Within-litter Weight Research Articles

Relationships between litter size, sex ratio and within-litter birth weight variation in a sow herd and consequences on weaning performance.

Routine selection for litter size has resulted in an increase in the proportion of lightweight piglets. There is a need to balance prolificacy with litter uniformity to maximize profit. A total of 3,465 piglets from 310 litter records obtained from 2016 until 2019 at the Pig Industry Board research unit, Arcturus, Zimbabwe were used to determine the relationships between litter size, sex ratio, and within-litter birth weight variation in the sow herd and consequences on performance at weaning. The regression procedure of SAS was used to determine the relationships between litter size, sex ratio, and within-litter birth weight variation. The regression procedure was also used to determine the relationships between number born alive, within-litter birth weight variation, and sex ratio, and litter performance traits at weaning. Parity of sow, year, and month of farrowing did not affect sex ratio (P > 0.05). The number born alive and number of piglets born had no relationship with sex ratio (P > 0.05). As the sex ratio increased, percent survival of piglets at weaning also increased linearly (P < 0.05). As the proportion of males in litters increased, within-litter birth weight variation and within-litter weaning weight variation increased reaching maximum as the proportion of males in litters approached 0.5 and then decreased onwards. As the proportion of males in litters approached 1, within-litter birth weight variation and within-litter weaning weight variation reached their least values. In conclusion, within-litter sex ratio does not vary with parity, year, and month of farrowing. Within-litter weight variation is highest in litters with equal number of male and female piglets and lowest in unisex litters. This implies that the production of unisex litters can help to reduce the variation in the weight of pigs at birth, weaning, and marketing which is one of the biggest economic challenges faced by pork producers.

Genetic study of litter size and litter uniformity in Landrace pigs

ABSTRACT We aimed to estimate litter size and litter uniformity genetic parameters and genetic trends of Landrace pigs at birth and at three weeks by using multitrait analyses for 2,787 litters. The following litter traits were evaluated: number of piglets born alive (NBA), within-litter weight mean at birth (MBW), within-litter weight standard deviation at birth (SDB), within-litter weight coefficient of variation at birth (CVB), number of piglets at three weeks (NT), within-litter weight mean at three weeks (MT), within-litter weight [...]

Hritabilities and genetic and phenotypic correlations of litter uniformity and litter size in Large White sows

Litter uniformity, which is usually represented by within-litter weight coefficient of variation at birth (CVB), could influence litter performance of sows and the profitability of pig enterprises. The objective of this study was to characterize CVB and its effect on other reproductive traits in Large White sows. Genetic parameters and genetic correlation of the reproductive traits, including CVB, within-litter weight coefficient of variation at three weeks (CVT), total number born (TNB), number born alive (NBA), number born dead (NBD), gestation length (GL), piglet mortality at birth (M0), piglet mortality at three weeks (M3), total litter weight at birth (TLW0), and total litter weight at three weeks (TLW3) were estimated for 2 032 Large White litters. The effects of parity and classified litter size on CVB, CVT, TNB, NBA, NBD, GL, M0, M3, TLW0, and TLW3 were also estimated. The heritabilities of these reproductive traits ranged from 0.06 to 0.17, with the lowest heritability for CVB and the highest heritability for TLW0. Phenotypic and genetic correlations between these reproductive traits were low to highly positive and negative (ranging from −0.03 to 0.93, and −0.53 to 0.93, respectively). The genetic correlations between TNB and CVB, and between M0 and CVB were 0.32 and 0.29, respectively. In addition, CVB was significantly influenced by parity and litter size class (P<0.05). All the results suggest that piglet uniformity should be maintained in pig production practices and pig breeding programs.

Effects of within-litter birth weight variation of piglets on performance at 3 weeks of age and at weaning in a Large White×Landrace sow herd

The effect of piglet birth weight variation on subsequent weight variations and litter performance in Large White×Landrace sows is not well understood. The objective of the current study was to determine the relationship between within-litter birth weight coefficient of variation (CVB) and performance of piglets at 3 weeks and at weaning. A total of 1836 litter records, collected between January 1998 and September 2010 at the Agricultural Research Council (ARC), Irene, were used. The CVB had a linear relationship with survival at 3 weeks (SURV3) (b=−0.20; P<0.05) and within-litter weight coefficient of variation at 3 weeks (CV3) (b=0.50; P<0.05). Litters with high CVB had more deaths at 3 weeks (P<0.05). Increase of CV3 with CVB varied with parity (P<0.05). The rate of increase of CV3 with CVB was highest in Parity 1 (b=0.41) followed by Parity 2 (b=0.36) then middle aged (Parity 3–5) sows (b=0.32). There was no significant relationship between CVB and litter weight at 3 weeks (LWt3) or mean litter weight at 3 weeks (MWt3) (P>0.05). Weight variation at weaning was positively skewed (skewness value of 0.81). The survival to 3 weeks (SURV3) ranged from 13.3% to 100% with a mean of 87.6%. The CVB had a linear relationship with both within-litter weaning weight coefficient of variation (CVW) (b=0.50; P<0.05) and percent survival to weaning (SURVW) (b=–0.04; P<0.05). There was an unfavorable positive relationship between CVB with both CVW and SURVW. It can be concluded that litter performance at weaning is related to CVB.

Death risk and preweaning growth rate of piglets in relation to the within-litter weight distribution at birth

This study investigated whether the death risk of piglets and the preweaning growth rate of the surviving piglets depend on the within-litter weight distribution at birth. The litters were produced either by sows from one of six commercial breeds ( n = 363) or by Dutch Landrace sows ( n = 456). The birth weight and sex of all piglets and the weight and age at weaning of piglets which survived the suckling period were known. All litters were classified as one of five litter types on the basis of the within-litter birth weight distribution. The results indicate that the within-litter birth weight distribution is neither an important determinant of the within-litter variation in birth weight, nor an important determinant of the preweaning death risk of liveborn piglets. The average preweaning growth rate differed between litter types, but this was entirely due to differences in average litter size at birth. Within each of the four litter types with two discrete subpopulations, the average growth rate of the piglet type with the lower average birth weight was less than that of the piglet type with the higher average birth weight. In two litter types this difference was still significant after correction for litter size and birth weight.

Weight distribution within litters at the early foetal stage and at birth in relation to embryonic mortality in the pig

This study investigated whether the within-litter weight distribution at birth is already established by the end of the embryonic stage of pregnancy (Day 35) and whether it is related to embryonic mortality rate. All data were obtained from Dutch Landrace gilts which had been inseminated with semen of Dutch Landrace boars. A total of 373 foetal litters (Day 27–Day 110) and 826 litters at term were classified into one of five litter types on the basis of the within-litter weight distribution. Independent of stage of pregnancy, within-litter weights were normally distributed in approximately 67% of all litters. The within-litter weight distribution at birth was already established by the end of the embryonic stage. Embryonic mortality rate was lower in litters with two discrete subpopulations than in litters with a normal distribution, except for litters with giants (growth-enhanced foetuses). The latter had the highest average embryonic mortality rate. The type of within-litter weight distribution might be a consequence of the very early existence of variation in embryonic development and the functioning of an intrauterine mechanism of selective mortality to reduce developmental variation before implantation.