No abstract

Data sets from 2 large Australian piggeries were used to estimate genetic parameters for the traits weaning to conception interval (WCIi-l,i) and farrowing interval (FIi-l,i), number born alive (NBAI), average piglet birthweight (BWi), 21-day litter weight (W21i), and sow stayability (STAYli) recorded for each ith parity, as well as sow average daily gain (ADG) and backfat (BF) recorded at the end of performance test. Over parities and herds, heritabilities for each trait were in the ranges: WCI/FI, 0.0-0.10; NBA, 0.09-0.16; BW, 0.11-0.35; W21, 0.12-0.23; STAYli, 0.02-0.09; ADG, 0.35-0.37; BF, 0.36-0.45. Genetic correlations between NBAl and NBA from later parities were significantly different from 1. In addition, in 1 herd negative genetic correlations (rg = -0.04 to -0.25) were found between sow stayability traits and NBA1, but not NBA recorded in later parities. Stayability was Unfavourably correlated with ADG and BF, and favourably correlated with WCI12. However, WCI12 was unfavourably correlated genetically with BF (rg = -0.24) but uncorrelated with ADG. Antagonistic relationships also existed between NBA and BW, NBA and W21, and BW and STAY. In addition to the traditional traits currently included in pig-breeding programs (e.g. ADG, BF, and NBA), traits such as WCI, BW, and STAY should also be considered as selection criteria to minimise the detrimental effects of antagonistic genetic relationships between traits.

Data from 9296 calves born to 2078 dams over 9 years across five sites were used to investigate factors associated with calf mortality for tropically adapted breeds (Brahman and Tropical Composite) recorded in extensive production systems, using multivariate logistic regression. The average calf mortality pre-weaning was 9.5% of calves born, varying from 1.5% to 41% across all sites and years. In total, 67% of calves that died did so within a week of their birth, with cause of death most frequently recorded as unknown. The major factors significantly (P < 0.05) associated with mortality for potentially large numbers of calves included the specific production environment represented by site-year, low calf birthweight (more so than high birthweight) and horn status at branding. Almost all calf deaths post-branding (assessed from n = 8348 calves) occurred in calves that were dehorned, totalling 2.1% of dehorned calves and 15.9% of all calf deaths recorded. Breed effects on calf mortality were primarily the result of breed differences in calf birthweight and, to a lesser extent, large teat size of cows; however, differences in other breed characteristics could be important. Twin births and calves assisted at birth had a very high risk of mortality, but <1% of calves were twins and few calves were assisted at birth. Conversely, it could not be established how many calves would have benefitted from assistance at birth. Cow age group and outcome from the previous season were also associated with current calf mortality; maiden or young cows (<4 years old) had increased calf losses overall. More mature cows with a previous outcome of calf loss were also more likely to have another calf loss in the subsequent year, and this should be considered for culling decisions. Closer attention to the management of younger cows is warranted to improve calf survival.

This study examined the effects of season on genetic parameters for production and reproductive traits and quantified within contemporary group effects of temperature on these traits using linear and plateau-linear regression models. From 2003 onwards, data were available on ~60 000 gilts for the routinely recorded production traits (BF: back fat; LADG: lifetime average daily gain) and ~45 000 litters for the sow reproductive traits (TB: total born; NBA: number born alive; BWT: average piglet birthweight). A subset of gilts were also recorded for test period daily gain (TADG), daily feed intake (ADI) and feed conversion ratio (FCR) and, later, as sows (n ~2000) for average daily lactation feed intake (LADI). Least-squares means for some production and reproductive traits significantly differed between seasons: summer and winter means were 2.28 ± 0.017 vs 2.54 ± 0.011 kg/day for ADI, 2.80 ± 0.022 vs 3.21 ± 0.011 kg/kg for FCR, and 1.61 ± 0.02 vs 1.54 ± 0.02 kg for BWT. However, some statistically significant differences (due to large n) were biologically insignificant. Trait variation also differed between seasons, but heritability estimates did not significantly differ from each other. Heritabilities were (summer vs winter): BF: 0.43 ± 0.03 vs 0.41 ± 0.02; LADG: 0.18 ± 0.02 vs 0.16 ± 0.02; TADG: 0.12 ± 0.10 vs 0.08 ± 0.06; ADI: 0.37 ± 0.15 vs 0.22 ± 0.07; FCR: 0.14 ± 0.11 vs 0.17 ± 0.06; TB: 0.09 ± 0.01 vs 0.10 ± 0.01; NBA: 0.06 ± 0.01 vs 0.07 ± 0.01 and BWT: 0.37 ± 0.03 vs 0.32 ± 0.04. Genetic correlations between the same trait recorded in different seasons were generally very high (>0.70), with the exception of TB, where the genetic correlation between spring and autumn was 0.65 ± 0.09, suggesting a genetic component to the effect of seasonal infertility on litter size. Regression models demonstrated that two selection lines had different responses to increasing temperature, despite concurrent selection in the same environment. Plateau-linear models were generally better than linear models for describing changes to production traits with temperature. Based on maximum temperature at the end of performance testing, the estimated temperature thresholds above which lifetime growth performance was compromised were 25.5 and 32.5°C in the two lines. There were only small linear relationships between reproductive traits and temperature. Overall, the ongoing acclimatisation to the thermal environment and the partial confounding of contemporary group with temperature variables (season explained 62% of variation in average daily temperature) are potentially contributing factors to the lack of major differences in heritability estimates between seasons, and the relatively small regression coefficients for the effects of temperature on performance. Nevertheless, temperature can be demonstrated to affect phenotypic outcomes within contemporary groups using commercial data.

Data from 2 large Australian piggeries were used to estimate genetic parameters and to examine fixed effects for weaning to conception interval (WCI) and farrowing interval (FI) measured in the first 3 reproductive cycles, and sow stayability from the first to later i parities (STAY1i,). WCI and FI recorded following the first farrowing had low heritabilities (h2 = 0.08-0. l0), but estimates did not significantly differ from zero when these traits were recorded in later parities. Heritability estimates for STAY increased with parity of recording, ranging from 0.05 for STAY12 to 0.06 (STAYl3) and 0.09 (STAYl4). Genetic correlations between WCI12 or PI12 and stayability traits ranged from -0.22 to -0.54. Selecting for short WCI following the first farrowing should have favourable consequences for longevity of sows. Important fixed effects for WCI and FI were lactation length and the number of piglets nursed. Both short (<20 days) and long (>29 days) lactation periods led to an increase in WCI12 relative to the optimum lactation length of 21-23 days. WCI also increased with the number of piglets nursed by 1 day/additional piglet for litters ranging in size from <7 to >10 piglets. STAY was little affected by correcting for the average number of piglets born in previous litters.

No abstract

Gilt progeny (GP) are born and weaned lighter than sow progeny (SP) and have higher rates of mortality. This study aimed to quantify the performance and survival differences between GP and SP throughout the entire production cycle from birth to sale. Furthermore, the study looked at the effects of segregating GP and SP compared with commingling during rearing within common pens. It was hypothesized that GP would be lighter than SP at every age and have lower rates of survival accompanied by higher rates of medication, and that segregating GP and SP would improve the growth and survival of both groups. All progeny born to 109 gilts (parity 1) and 94 sows (parities 2 to 8) were allocated to 4 postweaning treatments at birth: GP separately penned, GP mixed with SP in a common pen (GM), SP separately penned, and SP mixed with GP in a common pen (SM), with littermates split among treatments. The GM and SM pigs were penned together after weaning. Individual live weight of all progeny was recorded at birth (birth weight [BWT]), weaning (28 d; weaning weight [WWT]), 10 wk of age (10-wk weight [10WT]), and sale (22-23 wk; sale weight [SWT]). Individual HCW, backfat depth, loin depth, and dressing percentage were measured at slaughter. All postweaning mortalities and medications were recorded. The GP had a lighter BWT ( = 0.032), WWT ( < 0.001), 10WT ( < 0.001), and SWT ( < 0.001) than SP as well as a lower HCW ( < 0.001) and dressing percentage ( = 0.012). Postweaning performance differences were mostly attributable to the lighter WWT of GP compared with that of SP when WWT was fitted as a covariate. The GP had a higher mortality in the immediate postweaning period (weaning to 10 wk of age; = 0.028) and from weaning to sale ( = 0.012) than SP, which was also attributable to lower WWT. The GP exhibited a higher incidence of mortality ( = 0.011) due to respiratory tract infection in the grower-finisher period, despite similar medication rates ( = 0.83). Segregation of GP and SP between pens presented no benefit in terms of growth and survival of both groups while requiring added labor and production considerations and, therefore, is not recommended. This study confirms that GP are lighter than SP, on average, at every stage of life from birth to slaughter and that their performance before weaning is an important determinant for whole-of-life performance.

No abstract