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Suckling reduction and boar exposure to induce estrus in lactating sows
A total of 135 sows (PIC 1050) were used over 5 consecutive farrowing groups (Feb to Aug 2014) to determine an optimal lactational estrus induction strategy. Litter size was equalized within parity to 11.5 ± 1.1 pigs at d 2 post-farrowing. At d 18, sows were assigned to 1 of 5 treatments (n = 26 to 28) based on parity, farrowing date, and suckled litter size. Treatments were: 1) Control, 2) ALT (all but the 5 lightest BW pigs weaned on d 18, remaining pigs combined and alternated between paired sows at 12 h intervals), 3) SEP (pigs separated for 12 h/d from d 18 to 25), 4) Split-wean (SW; All but 5 lightest BW pigs weaned on d 18), or 5) 24HR (pigs removed for a 24 h period on d 18). Controls were weaned at d 21, with all other treatments weaned at d 25. From d 18 until weaning, all sows were provided daily boar exposure within the farrowing house by allowing 5 min of nose-to-nose contact with a mature boar. Creep feed access was provided from d 14 until weaning. Sow backfat and BW losses during lactation were similar across treatments. Sows in the 4 reduced suckling treatments had a decreased wean to estrus interval (WEI; -0.5 vs. 3.5 d; P<0.05) versus controls, resulting in similar post-farrowing day in estrus across treatments. A total of 80 of 106 sows (76%) subjected to reduced suckling treatments expressed lactational estrus, but SEP and 24HR reduced (P<0.05) pregnancy rate versus controls. Creep feed disappearance was greatest (P<0.01) from SEP and 24HR litters, but SEP decreased (P<0.05) pig BW versus other reduced suckling treatments; whereas SW and 24HR pigs were heavier (P<0.05) than controls at d 25. These data indicate that treatments altering nursing differ in their ability to induce lactational estrus and the weight gain of litters.
|
Control |
ALT |
SEP |
SW |
24HR |
SEM |
P< |
WEI, d |
3.5b |
-0.7a |
-0.5a |
-0.9a |
0.0a |
0.66 |
0.001 |
Day in estrus post-farrowing |
24.5 |
24.3 |
24.5 |
24.1 |
25.0 |
0.66 |
0.25 |
Mated in lactation, % |
--- |
79.3 |
73.3 |
86.7 |
64.3 |
0.17 |
0.06 |
Pregnancy rate, % |
96.7c |
78.3abc |
75.0ab |
92.0bc |
66.3a |
0.13 |
0.02 |
Creep feed use, g/pig/d |
14a |
17a |
34c |
13a |
26b |
2.3 |
0.001 |
Pig BW d 21, kg1 |
6.59d |
6.34b |
6.23a |
6.45c |
6.14a |
0.056 |
0.001 |
Pig BW d 25, kg1 |
7.09ab |
7.18b |
7.01a |
7.40c |
7.33c |
0.091 |
0.001 |
1 Initial BW covariate.
Keywords: lactational estrus, altered suckling, split weaning