Alternating dietary fat sources for growing-finishing pigs fed dried distillers grains with solubles: I. Growth performance, pork carcass characteristics, and fatty acid composition of subcutaneous fat depots.

Crossbred pigs (n = 216) were used to test the effects of phase-feeding beef tallow (BT) and yellow grease (YGr) on live performance, carcass characteristics, and fatty acid composition of subcutaneous (s.c.) fat depots of growing-finishing swine. Pigs were blocked by initial BW (26.0 ± 5.3 kg) before allotment to pens (6 pigs/pen), and pens (6 pens/block) were assigned randomly to 1 of 6 dietary treatments: 1) corn-soybean meal-based grower and finisher diets formulated with 4.7% YGr fed during all 5 feeding phases (YG15), 2) corn-soybean meal-based diets formulated with 5.0% BT fed during all 5 phases (BT15), 3) diets containing 5.0% BT fed during the first 2 phases and diets with 4.7% YGr fed the last 3 phases (YG345), 4) diets formulated with 5.0% BT fed during first 3 phases and diets containing 4.7% YGr fed during the last 2 phases (YG45), 5) diets containing 4.7% YGr fed during the first 3 phases and diets with 5.0% BT fed during the last 2 feeding phases (BT45), or 6) diets formulated with 4.7% YGr fed during the first 2 phases and diets with 5.0% BT fed during the last 3 phases (BT345). Overall performance was similar (P ≥ 0.06) among dietary treatments; however, overall ADG and ADFI increased (quadratic, P ≤ 0.05) with increasing days fed BT, but duration of dietary YGr did not affect ADG (P ≥ 0.22) or ADFI (P ≥ 0.30). There was no (P ≥ 0.23) effect of fat inclusion on carcass characteristics, but carcass lean yield decreased (linear, P = 0.02) as duration of YGr feeding increased from 37 to 103 d. Proportions of back fat SFA (quadratic, P = 0.03) and jowl fat MUFA (linear, P = 0.02) increased as the time fed BT increased from 47 to 103 d. Conversely, PUFA content of both s.c. fat depots increased (linear, P < 0.01) with increasing durations of dietary YGr. Moreover, quadratic slopes for linolenic (18:2n-6) and linolenic (18:3n-3) acids in jowl fat differed (P ≤ 0.05) between BT and YGr durations, indicating that the percentages of 18:2n-6 and 18:3n-3 increased at a greater rate with increasing time fed YGr than the rate of decreases in 18:2n-6 and 18:3n-3 associated with increasing time fed BT. Results of this study confirm that the fatty acid composition of s.c. fat depots are similar to that of the dietary fat source fed during the last 2 or 3 feeding phases, yet deposition rates of specific fatty acids appear to be dependent on the length of time pigs are fed a specific fat source.

Alternating dietary fat sources for growing-finishing pigs fed dried distillers grains with solubles: II. Fresh belly and bacon quality characteristics.

Crossbred pigs (n = 216) were used to test the effects of phase-feeding beef tallow (BT) and yellow grease (YGr) on fresh belly and bacon quality characteristics of growing-finishing swine fed dried distillers grains with solubles (DDGS). Pigs were blocked by initial BW (26.0 ± 5.3 kg) before allotment to pens (6 pigs/pen), and pens (6 pens/block) were assigned randomly to 1 of 6 dietary treatments: 1) corn-soybean meal-based grower and finisher diets formulated with 4.7% YGr fed during all 5 feeding phases (YG15); 2) corn-soybean meal-based diets formulated with 5.0% BT fed during all 5 phases (BT15); 3) diets containing 5.0% BT fed during the first 2 phases and diets with 4.7% YGr fed the last 3 phases (YG345); 4) diets formulated with 5.0% BT fed during first 3 phases and diets containing 4.7% YGr fed during the last 2 phases (YG45); 5) diets containing 4.7% YGr fed during the first 3 phases and diets with 5.0% BT fed during the last 2 feeding phases (BT45); or 6) diets formulated with 4.7% YGr fed during the first 2 phases and diets with 5.0% BT fed during the last 3 phases (BT345). All dietary treatments were formulated with 30% dried distillers grains with solubles (DDGS) during the first 3 phases, 15% DDGS in the fourth phase, and no DDGS during the last phase. Fresh belly quality data were collected on the left-side bellies, whereas bacon from the right-side bellies was prepared under commercial processing conditions. Additionally, USDA-certified No. 1 slices were collected for cooking characteristics and sensory panel evaluations. Bellies from the YG15-fed pigs were softer (P ≤ 0.05) than bellies from BT15-fed pigs; however, instrumentally measured belly firmness was not (P ≥ 0.06) different among treatments. Concentrations of palmitic, stearic, and oleic acids, as well as all SFA and all MUFA, were greater (P < 0.01) in bellies from BT15- than YG15-fed pigs. In contrast, proportions of linoleic acid, all PUFA, and iodine value were greater (P < 0.01) in belly fat from YG15-fed pigs in comparison with BT15-fed pigs. Yield of commercially processed bacon (P ≥ 0.06), mechanical bacon tenderness (P ≥ 0.69), and bacon palatability attributes (P ≥ 0.55) were not affected by the dietary treatments. Thus, results of this study indicated that phase-feeding BT to pigs fed diets formulated with DDGS produced minor improvements in fresh belly firmness due to greater proportions of SFA but had no effect on yields of commercially processed bacon or bacon quality characteristics.

Response of the upper respiratory tract of the rat to white spirit vapour.

The threshold limit value (TLV) adopted by industry for white spirit is that of Stoddard's solvent and is currently set at 100 ppm (525 mg/m3). Exposure of rats to atmospheres containing an average of 214 mg/m3, 4 h/day, for 4 consecutive days resulted in irritation of the membranes lining the upper respiratory tract but only minimal signs of lung injury. Histopathological changes were observed in the nasal cavity, trachea and larynx and included loss of cilia, mucous and basal cell hyperplasia and squamous metaplasia. These results suggest that in man exposure to white spirit at or around the TLV may result in irritation of the upper respiratory tract.