Interaction of somatotropin and genotype on the requirement for energy in two lines of finishing pigs

Impact of research with cattle, pigs, and sheep on nutritional concepts: body composition and growth

Studies with pigs, cattle, and sheep have provided a wealth of information regarding growth and body composition. Most of this information has been obtained using the standard methods for measuring the body composition of meat animals, which consist of dissection and chemical analysis. These methods have been used with meat animals to validate a variety of in vivo techniques that are used in both animal and human body composition studies. Research on the growth and body composition of meat animals has provided important concepts regarding the relation between growth and composition, including chemical maturity, the effects of severe undernutrition, partitioning of nutrients under various physiological conditions, the efficiency of nutrient utilization, and compensatory growth following a period of undernutrition. In addition, several genetic and physiological conditions affecting growth and body composition have been identified in meat animals that serve as important models for both animal and human growth.

Effects of dietary lysine and energy density on performance and carcass characteristics of finishing pigs fed ractopamine1

Two hundred sixteen crossbred barrows and gilts (84.3 kg BW) were used to test the effects of dietary energy density and lysine:energy ratio (Lys:ME) on the performance, carcass characteristics, and pork quality of finishing pigs fed 10 ppm ractopamine. Pigs were blocked by BW and gender, allotted to 36 pens (six pigs per pen), and pens were assigned randomly within blocks to dietary treatments (as-fed basis) arranged in a 2 x 3 factorial design, with two levels of energy (3.30 or 3.48 Mcal/kg) and three Lys:ME (1.7, 2.4, or 3.1 g lysine/Mcal) levels. Pigs were fed experimental diets for 28 d, and weights and feed disappearance were recorded weekly to calculate ADG, ADFI, and G:F. Upon completion of the feeding trial, pigs were slaughtered and carcass data were collected before fabrication. During carcass fabrication, hams were analyzed for lean composition using a ham electrical conductivity (TOBEC) unit, and loins were collected, vacuum-packaged, and boxed for pork quality data collection. Energy density had no (P > 0.22) effect on ADG or ADFI across the entire 28-d feeding trial; however, pigs fed 3.48 Mcal of ME were more (P < 0.02) efficient than pigs fed 3.30 Mcal of ME. In addition, ADG and G:F increased linearly (P < 0.01) as Lys:ME increased from 1.7 to 3.1 g/Mcal. Carcasses of pigs fed 3.48 Mcal of ME were fatter at the last lumbar vertebrae (P < 0.08) and 10th rib (P < 0.04), resulting in a lower (P < 0.03) predicted fat-free lean yield (FFLY). Conversely, 10th-rib fat thickness decreased linearly (P = 0.02), and LM depth (P < 0.01) and area (P < 0.01) increased linearly, with increasing Lys:ME. Moreover, FFLY (P < 0.01) and actual ham lean yield (P < 0.01) increased as Lys:ME increased in the diet. Dietary energy density had no (P > 0.19) effect on pork quality, and Lys:ME did not (P > 0.20) affect muscle pH, drip loss, color, and firmness scores. Marbling scores, as well as LM lipid content, decreased linearly (P < 0.01) as Lys:ME increased from 1.7 to 3.1 g/Mcal. There was a linear (P < 0.01) increase in shear force of cooked LM chops as Lys:ME increased in the finishing diet. Results indicate that 3.30 Mcal of ME/kg (as-fed basis) is sufficient for optimal performance and carcass leanness in pigs fed ractopamine. The Lys:ME for optimal performance and carcass composition seems higher than that currently used in the swine industry; however, feeding very high Lys:ME (> 3.0 g/Mcal, as-fed basis) to ractopamine-fed pigs may result in decreased marbling and cooked pork tenderness.

Recombinant human growth hormone modifies the inherent partition of nutrients in growing female and male BALB/c mice

BALB/c mice weaned at 21 days were used to investigate the effects of exogenous recombinant human growth hormone (rhGH) administration on the growth performance and carcass composition in females and males allowed to consume feed ad libitum. Forty mice were assigned within each sex (female [F] and male [M] to treatment of either 20 microL g-1 saline (Fs and Ms groups) or 74 ng rhGH g-1 body weight (BW) in 20 microL saline (FGH and MGH groups). At 50 d of age the mice were weighed and then killed by cervical dislocation. Treatment with rhGh improved feed conversion only in growing female mice by enhancing weight gain relative to feed protein intake and weight growth rate without modification of feed consumption, according to a multiple comparison test (LSD). Ms mice showed less carcass fat gain (162%), less fat accretion rate (129%), higher carcass water gain (12%) and higher water accretion rate (28%) than Fs mice. The administration of rhGH modified this distribution inducing an increase in gain and accretion rates of protein (34%), water (41%) and ash (33%) and a reduction in gain and accretion rate of fat (50%) in FGH mice, and only an increase of gain (91%) and accretion rate of fat (67%) in MGH mice compared to saline mice. As result, a decrease in protein gain:fat gain ratio of MGH mice compared to FGH (34%) and Ms (63%) mice was elicited by rhGH, inverting the inherent sexual propensity for fat and protein deposition in growing male mice, due to GH, sex, and to GH x sex interaction influence.

Porcine somatotropin decreases acetyl-CoA carboxylase gene expression in porcine adipose tissue

Crossbred barrows were treated daily with porcine somatotropin (pST; 4 mg/d) from 79 to 127 kg BW to determine whether pST regulates the activity and gene expression of adipose tissue acetyl-CoA carboxylase (ACC), the rate limiting enzyme in de novo fatty acid synthesis. Administration of pST reduced ACC enzyme activity, protein content, and mRNA abundance in adipose tissue by 40 to 50%. When comparisons were made among all pigs, ACC enzyme activity and mRNA abundance were closely associated (r2 = .94). In summary, our results indicate that pST decreases ACC enzyme activity and that this is associated with a significant reduction in ACC mRNA abundance. We speculate that decreased ACC enzyme activity results from a reduction in ACC protein and that this occurs because pST reduces the abundance of mRNA available for translation.