Diet Supplements Enhance Growth, Carcass Traits

Feeding diets with added fat to lean gilts increases production efficiency and pounds of pork produced per pig. Adding ractopamine and conjugated linoleic acid (CLA) to those diets improves growth efficiency and enhances carcass characteristics.

Table 1. Growth Performance (week 4-8) of Lean Gilts Fed Diets Containing Conjugated Linoleic Acid (CLA) or Soybean Oil (SBO) with 5% Choice White Grease (CWG), 5% Beef Tallow (BT) or 0% Added Fat with or without Ractopamine (RAC)
Item RAC
g/ton
CLA SBO
0% 5% CWG 5% BT 0% 5% CWG 5% BT
ADG, lb.
Wk. 4-6 0.0 1.97 2.04 2.00 2.14 2.03 2.14
9.0 2.68 2.39 2.60 2.51 2.49 2.68
Wk. 6-8 0.0 1.79 1.80 1.85 1.78 1.73 1.84
9.0 2.07 2.38 2.19 1.91 1.87 1.96
Wk. 4-8 0.0 1.88 1.92 1.93 1.88 1.88 1.99
9.0 2.38 2.38 2.39 2.21 2.18 2.32
ADFI, lb.
Wk. 4-6 0.0 5.71 5.32 5.26 5.52 5.52 5.63
9.0 5.70 5.45 5.47 5.65 5.22 5.56
Wk. 6-8 0.0 5.61 5.10 4.95 5.75 5.26 5.41
9.0 5.60 5.70 5.62 5.85 5.16 5.30
Wk. 4-8 0.0 5.66 5.21 5.10 5.64 5.39 5.52
9.0 5.65 5.57 5.55 5.75 5.19 5.43
F:G
Wk. 4-6 0.0 2.90 2.60 2.62 2.84 2.71 2.62
9.0 2.14 2.29 2.10 2.25 2.09 2.07
Wk. 6-8 0.0 3.13 2.86 2.65 3.26 2.99 2.96
9.0 2.71 2.38 2.56 3.10 2.75 2.74
Wk. 4-8 0.0 3.00 2.72 2.64 3.03 2.84 2.79
9.0 2.39 2.34 2.31 2.61 2.38 2.36
Initial weight, lb. 0.0 187.26 189.93 192.61 190.06 190.74 188.28
9.0 180.73 190.65 190.85 184.21 188.87 187.40
Final weight, lb. 0.0 239.93 243.72 246.47 242.62 242.46 244.00
9.0 247.26 255.27 257.86 246.00 252.12 252.25


Table 2. Carcass Characteristics of Genetically Lean Gilts Fed Diets Containing Conjugated Linoleic Acid (CLA) or Soybean Oil (SBO) with 5% Choice White Grease (CWG), 5% Beef Tallow (BT) or 0% Added Fat with or without Ractopamine (RAC)
Item RAC
g/ton
CLA SBO
0% 5% CWG 5% BT 0% 5% CWG 5% BT
Carcass weight, lb. 0.0 170.3 174.4 174.77 172.6 177.2 172.7
9.0 178.4 182.8 187.5 177.5 184.1 183.0
Dressing percentage 0.0 70.74 70.67 71.39 70.72 71.48 71.01
9.0 70.89 72.51 72.76 72.59 73.15 72.59
Lean percentagea 0.0 56.31 56.50 57.21 55.39 55.68 56.37
9.0 59.72 57.57 57.88 56.25 57.19 58.10
Backfat, in.
10th rib inner layer 0.0 0.36 0.40 0.33 0.36 0.43 0.34
9.0 0.30 0.36 0.36 0.38 0.38 0.33
10th rib 0.0 0.67 0.73 0.64 0.70 0.79 0.69
9.0 0.57 0.67 0.66 0.71 0.73 0.64
Longissimus muscle
Area, sq. in. 0.0 6.93 7.45 7.33 6.71 7.36 7.12
9.0 8.24 7.95 8.21 7.32 7.98 7.96
pH at 45 min. 0.0 6.45 6.53 6.52 6.41 6.46 6.49
9.0 6.45 6.46 6.45 6.52 6.54 6.53
pH at 24 hr. 0.0 5.65 5.59 5.66 5.64 5.61 5.59
9.0 5.60 5.60 5.63 5.61 5.65 5.66
aCarcass lean was calculated using the equation for ribbed carcasses (National Pork Producers Council, 1991).


This experiment by Purdue University researchers supports previous studies in which adding fat to diets increases feed conversion efficiency.

The latest work also points out that the two sources of fat were comparable in achieving growth performance. Feeding 5% added fat to lean gilts increases carcass weight without affecting carcass percent lean.

In the presence of ractopamine Paylean growth performance and carcass yield both improved.

The addition of CLA enhanced feed efficiency and percent lean as well as increased belly quality.

Newsham hybrid gilts were divided into two phases in the eight-week experiment. Gilts went on test in phase one at 130 lb., which tested a 1% commercially available CLA product or 1% soybean oil. Also tested were three fat treatments: diets containing 0% added fat, diets with 5% choice white grease or diets with 5% beef tallow. This first phase lasted until gilts reached 189 lb.

During the second phase (189-247 lb.), ractopamine treatments were added to the feeding trials for the final four weeks gilts were on test.

Growth performance is compiled in Table 1. Gilts fed ractopamine had greater daily gains and feed conversion. Gilts fed CLA were more feed efficient during the last four weeks of the trial. Adding 5% fat decreased feed intake during weeks 4-8 and 6-8 while improving feed efficiency.

For the overall eight-week trial, gilts fed 9 g./ton of ractopamine produced greater daily gains and improved feed efficiencies than the control group. Feeding ractopamine and 5% added fat also boosted final body weights.

Feeding ractopamine the last four weeks increased carcass weight 8.6 lb. and dressing percentage by 1.4%. Adding 5% fat to the diet the last eight weeks increased carcass weight 4.9 lb. and increased dressing percentage by 7%.

Backfat depth was decreased when gilts were fed ractopamine or CLA. Adding fat to the diet slightly increased backfat depth.

The 5% added fat and ractopamine increased loineye area; feeding CLA to gilts also somewhat enhanced loineye area (Table 2).

Researchers: Tom Weber, K. Enright, Brian Richert and Allan Schinckel, Purdue University; Phone (765) 496-6840 or e-mail tweber3@purdue.edu.

Chlorate Concentrations Reduce Salmonella Prior to Slaughter

Administering sodium chlorate (NaClO3) as a drinking water supplement effectively reduces intestinal levels of salmonella in weaned and finished pigs prior to slaughter.

A research project at USDA's Agricultural Research Service (ARS) facility at College Station, TX, sought to reduce salmonella in the gut before slaughter to minimize the risk of contaminated pork products.

The goal of the National Pork Board project was to find out, through several studies, whether chlorate could kill salmonella without harming beneficial microbes.

Salmonella levels were cut up to 1,000-fold in the gut of chlorate-treated pigs, compared to concentrations in control pigs.

Also, none of the pigs were harmed by the chlorate and water consumption was not affected.

In the first study, 90 weaned, 26- to 29-day-old pigs were orally infected with Salmonella typhimurium. Eight to 16 hours later, they were given 0, 213 mg. or 426 mg. NaClO3. The pigs were euthanized at eight-hour intervals after treatment, necropsied and tested for salmonella. Results showed salmonella levels were greatly reduced.

Groups of weaned and finished pigs in subsequent studies were experimentally infected as in the first study. They were provided unlimited access to water 24 hours later, which contained 1.6 or 3.2 mg. socium chlorate per ml. Pigs were sacrificed 36 to 48 hours after challenge, with positive results in reductions of salmonella levels in the gut.

The NaClO3 treatment did not affect the beneficial bacteria in the gut of the treated pigs.

Researcher: Robin Anderson, USDA/ARS. Phone Anderson at (979) 260-9317 or fax (979) 260-9332.

Electrical Stimulation Aids Study of PSE Pork

Using electrical stimulation to aid in detection and prevention of PSE (pale, soft, exudative pork) has been confirmed by a team of researchers at the Purdue Research Foundation.

A new cotton implant technique has been developed to advance understanding of the natural water-holding ability and capacity of muscles and their release of water during processing.

For the study, 64 PIC pigs were transported from Franklin, KY, to the Purdue University Meat Science Research and Education Center at West Lafayette, IN, where they were fed for about 16 hours before being slaughtered.

Half the group were electrically stimulated 3 to 6 min. after sticking; the other half served as the control group. Meat characteristics, including final pH, were collected 24 hours postmortem.

In short, the data supported pork carcass electrical stimulation as a means of rapidly dropping muscle pH and raising carcass temperature, signs of PSE development.

Other studies pointed out that the susceptibility of a pig carcass to develop PSE (via electrical stimulation) takes place within the first 25 min. after sticking.

Moreover, electrical stimulation provides a better understanding of how adverse pork quality develops within a genotype as environmental stimuli change.

Researchers: David Gerrard, Mark Morgan, John Forrest and Alan Grant, Purdue Research Foundation. Phone Gerrard at (765)494-8280 or fax (765)494-6816.

Adding Magnesium May Enhance Pork Quality

Short-term feeding of low levels of magnesium salts just prior to slaughter may provide a cheap way to boost pork quality.

A team from the University of Illinois has been studying ways to supplement diets to boost pork quality and producer returns.

A pilot study confirmed that feeding supplemental magnesium for five days before slaughter improved the color, firmness and water-holding capacity of pork.

To further define the level and time of feeding magnesium for consistent improvement in pork quality, the team studied two low feeding levels, three feeding times prior to slaughter and three sources of magnesium (sulfate heptahydrate, diproprionate and proteinate).

Magnesium was fed at 0.56 oz. and 0.11 oz., for one, two and five days before slaughter.

The trial involved 192 barrows and gilts on test at 245 lb. They were evaluated for growth performance during the feeding period and slaughtered for meat quality evaluation.

Feeding additional magnesium short periods before slaughter had no impact on the growth or health of the pigs.

Both feeding levels improved pork quality. Supplemental magnesium produced darker-colored pork and better water-holding capacity compared to a control group.

The three magnesium sources produced pork with lower Minolta L* values when compared to the controls. Minolta L* values are objective measures of color. Lower values refer to darker-colored pork.

However, water-holding capacity was only improved by the magnesium sulfate treatment, which cut drip loss by 1.5%.

The shortest (one day) and longest (five days) feeding periods produced the largest improvements in loin color and water-holding capacity.

Total cost for supplemental magnesium is estimated at less than 12 cents/pig.

Researchers: Daniel Hamilton, Floyd McKeith and Michael Ellis, University of Illinois; phone Ellis at (217) 333-6455 or e-mail m-ellis7@uiuc.edu.