In Exp. 1 two groups of 18 sows were used to evaluate the effects of supplemental dietary fat on sow and litter performance and milk production and composition. Sows were provided ad libitum access to either a corn-soybean meal (control) diet or a similar diet containing 10% tallow. Feed intake, ME intake, and milk yield did not differ (P > .10) between treatments. The percentage of solids in milk was greater (P < .05) for sows fed the tallow diet, due to an increase (P < .05) in the fat and ash content. Compared with percentages of fatty acids in milk of sows fed the control diet, the percentages of C10:0, C14:0, C16:0, C16:1, and C18:3 fatty acids were lower (P < .05) and the percentages of C18:0 and C18:1 fatty acids were higher in milk of sows fed tallow diets (P < .05). In Exp. 2, 30 sows were fed diets similar to those fed in Exp. 1, and the effects of a tallow diet on pig carcass composition at weaning were determined. Litter size was standardized to 10 pigs. There were no differences (P > .10) in ADFI of sows. Daily ME intake was greater for sows fed tallow than for control sows during wk 2 (P < .05), wk 3 (P < .10), and the entire lactation (P < .05) period. Litter weaning weight was greater (P < .05) for pigs from sows fed tallow diets than for pigs from control sows. Pigs from tallow-fed sows had greater carcass fat weight and fat percentages (P < .05) and lower water and protein percentages (P < .05). These data indicate that the increased fat content of milk from sows fed tallow diets resulted in an increased weight gain for litters nursing these sows. The composition of the increased weight gain is almost exclusively fat.

Preference tests and meal pattern analyses were conducted to examine the feed intake response of weanling pigs to spray-dried porcine plasma (SDPP). In Exp. 1, 36 weanling pigs (mean +/- SD; 6.2 +/- .8 kg and 26 d of age) were allowed to choose between a SDPP diet (8.5% SDPP, 20% dried whey, 10% lactose, and .13% DL-methionine) and a dried skim milk (DSM) diet (20% each of DSM and dried whey) throughout 21 d postweaning. Twenty-eight pigs preferred the SDPP diet and seven pigs preferred the DSM diet. Preference for SDPP became apparent by d 2 (60% of total feed consumption) and increased (P < .01) to d 21 (71% of total feed consumption). Average daily feed consumption was 371 and 172 g for the SDPP and DSM diets, respectively (P < .01). The meal patterns of 16 weanling pigs (mean +/- SD; 7.2 +/- .3 kg and 26 d of age) offered either the SDPP or the DSM diet were examined in Exp. 2. On d 3, 7, and 14 postweaning, feeding behavior was observed continuously for 18 h (0600 to 2400). Time spent consuming feed and time between periods of feeding were recorded. Although the difference was not significant, pigs fed the SDPP diet consumed 27 and 6% (P = .38) more feed than pigs fed the DSM diet during the first 7 d and during the entire 21-d period, respectively. This difference was reflected in increased (P < .05) rate of feed consumption on d 3 and 7. Diet had no effect (P > .10) on meal size, the number of meals, or the percentage of time spent consuming feed. Weanling pigs prefer diets containing SDPP to those containing DSM, and the increased consumption of diets containing SDPP may be due to greater palatability.

To determine the effect of energy and protein intakes on boar libido, semen characteristics, and plasma hormone concentrations, 24 crossbred boars (1 yr of age) were allotted to one of three dietary treatments. Two protein levels (7.7 and 18.1 g/d of lysine) and two energy levels (6.1 and 7.7 Mcal/d of ME) were combined to create 1) low-energy and low-protein (ep), 2) low-energy and high-protein (eP), and 3) high-energy and high-protein (EP) treatments. Semen was collected two times per week for 27 wk. During wk 28, blood samples were collected before and after a intravenous injection of GnRH (375 ng/kg of BW). The EP boars had higher (P < .01) ADG than the eP boars (373 vs 169 g), which had higher (P < .01) ADG than the ep boars (169 vs 92 g). Fewer EP and eP boars (zero of eight and two of eight, respectively) than ep boars (five of eight) consistently refused to mount the collection dummy (P < .05). During the final 20 wk of the semen-collection period, EP and eP boars had 33% longer durations of ejaculation (P < .04), had 60% greater semen and gelatinous fraction volumes (P < .03), but had 25% lower sperm concentration in their semen (P < or = .12) than ep boars. The EP boars produced 38% more sperm than the ep boars (P < .10). Baseline LH concentration, LH pulse frequency, LH pulse amplitude, testosterone concentration, and estradiol-17 beta concentrations were not affected by treatment (P > .10).(ABSTRACT TRUNCATED AT 250 WORDS)

Four experiments were conducted to determine the effects of dietary fat on lipolysis in lactating sows. In Exp. 1, a 6 x 6 Latin square was used to determine the optimal dosage of epinephrine for use in a subsequent epinephrine challenge. Peak concentrations of plasma glucose and response area increased linearly (P < .10) with epinephrine dosage. However, plasma NEFA peak and response area were quadratically affected (P < .05 and .06, respectively) by epinephrine dosage, with a minimum NEFA peak concentration observed at .4 microg/kg and a maximum at 1.6 microg/kg. In Exp. 2, the effect of dietary tallow on the response to epinephrine infusion (1.6 microg/kg BW) was examined. No differences (P > .10) between treatments were observed in NEFA, glycerol, or peak concentrations of plasma glucose following epinephrine administration. In Exp. 3, the effect of dietary fat on hormone-sensitive lipase activity was examined. Sows (n = 36) were fed diets containing either 0 or 10% added tallow. Hormone-sensitive lipase activity on d 28 of lactation was increased by the addition of tallow to the diet (P = .06). No effect of dietary tallow was observed on hormone-sensitive lipase activity of adipose tissue on d 21 of lactation (P > .10) in Exp. 3 (n = 16 sows) and Exp. 4 (n = 30 sows). In summary, diets containing 10% added tallow did not alter the rate of lipolysis, as measured by exogenous epinephrine challenge, in adipose tissue of lactating sows.