Abstract
Simple SummaryFinding strategies to manage variability in growing pig operations is of major importance to avoid the extra costs associated with inefficient barn usage or penalties at the processing plants when pigs are not correctly sorted. The aim of this study was to determine whether dietary amino acid density can have an impact on body weight variability in a population of growing pigs. Feeding diets with a reduced amino acid density had a negative effect because they increased body weight variability of pens composed of the smallest pigs. For instance, in those pigs, the coefficient of variation, which is used as a measure of variability, increased significantly at the end of the experiment when dietary amino acid density was reduced. It was observed that this effect was explained by a growth restriction that was more severe the lightest the pigs were at the start of the trial. Hypothesizing that posteriorly there would be no differences in growth between those restricted pigs and the normally fed ones, the differences in growth would result in around 5–10 additional days to reach marketing weight. In conclusion, severe nutritional restrictions can negatively affect growing pigs’ body weight variability.The goal of this experiment was to determine the implications of dietary standardized ileal digestible lysine (SID Lys:NE) on body weight variability of growing pigs grouped in three initial body weight categories (BWCAT). Animals (N = 1170) were individually weighed and classified in 3 BWCAT (Lp: 32.1 ± 2.8 kg, Mp: 27.5 ± 2.3 kg, and Sp: 23.4 ± 2.9 kg). Afterward, pens were randomly allocated to five dietary SID Lys:NE treatments (3.25 to 4.88 g/Mcal) that were fed over 47 days. Pen coefficient of variation of Sp at day 47 was linearly increased when reducing SID Lys:NE (p < 0.01), from 9.8% to 15.4% between the two extreme dietary levels. The linear effect was different in Sp compared to Lp (p < 0.05) as no effect of SID Lys:NE was reported in the latter BWCAT (p = 0.992). Further analysis showed that this effect was explained by a growth restriction that was more severe the lightest the pigs were at the start of the trial. To summarize, swine body weight variability can be negatively affected when SID Lys requirements are not fulfilled.
Highlights
The latter is clearly observed in studies showing how body weight (BW) variability in absolute magnitude, usually expressed as the standard deviation (SD)s increases with the age of the pigs, whereas the coefficient of variation (CV) decreases [5,9]
The Results section is further divided into three different analyses performed to evaluate the effects of SID Lys:NE on body weight variability in growing pigs
Initial CV was used as a covariate to account for the differences observed in the initial distribution, and sex was excluded from the model for its absence of significance
Summary
In a population of growing pigs, variation in BW at the start of the growing period might result in differences of around 30–40 days to reach the same marketing BW [5] This longer time entails a reduction in the number of batches per barn and year, representing relevant economic losses for the farmer and the system in general [1]. Nursery exit weight is considered a risk factor for slow growth [7], while other studies have proved the capacity of small pigs to catch up with their heavier counterparts during fattening [8] The latter is clearly observed in studies showing how BW variability in absolute magnitude, usually expressed as the standard deviation (SD)s increases with the age of the pigs, whereas the coefficient of variation (CV) decreases [5,9]. Showing that part of the variability is yet generated during the growing period
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