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Changes in sow body composition during lactation and their impacts on litter performance and sow reproductive success

Muller, Tracy Louise (2021) Changes in sow body composition during lactation and their impacts on litter performance and sow reproductive success. PhD thesis, Murdoch University.

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Abstract

During lactation, sows undergo increased metabolic demand whereby tissue mobilisation may be required to support litter growth. Excessive lactational catabolism can subsequently impact litter performance and the sows’ ability to rebreed. Current on-farm methods to measure sow body condition are subjective and/or lack the ability to capture a change in muscle mass perhaps of more importance in the leaner sow. Advances are required in the practical measurement of sow body composition with an understanding of how management of sows in response to these measurements can improve overall productivity and efficiency of the herd. The core objectives of the current thesis were to a) develop a practical method for the measurement of sow body composition, b) investigate the impact a change in body composition during lactation has on litter performance and subsequent reproduction status, and c) examine lactational dietary energy and lysine requirements using a two stage feeding program to minimise changes in sow body composition without negatively impacting litter growth or subsequent reproductive success. A series of experiments were carried out to validate a method of estimating body tissue masses, with a focus on muscle mass, and test the general hypothesis that excessive body protein mobilisation in lactation negatively impacts litter growth, sow rebreeding and subsequent reproductive success.

Chapter 3 provided an assessment of the agreement between bioelectrical impedance spectroscopy (BIS) with dual energy x-ray absorptiometry (DXA) in sow carcasses. Dual energy x-ray absorptiometry is used to provide a highly accurate prediction of fat and fat-free mass in pigs. Bioelectrical impedance spectroscopy requires calibration against a standard reference method of predicting composition, such as DXA. Due to abattoir requirements in the slaughter process and DXA scanning weight restrictions, validation was carried out on sow carcasses. The BIS was in close agreement with DXA, underestimating total carcase fat-free mass by -0.5 %.

Validation in the sow carcase was then followed by validation in the live sow. The agreement between bioelectrical impedance spectroscopy and dilutional measurements in the live sow was assessed in Chapter 4. A second objective of Chapter 4 was to provide a cross-validation of current methods used on-farm to measure body composition against BIS. Experiment 2 was conducted to develop apparent resistivity coefficients for extra- (431.1 ohm.cm) and intra-cellular (1827.8 ohm.cm) water against standard reference tracer dilution methods and a body geometry factor (1.09 ± 0.14) necessary for assessment of body composition. Given that BIS quantifies body fluid masses, validation of BIS was necessary in dry sows. The BIS predictions of fat-free mass were compared against the deuterium dilution method, existing impedance predictors and published prediction equations in the live sow. Method validation revealed mean differences between predicted (BIS) and measured (deuterium dilution method) fat-free mass values ranged from -8.2 to 32.7% but were not statistically different (P > 0.05). The relatively wide limits of agreement suggested BIS as an impractical option for assessing body composition in the individual sow. Equivalence testing revealed the prediction equations of Dourmad et al. (1997) exhibited the lowest bias and percentage equivalence, with narrow limits of agreement against impedance predictions and BIS.

Chapter 5 investigated the use of creatinine, a by-product of muscle metabolism, as a biomarker of muscle mass change. The aim of this experiment was to investigate the potential for serum creatinine to indicate a predicted loss in sow muscle mass over lactation, validated against an increase in serum 3 methyl histidine (3MH) and blood urea nitrogen (BUN), which are markers of dietary and/or body protein breakdown. To further provide an indication of a change in sow body composition, backfat depth at the P2 site was measured using ultrasound and sow condition measured using a sow caliper. Although sows did not experience a statistically significant change in backfat depth, caliper score and serum analytes over lactation (P > 0.05), 3MH concentrations were higher in the sows of a lower body mass at the end of lactation (P < 0.05), which correlated with BUN concentrations (P < 0.001; R2 = 0.691). These data suggested that although sows may have experienced body protein mobilisation, serum creatinine and BUN may have been the net result of dietary and/or body protein breakdown. Serum creatinine was, therefore, not a reliable marker of changes in muscle mass in the testing conditions. Experiments 1 to 3 identified that currently, the most precise prediction of sow body composition on the investigated population is the equation developed by Dourmad et al. (1997). From this point forward, sow body fat and protein mass and their change in lactation were predicted using these equations.

Chapters 6 and 7 were conducted to understand the degree of tissue mobilisation sows experience during lactation and the impact on litter performance and subsequent sow reproductive success. The objective of Experiment 4 was to use diet type (standard commercial formulations of gestation diet, 13.0 MJ dietary energy (DE)/kg 0.42 standardised ileal digestible (SID) g lysine/MJ DE versus lactation diet, 14.3 MJ DE/kg 0.62 g SID lysine/MJ DE) and feed allowance (reduced allowance of 7.5 kg/d versus ad libitum-fed) to impose varying levels of DE and SID Lys intake throughout lactation. Although dietary treatments applied were able to impose a calculated negative energy and Lys balance on lactating sows (parities 2-6), dietary treatments did not alter change in sow body fat or protein mass over lactation, litter growth, reproductive hormones (insulin and IGF-1) or total piglets born in the subsequent litter (P > 0.05). There was a tendency for sows which were fed the reduced allowance to have an extended time between weaning and next service by 0.3 ± 0.2 days (mean ± SEM) (P < 0.010). Under the current experimental conditions, a calculated negative energy and Lys balance over lactation had little to no impact on litter performance and subsequent sow reproduction. Sows in this experiment experienced minimal body tissue mobilisation. It was expected that sows would have experienced body tissue catabolism in response to daily changes in energy and Lys requirements as lactation becomes a priority and energy is partitioned for milk production. A more detailed investigation into energy and Lys requirements of sows fed ad libitum, to determine sow body composition changes and litter growth at different stages of lactation was required.

Experiment 5 was designed to evaluate the impact of a two-diet feeding program in lactation on sow body mobilisation, litter growth, rebreeding and subsequent reproduction. Sows were either fed a lactation diet to weaning, a gestation diet to weaning, or a gestation diet to day 6 of lactation and a lactation diet from day 7 to weaning. There was no dietary treatment response over the first 6 days of lactation on sow body composition or litter growth. From day 7 to weaning, sows fed the gestation diet lower in DE and SID Lys content tended to lose body protein (P > 0.10) and display a reduced litter growth (P < 0.05). Overall loss in body composition across all groups were minimal with no negative impacts on rebreeding or subsequent reproduction. A two-diet feeding program in lactation, which transitioned from a gestation to a lactation diet on day 7, had no impact on litter growth or changes in body composition, rebreeding or reproductive success.

In conclusion, data from this thesis showed that although BIS provided an accurate measure of fat-free mass in sow carcasses, this technology was not suitable for measures in the individual sow due to inherent biological and methodological variability in the live animal. Serum creatinine was not able to provide a reliable prediction of change in sow muscle mass as concentrations may have been influenced by both dietary Lys intake and/or body protein turnover. The prediction equations of Dourmad et al. (1997), based on body weight and a measure of backfat depth at the P2 site, provided the most reliable indication of sow body fat and protein mass against current impedance predictors and published prediction equations. Despite imposing varying degrees of dietary energy and Lys restrictions, sows used in these experiments did not excessively mobilize body tissues during early or late lactation with little to no impact on litter performance and sow reproductive success. It would appear that at least with the sows used in these experiments and the nutritional treatments imposed, there was limited lactational catabolism thus allowing opportunity for feeding strategies to target the growth and survival of piglets without compromising rebreeding and total piglets born in the subsequent litter. Further experiments are recommended to validate a prediction equation for estimating body protein mass using measures of body weight and loin muscle depth in sows across different parities and stages of lactation. There is also a need to update nutritional requirements of the leaner, lactating sow with a focus on delivering two diets formulated to meet DE and SID Lys requirements for maintenance in the first 6 days of lactation and rapid litter growth through to weaning. Future research is required to examine the impact of reduced body composition loss during lactation on subsequent reproductive cycles and sow longevity in the herd.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): Veterinary Medicine
United Nations SDGs: Goal 15: Life on Land
Supervisor(s): Pluske, John, Miller, David, Plush, K., D'Souza, Darryl and van Barneveld, R.
URI: http://researchrepository.murdoch.edu.au/id/eprint/64107
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