Interrelationships between dietary lysine, sex, and porcine somatotropin administration on growth performance and protein deposition in pigs between 80 and 120 kg live weight

Sixty male and 60 female crossbred pigs were allocated to an experiment to investigate the effects of porcine somatotropin (pST) administration (0 or 6 mg/d) and dietary lysine content on growth performance, tissue deposition, and carcass characteristics over the live weight range of 80 to 120 kg. Pigs receiving pST were given diets containing 6.9, 7.8, 8.8, 9.7, 10.6, or 11.5 g lysine/kg, whereas control pigs received diets containing 4.8, 5.8, 6.9, 7.8, 8.8 or 9.7 g lysine/kg. These dietary levels ranged from 0.40 to 0.70 g available lysine/MJ of DE for pST-treated pigs and from 0.28 to 0.58 g available lysine/MJ of DE for control pigs. Pigs were individually housed in pens, and there were five replicates of each treatment. All diets contained 14.5 MJ of DE/kg and were offered for ad libitum consumption to pigs between 80 and 120 kg live weight. Growth rate increased exponentially and food conversion ratio (FCR) decreased exponentially with increasing levels of lysine. In addition, there was a significant sex x pST interaction such that pST reduced the sex difference in FCR. Growth rate was faster in boars than in gilts and was increased by pST at the higher levels of dietary lysine. Similarly, FCR was lower for boars than for gilts and was decreased by pST at the higher dietary lysine levels. The optimum growth rate and FCR were defined as the lysine level at which growth rate and FCR were 95% and 105%, respectively, of the lysine plateau. The optimum growth rate and FCR were achieved at similar dietary lysine contents and were approximately 0.35 and 0.52 g available lysine/MJ of DE for control and pST-treated pigs, respectively. Protein deposition in the carcass increased exponentially with increasing dietary lysine level, was higher in boars than in gilts, and was increased by pST at the higher dietary lysine contents. Sex had no effect on dietary lysine required to maximize protein deposition. The dietary lysine contents required to ensure 95% of plateau protein deposition of 104 and 153 g/d were 0.39 and 0.55 g available lysine/MJ of DE for control and pST-treated pigs, respectively. The increase in lysine requirement with pST seems to be commensurate with the increase in protein deposition.     

Maternal-neonatal immunoregulation: suppression of de novo synthesis of IgG and IgA, but not IgM, in neonatal pigs by bovine colostrum, is lost upon storage

Fifty-four neonatal pigs were allotted to 4 groups and reared in an electrically controlled automatic feeding device (autosow). Each group was reared on a different pool of bovine colostrum: fresh, stored 1 month, stored 6 months, and stored 8 years. Bovine and porcine immunoglobulins in the sera of these pigs, and in a group of conventionally reared pigs, were measured periodically during the first 42 days after birth. The maximal concentration of absorbed bovine immunoglobulin was reached between 12 and 18 hours and equaled or exceeded the amount of porcine immunoglobulin absorbed by the conventionally reared pigs. Large differences in the concentrations of the bovine immunoglobulin isotypes among the various pools of colostrum were positively correlated with concentration of these isotypes in the sera of the neonatal pigs fed these pools. Relative to their concentrations in colostrum, approximately 41% of the IgG1, 55% of the IgG2, 29% of the IgM, and 67% of the IgA was absorbed. The IgA was absorbed the best and IgM was least absorbed. Significant trends or differences in absorption were not observed among groups. Neonatal pigs given fresh colostrum, which had a higher fat content, had significantly more weight gain (P less than 0.05). This occurred, despite the fact that the fresh colostrum had the lowest concentration of bovine immunoglobulin. Serum half-lives for bovine IgG1 and IgG2 were significantly less than for porcine IgG (P less than 0.05), whereas the half-lives for bovine and porcine IgM and IgA were similar. De novo-synthesized immunoglobulins were detectable in serum after 6 days; IgM concentrations reached a maximum at 15 days in neonatal pigs given stored, but not fresh, colostrum.(ABSTRACT TRUNCATED AT 250 WORDS)     

Energy balance and pulsatile LH secretion in early postpartum dairy cattle

The relationships between energy balance (EB), pulsatile LH secretion and circulating levels of insulin and various energy metabolites were assessed in ten lactating Holstein cows. Cows were blood sampled every 12 min via indwelling jugular catheters for 8 hr twice weekly beginning in the first week postpartum (PP) through first ovulation (1stOV). Days to negative EB nadir and days to 1stOV were highly correlated (P less than .02). LH pulse frequency (P less than .01), LH baseline (P less than .05) and mean LH (P less than .1) increased, while LH pulse amplitude tended to decrease when comparing the frequent sampling series immediately before and after the negative EB nadir. Plasma levels of non-esterified fatty acids (NEFA, r = -.40, P less than .01), insulin (r = .38, P less than .01), glucose (r = .31, P less than .01) and beta-hydroxybutyrate (r = .19, P less than .06) were correlated with EB. For within animal comparisons, NEFA was significantly correlated (r = -.44 to -.89, P less than .05) with EB in 8 of 10 cows, but no other correlations were significant. Additionally, none of the metabolites nor insulin were significant in multiple regression models for 1stOV. Therefore, it appears that pulsatile LH secretion is suppressed until the negative EB nadir is reached, at which time LH pulse frequency increases stimulating 1stOV. Since NEFA and EB are directly related, NEFA may serve as a peripheral signal of EB to the central nervous system.     

Effect of exogenous glucagon and free fatty acids on gluconeogenesis in fasting neonatal pigs

Thirty-two pigs (1 d old) were used to determine if exogenous glucagon and(or) free fatty acids (FFA oleic acid) would enhance gluconeogenesis and glucose homeostasis during fasting. Pigs were acquired at birth, fitted with an indwelling arterial cannula (via umbilicus) and fasted 24 h to deplete liver glycogen. A jugular cannula was inserted nonsurgically 8 to 10 h before initiation of a primed-continuous infusion consisting of control (excipient), glucagon (Glu), oleic acid (FFA), or both glucagon and oleic acid (Glu-FFA). Plasma Glu averaged 395 pg/ml preinfusion and was similar across treatments. The concentration increased fivefold (P less than .05) by 80 min for Glu and Glu-FFA pigs and remained constant thereafter (160 min: 2,379, 2,258 pg/ml; 240 min: 2,355, 2,274 pg/ml, respectively). Glucagon infusion did not alter plasma glucose after 240 min of infusion (control, 50 vs Glu, 51 mg/dl); however, Glu-FFA effected an increase (60 mg/dl, P less than .10). In contrast, pigs infused with FFA alone had a lower glucose concentration (40 mg/dl, P less than .10). Rate of glucose synthesis was determined using liver slices, acquired immediately postinfusion, with alanine and lactate as substrate (7.5 mM). The rate of synthesis was not altered by Glu or Glu-FFA infusion (2.91, 2.43 mumol glucose X g-1 X h-1 vs 2.91 for control). In contrast, exogenous FFA reduced synthesis to 1.85 mumol glucose X g-1 X h-1 (P less than .05) with lactate as substrate. It appears that Glu is not the primary factor limiting gluconeogenesis in fasting newborn pigs.(ABSTRACT TRUNCATED AT 250 WORDS)     

In vitro interactions between Neoparamoeba sp. and Atlantic salmon epithelial cells

Neoparamoeba sp., including the putative aetiological agent of amoebic gill disease in cultured fish (N. pemaquidensis), were incubated in vitro with an Atlantic salmon gill epithelium (RGE-2) cell line. Proliferation by the amoeba population was dependent upon culture osmolarity; no growth occurred at 330 mm x kg(-1) but a sixfold increase was observed at 1000 mm x kg(-1). At 780 mm x kg(-1) there was a fourfold increase in the amoeba population but a concurrent decrease in RGE-2 cell density that was significantly greater than that caused by the high culture osmolarity alone. This apparent cytopathic effect (CPE) developed rapidly and resulted in complete cytolysis of the monolayer in 5 days. CPE occurred in multiple foci and presented as cell vacuolation, rounding and clumping, and the rapid clearance of large areas of the cell monolayer. The possibility that CPE is because of the presence of Neoparamoeba sp. derived cytolytic products is discussed in the context of the pathology of the disease in vivo and the occurrence of secreted cytopathogenic compounds in other amoeba species.     

Genestic differences between successive year classes of two strains of reared rainbow trout, Oncorhynchus mykiss (Walbaum)

The genetic composition of consecutive year classes of two farmed rainbow trout, Oncorhynchus mykiss (Walbaum), strains was assessed, using starch gel electrophoresis of 11 enzymes encoded by a minimum of 23 loci, many of which have been shown to be polymorphic in previous studies. Angle frequencies at the majority of polymorphic loci varied significantly between year classes of each strain. Several alleles which were present at low frequency in the 1900 year classes, were absent in the samples from the 1991 cohorts. However, mean heterozygosity per locus (H) did not differ significantly between year classes of either strain, illustrating that allelic diversity is a more sensitive indicator of loss of genetic variability than mean heterozygosity. This heterogeneity between cohorts is probably due either to broodstock maintenance practices such as the use of insufficient numbers of spawners, or, in the case of one strain, to bottlenecking caused by selection for late maturation and increased growth rate. Genetic monitoring of all year classes of reared strains is suggested, if insufficient breeding and distribution records are available from egg producers. Such records are often unavailable in commercial situations.