The effect of within-litter weight variation on pig productivity is poorly understood. The aim of the study was to determine the effect of within-litter variation in birth weight on litter performance at three weeks of age and at weaning.
General Introduction
Justification
Sows that produce uniform piglets at birth significantly reduce production costs (Foxcroft and Town, 2004). Understanding birth weight variation within the litter and its impact on future performance will help improve litter homogeneity at birth.
Objectives
The lack of understanding of the role of piglet weight variation at birth largely explains why most commercial farmers are reluctant to record individual piglet weights at birth. There is a relationship between CVB and intra-litter weight variation, percent survival and litter weight at three weeks; and.
Changes in birth weight in the domestic pig: effects on offspring survival, weight gain and sucking behaviour. Genetic determination of individual birth weight and its association with sow productivity traits using Bayesian analyses.
Review of Literature
Introduction
Pig statistics and production systems in South Africa
- Pig production statistics
- Production systems
Large-scale pig production in South Africa usually placed all age groups either in outdoor pens or inside buildings in close proximity to each other (Honeyman, 2005). Commercial outdoor pig production has been introduced in parts of South Africa and there is potential for further expansion (Honeyman, 2005).
Traits of economic importance in pigs
Sow performance is reflected in reproductive traits such as NBA, number of stillbirths (NBD) and litter weight at birth (TBWT) (Kanis et al., 2005). In general, pig reproductive traits have been found to be poorly heritable (Norris et al., 2010).
Within-litter birth weight variation
Coefficient of variation values between 0.22 and 0.26 have been reported for birth weight of pigs within a litter in the USA (Patience et al., 2004). There are no reported estimates of birth weight within litters in South African pig herds.
Impact of within-litter birth weight variation on litter performance
- Effect of within-litter birth weight variation at three weeks
- Effect of within-litter birth weight variation on performance at weaning
- Effect of within-litter birth weight variation on piglet survival
- Effects of within-litter birth weight variation on post-weaning
There have been conflicting reports on the effect of within-litter variations in birth weight on piglet mortality. Neither study predicted survival estimates using within-litter variation in birth weight.
Factors affecting within-litter birth weight variation
- Litter size
- Genotype
- Season of farrowing
- Parity
- Sex ratio
- Nutrition
The aim of the study was to characterize intra-litter birth weight variation in piglets. P x CVB is the interaction between Parity of sow and intra-litter birth weight variation β0 = intercept.
Conclusions
Sex ratio of offspring in pigs: farm variability and relationship to litter size and piglet birth weight. Genetic parameters for within-litter variation in piglet birth weight and change in within-litter variation during lactation.
Partitioning of within-litter birth weight variation and its distribution in piglets
Introduction
The farrowing performance of sows is among the most important determinants of pig farm profitability (Fix et al., 2010). However, the heritability of birth weight of individual piglets has been reported to be higher than that of litter traits (Roehe, 1999; Chimonyo et al., 2006). Uniform piglets at birth are likely to produce uniform pigs at weaning and also at marketing (Fix et al., 2010).
Materials and methods
- Study site
- Herd management
- Data structure and preparation
- Descriptive statistics for birth weight variation
- Model development and analyses
The extent to which these factors influence within-litter variation in birth weight has not been established. The aim of the study was to identify factors that influence the variation in birth weight within the litter of pigs. From these records, MBWT, TBWT, within-litter standard deviation of birth weight (SDB), CVB, minimum birth weight (MinB) and maximum birth weight (MaxB) were calculated.
Results
- Summary statistics
- Number born alive
- Litter weight
- Maximum and minimum birth weights
- Mean birth weight
- Birth weight variation
- Correlations
NB: CVB = coefficient of variation for birth weight within the litter; MaxB = Maximum birth weight within a litter; MBWT = Mean Birth Weight;. MinB = Minimum birth weight within a litter; NBA = Number of live births; SDB = Within litter birth weight standard deviation; TBWT = Litter weight at birth. Interactions between parity and race, parity and farrowing month had no significant effect (P>0.05) on MBWT.
Discussion
Piglets from primiparous sows were more uniform than pigs from older sows, this is related to the parity effect in NBA (Milligan et al., 2002). In support of this, English et al. 1988) reported an increased incidence of stillbirth after Parity 6. This finding contradicts that of Mungate et al. 2000) who found distinction in the NBA over two seasons.
Conclusions
The similarities in NBA observed in the hot-wet season and the cold-dry season explain why there were no seasonal effects in CVB. The effect of NBA on MinB and MaxB may be related to the effect of litter size in utero on pig birth weight. There were no effects of interactions between breed, sow parity, and farrowing month on litter weight.
Genetic parameters of piglet mortality, within-litter variation of birth weight, litter size and litter birth weight. Within-litter birth weight variation in domestic pigs and its relationship to pre-weaning survival, weight gain and variation in weaning weights. Within-litter variation of birth weight in hyperproductive Czech Great White sows and its relationship to litter size traits, stillborn piglets and losses to weaning.
Effect of within-litter birth weight variation on percent survival, mean litter
Introduction
As with birth, farmers record litter characteristics such as litter size at three weeks (LST) and total litter weight at three weeks (LWTT), rather than the weight of individual pigs. The effects of litter characteristics at birth on performance up to three weeks of age are not clearly understood. In addition, it helps to understand how selection of litter traits at birth can affect performance at three weeks.
Materials and methods
- Study site
- Data structure and preparation
- Descriptive statistics
- Model development and analyses
CVT = intra-litter weight variation at three weeks MWWT = mean litter weight at three weeks. LWTT = total litter weight at three weeks SURVT = percentage survival to three weeks CVB= intra-litter birth weight variation NBA= number of live births. MBWT= average birth weight TBWT= total litter weight at birth LST = litter size at three weeks P = Parity of sow.
Results
- Summary statistics
- Mean litter weight at three weeks
- Litter weight at three weeks
- Survival at three weeks
- Within-litter coefficient of variation at three weeks
NB: CVB = intra-litter birth weight variation; CVT = Intra-litter weight variation at three weeks; MWTT = Average litter weight at three weeks; LWWT= Total litter weight at three weeks; SURVT = Percent survival up to three weeks; N = Experimental litters = 1495. P<0.05 * *P<0.01 PS- Not significant; NBA: number born alive; CVB: intra-litter birth weight variation; MBWT: mean birth weight; MWTT: average weight at three weeks; TBWT: total litter weight at birth; LWTT: total litter weight at three weeks; LST: litter size at three weeks; SURVIVAL: percent survival up to three weeks; CVT: intra-litter weight variation at three weeks. The CVB was stepwise selected as the most powerful predictor of CVT with a partial R-squared of 0.098 followed by MWTT, Parity of sow, MBWT, LST and NBA in that order (P<0.15).
Discussion
Conflicting results from studies by Wolf et al. 2008) suggest that CVB is a major contributor to SURVT. This may be due to the strong positive correlation between MBWT and minimal birth weight in a litter (Wolf et al., 2008). This confuses with Milligan et al. 2002) who found similar correlation coefficients (0.4) between both NBA and CVB with within-litter weight variation after four weeks.
Conclusions
Effect of pig birth weight on postnatal growth performance, tissue lipogenic capacity and muscle histological traits at market weight Livestock Production Science. Effect of litter size and litter weight on preweaning performance of cross-fed low birth weight pigs. Consequences of birth weight for postnatal growth performance and carcass quality in pigs in relation to myogenesis.
Effect of within-litter birth weight variation on percent survival, mean litter
Introduction
Piglets are typically weaned at four to five weeks of age (Andersen et al., 2005). Traditionally, improving NBA has been a major focus to maximize sow productivity (Zhu et al., 2008; Dube et al., 2011). Although there is some evidence that intra-litter birth weight variation influences intra-litter weaning weight variation, mean weaning weight and survival to weaning (Milligan et al., 2002; Wolf et al., 2008), little effort has been made to predict weaning performance using within-litter birth weight variation.
Materials and methods
- Study site
- Data structure and preparation
- Descriptive statistics for CVB, CVW, MWWT, LWWT and SURVW
- Model development and analyses
One way to reduce weaning weight variation (so market weight variation) may be to select for sows that produce more uniform litters (Foxcroft and Town found that within-litter birth weight is positively related to within-litter weight variation at weaning. The objective of the present study was to determine the relationship between intra-litter birth weight variation and within-litter weight variation, litter weight and weaning survival rate. Birth weight variation, NBA= number born alive,
Results
- Mean litter weight at weaning
- Litter weight at weaning
- Percent survival at weaning
- Within-litter coefficient of variation at weaning
P<0.05 * *P<0.01 NS- Not significant; NBA: number of live births; CVB: variation in birth weight within the litter; MBWT: average birth weight; MWWT: average weaning weight; TBWT: total litter weight at birth; LWWT: total weaning weight; LSW: litter size at weaning; CVW: Variation in weaning weight within the litter; SURVW: percentage survival to weaning. NBA: number of live births; CVB: variation in birth weight within the litter; MBWT: average birth weight; MWWT: average weight at weaning; TBWT: total litter weight at birth; LWWT: total weaning; LSW: litter size at weaning; CVW: Variation in weaning weight within the litter; SURVW: percentage survival to weaning.
Discussion
Our finding that CVB is the strongest predictor of CVW is consistent with Milligan et al. 2002) found similar correlation coefficients (0.4) between both NBA and CVB with CVW. The finding that CVB had no significant relationship with MWWT was consistent with Milligan et al. The effect of NBA and MBWT on MWWT found in this study confirmed Mungate et al.
Conclusion
This increase in birth weight within the litter can be critical to litter performance at three weeks. Further research should focus on ways to reduce birth weight variation within litters in pig herds. To determine acceptable levels of within-litter on-farm birth weight variation that farmers can target.
General discussion, conclusion and recommendations
General discussion
Like other reproductive traits, the heritability of within-litter variation in birth weight is expected to be low. Much of the variation in birth weight within the litter can be explained by non-genetic factors. Within-litter variation in birth weight was lowest in litters of gilts and highest in litters of multi-paired sows.
Conclusions
This tends to propagate or increase CVB for up to three weeks in sows in their early gestation. The variation in sow performance at weaning with CVB showed the same pattern as after three weeks. It is expected that litters with high CVB will have higher losses up to three weeks and weaning than litters with low CVB.
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