Approximately 100 weaned sows were used to study factors that might alter rebreeding of sows. Days required to return to estrus did not affect reproductive measures. Number of times mated also was not found to alter reproductive rates. Certain boars were found to influence litter size

Allrich, R. D.

Johnson, J. N.

Marcheno, M. J.

Slanger, William D.

Tilton, J. E.

Zimprich, R. C.

NDSU Libraries Institutional Repository

FACTORS AFFECTING REB REEDING PE RFORMANCE OF WEANED SOWS R. D. AUrich, J. E. Tilton, J. N. Johnson, W. D. Slanger, R. C. Zimprich and M. J. Marcheno Approximately 100 weaned sows were used to study factors that might ru ter rebreeding of sows. Days required to return to estrus did not affec t reprod­uctive measures. Number of times mated also was not found to aJte r reprod­uctive rates. Certain boars were fo und to influence litter size. Rebreeding p rformance encompasses the following events in the sow; ovulation rate, number of normal em­bryos in the utt-fIIS 2.5 days post-breeding, per cent e m­bryo snrvival, number of pigs born and number of pigs born alive at th subsequent parturition. Numerous fac­tors influ nee the weaned sow's rebreeding ability and performance. The fo llowing factors have be n examined in rest:arch trials at the North Dakota State niversitv H ON Farm: nu mber of days to return to estrus aft or w aning, number of breedings, boar fertility, number of corpora lutea, !lumber of normal embryos and number of pigs born. By evaluating what effect thesu factors have on rebrecding performance, hog producers could ac­quire a more comprehensive understanding of swine re­production. PROCEDURE Four trials involving approximately 100 sows were conducted over a period of 1.5 years. Lactating Duroc sows were wean d after an average lactation length of27 days. Piglets were fos tered to various litters to maintain an average of eight nursing piglets per sow. During lactation, gilts were fed at a rate of 1. 8 kg feed (15% crud protein) plus 0.45 kg per nursing pig per day. On -half of the ration was fed in the morning and one­half was f4 d in the vening. After weaning, sows were fed 2.3 kg feed (16% crude protein) per day. Following weaning th sows were checked for estrual activity twice daily (0800 and 2000 hours) and were bred by D uroc hoars aft r the onset of estrus. Sows were mated two, thre or four times to the same boar. Afte r mating, on -half of each treatment group was randomly designated for slaughter at 2.5 days' post-br eding. The remaining one-half were allowed to complete gestation and fc'lHOW. At laughter the following data w re collected: number of corpora lutea present on the ovaries ~md number of nonnaI, viable e m bryos . Corpora lutea pres­ent on the ovaries were assumed to represent the number of ova shed at estrus. Normal embryos were characterized by an embryo with the presence of a heartbeat and being of a size comparable to its contem­poraries. Per cent embryo survival was defined as the number of normal embryos p resent per 100 corpora lutea. Farrowing data includ d number of pigs born and number of pigs born alive . RESULTS AND D ISCUSSION Return to Estrus The number of days taken to return to strus after weaning did not significantly influence number of cor­pora lutea, numb r of normal embryos or per cent m­bryo survival at 2;5 days of gestation (Table 1). It may be speculated that sows returning to strus in a shorter interval than othe r sows may have a more functional pituitary, an ability to release grea[er amounts of gonadotropins, or more responsive ovaries. Aherne et al., (1976) have examined gonadotropin tevels in the weaned sow. M an FSH plasma concentrations were highest on the day of weaning and the first day after weaning. Mean LH concentrations W r low at weaning but increased abruptly on th day prior to strus. With­holding f4 ed and water for 24 hours after wean ing had no significan t influence on gonadotropin levels. The number of pigs born and the number of pigs born aliv w re not significantly affected by the length of time required by the sow to return to estrus (Tab I 2) . Seventy-eight per cent of the sows (76 of98) returned to estrus in six days or less. By 12 days after weaning 93 per cent of the sows (91 of 98) had returned to estrus. It is the prod uc r's goal to have sows return to estrus in a short and concentrated interval after weanin . This re ­sults in a minimum rebreeding tim and en ur s that th farrowing interval (time betwe n consecutiv parturi­tions) of the sow are as short as poss ible. This allows for maximum productivity from each sow, prov iding boar power during rebreeding is adequate . Number of Breedings As stated in th experimental procedure, sows were mated during the first strus followin g \ eaning. Because of extended estrus periods or manag ment reasons, sow ' were sometim s mated more than two times. The times of matings in this study ""ere 12, 23, 36 and 48 hours afte r the onset of estrus. Th eHect number ofbree dio crs had on number of corpora lutea. normal embryos and per cent embryo survival at day 25 of gestation is shown in Table 3. Number of breedings did not significc ntly 7 influence any of the previously mentioned parameters. Numbe r of breedings also had no significant Lfect on number of pigs born or number of pigs born alive (Table 4). From the data obtained, it would appear that there was no advantage to breeding sows more than two times during estrus. Signoret et al., (1972) examined the effect mating had on the onset and duration of ovulation in the sow. He concluded that mating hastens the onset of ovu­lation by four hours and shortens the duration by 2.8 hours. Zimmerman (1971) also has reported studies with similar results. Boars There were no significant effects of boars on number of corpora lutea, number of normal embryos and per cent embryo survival at 25 days of gestation (Table 5). This indicates that the boars used in the present study did not statistically alter data obtained at slaughter. Swierstra and Dyck (1976) have indicated that boars can influence embryonic survival, with ranges of embryo survival from 24 to 84 per cent for various boars. Boars had a significant (P < .025) influence on number of pigs born and number of pigs born alive (Table 6). Studies by Swierstra and Dyck have also shown that boars can influ­ence number of pigs born and number of pigs born alive. In the present study, boars were mated an el[ual number of times to sows in eaeh treatment group. In this way, although boars ean influence number of pigs born and number of pigs born alive, they will affect eaeh treat­ment group equally and therefore not alter the statistical analysis. Corpora Lutea The number ofcorpora lutea and its effect on number of normal embryos and per cent embryo survival are shown in Table 7. As number of corpora lutea increase, from 8 to 19, number of normal embryos increase also. This was expected because corpora lutea represent the number of ova ovulated and fertilization rates in swine approach 100 per cent. Per cent embryo survival was not altered significantly by number of corpora lutea. Martin et ai., (1977) have shown that if the number of corpora lutea is less than five, abortion will oecur. Normal Embryos The effect of number of normal embryos at day 25 of gestation on per cent embryo survival is shown in Table 8. Embryo survival increases as number of normal em­bryos incr ases up to 14 normal embryos, at which point survival appears to plateau. It may b that any more than 14 normal embryos causes a crowding situation f(Jr the embryos. Dzuik (1968) has stated that crowding is not a factor un til after day 25 of gestation. Another expt nation for increased survival as embryo nUlllbers increase was that embryos may have a compIementary relationship with each other, i.e., one embryo improve s the survival chances of other embryos. vVhen the number of · rnbryos was three or less, embryo survival was severely de­pressed. This phenomenon may be the ,. suit of the uterus not recognizing the pregnancy with so few em­bryos present. Pigs Born As the number of pigs born increases the number of pigs born alive also increases (Table 9). There appears to be no detrimental effect of increased pig numbcrs on the survival of the pig during parturition. It may be specu­lated that when large numbers of pigs are born, a detri­mental effect may he seen due to the extended time to com plete parturition. SUMMARY Four trials utilizing approximately 100 weaned sows were conducted to determine if the interval of return to cyclic activity, number of breedings, boars, corpora lutea, normal embryos and number of pigs born would influence r breeding performance. Days to r turn to estrus after weaning had no signifi­cant influence on number of corpora lutea, number of normal embryos and per cent embryo survival. Number of pigs born and number of pigs born alive also we re not affected by the number of days taken to return to estrus. The number of breedings did not significantly alte r any of the variables measured. There fore, ther is no advan­tage to mating sows more than two times during estrus. In the present study, the boar was found to have a Significant (P < .025) influence OIl the number of pigs born and number of pigs born alive. Hog produ "ers should keep accurate reeords so that boars with low fer­tility rates may be culled. In conclusion, the hog produce r who has a basic un­derstanding of swine reproduction will find him. e lf be t­ter prepared to meet the challenges of swinc production. tion. TABLE 1. CORPORA LUTEA, NORMAL EMBRYOS AND PER CENT EMBRYO SURVIVAL AS INFLUENCED BY DAYS TO RETURN TO ESTRUS Number of Number of Days to Corpora Lutea Normal Embryos Embryo Survival Return N ± SEM ± SEM (Per cent) ± SEM 1-6 45/42/42 1.3.5 ± 0.8 10.4 ± 0.7 77.2 ± 4.5 7-12 08/07/07 13.5 ± 0.9 10.6 ± 1.0 78.0 ± 13.0 13- 20 04/04/04 15.8 ± 0.9 U.8 ± 1.8 73.4 ± 8.0 N = Number of sows contributing data. N /N IN/refers to variables named, respectively. SEM = Standard error of the mean. 8 TABLE 2. PIGS BORN AND PIGS BORN ALIVE AS AFFECTED BY DAYS TO RETURN TO ESTRUS Number of Days to Number of Pigs Born Return N Pigs Born Alive SEM 1-6 12 10.2 9.5 0.6 7 -12 7 9.7 9.7 1.1 13 - 20 .3 10.0 9.7 1.8 TABLE 3. CORPORA LUTEA, NORMAL EMBRYOS AND PER CENT EMBRYO SURVIVAL AS INFLUENCED BY NUMBER OF BREEDINGS Number of Number of Number of Corpora Lutea Normal Embryos Embryo Survival Breedings N ± SEM ± SEM (Per cent) ± SEM 1 01101101 17.0 ± 0.0 9.0 ± 0.0 53.0 ± 0.0 2 28/26/26 13.4 ± 0.4 10.3 ± 0.6 77.3 ± 3.7 3 16/15/15 14.1 ± 0.7 10.9 ± 0.8 77.8 ± 4.6 4 10/09/09 13.2 ± 0.8 10.4 ± 0.9 76.6 ± 4.1 5 01101101 14.0 ± 0.0 13.0 ± 0.0 92.9 ± 0.0 6 01101101 16.0 ± 0.0 11.0 ± 0.0 68.8 ± 0.0 TABLE 4. PIGS BORN AND PIGS BORN ALIVE AS AFFECTED BY NUMBER OF BREEDINGS Number of Number of Number of Pigs Born BFeedings N Pigs Born Alive SEM 2 14 10.2 9.6 0.8 3 7 9..3 9.1 1.0 4 1 12.0 9.0 0.0 TABLE 5. CORPORA LUTEA, NORMAL EMBRYOS AND PER CENT EMBRYO SURVIVAL AS INFLUENCED BY BOAR Number of Number of Corpora Lutea Normal Embryos Embryo Survival Boar N ± SEM ± SEM (Per cent) ± SEM D4-1 04/04/04 13.0 ± 0.4 10.3 ± 0.6 78.9 ± 4.6 D14-2 13/13/13 13.9 ± 0.9 10.7 ± 0.8 77.8 ± 6.0 D97-12 12/12/12 14.1 ± 0.7 10.3 ± 1.1 73.3 ± 6.5 D98-1 07/06/06 14.4 ± 0.9 11.0 ± 1.4 74.6 ± 7.0 D98-6 1S/13/13 13.1 ± 0.8 10.8 ± 5.6 82.6 ± 5.6 D111-7 OS/04/04 13.2 ± 0.4 10.0 ± 1.4 74.6 ± 8.S 9 TABLE 6. PIGS BORN AND PIGS BORN ALIVE AS AFFECTED BY BOAR Number of Number of Boar N Pigs Born Pigs Born Alive SEM 0111-7 4 7.Oab 7.Oab 0.4 014-2 1 6.0 6.0 0.0 097-12 5 11.& 10.00 1.0 098-1 4 9.8 9.3 1.2 098-6 8 11.0b 1O.9b 0.9 a,b Means with the same superscipt differ at P < .025. TABLE 9. PIGS BORN ALIVE AS AFFECTED BY PIGS BORN TABLE 7. 	 NORMAL EMBRYOS AND PER CENT EMBRYO SURVIVAL AS AFFECTED BY Number of CORPORA LUTEA Number of Pigs Born Alive Embryo Number of Survival Number of Normal Embryos (Per Cent) Corpora Lutea N ± SEM ± SEM 8 1 8.0 ± 0.0 100.0 ± 0.0 9 1 6.0 ± 0.0 66.7 ± 0.0 10 3 9.0 ± 0.6 90.0 ± 5.8 11 4 9.0 ± 0.0 81.8 ± 0.0 12 6 8.8 ± 0.7 73.6 ± 5.9 13 10 10.3 ± 0.5 79.2 ± 4.1 14 12 10.9 ± 0.9 78.0 ± 6.4 15 1 14.0 ± 0.0 93.3 ± 0.0 16 7 10.9 ± 1.5 67.9±9.2 17 4 11.5 ± 1.7 67.7 ± 9.7 18 2 13.5 ± 1.5 75.0 ± 8.3 19 2 15.0 ± 0.0 78.9 ± 0.0 TABLE 8. PER CENT EMBRYO SURVIVAL AS AFFECTED BY NORMAL EMBRYOS Number of Embryo Survival Normal Embryos N (Per Cent) ± SEM 2 1 14.3 ± 0.0 3 1 25 .0 ± 0.0 6 2 58.4 ± 8.4 7 1 53.8 ± 0.0 8 4 74.2 ± 10.6 9 11 73.8 ± 3.6 10 7 78.8 ± 3.9 11 7 80.2 ± 3.3 12 8 81.0 ± 3.2 13 3 95.3 ± 2.4 14 2 96.7 ± 3.4 15 5 85.7± 3.4 16 1 94.1 ± 0.0 Pigs Born N ± SEM 6 2 6.0 ± 0.0 7 4 7.0 ± 0.0 8 2 8.0 ± 0.0 9 1 8.0 ± 0.0 10 3 8.7 ± 0.9 11 3 11.0 ± 0.0 12 2 10.5 ± 1.5 13 3 12.7 ± 0.3 14 1 14.0 ± 0.0 15 1 15.0 ± 0.0 REFERENCES CITED 1. 	Aherne, F . X., R. J. Christopherson, J. R. Thompson and R. T. Hardin . 1976. Factors Affecting the Onset of Puberty, Post-weaning Estrus and Blood Hormone Levels of Lacombe Gilts. Can. J. Anim. Sci. 56:681. 2. 	 Dzuik, P. J. 1968. Effect of Number of Embryos and Uterine Space on Embryonic Survival in the Pig. J. Anim. Sci. 27:673. 3. Martin , 	P. A. , H. W. Norton and P. J. Dzuik. 1977. The Effect of Corpora Lutea Induced During Pregnancy on the Length of Gestation in the Pig. BioI. Reprod. 17:712. 4. 	Signoret, J. P., F. du Mesnil du Buisson and P. Mauleon. 1972. Effect of Mating on the Onset and Duratio'n ofOvula­tion in the Sow. J. Reprod. Fe rt. 31:327. 5. Swierstra, E. 	E. and C. W. Dyck. 1976. Influence of the Boar and Ejaculation Frequency on Pregnancy Rate and Embryonic Survival in Swine. J. Anim. Sci. 42:45;3. 6. 	 Zimmerman, D. R. and C. Nahe r. 1971. Influence of Mat­ing on Ovulation Time in the Pig. J. Anim. Sci. 33:273 (abstr. ). 10 

Factors Affecting Rebreeding Performance of Weaned Sows

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