection of puberty by
providing fence line and direct contact (15 min daily)
with mature boars over an intensive 28-d period, starting
at approximately d 160 (d 0). At d 14, nonpubertal
gilts were mixed in new pen groups. At d 23, noncyclic
“opportunity” gilts with no record of vulval development
and required to meet breeding targets, were
eligible for treatment with PG600 to induce puberty.
Overall, 77.6% (n = 3,475) of gilts exhibited standing
estrus (NAT = 2,654; PG600 = 821) and were eligible
for shipping to the SF at approximately 35 d, and
76.6% of gilts that were administered PG600 exhibited
the standing reflex within 13 d of treatment. Ultimately,
72.0% of gilts entering the GDU were delivered to the
SF as breeding-eligible females. Considering the gilts
delivered, a greater proportion of NAT than PG600
gilts were successfully bred (P < 0.001) and had better
farrowing rates to first service, and overall farrowing
rates (including gilts that returned to estrus and were
rebred) were greater for NAT compared to PG600 gilts
(P < 0.001) . Farrowing rates at second and third parity
were similar between NAT and PG600 gilts; however,
at fourth parity, a greater proportion of NAT gilts farrowed.
In comparison, considering only gilts served,
there was no difference (P > 0.05) in the proportion
of NAT and PG600 gilts farrowing a third litter, but a
greater proportion of NAT than PG600 gilts farrowed
their fourth litter (P < 0.001). There was no difference
between NAT and PG600 gilts for litter size at parity 1
through 4 or total pigs born over 4 parities (P > 0.05). A
negative correlation (P < 0.0001) was detected between
age at puberty and lifetime growth rate at puberty, and
growth rate classification affected age and weight at
puberty. However, retention rates and total sow productivity
to parity 4 were not affected by growth rate
classification at puberty.