Assessment of chromium tripicolinate supplementation and dietary protein level on growth, carcass, and blood criteria in growing pigs.

This study was conducted to evaluate potential interactive effects of supplemental Cr and dietary protein levels in growing pigs. Thirty-six individually penned barrows, 22 to 63 kg, were used in a 2 x 3 factorial arrangement of supplemental Cr (0 or 200 ppb from chromium tripicolinate) and protein level (76, 83, or 90% of lysine requirement). A corn-soybean meal basal diet was designed to supply all mineral and vitamin needs, 90% of the estimated metabolizable energy need, and 76% of the estimated protein need at 70% of ad libitum feed intake. Additional protein to 83 or 90% of the lysine requirement was provided by a soy protein isolate supplement. Growth data were collected for a 50-d period, and pigs were killed at a mean of 63 kg BW. Increasing lysine levels linearly (P < 0.01) increased ADG and liver weight. Lysine level had a quadratic effect on 10th rib backfat thickness (P < 0.05) and cooler shrink (P < 0.01) with the highest responses at the 83% lysine level. Increasing lysine level linearly decreased (P < 0.05) carcass content of ash and lipid and quadratically increased the carcass water content (P < 0.01). Carcass accretion rate showed a linear increase for protein (P < 0.01) and water accretion (P < 0.01). Dry matter composition of the longissimus muscle showed linear increases of ash (P < 0.05) and protein (P < 0.01) and a linear decrease of lipid content (P < 0.01) resulting in a linear increase (P < 0.05) of the protein to lipid ratio based on the increasing lysine levels. Pre-feeding insulin levels were increased (P < 0.05) with increasing level of lysine. One hour post-feeding, a quadratic lysine response for plasma glucose (P < 0.05) was observed with the lowest concentration at 83% lysine. Cr addition increased 10th rib backfat thickness (P < 0.10). There was no Cr x lysine level interaction (P > 0.10) observed for any of the growth or carcass traits. Plasma glucose concentrations pre-feeding were lower for Cr-supplemented pigs (P < 0.01). As expected, increasing protein levels in protein-deficient diets increased protein accretion while decreasing lipid accretion in 22 to 63 kg growing pigs; however, these effects were more clearly seen in the longissimus muscle than in the entire carcass. Supplementation of Cr exerted only minor effects with few Cr x lysine interactions observed in this study.

Assessment of chromium tripicolinate supplementation and dietary energy level and source on growth, carcass, and blood criteria in growing pigs.

Two experiments were conducted to evaluate potential interactive effects of supplemental Cr and dietary energy supply in growing pigs. Experiment 1 used 36 individually penned barrows, 25 to 65 kg, in a 2 x 3 factorial arrangement of supplemental Cr (0 or 200 ppb) and energy level (70, 80, or 90% of ME requirement). A corn-soybean meal basal diet was designed to supply all protein, mineral, and vitamin needs and 70% of the estimated ME need at 70% of ad libitum feed intake. Additional energy to 80% or 90% of the ME requirement was provided by a cornstarch/corn oil blend. In Exp. 2, 30 individually penned barrows, 23 to 68 kg, were used in a 2 x 4 factorial arrangement of supplemental Cr (0 or 200 ppb) and added energy source (none, cornstarch, corn oil, or choice white grease) with basal diets identical to Exp. 1. The various energy sources were added to 90% of the ME requirement. In both experiments, growth data were collected over a 50-d period and pigs were killed at 70.1 kg. Increasing energy levels increased (linear, P < 0.01) ADG, average backfat thickness, 10th rib backfat thickness, and cooler shrink and decreased (linear, P < 0.01) longissimus muscle area in Exp. 1. Carcass composition increased (linear, P < 0.01) in lipid and decreased in protein, water, and protein:lipid ratio in response to increasing ME levels. Similar results were observed in Exp. 2 in response to added energy, regardless of the energy source used. In response to ME, linear increases (P < 0.05) in plasma insulin concentration before feeding and after feeding were observed in Exp. 1. In Exp. 2, plasma insulin concentration was lower for the basal diet before feeding (P < 0.05) and higher for the starch diet after feeding (P < 0.01); insulin:glucose ratio increased (P < 0.01) after feeding for starch compared to oil and fat. No consistent effect of Cr or Cr x ME level on performance or carcass was observed (P > 0.10) in these experiments. Similarly, no Cr effect or Cr x ME interaction (P > 0.10) was observed in plasma glucose or insulin levels. Dietary energy levels markedly affected growth criteria in growing pigs (23 to 68 kg) in these experiments, as anticipated, but supplemental Cr was without effect on performance or carcass responses.

A technique for assessing the effects of olfaction on feed preference in lactating Holstein cows.

Our objective was to develop a method for assessing the effects of olfaction on feed preference. Two multiparous lactating Holstein cows were offered a totally mixed ration consisting of corn silage, alfalfa haylage, and a ground corn and soybean meal-based concentrate mixture (25:25:50 on a DM basis) for their ad libitum consumption in four consecutive 2.5-h periods daily for 5 d. An apparatus was developed that allowed odorants to be distributed at a set rate over two feeding containers with limited possibility of odor carryover. Four odorants and a control (no odorant) were compared against each other. All possible comparisons were conducted on the left and right feeding sides to avoid potential lateral-preference effects. Rank values of 0 or .5 were assigned to each odorant based on the percentage of total feed consumed in a period. A test of overall equality based on the sums of squares of ranks was used to determine whether odors affected preference. The limited results indicated that inhalation of odorants did not affect preference. Rank values were doubled for several odorants when compared with others, which suggested that the sample size limited experimental sensitivity. To attain reasonable power, we estimated that at least six cows were needed per study. Large effects of odorants on feed preference would have been required to reach statistical significance in this trial; however, the method provides a practical technique for testing the effects of olfaction on feed preference in cattle when the suggested number of cows is used.