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Forty-one Holstein cows were injected with 0, 5, or 14 mg/d of bST for the last 46 +/- 6 d before parturition. Compared with data for controls, the 5- and 14-mg doses of bST increased apparent protein synthesis about 16% before parturition. Exogenous bST before parturition increased apparent protein degradation 30% during wk 1 after parturition. During wk 1 of lactation, 14 mg of bST also increased milk protein yield 33%. No treatment differences were present in concentration of serum NEFA, body condition score, or thickness of subcutaneous fat. Therefore, administration of bST before parturition did not alter metabolism of subcutaneous fat. Prepartum treatment with 5 and 14 mg of bST increased and maintained serum somatotropin at 6.5 and 22.7 ng/ml, respectively, compared with 1.6 ng/ml in controls. Concentrations of serum IGF-I were initially increased but were not maintained as parturition approached. On d -23, IGF binding protein 3 was increased 65% but was not different among groups by d -7. For groups administered the 5 and 14 mg/d of bST, IGF binding protein 2 was decreased 40%. Administration of bST before parturition increased protein reserves and stimulated milk protein yield for 1 wk but did not alter metabolism of subcutaneous fat. Furthermore, energy balance appeared to be a major regulator of concentrations of IGF binding protein 3 and responsiveness of IGF-I to exogenous somatotropin before parturition.

The objective of this study was to investigate the effect of the degree and duration of early dietary AA restrictions on subsequent and overall pig performance and physical and sensory characteristics of pork. For the grower (G) and finisher-1 (F1) phases, 3 corn-soybean meal diets were formulated to contain 100, 80, or 60% of the 1998 NRC total Lys recommendations (100G, 80G, or 60G, and 100F1, 80F1, or 60F1, for the G and Fl phases, respectively). For the finisher-2 (F2) phase, a common corn-soybean meal diet was formulated to satisfy the 1998 NRC total Lys recommendation. Thirty gilts and 30 castrated males (2 gilts or 2 castrated males/pen) were randomly assigned to 5 dietary treatments (100G-100F1, 80G-100F1, 80G80F1, 60G-100F1, and 60G-60F1) when BW was 22.7 ± 0.3 kg. Pigs were switched to F1 and F2 diets at 50.7 ± 0.4 and 79.9 ± 0.5 kg of BW, respectively. Pigs had ad libitum access to feed and water. All pigs were slaughtered at 110.7 ± 0.5 kg of BW, and LM samples were collected. Pigs fed the 60G diet had less (P ⩽ 0.05) ADG during the G phase and greater (P ⩽ 0.05) ultrasound backfat (UBF) at the end of the C phase than those fed the 100G diet. The ADG decreased linearly (R2 = 0.70; P < 0.001) as the degree of AA restrictions became more severe. Although serum total protein (TP) and albumin concentrations in pigs fed the 60G-100F1 diets were less (P < 0.05) than those fed the 100G-100F1 diets at the end of the G phase, TP concentration was similar between the 2 groups at the end of the Fl phase. Likewise, ADG during the Fl phase and UBF at the end of the Fl phase in pigs fed the 60G-100F1 diets were similar to those fed the 100G-100F1 diets. Feeding the 80G diet resulted in numerically decreased ADG during the G phase, but there was no difference in ADG during the F1 and F2 phases or UBF at the end of Fl and F2 phases between pigs fed the 80G and 100G diets. Overall, pigs fed the 80G-80F1 diets had similar ADG, but less (P ⩽ 0.05) fat-free lean gain (LG) than those fed the 100G-100F1 diets. These pigs also had less (P ⩽ 0.05) serum TP and albumin concentrations than pigs fed the 100G-100F1 diets throughout the study. Pigs fed the 60G-60F1 diets had less (P < 0.05) overall ADG and G:F and less (P < 0.05) LM area and LG than those fed the 100G-100F1 diets. However, they had a greater (P ⩽ 0.05) subjective marbling score than those fed the 100G-100F1 diets. The results indicated that pigs fed the 80G-80F1 diets may have exhibited compensatory growth in BW gain, but not in terms of lean accretion. Growth performance and carcass traits of pigs fed the 60G-60F1 diets were reduced, indicating that the restriction may have been too severe or too long or both. Early dietary AA restrictions had no clear effect on physical and sensory characteristics of pork. [ABSTRACT FROM AUTHOR]