HP Feeding Research Articles

Hormonal growth-promotant effects on grain-fed cattle maintained under different environments

Six steers (3/4 Charolaisx1/4 Brahman) (mean body weight 314+/-27 kg) and six spayed heifers (3/5 Shorthornx2/5 Red Angus) (mean body weight 478+/-30 kg) were used to determine the effects of climatic conditions and hormone growth promotants (HGP) on respiration rate (RR; breaths/min), pulse rate (beats/min), rectal temperature (RT; degrees C), and heat production (HP; kJ). Cattle were exposed to the following climatic conditions prior to implantation with a HGP and then again 12 days after implantation: 2 days of thermoneutral conditions (TNL) [21.9+/-0.9 degrees C ambient temperature (T(A)) and 61.7+/-22.1% relative humidity (RH)] then 2 days of hot conditions [HOT; 29.2+/-4 degrees C (T(A)) and 78.3+/-13.2% (RH)], then TNL for 3 days and then 2 days of cold conditions [COLD; 17.6+/-0.9 degrees C (T(A)) and 63.4+/-1.8% (RH); cattle were wet during this treatment]. The HGP implants used were: estrogenic implant (E), trenbolone acetate implant (TBA), or both (ET). Both prior to and following administration of HGP, RRs were lower (P<0.05) on cold days and greater (P<0.05) on hot days compared to TNL. On hot days, RTs, were 0.62 degrees C higher after compared to before implanting. Across all conditions, RTs were >0.5 degrees C greater (P<0.05) for E cattle than for TBA or ET cattle. On cold days, RTs of steers were >0.8 degrees C higher than for the heifers, while under TNL and HOT, RTs of steers were 0.2-0.35 degrees C higher than those of heifers. Prior to implantation, HP per hour and per unit of metabolic body weight was higher (P<0.05) for cattle exposed to hot conditions, when compared to HP on cold days. After implantation, HP was greater (P<0.05) on hot days than on cold days. Under TNL, ET cattle had the lowest HP and greatest feed intake. On hot days, E cattle had the lowest HP, and the highest RT; therefore, if the potential exists for cattle death from heat episodes, the use of either TBA or ET may be preferred. Under cold conditions HP was similar among implant groups.

Effects of diet composition on food intake and carcass composition in rats

Since most of the weight-reduced obese humans are in a protein deficit state, this study was designed to examine whether a high protein diet (HP) enhances the restoration of lean body mass and facilitates the maintenance of weight loss. Obesity in rats was produced by 16 weeks of high fat diet (HF) feeding. In the 17th week, all HF-fed obese rats were fed a limited amount of control diet to normalize their body weights, but they still had more body fat content. The HF-fed rats were then divided into subgroups with different diets offered for 5 weeks: HP, HF or chow diet. A control group was fed the chow diet throughout the study. HP feeding maintained normal body weight and carcass composition in weight-reduced obese rats by reducing feeding efficiency levels to within normal ranges. Weight-reduced rats fed a chow diet, however, had more fat mass than controls and HF feeding stimulated weight gain again. Therefore, a HP diet has a higher probability of enhancing weight loss maintenance in weight-reduced obese subjects than does a usual well-balanced diet.

タンパク質および脂質添加量の異なる飼料を給じしたサクラマス１才魚の成長およびスモルト出現数

Among one year cherry salmon Oncorhynchus masou reared in freshwater, we found that non-polar lipid contents in the whole body, dorsal muscle, and liver of the smolt were lower than those of the parr. During March through May, nonesterified fatty acid levels in the plasma of the smolt were higher than those of the parr, but the neutral fat levels in the smolt were lower. Later, growth response and smolt production in 1 yeaz cherry salmon with mean weight of about 16g were studied by feeding the following four diets for 120 days: HPHL, high protein (41%)-high lipid(16%);HPLL, high protein(41%)-low lipid(4%);LPHL, low protein(24%)-high lipid (14%); LPLL, low protein (24%)-low lipid (2%). The growth response to these dietary treatments was as follows: HPHL (final mean body weight, 44.41g)_??_HPLL (36.47g)_??_LPHL (24.04g)_??_LPLL (28.02g). Only in the HP diets, both growth rate and feed efficiency were clearly improved by addition of lipid. In all treatment groups, the growth, feed efficiency, and feed consumption rate were accelerated with the onset of smoltification. Percentages of smolt pro-duced were 74.5%, 47.3%, 29.1%, and 16.4%for HPHL, HPLL, LPHL, and LPLL, respectively. Thus, supplementation of lipid to diet seems to be one of the valuable method to promote smolt production.

Effect of Plane of Nutrition from Starting Through the Breeder Period on the Reproductive Performance of Tom Turkeys

Large type breeder toms were given high (HP) or low (LP) planes of nutrition from hatching to 29 weeks of age. Birds from each rearing treatment were divided and HP or LP breeder rations were fed to 58 weeks. Protein and energy levels of the HP feeds approximated National Research Council (NRC, 1977) recommendations while LP feeds involved substitution of corn, fat, and soybean meal for wheat, barley, and oats. Energy-protein ratio and relative essential amino acid levels were similar between treatments, respective of age.Toms given LP feeds weighed less than HP through the first 9 weeks after hatching, but they were similar thereafter until 29 weeks. Reduction in feed conversion with the LP regimen was only significant during the 18 to 21-week interval. Feed intake during the breeder period was unaffected by treatments. Toms receiving the LP breeder feed reduced their weight, particularly when preceded by LP rearing. Mortality was inversely related to average body weight with each treatment. Reproductive capacity, as judged from semen yield and sperm concentration, was more favorable when toms were reared on LP than HP feeds but only during the first few weeks of the breeder period. The LP feed given through the breeder period also proved more favorable than HP feed, particularly at the end of production. Carcass evaluations at 29 and 58 weeks indicated that the LP regimens reduced depot fat while increasing relative testes weight.

A nonsuppressible increase of glucagon secretion by isolated islets of high-protein-fed rats.

We recently demonstrated increased plasma glucagon but nomal insulin in rats fed a high-protein, carbohydrate-free (HP) diet; however, other investigators have reported that both plasma glucagon and insulin are increased after protein feeding. For this reason, we have investigated the ffects of an HP diet on pancreatic secretion of insulin and glucagon. Male rats were fed an HP or control diet for one, three, or five days, and, at the end of the feeding period, blood was taken for glucose, insulin, and glucagon determinations. Additional animals fed the HP and control diets for up to 10 days were sacrificed, the pancreases removed, and islets of Langerhans isolated. Islets were incubated for 30 minutes in media with glucose concentration of1.7, 8.3, 16.7, or 33.4 mM. Insulin and glucagon secreted into the media were determined by radioimmunoassay. Plasma insulin was markedly reduced after one day of HP feeding but gradually returned to normal by the fifth day. Plasma glucagon was not altered on day 1 but was significantly increased after three days of HP feeding. The I/G molar ratio, which declined precipitously on day 1, increased thereafter but, as shown previously, remained at a level that promotes gluconeogenesis for up to 10 days. Insulin secretion by isolated islets of control and HP rats increased more than 10-fold as medium glucose was raised from 1.7 to 16.7 mM. There was no difference in insulin release by the two groups of islets. Glucagon secretion by HP islest at low medium glucose remained normal during the first five days; however, beginning on day 3 there was gradual loss of the suppressive effect of high medium glucose on glucagon secretion. After one week of HP feeding, glucagon secretion at low medium glucose was doubled and there was complete lack of suppression of the elevated hormone production by high medium glucose. The alterations of alpha-cell function induced by HP feeding are similar to those found in human and experimental diabetes.

Glucagon stimulation of hepatic gluconeogenesis in rats fed a high-protein, carbohydrate-free diet

We previously observed increased gluconeogenesis in isolated liver of rats fed a high protein, carbohydrate-free (HP) diet and postulated that this was due to enhanced secretion of glucagon. To test this hypothesis, the effects of glucagon, dibutyryl cyclic AMP (DB-CAMP), and insulin on hepatic gluconeogenesis were examined. In perfused liver of control rats, alanine conversion to carbohydrate amounted to 20.39 ± 3.15 μmole/100 g body wt/90 min. Gluconeogenesis was increased to 35.14 ± 2.66 by glucagon; to 31.40 ± 1.0 by DB-CAMP, and suppressed to 14.56 + 1.15 by insulin. When both glucagon and insulin were added to the medium, only the stimulatory action of glucagon was evident. In perfused liver of HP-fed rats, alanine incorporation into carbohydrate totalled 51.79 ± 4.36. Gluconeogenesis was elevated by glucagon to 65.23 + 1.78, by DB-CAMP to 62.27 + 2.41, and was unaffected by insulin, 49.73 + 3.11. In the presence of both glucagon and insulin, only the glucagon effect was apparent. Levels of intermediary metabolites involved in gluconeogenesis were determined in control and HP livers. Concentrations of alanine, lactate, and pyruvate were reduced in HP liver, while phosphoenol-pyruvate (PEP) was increased, findings that suggest enhanced conversion of pyruvate to PEP. Fructose diphosphate concentration was normal; however, fructose-6-phosphate was greatly elevated, suggesting that fructose diphosphatase was stimulated by HP feeding. Similar changes in hepatic metabolites have been found following exposure of normal liver to glucagon. Plasma insulin values were not altered by HP feeding (C = 36.7 ± 3.7 μU/ml; HP = 32.3 ± 2.8). Plasma-glucagon levels were higher in HP rats than in controls (C = 80 ± 7.5 pg/ml; HP = 137.8 ± 16.7; p < 0.01). When the molar ratio of insulin to glucagon in plasma was calculated, the value in HP-fed rats was reduced, thus demonstrating a relative as well as an absolute rise of glucagon concentration (C = 11.1 ± 1.1; HP = 5.76 ± 0.6; p < 0.001). Liver cyclic AMP was greater in HP-fed rats than in controls (C = 0.83 ± 0.04 nmole/g; HP = 1.17 ± 0.07; p < 0.001), a finding that indicates that the liver was exposed to an increased amount of glucagon.