Selekcija svinja na veličinu legla u zadnjih dvadesetak godina pokazala se kao jedan od najvažnijih ekonomskih ciljeva u intenzivnoj svinjogojskoj proizvodnji. To je dovelo do stvaranja linija visokoplodnih krmača. Sa nastankom krmača visoke plodnosti javio se problem nemogućnosti tih istih krmača da othrane svu oprasenu prasad. Najčešći razlozi proizlaze iz toga što u velikim leglima dolazi do smanjenja porodnih masa prasadi, kao i do veće varijabilnosti u porodnim masama, a broj funkcionalnih sisa je često manji od broja oprasene prasadi. Prasad manje porodne mase ima sporiji rast i veći postotak uginuća u zadnjoj fazi gravidnosti i tijekom laktacije. Cilj ovog istraživanja je bio utvrditi značajnost utjecaja veličine legla, porodne mase i spola na svojstva rasta i preživljavanja prasadi visokoplodnih krmača, odnosno utvrditi da li u velikim leglima sa prasadi manje porodne mase uz određeni utjecaj spola dolazi do negativnog utjecaja na svojstva rasta i preživljavanja te iste prasadi. Podaci su dobiveni na svinjogojskoj farmi OPG Jančo čiji se uzgoj temelji na visokoplodnoj liniji krmača Pen Ar Lan. U prasilištu je slučajnim odabirom odabrana prasad iz pedeset legala. Prasad je nakon prasenja jedinstveno označena radi praćenja tijekom istraživanja, pojedinačno je izvagana je, određen je spol svakom prasetu, te zabilježeni podaci o rednom broju legla, kao i podaci o ukupno oprasenoj prasadi te o broju mrtvooprasene prasadi. Tijekom laktacije i uzgoja svako prase je vagano pet puta. U fazi laktacije prasad je vagana digitalnom vagom Libela, dok je u fazi uzgoja vagana malom stočnom vagom. Na temelju raspodjele i rezultata osnovne statistike svaki sistematski utjecaj je definiran kao utjecaj s nivoima. Za svojstva veličine legla testirani su utjecaji broj ukupno oprasene prasadi, broj živooprasene prasadi te broj mrtvooprasene prasadi. Utjecaj porodne mase definiran je kao utjecaj s pet nivoa, a spol prasadi kao utjecaj s dva osnovna nivoa: muški i ženski, te kao utjecaj legla s obzirom na odnos muških i ženskih jedinki (pretežno muška, mješovita legla, i pretežno ženska legla. Preživljavanje prasadi praćeno je preko svojstava broj mrtvooprasene prasadi i broj prasadi uginule tijekom laktacije. Svojstva rasta prasadi praćena su preko tjelesnih masa prasadi i dnevnih prirasta u nekoliko razdoblja od prasenja do završetka uzgoja prasadi. Osnovna statistika izračunata je primjenom procedura MEANS i UNIVARIATE. Analiza varijance i testiranje sistematskih utjecaja izvršeno je pomoću PROC GLM statističkog paketa SAS, a razlike između nivoa određene su Tukey i F-testom.
Istraživanjem je utvrđen značajan utjecaj svojstava veličine legla i porodne mase na preživljavanje i svojstva rasta prasadi, dok nije utvrđen utjecaj spola na preživljavanje i svojstva rasta prasadi visokoplodnih krmača. Najmanje mrtvooprasene i prasadi uginule tijekom laktacije utvrđeno je u leglima u kojima je zabilježeno manje od 17 ukupno oprasene prasadi. U leglima s manje od 14 živooprasene prasadi utvrđen je najveći broj mrtvooprasene prasadi, ali i najmanji broj prasadi uginule tijekom laktacije. Najmanja porodna masa utvrđena je u leglima s više od 16 živooprasene prasadi. Najveći dnevni prirasti utvrđeni su u leglima s manje od 17 ukupno oprasene prasadi i u leglima s 14 -16 živooprasene prasadi. Nakon odbića prasadi veličina legla nije utjecala na dnevni prirast. Iako postoji trend smanjivanja uginuća s rastom porodne mase, razlike u broju mrtvooprasene prasadi i broju prasadi uginule tijekom laktacije nisu značajne. Prasad manje porodne mase ima manju masu pri odbiću i manju masu na kraju faze uzgoja. Prasad manje porodne mase ima manje dnevne priraste u svim razdobljima do kraja uzgoja. Nije utvrđen utjecaj spola na preživljavanje te masu i dnevne priraste prasadi (P>0,05). Primjena suvremenih načina upravljanja proizvodnjom omogućava preživljavanje prasadi niže porodne mase i bolje iskorištenje visokoplodnih krmača.
Litter size and birth weight are important traits in pig production. Selection for improved litter size has increased the number of piglets born alive, and the creation of highly prolific sow lines. However, improvement at birth is not completely realized at weaning due to higher postnatal mortality. The number of piglets weaned per sow is a trait of major economic importance in pig production. At least partly, mortality during lactation is related to the decrease in average piglet birth weight. Birth weight is the result of the intrauterine growth of piglets and is considered to be one of the most important factors influencing pig survival. But a whole litter of the sow, the distribution of the birth weight within the litter (mean birth weight and variability within the litter) is of importance for the overall productivity of the sow. Litters with high levels of birth weight variation are claimed to have reduced survival because direct competition excludes light littermates from access to functional and productive teats. As birth weight decreased pigs were more likely to suffer mortality before weaning and during the nursery phase. Not only the survival rate but also postnatal growth performance can be compromised by low birth weight. Piglet birth weight and uniformity of litter are also affected by parity, and sex of piglets.
The aim of this study was to determine the effect of litter size, birth weight, and sex on survival and growth traits of piglet in highly prolific sows. Additionally, the variability of birth weight and growth of piglets in the hyper-prolific sow line in one of the top commercial pig farms in Croatia.
The experimental herd consisted of 50 Pen Ar Lan Naima sows farrowed between December 2014 and January 2015. Gestating sows were moved to the farrowing rooms one week before the expected parturition day. Sows were treated with d-cloprostenol on day 112 of the gestation period. Each pen was equipped with a commercial crate. One infrared heat lamp was placed in each farrowing crate to provide additional heat to piglets. On average, piglets were weaned at 28 days. From the 5th day after farrowing until weaning, sows were fed ad libitum. Within the first 18 hours of life, piglets were individually weighted, teeth clipped, and tail docked, as well as individuals identified and determined by sex. The third day after farrowing, piglets were injected with iron. Litter size was equalized by cross-fostering within two days after farrowing by moving piglets of smaller birth weight. Male piglets were castrated on the third day of life. During the survey, 720 piglets (Naima sows x P76 Pen Ar Lan hybrid boars) from 50 litters were weighted five times: the 1st day after farrowing (BW), 14th day of life (W2), at weaning on 28th day (W3), 30th day of nursery period (W4), and at the end of nursery period when piglets were old 83 days (W5). The normality of birth weight (BW) was tested using PROC UNIVARIATE (SAS, 2013). Standard deviation (SD) and range were measures of the variability of the birth weight (BW) and other weight measures. The coefficient of variation (CV) related the variability to the mean. Minimal and maximal birth weight showed the extremes in the distribution. Analysis of variance and testing of main effects in the model for live weight at
weaning (W3) was performed using PROC GLM (SAS, 2013). The statistical model included effects with levels: litter size, birth weight, and sex of piglets. The effect of liter size is analyzed through the number of piglets total, a number of piglets born alive, and the number of stillborn piglets. Each trait I defined as a trait with levels determined previously by basic statistical analysis using PROC MEANS and PROC UNIVARIATE. Litter size presented as a number of piglets born total is categorized into three groups: <17, 17 – 19, and >19 piglets. Litter size presented as a number of piglets born alive is categorized into three groups: <14, 14 – 16, and >16 piglets. Litter size presented as a number of stillborn piglets is categorized into three groups: 0 -1, 2 -3, and >3 piglets. The effect of the sex of the piglets was analyzed in two ways: firstly, in the usual way as the effect of male or female piglet, and secondly as the ration between piglets in litter according to sex as mainly male litters, mixed litters, and mainly female litters. For analysis purposes, BW was categorized into five classes: ≤1,000 kg, 1,001 – 1,200 kg, 1,201 – 1,400 kg, 1,401 – 1,600 kg, and >1,600 kg.
Number of piglets born total influenced piglets survival presented as the number of stillborn piglets, number of piglets dead at weaning, and number of total dead piglets (P<0,0001). The number of piglets born alive influenced also all survival traits at the level of significance P<0,01. The number of stillborn piglets influenced the number of piglets weaned. The highest level of the mortality rate was observed in litters with 2 or 3 stillborn piglets. There was no difference between birth weight from different classes of the number of piglets born total (P>0,05), but there is evidence that birth weight is smaller in litters of more than 16 piglets born alive (P<0,05). Bodyweight of piglets at weaning generally decreased as litter size increased. The largest body weight at the end of the nursery period was observed in the smallest litters, with a tendency of no difference between different classes of the number of piglets born alive. The effect of litter size presented as the number of piglets born total on the growth rate of piglets showed that piglets in smaller litters had faster growth presented as daily gain in different periods from farrowing to the end of the nursery period. Further, daily gains of piglets were the highest in the litters of 14 to 16 piglets born alive in the period until weaning. After weaning there is no difference in daily gains according to different litter size classes of the number of piglets born alive.
Pre-weaning mortality averaged 17.2% of piglets born alive. In BW class below 1.000 kg, almost 44% of piglets died during the lactation period, mainly between the first (BW) and the second weighing (W2). Except for the crushing of piglets by the sow, early life mortality is most likely attributable to insufficient colostrum consumption and less milk consumption. Variability of birth weights (BW) was the largest in piglets with BW less than 1.000 kg. The highest number of piglets belongs to the BW class between 1.201 and 1.400 kg. The effect of birth weight on piglet survival is not so obvious, because there is a tendency of decreasing of a number of stillborn piglets with increasing birth weight, but these differences were not significant among birth weight classes. Similar conclusions could be drawn for the number of piglets weaned (P>0.05). The birth weight of piglets had a significant influence on pre-weaning mortality and subsequent growth performances.
Pearson correlation coefficients among body weight traits ranged between 0.48 and 0.93. The lowest value of correlation coefficients was observed between birth weight and weight of piglets at weaning. The highest values of correlation coefficients were noticed between weight measurements in the nursery phase. The birth weight significantly influenced the bodyweight of piglets at weaning, as well as body weight at the end of the nursery period.
Piglets with BW less than 1.200 kg do not achieve critical live weights of a minimum of 7 kg at weaning, which means they need a prolonged lactation period. The difference in the final live weight at the end of the nursery period between the lightest and the heaviest piglets was more than 10 kg. In all observed periods, there is a significant effect od birth weight on daily gains determined (P<0.05). Piglets with larger birth weight had larger daily gains. The difference in average daily gain between piglets with birth weight less than 1.000 kg and piglets with birth weight more than 1.600 kg was around 110 grams.
From all sources of variation included in the statistical model for traits, birth weight had the most important effect (P0.0001). Litter size showed a moderate level of significance, but the effect of sex on weaning weight was not determined in this study, although male piglets in our study had higher birth weight than female piglets.
In large litters produced by highly prolific sows, a variability of birth weight of piglets, together with an increased number of lighter piglets, become a new challenge for pig producers. Advantages in litter size of highly prolific sows could be only useful if the mortality of piglets reduced and if appropriate growth performance in piglets will be assured.