D. Suster

Conjugated linoleic acid decreases fat accretion in pigs: evaluation by dual-energy X-ray absorptiometry

Thirty female Large White x Landrace pigs (average weight 57.2 (sd 1.9) kg) were allocated to one of six dietary treatments containing 0, 1.25, 2.5, 5.0, 7.5 or 10.0 g 55 % conjugated linoleic acids (CLA) isomers (CLA-55)/kg diet and fed for 8 weeks. Each pig was scanned at 0, 28 and 56 d and again at post slaughter using dual-energy X-ray absorptiometry (DXA) to determine the temporal pattern of body composition responses. Values determined by DXA were adjusted using regression equations generated from validation experiments between chemically and DXA-predicted values. Overall, there was a significant linear reduction in fat content with the increasing levels of CLA in the diet (P=0.007, P=0.011, P=0.008 at week 4, week 8 and for the carcass, respectively). The greatest improvement was recorded at the early stages of CLA supplementation and for the highest dose of CLA (week 4, -19.2 % compared with week 8, -13.7 %). In the first 4 weeks of feeding CLA, pigs receiving 10 g CLA-55/kg diet deposited 93 g less fat/d than pigs fed basal diets (P=0.002) compared with only 6 g less fat than control animals in the final 4 weeks. Lean content and lean deposition rate were maximised at 5 and 2.5 g CLA-55/kg diet for the first 4 weeks (P=0.016) and the final 4 weeks of treatment respectively. DXA estimates of bone mineral content and bone mineral density were not affected by CLA supplementation throughout the experiment. These data demonstrate that dietary CLA decreases body fat in a dose-dependent manner and that the response is greatest over the initial 4 weeks of treatment.

Accuracy of dual energy X-ray absorptiometry (DXA), weight and P2 back fat to predict whole body and carcass composition in pigs within and across experiments

Abstract An Hologic QDR4500 dual energy X-ray absorptiometer (DXA) was used to measure body composition in 151 pigs ranging from 10 to 120 kg live weight. Large White×Landrace pigs of mixed sexes were selected from five different experiments to evaluate DXA accuracy within and across experiments. Values predicted by DXA including total tissue mass, fat tissue mass, lean tissue mass and bone mineral content, for the live animal, carcass and half carcass were evaluated by comparison with chemically-determined values. Relationships between chemically-determined values and measurements of weight and backfat at the P2 site were also evaluated. Chemically-determined values were strongly related with DXA-derived values, more so than with weight and P2 or a combination of both, particularly in the measurement of fat composition. In contrast to estimates derived from weight and P2, DXA-derived estimates remained accurate when between experiment variation was included. Incorporation of subregions into a whole body software analysis influenced DXA’s ability to predict fat tissue mass with the most accurate measurements achieved by placing the entire scan image in the left arm region of the regional analysis grid. These results demonstrate the efficacy of DXA as a nondestructive method for determining body composition in the live animal and carcass, and its greater accuracy than current routinely used methods.

A GnRF vaccine (Improvac®) and porcine somatotropin (Reporcin®) have synergistic effects upon growth performance in both boars and gilts

The use of a vaccine (Improvac) directed against gonadotrophin-releasing factor (GnRF), to prevent boar taint in male pigs, is also associated with an increase in feed consumption, growth, and higher deposition of subcutaneous fat. Daily administration of porcine somatotropin (pST) consistently increases average daily gain, and feed conversion efficiency, and reduces subcutaneous fat, particularly in gilts. The objective of this study was to examine the effect of combining these treatments in boars and gilts. Forty-eight pigs (Large White × Landrace), housed individually, were used in a 2 × 2 × 2 factorial experiment with the respective factors being vaccination with GnRF vaccine (at 14 and 18 weeks of age), daily injection with pST (from 18 weeks to slaughter at 22 weeks), and sex (boars and gilts). Performance was measured over the period of pST administration. Over the entire 28 days of the study, daily gain was lower for gilts than for boars (1216 v. 1410 g/day, P < 0.001), was increased by pST (1219 v. 1407 g/day, P < 0.001), but not significantly altered by vaccination against GnRF (1284 v. 1342 g/day, P = 0.15). However, GnRF vaccination increased daily gain in the second 2 weeks of the study, and overall, there were interactions such that the vaccine increased gain in all groups except boars not receiving pST. Feed intake over the study period was less for gilts than for boars (3139 v. 3407 g/day, P < 0.001), was decreased by pST (3537 v. 3009 g/day, P < 0.001), and increased by vaccination against GnRF (3139 v. 3407 g/day, P < 0.001). When averaged over the entire study, feed conversion ratio (FCR) was higher for gilts than for boars (2.76 v. 2.51, P = 0.013), was decreased by pST (3.05 v. 2.22, P < 0.001), but unchanged by vaccination against GnRF (2.62 v. 2.65, P = 0.70). Fat deposition was lower in gilts than in boars (335 v. 378 g/day, P = 0.037), was decreased by pST treatment ((442 v. 271 g/day, P < 0.001), and increased by vaccination against GnRF (333 v. 379 g/day, P = 0.026). In boars, fat androstenone was reduced by vaccination against GnRF (0.10 v. 2.47 μg/g, P < 0.001) and tended to be reduced by pST (1.71 v. 2.44, P = 0.10), but only vaccination against GnRF reduced skatole (0.174 v. 0.050 μg/g, P < 0.001). The combination of the treatments in all cases was at least additive, and in some cases synergistic. The concomitant vaccination against GnRF and treatment with pST affords an opportunity to increase growth rate and feed intake above control levels and above those of pigs treated with either treatment alone.

The accuracy of dual energy X-ray absorptiometry (DXA), weight, and P2 back fat to predict half-carcass and primal-cut composition in pigs within and across research experiments

A Hologic QDR4500A dual energy X-ray absorptiometer (DXA) was used to measure body composition in 199 half-carcasses ranging from 15 to 48 kg. Half-carcasses were from animals of mixed sex and of either Large White × Landrace or Large White × Landrace × Duroc descent. Half-carcasses were selected from 5 different experiments to evaluate DXA accuracy within and across experiments. Values determined by DXA including total tissue mass, fat tissue mass, lean tissue mass, and bone mineral content, for the half-carcass and the shoulder, loin, belly, and ham primal cuts were evaluated by comparison with manually dissected composition. Relationships between manually dissected values and measurements of weight and backfat at the P2 site were also evaluated. Manually dissected values were strongly related to DXA-derived values, more so than with weight and P2 or a combination of both, particularly in the measurement of fat composition. In contrast to estimates derived from weight and P2, DXA-derived estimates remained accurate even when between-experiment variation was included. However, because DXA estimates were different from manually dissected values, they would need to be adjusted with the use of appropriate regression equations to correct the in-built algorithms. These results demonstrate the efficacy of DXA as a non-destructive method for determining the composition of the half-carcass and primal cuts, and its greater precision than current routinely used methods. Additional keywords: dissection, lean tissue, fat, belly, REML.

Interrelationships between porcine somatotropin (pST), betaine, and energy level on body composition and tissue distribution of finisher boars

Fifty-six individually penned boars (initial weight 64 kg) were used to investigate the interactions between dietary betaine, dietary energy, and porcine somatotropin (pST) treatment. The study was a 2 × 2 × 2 factorial experiment with the respective factors being dietary betaine (0 or 1.5 g/kg) and energy level (80% or 100% ad libitum) and treatment with pST (0 or 5 mg/day). A Hologic QDR4500A Dual Energy X-ray Absorptiometer (DXA) was used to determine body composition of pigs at the beginning and end of the study at Day 35. After slaughter, the composition of the whole half-carcass as well as the shoulder, ham, belly, and loin primal cuts was determined with DXA and verified with manual dissection. The main effects of dietary betaine were most pronounced when dietary energy was restricted. Under these conditions, daily gain was increased by dietary betaine (1188 v. 1271 g/day, P = 0.049) and pST (1115 v. 1344 g/day, P < 0.001). When dietary energy was restricted, lean tissue deposition was increased by dietary betaine (830 v. 908 g/day, P = 0.032) and pST (764 v. 974 g/day, P < 0.001), and these effects were additive. As a result, the lean meat yield in the half-carcass was increased by both dietary betaine (23.9 v. 25.1 kg, P = 0.043) and pST (23.3 v. 25.7 kg, P < 0.001). Lean tissue responses in primal cuts were more variable but followed a similar pattern. There was little effect of either dietary betaine or pST on fat deposition. These data demonstrate that when energy intake is limiting the potential for growth (as is normally the case for the improved boar), then both dietary betaine and pST treatment, either alone or in combination, can increase lean tissue deposition without increasing fat deposition.

Longitudinal DXA measurements demonstrate lifetime differences in lean and fat tissue deposition between boars and barrows under individual and group-penned systems

Thirty-two Large White × Landrace male pigs were used to determine the relationships between the rates of tissue deposition and age, in boars and barrows under 2 housing systems. A 2 × 2 factorial design was used, with the respective treatments being sex (boar or barrow) and housing condition (individually penned system or group- penned system). Surgical castration was performed at 7 days of age. Individually housed pigs were used to provide an estimate of potential growth and were weaned at 10 days into individual cages and provided with supplemental fermented skim milk for 2 weeks. Group-housed pigs were weaned at 24 days of age and reared in group pens of boars and castrates typical for commercial production. Conventional weaner, grower, and finisher diets were provided ad libitum to all pigs from weaning onwards. A Hologic QDR4500A dual-energy X-ray absorptiometer (DXA) was used to determine lean, fat, and bone composition at 4-weekly intervals from 10 until 150 days of age. Over the 20 weeks of the study, boars deposited less fat than barrows (136 v. 179 g/day, s.e.d. = 6.49, P 0.1). This was more pronounced in the final 4 weeks of growth when individually penned boars deposited 200 g/day more lean than barrows (P < 0.001), with no increase in group-penned animals. However, during this growth phase, group penning further increased the fat deposition margin between boars and barrows where boars deposited 90 g/day less fat when individually penned (P < 0.001), but 140 g/day less fat (P < 0.001) when group penned. The results show that the advantages of boars in terms of growth and lean tissue composition are substantially reduced in group- penned situations. However, because of fat deposition, boars retain some advantage over barrows in group-penned systems at liveweights over about 50 kg. These data may aid in the accurate prediction of the nutrient requirements and optimum slaughter weight for barrows.

Accuracy of dual energy X-ray absorptiometry, weight, longissimus lumborum muscle depth and GR fat depth to predict half carcass composition in sheep

A Hologic QDR4500W dual energy X-ray absorptiometer (DXA) was used to measure body composition in 60 sheep half carcasses ranging from 8 to 28 kg. Half carcasses were from ewes and wethers of mixed genetics. Values determined by DXA, including total tissue mass (TTM), lean tissue mass (LTM), fat tissue mass (FTM) and bone mineral content (BMC), for the half carcass were evaluated by comparison with chemically determined composition. In the case of BMC, the relationship was with chemically determined ash content. Liveweight and chemically determined lean, fat and ash were strongly related to DXA-derived values for TTM, LTM, FTM and BMC, respectively (R2 = 0.999, 0.986, 0.989 and 0.920, respectively). However, because DXA estimates were different from chemically determined values in this sample of carcasses, they needed to be adjusted with the use of appropriate regression equations to correct the in-built algorithms. These data demonstrate the efficacy of DXA as a non-destructive method for determining the composition of the sheep half carcass.

Exogenous porcine somatotropin administered to neonatal pigs at high doses can alter lifetime fat but not lean tissue deposition.

The growth rate of the young pig is generally much less than its potential and may be constrained by endocrine status as well as nutrient intake. The aim of the present study was to determine whether porcine (p) somatotropin (ST) treatment of the sucking pig could alter subsequent body composition. Twelve mixed-parity cross-bred sows with an average litter size of ten piglets were used to nurse pigs for the present study. On day 1 of lactation, the median two male pigs (by weight) from each litter were randomly allocated to one of two doses of pST (0 or 1 mg/kg per d) until weaning on day 21. Pigs were weaned and offered feed ad libitum until slaughter at 134 d of age. Body composition was measured using dual-energy X-ray absorptiometry (DXA) at 21, 49, 77, 105 and 133 d of age. There was no significant difference in growth rates between day 1 and 21 of lactation in pigs injected with either saline (9 g/l NaCl/l) or pST (258 v. 246 g/d for control and pST-treated pigs respectively, P=0.61), and as a consequence there was no significant difference in liveweight at weaning (7.13 v. 6.84 kg, P=0.59). However, fat mass at weaning tended to be decreased (1.18 v. 0.96 kg, P=0.064), while the % fat in the body at weaning was significantly (16.7 v. 13.9 %, P=0.008) decreased by exogenous pST treatment. In the immediate post-weaning period there was a reduction in lean tissue deposition (347 v. 300 g/d, P=0.021) but no effect on fat deposition (35 v. 33 g/d, P=0.72). Over the entire weaning-to-slaughter period, pST treatment of neonatal pigs decreased the rate of fat deposition (130 v. 112 g/d, P=0.033), but had no effect on lean tissue deposition (550 v. 538 g/d, P=0.49). Therefore, treatment of nursing pigs with high doses of pST for a short period before weaning may provide a means of reducing the fat content of pork and pork products.

Porcine somatotropin alters body composition and the distribution of fat and lean tissue in the finisher gilt

The present study was designed to determine whether porcine somatotropin (pST) reduces whole animal and belly fat using dual energy X-ray absorptiometry and manual dissection. The study utilised 24 Large White × Landrace gilts selected at 16 weeks of age with an approximate liveweight of 80 kg and housed in individual pens. Gilts were stratified on liveweight into 8 blocks and 1 pig from each block was assigned to either 0, 5 or 10 mg per day of pST. Pigs were fed ad libitum a wheat-based diet containing 200 g crude protein, 10.2 g available lysine and 14.6 MJ DE/kg, to ensure that responses to pST were expressed. Feed intake and liveweight were measured on a weekly basis. An Hologic QDR4500A dual energy X-ray absorptiometer was used to determine lean, fat and ash composition of pigs initially and again 4 weeks later at the end of the experiment. After slaughter, the composition of the whole half carcass as well as the shoulder, ham, belly and loin primal cuts was determined with dual energy X-ray absorptiometry and verified with manual dissection. Daily pST treatment decreased feed intake (3440, 2710 and 2537 g/day for 0, 5 or 10 mg pST per day, respectively; P<0.001) and decreased feed conversion ratio (2.95, 2.18 and 2.03 g/g; P<0.001) even though there was no significant effect on daily gain. Pigs treated with pST deposited more lean tissue (620, 839 and 873 g/day; P<0.05) and less fat (384, 218 and 176 g/day; P<0.001) than control animals, but there was no effect of pST on ash deposition. As a consequence, pigs treated with 5 and 10 mg pST/day contained 5 and 9 kg less dissectible fat than control gilts, respectively. A dose dependent decrease in belly, loin, ham and shoulder fat was also observed, although the decrease in belly fat was more pronounced than for the whole carcass and other primal cuts. Overall, pST treatment has the potential to decrease carcass and especially belly fat in pigs and increase consumer acceptance of pork in markets that place a premium on carcass fat and lean yield in the belly region. The results determined with dual energy X-ray absorptiometry were confirmed by manual dissection.

Dual energy X-ray absorptiometry predicts the effects of dietary protein on body composition of pigs

The present study investigated the potential of dual energy X-ray absorptiometry to determine the effect of dietary protein on live pig body composition compared with the standard methods. The experiment utilised 48 Large White × Landrace gilts, stratified on liveweight at 17 weeks of age (initial liveweight about 60 kg), and allocated within strata to diets containing either 85 or 100% of dietary protein requirements. The diets were fed ad libitum and contained 14.6 or 16.7% protein, respectively. Pigs were housed individually to allow weekly measurement of feed intake and liveweight. A Hologic QDR4500A dual energy X-ray absorptiometer was used to determine lean, fat and ash composition of pigs initially and 4 weeks later at the end of the experiment. Daily gain was increased by about 200 g in pigs fed the protein-adequate diet, but feed intake was not affected. Therefore, pigs fed adequate protein had a lower feed conversion ratio (2.92 v. 3.52 g/g, P<0.001). Feeding the protein-adequate diet increased lean deposition by about 150 g/day (577 v. 429 g/day, P<0.001) and ash deposition by about 4 g/day (28.7 v. 25.0 g/day, P<0.001), but did not affect fat accretion. This resulted in carcasses with a higher lean content (54.0 v. 50.7 kg, P<0.001) and ash content (2.35 v. 2.28 kg, P<0.05) but unaltered fat content. Therefore, an inadequate level of dietary protein leads to suboptimal growth in lean tissue and bone mineral, with no pronounced effect on fat. These observations were substantiated by chemical analysis and available corrective equations were useful in correcting differences between dual energy X-ray absorptiometry outputs and chemical values. After correction, dual energy X-ray absorptiometry estimates differed less than 5% from the chemical values for lean, protein, water and ash and 10% for lipid. In addition, reduced standard error of the differences around most dual energy X-ray absorptiometry measurements, relative to chemical analysis, allowed small changes in body composition to be detected with increased confidence. These data support the efficacy of using dual energy X-ray absorptiometry in nutritional studies of pigs.