No abstract

We used 35 primiparous sows to investigate the link between body fatness at farrowing and voluntary feed intake (VFI) during lactation. Two groups of sows were fed differently throughout gestation (either 2.3 kg/d of a diet containing 5.8% CP and 14.6 MJ DE/kg as fed or 1.7 kg/d of a diet containing 15.6% CP and 14.5 MJ DE/kg as fed) so that they commenced lactation at a similar body weight (158 to 152 kg) but with different body compositions: either 340 (fat) or 280 (lean) g of body fat/kg BW (P < .001). During lactation, sows were offered either a low-protein diet (7.9% CP and 15.5 MJ DE/kg as fed) or a high-protein diet (19.0% CP and 15.6 MJ DE/kg as fed) on an ad libitum basis. During lactation, VFI was measured daily, and sow body weight and backfat were measured weekly. Blood samples were collected from sows on d 110 of gestation and d 14 and 28 of lactation, and plasma was analyzed for NEFA, glycerol, insulin, glucose, and beta-hydroxybutyrate. Fat sows ate 30% less than their lean counterparts during lactation (P < .001), which corresponded to a 70% higher concentration of NEFA in plasma (P = .01) and a 30% higher concentration of glycerol (P = .15). The VFI during the first 2 wk of lactation was affected only by body fatness and not by the protein content of the lactation diet. The dietary supply of protein influenced VFI during wk 3 and 4 of lactation, possibly by affecting milk production and hence the drive to consume feed. Weight loss, particularly lean tissue loss, was minimized by feeding the high-protein diet during lactation (P < .002).

The production performance and financial outcomes associated with weaner diet complexity for pigs of different weight classes at weaning were examined in this experiment. A total of 720 weaner pigs (360 entire males and 360 females) were selected at weaning (27 ± 3 d) and allocated to pens of 10 based on individual weaning weight (light weaning weight: pigs below 6.5 kg; medium weaning weight: 6.5 to 8 kg; heavy weaning weight: above 8.5 kg). Pens were then allocated in a 3 × 2 × 2 factorial arrangement of treatments with the respective factors being weaning weight (heavy, medium and light; H, M and L, respectively), weaner diet complexity (high complexity/cost, HC; low complexity/cost, LC), and gender (male and female). Common diets were fed to both treatment groups during the final 4 weeks of the weaner period (a period of 39 days). In the first 6 d after weaning, pigs offered the HC diets gained weight faster and used feed more efficiently than those offered the LC diets (P = 0.031). Pigs fed a HC diet after weaning tended to be heavier at the sale live weight of 123 d of age compared with pigs fed the LC diet (P = 0.056). There were no other main effects of the feeding program on growth performance through to slaughter. Weaning weight had a profound influence on lifetime growth performance and weight at 123 d of age, with H pigs at weaning increasing their weight advantage over the M and L pigs (101.3, 97.1, 89.6 kg respectively, P < 0.001). Cost-benefit analyses suggested there was a minimal benefit in terms of cost per unit live weight gain over lifetime when pigs were offered a HC feeding program to L, with a lower feed cost/kg gain. The results from this investigation confirm the impact of weaning weight on lifetime growth performance, and suggest that a HC feeding program should be focused on L weaner pigs (i.e., weaning weight less than 6.5 kg at 27 d of age) in order to maximise financial returns.

Sows that were either fat or lean at farrowing (340 or 280 g of body fat/kg BW, respectively) were offered either a low-protein (LP; 7.9% CP and 15.5 MJ DE/kg as fed) or a high-protein (HP; 19.0% CP and 15.6 MJ DE/kg as fed) diet on an ad libitum basis throughout a 4-wk lactation to test the hypothesis that the amount of milk and its composition are responsive to the supply of endogenous (body reserves) and exogenous (diet) substrates. Pigs were weighed at birth and weekly during lactation, milk yield was estimated using deuterium oxide in early (d 4 to 8) and late lactation (d 24 to 28), and milk samples were collected to determine composition in early (d 4 to 6) and late lactation (d 25 to 27). Throughout lactation, milk yield and composition were mainly associated with differences in litter size. Milk yield was about 15% higher in lean than in fat sows and in sows fed HP rather than LP, but large CV (17 to 32%) prevented these differences from attaining significance (P > .273). The responses in milk yield were reflected in pig growth. Differences in milk composition between treatment groups were not significant; however, during early lactation there was a tendency for fat sows to produce milk with a fat content 21% higher, and a protein content 12% lower, than that of lean sows. Changes in the protein:energy ratio of milk during the course of lactation and small changes in milk yield composition collectively suggested that in early lactation, sow body composition affected milk production but, as lactation progressed, the dietary supply of precursors for milk synthesis became more important.

Gilt progeny have lighter weaning weights and greater postweaning medication and mortality rates compared with the progeny of older parity sows. Because weaning weight has been positively correlated with postweaning survival, this study aimed to determine whether the provision of supplemental milk preweaning could improve weaning weight and subsequent weights as well as postweaning survival of gilt progeny. The study was replicated in summer and winter as the effects of supplemental milk were expected to vary with season. The progeny of 80 gilts (parity 0) and 80 sows (parity 2 to 5) were allocated to both treatments: with or without supplemental milk in these 2 seasons with 5 sheds/season. Litter size was standardized (10 to 11 piglets) and each piglet was weighed at birth, d 21, weaning (4 wk), and 10 wk of age. Medications and mortalities were recorded both preweaning and postweaning. Pigs were housed within treatment groups postweaning, and ADFI and G:F were measured. Gilt progeny were 200 g lighter at birth in both replicates (P < 0.001) and were 500 g lighter at weaning in the winter replicate (P < 0.05) compared with sow progeny. The provision of supplemental milk improved weaning weight for both gilt and sow progeny by 800 g in summer (P < 0.05) and by 350 g in winter (P < 0.05). This improvement in weaning weight had no effect on the incidence of death or disease in milk-supplemented progeny of either gilts or sows (P > 0.05). Supplemental milk disappearance (the daily difference between the volume of milk provided and the residue left in the drinker) was greater in summer than winter (by 130 mL/piglet d(-1); P < 0.05) as were the associated weaning weight benefits. The weaning weights of supplemented gilt progeny reached or exceeded that of nonsupplemented sow progeny. Gilt progeny had greater postweaning mortality (2.6%) and medication rates (6.2%) than sow progeny (1 and 2.2%, respectively; both P < 0.05) in both seasons, but medication rates were greater in winter (7.2%) for both treatment groups than in summer (1.9%; P < 0.05). Gilt progeny also had less postweaning ADFI than sow progeny in winter (528 and 636 g, respectively; P < 0.05) with no dam parity effect on G:F (both P > 0.05). The hypothesis that supplemental milk provision did increase gilt progeny weaning weight was supported (especially in summer) but the supplementation had no effect on postweaning weights and survival. Efforts to improve gilt progeny postweaning growth and survival need to be aimed at improving health and immunity, not just weaning weight.