No abstract

Lipid compared with carbohydrate calories in the diet of peripartal sows was examined for specific metabolic effects. Blood samples from second-parity Yorkshire sows fed isocaloric-isonitrogenous diets that differed by either glucose or corn oil supplying 20% of the daily metabolizable energy intake were assayed for growth hormone (GH), insulin and prolactin (PRL) concentrations. On d 97 to 103 of gestation, serum GH levels were reduced following feed intake; the reduction was greater (P less than .05) in glucose-fed sows during the postprandial period. Insulin concentration was increased following consumption of either diet, but to a greater (P less than .05) extent in glucose-fed sows corresponding to the greater (P less than .05) blood glucose response. Basal, fasting concentrations of PRL were not affected by dietary energy source; however, thyrotropin-releasing hormone (TRH) infusion resulted in a greater (P less than .05) PRL response of fat-fed sows. Samples obtained on d 8 to 11 of lactation revealed that TRH stimulated (P less than .05) GH secretion and the response was greater (P less than .05) in fat-fed sows. Plasma insulin concentration was increased (P less than .05) following feeding, and the increase was greater (P less than .05) in glucose-fed sows. Similar to the response measured in gestating sows, TRH-induced increases in PRL was greater in fat-fed, lactating sows. Sham-nursing did not influence maternal PRL concentration compared with the immediate increase noted following natural nursing. No effect of dietary energy source on reproductive performance characteristics was noted. Results of this study have shown that dietary lipid, compared with carbohydrate, selectively increased the sensitivity of the pituitary gland to a GH and PRL secretagogue such as TRH. The beneficial effects of lipid in the diet of peripartal swine may be attributable, in part, to the effect of dietary lipid on maternal pituitary PRL synthesis and(or) release.

Trace mineral status was evaluated in a 2 x 3 factorial treatment array with a total of 34 barrows growing from 25 to 55 kg live weight. Treatments included three levels of feed intake (100, 80 and 60% of ad libitum intake) and exogenous pituitary growth hormone (pGH) therapy (0 and 100 micrograms/kg BW daily). Blood was collected prior to slaughter for the determination of hematocrit and serum trace metal concentrations; tissues (liver, heart, kidney, bone and muscle) were obtained when pigs were slaughtered at 55 kg. Hematocrits and serum Fe were lower in pGH-treated pigs than in controls at all levels of feed intake. Serum Cu was increased by feed restriction but was not altered by pGH therapy. The concentration of serum Zn was not affected by either treatment. Concentrations of hepatic Fe and Cu were lower in pGH-treated pigs than in controls but were higher in feed-restricted pigs than in ad libitum-fed pigs. However, the total amounts of hepatic Fe and Cu were similar in pGH-treated pigs to concentrations in controls. The concentration of hepatic Zn was not influenced by either pGH treatment or feed intake. Femur weights were marginally greater in pGH-treated pigs, probably due to elevated water content. Iron concentration in bone was higher in pGH-treated pigs than in control pigs, whereas Ca, Cu and Zn were not influenced by pGH treatment or feed restriction. Feed intake and pGH treatment did not influence the concentrations of Fe, Cu or Zn in muscle. These findings indicate that pGH therapy affects the metabolism of Fe but has little impact on the overall composition of body ash.

Material and Methods Male rats, 36 weeks of age, were sacrificed in the fed state and liver and adipose tissue plasma membranes were prepared by differential centrifugation (Chang, Bennett and Cuatrecasas 1975). Insulin receptor characteristics were detennined by the method of MarshalI, Underwood, Viona, Foushee and Van Wyk (1974) and insulin degradation was estirnated by the loss of trichloroacetic acid precipitable radioactivity (Varandani and Nafz 1976). The marker enzyme for plasma membrane was 5'-nucleotidase (E.C 3.1.3.5) as detennined by Ray 1970). Serum was assayed for insulin (Morgan and Lazarow 1963). Results were evaluated by Student's t-test.

1. Broiler chickens growing from 7 to 28 d of age were given: (I) a 210 g protein/kg control diet for the entire experimental period, (2) an intermittent feeding regimen (210 g protein/kg diet for either 1 or 2 d followed by a 1 d fast), or (3) a daily change in the dietary protein level from 120 to 300 g/kg diet. Treatment variables examined were lipogenesis and glucose production in vitro, and circulating concentrations of insulin, triiodothyronine (T,) and thyroxine (TJ to determine the effects of chronic or acute dietary treatments.2. Giving the 300 g protein/kg diet or withholding feed for 1 d decreased (P < 005) lipogenesis in vitro compared with controls.3. Giving the 120 g protein/kg diet or refeeding with a 210 g protein/kg diet for 1 or 2 d increased (P < 0.05) lipogenesis in vitro compared with controls. Glucose production was affected in the same manner. 4.Fasting decreased (P < 0.05) plasma insulin and T, and increased T,. Both refeeding and a low-protein diet increased T,. Refeeding increased and a low-protein diet decreased insulin.5. Chronic use (7-28 d of age) of either an alternating protein or intermittent feeding regimen caused greater responses compared with acute bouts (single cycle) of either of the regimens.