LE Diet Research Articles

Fertility response of yearling beef heifers after prebreeding energy manipulation, estrous synchronization and timed artificial insemination

The effect of dietary energy and weight class on the fertility of yearling beef heifers (Angus, Hereford, and Angus × Hereford) was investigated over 2 years. In year 1, heifers ( n = 58) were classed as heavy (HW; ≥340 kg) or light weight (LW; <340 kg) and then assigned to receive either a low (LE; 0.23 kg/day) or high energy (HE; 0.68 kg/day) diet. In year 2, heifers ( n = 60) were also classified as heavy (≥335 kg) or light weight (<335 kg), but the energy content of the diet was raised so that heifers on the LE and HE were targeted to gain 0.46 and 0.79 kg/day, respectively. Heifers in the four groups, LELW ( n = 14 and 12), LEHW ( n = 16 and 17), HELW ( n = 13 and 15), and HEHW ( n = 15 and 16) received restricted amounts of concentrate (HE > LE) and free choice hay over 47 or 42 days (year 1 and year 2, respectively). To synchronize estrus, heifers were fed capsules containing MGA (0.5 mg/animal each day) beginning 11 days before the end of the feeding trial (day 0), PGF 2α (25 mg i.m.) and estradiol benzoate (Eβ; 400 μg i.m.) was given on days 8 and 10, respectively. Estrous behavior was observed (days 10 and 11) and all heifers were inseminated on day 11. Following AI, heifers were re-grouped and a bull was introduced (days 27–39) for the second service in both years. Pregnancy diagnosis for the first (days 41–42) and second services (days 69–97) was performed by transrectal ultrasonography. Transrectal ultrasonic observations of ovarian follicle number and size were completed for a subset of heifers ( n = 5–8) from each experimental group at the end of the feeding trial. The effect of year was not significant for any of the reproductive performance variables measured. The mean ADG was (0.72 ± 0.04 kg/day) and was greater in LW than HW heifers and in heifers in the HE than LE treatment groups ( P < 0.05). In heifers receiving the LE diet, ADG was lower in HW than LW heifers (weight × diet; P = 0.02; 0.54 ± 0.04 and 0.62 ± 0.03 kg/day for HW and LW heifers, respectively). The diameter of the largest follicle was greater in heifers receiving the HE diet ( P < 0.05; 11.3 ± 0.4 mm) than those on the LE diet (10.3 ± 0.3), and in LW ( P < 0.05) compared to HW heifers. The HE diet increased the size of the largest follicle in LW but not HW heifers (diet × weight, P < 0.05). The percentage of pubertal heifers at the end of the feeding period (59.3%), estrous response (56.4%), conception rate (47.7%), ovulation rate (88.9%), and first service pregnancy rate (36.2%) were not significantly affected by initial weight or diet. There was a tendency for first service pregnancy rates to be greater in LW than HW heifers consuming the LE diet (diet × weight, P < 0.1; 54.2 ± 15 and 30.3 ± 10% for LELW and LEHW heifers, respectively). Pregnancy rate after two services was greater ( P = 0.01) in LW (82 ± 10%) than in HW (64.5 ± 10%). The LE diet achieved moderate rates of gain and allowed high level of reproductive performance in LW but not HW heifers.

Heart and blood pressure adaptations in Wistar rats fed with different high-fat diets for 18 months

Objective We investigated the effect of long-term administration of four different high-fat diets on systolic blood pressure (SBP), body and heart biometry, and left ventricular myocyte nuclei number (N[lvm]). Methods Twenty-four Wistar rats were assigned to one of four groups from weaning to age 18 mo. The rats were fed experimental diets containing soybean oil (S group), canola oil (CA group), lard and egg yolk (LE group), and canola oil plus lard and egg yolk (CA + LE group). N(lvm) was measured with the disector method in isotropic uniform random sections of the left ventricular myocardium. Results There were no significant differences across experimental groups in morphometric indices. SBP was higher in the LE group at all ages and lower in the 18-mo CA group. The myocardium structure analysis separated the animals in three major categories: the CA and LE groups as the extreme and the S and CA + LE groups as the intermediary. In the LE group the myocardium presented more important structural changes: cardiac myocytes were enlarged and surrounded with thick collagen bundles, and some regions exhibited myocardial necrosis. Conclusion Long-term intake of the CA diet was more efficient in maintaining normal N(lvm) and SBP than the S and LE diets. The CA + LE diet resulted in balanced levels of SBP and N(lvm) in rats, suggesting that canola oil reduces cardiovascular injury caused by intake of lard and egg yolk.

Meat quality of Boer goat kids and Mutton Merino lambs 2. Sensory meat evaluation

AbstractThe meat palatability, water-holding capacity, colour and shear force values of 32 Boer goat (BG) kids and 32 South African Mutton Merino (MM) lambs were investigated. Two pelleted diets (offered to 16 animals per species) with either a low (LE, 9·9 MJ/kg dry matter (DM)) or a high (HE, 12·1 MJ/kg DM) metabolizable energy level were given to the animals for either 28 or 56 days. Thereafter the animals were slaughtered, the meat cooked and presented to a trained sensory panel. Organoleptically, a difference between goat and lamb was noted. Each one had a specific species flavour, which was not influenced by energy level of the diet. BG meat was perceived to be stringier than that of the MM, but there was no significant difference in Warner-Bratzler shear force values. Tenderness declined with age in both species and there was also a tendency for goat meat to be less juicy than lamb. Chevon had a more pronounced after-taste than lamb. No objective difference could be distinguished between the colour of the cooked goat and lamb, but there was a tendency for fresh lamb to have a higher a*-value (redness) than goat. Although diet did not influence drip loss, drip loss increased with an increase in slaughter age. Only after 56 days did the m. semimembranosus of MM have a significantly higher drip loss than that of BG (LE: 4·84 v. 3·43%; HE: 4·72 v. 3·23%). In the m. semimembranosus of both species cooking loss increased with an increase in slaughter age. It can be concluded that goat meat compares favourably with lamb in terms of water-holding capacity, colour and shear force values. If goats are finished in the feedlot, it can be done on a LE diet, since diet does not influences any of the mentioned characteristics. This may render a direct economic advantage for BG feedlot finishing.

Effects of Dietary Energy Level and Number of Meals on Growth and Body Composition of Nile Tilapia Oreochromis niloticus (L.) During Summer and Winter Seasons

AbstractTwo feeding trials (experiments 1 and 2) were conducted to determine the combined effect of dietary energy levels (low energy, LE and high energy, HE) and number of daily meals (one meal with the entire daily amount, two meals with half of the daily amount, and three meals with one‐third of the daily amount) on the growth and body composition of Nile tilapia Oreochromis niloticus in a recirculating system at different water temperatures, representing winter and summer seasons. In experiment 1 (winter), weight gain and specific growth rate (SGR) were significantly (P &lt; 0.05) affected by dietary energy levels, but not by number of meals. Weight gain and SGR for fish fed the LE diet one daily meal were significantly (P &lt; 0.05) higher than for fish fed the HE diet in one daily meal. Feed efficiency ratio (FER) and energy efficiency ratio (EER) were significantly (P &lt; 0.05) affected by dietary energy levels, but not by number of meals. Protein efficiency ratio (PER) was not significantly (P &gt; 0.05) affected by either dietary energy levels or number of meals. However, protein retention was significantly (P &lt; 0.05) affected by both dietary energy levels and number of meals. The chemical composition (moisture, protein, lipid, and ash) of fish muscle was not significantly (P &gt; 0.05) affected by either dietary energy levels or number of meals. However, visceral fat content was significantly (P &lt; 0.05) affected by dietary energy levels, but not by number of meals. In experiment 2 (summer), weight gain and SGR were significantly (P &lt; 0.05) affected by number of meals, but not by dietary energy levels. Weight gain and SGR for fish fed the LE and HE diets in two daily meals were significantly (P &lt; 0.05) higher than those fed one daily meal. FER and PER were significantly (P &lt; 0.05) affected by number of meals, but not by dietary energy levels. The highest FER and PER were observed in fish fed two daily meals. EER was significantly (P &lt; 0.05) affected by both dietary energy levels and number of meals. Moisture and protein content of the whole fish were not significantly (P &gt; 0.05) affected by either dietary energy levels or number of meals. Lipid content was significantly (P &lt; 0.05) affected by dietary energy levels, but not by number of meals. Based on the results of these experiments, Nile tilapia should not be fed high‐energy diets to improve fish performance even under a limited feed allowance during winter or summer. Fish grew rapidly when fed two daily meals during summer, but number of meals had no effect on fish performance during winter.

Níveis de Energia e Peletização no Desempenho e Rendimento de Carcaça de Frangos de Corte com Oferta Alimentar Equalizada

Foi realizado um experimento para avaliar os efeitos dos níveis de energia (2900-BE- e 3200-AE- kcal EM/kg), da forma física da ração (farelada-RF, peletizada em matriz de 2 mm-RP2 e de 4 mm-RP4) e da uniformização de consumo, através da restrição (Rs) alimentar quantitativa baseada no consumo de ração (CR) obtido de rações oferecidas ad libitum (Ad)/RF/AE, sobre o desempenho e o rendimento de carcaça de frangos de corte, machos, dos 21 aos 42 dias de idade. Foram empregados oito tratamentos, cinco repetições, 12 aves/repetição. Foram oferecidos somente peletes íntegros das RP. Nestas condições não houve diferença no desempenho e nos parâmetros de carcaça entre RP2 e RP4, embora a RP2/BE tenha tido menor porcentagem de finos (12%) do que a RP4/BE (27%). A equalização do consumo entre RF/AE e RP2+RP4/BE resultou em GP (ganho de peso) similares (P&gt;0,05), porém melhor conversão calórica (CC) (P&lt;0,06) para RF/AE. Entre as dietas BE, apesar do CR ter sido significativamente menor nas RP/Rs (P&lt;0,001) comparado com RF/Ad, não houve diferenças para GP, CA (conversão alimentar) e CC. Comparando energia e forma física, as dietas RP/BE/Ad proporcionaram maior CR, GP, maior porcentagem de gordura abdominal e melhor CC, mas pior CA, quando comparadas com RF/AE/Ad. Também tiveram maior retorno econômico do que RF/Ad, em ambos os níveis de energia. A peletização parece evidenciar-se mais vantajosa com rações de baixa energia.

Comparison of the effect of dietary fat restriction with that of energy restriction on human lipid metabolism

Dietary fat and energy have been implicated as factors controlling circulating total and LDL-cholesterol concentrations. Whether these factors work independently or synergistically in regulating human cholesterol metabolism remains to be fully elucidated. The objective was to determine whether the effects of fat restriction on circulating lipid concentrations and synthesis differ from those of energy restriction in hypercholesterolemic subjects fed controlled diets. Eleven men (LDL > 3.6 mmol/L) participated in a randomized crossover study. Subjects consumed 4 prepared diets, each for 4 wk and separated by 6 wk, that contained either typical amounts of fat and energy (TF), low amounts of fat but adequate energy (LF), low amounts of fat and energy through carbohydrate restriction (LFE), or typical amounts of fat and low energy through carbohydrate restriction (LE). Body weights declined (P < 0.001) after the LE and LFE diets. Total cholesterol concentrations were not significantly different between the diets. LDL cholesterol was lower (P < 0.05) after the LF and LFE diets (8.2% and 8.0%, respectively) than after the TF diet. The LE diet increased HDL cholesterol (46.8%) and decreased triacylglycerols (22.7%), whereas the LF diet increased triacylglycerols (23.6%), relative to the TF diet. LDL:HDL decreased after the LE and LFE diets (P < 0.05). Cholesterol fractional synthesis rates after the LF, LE, and LFE diets were lower (35.2%, 27.7%, and 25.5%, respectively; P < 0.05) relative to the TF diet. Reductions in both dietary fat and energy may modify LDL cholesterol by lowering cholesterol biosynthesis; however, the increase in HDL cholesterol and the suppression of triacylglycerol concentrations and LDL:HDL suggests that favorable plasma lipid profiles were also achieved through energy restriction alone.

Effects of feeding frequency and dietary energy level on growth and body composition of juvenile flounder, Paralichthys olivaceus (Temminck &amp; Schlegel)

A two (dietary energy levels; low energy, LE and high energy, HE) × 4 (feeding frequency; one feeding in 2 days, one feeding daily, two times daily and three times daily) factorial experiment was performed to determine the effects of dietary energy level and/or feeding frequency on the growth and body composition of juvenile flounder Paralichthys olivaceus. The survival rate was not significantly different among treatments. Weight gain of fish fed the LE and HE diets significantly increased as feeding frequency increased. The weight gain of fish fed the LE diet was higher at each level of increasing feeding frequency. The weight gain of fish fed the HE diet was higher than that of fish fed the LE diet once in 2 days and once daily, but weight gain of fish fed the HE diet was lower than the LE diet three times daily. Daily feed intake was significantly influenced by feeding frequency, but not by dietary energy level. Feed efficiency of fish fed the HE diet once daily was significantly higher than that of fish fed the LE diet once in 2 days, but no significant difference in feed efficiency was observed among other groups of fish. The protein efficiency ratio of fish fed the LE diet once in 2 days was the lowest. Feeding frequency and dietary energy level had a significant effect on the body lipid content. A feeding frequency of two times or three times daily would be effective, depending on dietary energy level for maximum growth of juvenile flounder grown from 3.5 to 15 g.

Effect of feeding time on digestibility, growth performance and protein metabolism in the rainbow trout Oncorhynchus mykiss: interactions with dietary fat levels

The effect of feeding time was studied in rainbow trout fed different dietary levels of fat. Fish were fed either 1 h after light on in the morning or 1 h after light off in the evening with a low energy diet (LE, 6 % lipid) or a high energy diet (HE, 23 % lipid). Regardless of the diet, apparent digestibility and post-prandial protein synthesis were higher in fish fed in the morning than in those fed at the beginning of the night. In fish fed the LE diet in the morning, growth performance and nutrient retention efficiency tended to be higher than in those fed at the beginning of the night. In contrast, fish fed the HE diet in the morning had lower protein growth rate, protein content and protein retention efficiency than those fed in the evening. These results suggest that protein metabolism might be involved in the effect of feeding time on growth and that there is an interaction between the time of feeding and dietary level of fat on growth.

The efficiency of sand rat metabolism is responsible for development of obesity and diabetes.

Two separate lines--diabetic and partially diabetes-resistant--have been isolated from the sand rat (Psammomys obesus), each with different growth characteristics in response to diets of varying digestible caloric densities (high energy, HE, 2.93 kcal/g, or low energy, LE, 2.38 kcal/g). Over a two week period all animals consumed similar quantities (c. 125 g) irrespective of the diet consumed. Weight gains were as follows: diabetic line on HE diet - 59.7 g, on LE - 46.2 g; non-diabetic animals from the diabetes-resistant line on HE - 44 g. Only animals from the diabetic line, fed the HE diet, developed hyperinsulinemia, obesity and diabetes. The energy cost of weight gain for the diabetic line fed either HE or LE diets was 6.0 - 6.3 kcal/g whereas for the diabetes-resistant line on the HE diet, the cost of growth was 50% higher at 9.3 kcal/g. These differences could be due either to alterations in the content of tissue laid down or to differences in energy expenditure. It has already been established that diet-induced obesity and diabetes develop in the diabetic line with features typical of insulin resistance in the metabolism of the pancreas, liver and peripheral tissues. Some of the animals of the diabetes-resistant line may also develop diabetes over a long time period and go through a phase of transient hyperinsulinemia-normoglycemia. This may represent an intermediate stage in the development of the diabetic syndrome and serve as a model of type 2 diabetes in man.

The effect of changes in dietary protein and energy on growth, body composition and mohair fibre characteristics of British Angora goats

AbstractTwenty-four castrated male British Angora goats of Australasian origin aged 11 months and weighing 23·5 kg live weight were studied in a 112-day experiment. They were allocated in a 2 × 2 factorial design to receive diets containing, per kg dry matter, concentrations of estimated metabolizable energy (ME) of 10·2 M] (LE) or 11·9 MJ (HE) and crude protein concentrations of 108 g (LP) or 180 g (HP). The HE diets were offered to provide a dry-matter intake of 30 g/kg live weight and the LE diets to provide 0·85 of the ME intake of HE diets.In comparison with LE diets, the HE diets, on average, increased live-weight gain, food conversion efficiency, carcass weight, killing-out proportion, empty body weight, cross-sectional area of m. longissimus dorsi and fat thickness over m. serratus dorsalis and weights in the carcass for dissected lean tissue, crude protein (N × 6·25) and dissected and chemically extracted fat. Weights of shoulder, hind barrel, and best-end joints and their weights of dissected lean and fat were increased on HE diets. No consistent effects due to dietary energy were observed for yield or diameter of mohair fibres.The greater intake of dietary protein resulted, on average, in increased values for live-weight gain, efficiency of food conversion, carcass weight, weight of dissected carcass lean tissue and crude protein, killing-out proportion and cross-sectional area of m. longissimus dorsi. The greater intake of dietary protein increased significantly both yield and diameter of mohair fibre.Significant interactions between protein and energy for empty body weight, carcass weight and carcass fat indicated that increasing dietary protein intake had a greater positive effect on the low than on the high energy diets. Similarly, increasing the dietary energy consumption on the LP diets produced a greater positive effect than that recorded on the HP diets.The results indicated that growth and lean tissue deposition were affected by both protein and energy intakes but that mohair fibre characteristics were affected consistently only by protein nutrition.

Follicular dynamics, plasma metabolites, hormones and insulin-like growth factor I (IGF-I) in lactating cows with positive or negative energy balance during the preovulatory period.

The effect of dietary energy balance (EB) on growth of ovarian follicles was tested. Cows (n = 9) were fed a high energy diet (HE diet; positive EB; n = 4) or switched to a low energy diet (LE diet; negative EB; n = 5) during the preovulatory period. Non-esterified fatty acids (NEFA) were greater in cows fed the LE diet. Concentrations of luteinizing hormone (LH) were similar in HE and LE cows. However, the growth of preovulatory follicles in cows fed the LE diet was 50% that of cows fed the HE diet. Insulin-like growth factor-I (IGF-I) in plasma was less in LE-fed cows compared with HE-fed cows, and plasma IGF-I was positively correlated to estrogen: progesterone ratio in follicular fluid of dominant follicles. In summary, slower follicular growth in cows fed an LE diet occurred despite normal plasma LH and coincided with reduced IGF-I and elevated NEFA in plasma.

Influence of direction of body weight change on pattern of gonadotropin secretion in ovariectomized beef heifers of equivalent body weight.

Our hypothesis was that alterations in pattern of gonadotropin secretion induced by level of dietary energy intake are dependent on direction of BW change. Beef heifers were assigned to one of two treatments 21 d after ovariectomy: 1) increasing followed by decreasing BW (I-D; n = 9) or 2) decreasing followed by increasing BW (D-I; n = 9). Heifers assigned to the I-D treatment received 15.4 Mcal ME/d (HE) from wk 0 to 8 followed by 4.3 Mcal ME/d (LE) from wk 9 to 16. Heifers assigned to the D-I treatment received the LE diet for the initial 8 wk followed by the HE diet for the subsequent 8 wk. At 2-wk intervals blood samples were collected at 10-min intervals for 11 h to determine the pattern of secretion and(or) concentration of gonadotropins in circulation (LH and FSH) and pituitary responsiveness to administration of 750 ng and 50 micrograms of LHRH. Frequency of LH pulses increased (P less than .05) in a quadratic fashion with increasing ADG in heifers in both treatment groups. Amplitude of LH pulses decreased (P less than .05) in a linear fashion with increasing ADG in heifers in both treatment groups and magnitude of this decline was greater (P less than .05) in heifers receiving the D-I treatment. Amplitude of response to 750 ng of LHRH decreased (P less than .05) in a linear fashion with increasing ADG in heifers receiving the D-I treatment but was unrelated to changes in ADG (P greater than .05) in heifers receiving the I-D treatment. When heifers in both treatment groups attained similar BW (P greater than .05; wk 14), amplitude of LH pulses, responsiveness to 750 ng of LHRH and mean concentration of FSH in serum were higher (P less than .05) in heifers receiving the I-D than in heifers receiving the D-I treatment. Thus, we accept the hypothesis that alterations in pattern of gonadotropin secretion in heifers fed diets with a low energy content are dependent on direction of BW change.

Effect of Early Protein and Energy Restriction of Large Turkey Toms Fed High-Fat or Low-Fat Realimentation Diets.: 1. Performance Characteristics

The effect of early protein and energy restriction on the performance of large turkey toms fed a high or low fat realimentation diet was studied. Two levels of protein [100% (HP) and 70% (LP) of 1984 National Research Council (NRC) recommendations] were available ad libitum in a factorial arrangement with two levels of energy [100% (HE) and 90% (LE) of 1984 NRC reference level] to Nicholas toms from 10 days to 6 wk of age. Subsequently, the four treatment groups were fed diets containing either 4 or 8% fat; other nutrients were kept consistent with 1984 NRC recommendations until the toms were 20 wk of age. The LP or LE diets reduced weight gain (WG) and increased feed:gain (F:G) ratio from 10 days to 6 wk of age (P<.005). Feeding LP diets significantly reduced protein consumption per unit gain and increased energy consumption per unit per gain, but the converse was observed with LE. In contrast to toms fed the HP diets, those fed the LP diets from 6 to 20 wk of age were consistently lighter in 20-wk body weight (14.1 kg versus 14.6 kg, P<.005) and had a lower F:G ratio (2.96 versus 3.04, P<.005). Toms fed the LE diets were lighter than those fed HE diets until 18 wk (P<.05), and they had a lower F:G ratio (2.97 versus 3.03, P<.05) from 6 to 20 wk of age. Supplemental fat increased WG and decreased F:G ratio during realimentation, but interaction effects of fat with protein or energy were not observed. Toms responded more favorably to early protein than energy restriction, regardless of the fat content of the realimentation diet

Effect of dietary energy, body condition and calf removal on pituitary gonadotropins, gonadotropin-releasing hormone (GnRH) and hypothalamic opioids in beef cows

Beef cows (n = 64) were slaughtered to evaluate effects of dietary energy and calf removal (CR) on hypothalamic and adenohypophysial endocrine characteristics. From d 190 of gestation until parturition, cows received maintenance (ME; n = 32) or low (LE; n = 32) energy diets (ME = 100%, LE = 70% NRC recommendations). After parturition, half (n = 16) of each prepartum diet group received low (LE; n = 32) or high (HE = 130% NRC; n = 32) energy diets. At 30 d postpartum, cows were slaughtered 0 or 48 hr after CR. Hypothalami [preoptic area (POA), hypothalamus (HYP), stalk-median eminence (SME)] and pituitaries were collected. Basal and K +-induced release of GnRH from SME, and pituitary luteinizing hormone (LH) and follicle stimulating hormone (FSH) did not differ among groups (P>.05). Hypophyseal LH was correlated (P<.01) with body condition score (BCS) at parturition and slaughter (r = .36 and .47, respectively). Prepartum LE diet increased (P<.05) met-enkephalin in POA compared to prepartum ME (.59 ± .05 vs. .44 ± .04 pmol/mg) regardless of postpartum diet or suckling status. Concentrations of β-endorphin in combined HYP + POA were decreased (P<.05) by 48 hr CR (15.1 ± 1.1 vs. 18.1 ± 0.7 fmol/mg). Content of GnRH in HYP was decreased (P<.05) by 48 hr CR in animals on ME prepartum diets (17.0 ± 2.4 vs. 9.4 ± 0.7 ng). Cows on LE-HE diets had lower (P<.01) content of GnRH in POA than cows on LE-LE diets (7.8 ± 0.8 vs. 13.1 ± 0.7 ng, respectively). Overall, GnRH in HYP was decreased (P<.05) by 48 hr CR (11.3 ± 1.0 vs. 14.8 ± 1.4 ng) and content of GnRH in POA was lower (P<.05) in cows on HE postpartum diets compared to LE postpartum (8.9 ± 0.7 vs. 11.2 ± 0.7 ng, respectively). In summary, prepartum/postpartum effects of dietary energy/body condition on reproductive responses to CR were associated with changes in hypothalamic and preoptic levels of GnRH, met-enkephalin and β-endorphin.

Effects of environmental temperature, dietary energy, sex and age on nitrogen and energy retention in the edible carcase of broilers

Abstract 1. Two environmentally‐controlled houses, one set at constant 21°C (low temperature, LT) and the other set at diurnally cycling 21°C to 30°C (high temperature, HT), and two dietary energy concentrations of 13 MJ ME/kg (low energy, LE) and 13.8 MJ ME/kg (high energy, HE) were used to study nitrogen and energy retention in the edible carcase of male and female broilers slaughtered at 34 and 54 days. 2. Carcase nitrogen was higher in males than in females, and in birds reared at LT than in those reared at HT. 3. Birds at LT and on HE diet, regardless of sex, retained more energy as fat in their carcases than those at HT and on LE diet respectively. 4. Maintenance energy requirement averaged 6.70, 7.67, 7.43 and 9.01 kJ per g metabolic body size (kJ/gW 0.66) for broilers at HT and LT up to 34 d and at HT and LT up to 54 d, respectively. 5. There was a similar increase with age in the energy requirement for growth but with requirements of broilers at LT consistently lower than for those at HT.

Effects of recombinant DNA-derived somatotropin and dietary energy intake on development of beef heifers: I. Growth and puberty.

The effects of dietary energy intake and somatotropin (STH) on growth and puberty were studied in 40 Angus heifers. At an average age of 7 mo (208 +/- 8 d), heifers were assigned to four treatment groups: 1) vehicle (V) + high energy (HE; 2.68 Mcal ME/kg DM), 2) recombinant DNA-derived STH (20.6 mg/d; s.c.) + HE, 3) V + low energy (LE; 2.22 Mcal ME/kg DM) or 4) STH + LE. Animals remained on treatments until 15.5 mo of age. Body weights (BW), hip heights (HH) and areas of pelvic openings (PA) were measured every 28 d and backfat thicknesses (BF) were measured every 56 d. Plasma progesterone was measured in blood samples taken three times per week beginning at 9 mo of age to determine age at first ovulation. Heifers fed HE were heavier (P less than .01), gained faster (P less than .01) and had greater BF (P less than .01) than those fed LE. Animals treated with STH gained faster (P less than .01) and were heavier (P less than .05) between 12 and 15 mo of age than V-treated heifers. Heifers treated with STH also had less BF (P less than .05) and a tendency for a greater (P = .08) increase in HH than in V-treated heifers. Somatotropin interacted with energy (P less than .05) and age (P less than .01) to influence PA. Somatotropin increased (P less than .01) PA in heifers fed the HE diet but not in those fed the LE diet.(ABSTRACT TRUNCATED AT 250 WORDS)

POSTWEANING GROWTH RATE AND FEED CONVERSION RATIO OF LAMBS FED DIETS BASED ON CONCENTRATE VERSUS ROUGHAGES

Sets of twin lambs from both sexes representing 11 genetic groups were fed either concentrate (HE) or roughage (LE) diets from weaning to 32 kg liveweight. One lamb from each set received the HE diet while the other received the LE diet. Data on average daily gain (ADG), relative ADG (RADG) and feed conversion ratio (FCR) were analyzed to test for the presence of a genotype × diet interaction; this effect was significant for RADG. Although the ranking of the genetic groups with respect to RADG depended upon diet, the group ranking highest on HE was also the highest on LE. The set of twins × diet interaction was not significant for ADG or RADG. The results support the present practice in test stations of feeding lambs concentrate rations to identify their potential for growth and basing growth comparisons on a within genetic group basis. Key words: Genotype × diet interaction, growth rate, feed conversion ratio

Effects of recombinant DNA-derived somatotropin and dietary energy intake on development of beef heifers: II. Concentrations of hormones and metabolites in blood sera.

The effects of somatotropin (STH) and energy intake on serum concentrations of glucose (GLU), insulin (INS), nonesterified fatty acids (NEFA), urea nitrogen (UN) and insulin-like growth factor-I (IGF-I) were determined in 40 Angus heifers. At 7 mo (208 +/- 8 d) of age heifers were assigned to four treatment groups: 1) vehicle (V) + high energy (HE; 2.68 Mcal ME/kg DM), 2) recombinant DNA-derived STH (20.6 mg/d; s.c.) + HE, 3) V + low energy (LE; 2.22 Mcal ME/kg DM) or 4) STH + LE. Animals remained on treatments until an average of 15.5 mo of age. Blood samples were taken every 30 min for 4 h at 9, 11, 13 and 15 mo of age to determine circulating concentrations of metabolites and hormones. Serum IGF-I was increased (P less than .01) by STH injections, but this effect appeared to diminish with age (STH x age; P less than .01). Energy intake did not influence IGF-I levels. Somatotropin increased (P less than .01) serum GLU in heifers fed the HE diet but only tended (P = .08) to increase GLU in those fed the LE diet (STH x energy; P = .05). Although STH increased (P less than .01) serum INS in both energy groups, the response in heifers fed the HE diet was greater (P less than .02) than that in heifers fed the LE diet (STH x energy; P less than .05). Heifers fed LE had higher (P less than .01) concentrations of NEFA than heifers fed HE.(ABSTRACT TRUNCATED AT 250 WORDS)

Deer and Cattle Diets on Heavily Grazed Pine-Bluestem Range

We studied dietary overlap between captive white-tailed deer (n = 3) (Odocotleus tir@nlanus) and cattle (n = 4) for 3 years on 2 rotationally burned, 54-ha longleaf pine (Pinus paZustris)-bluestem (Andropogon spp.) pastures in central Louisiana. A third of each pasture was burned each year in late February. One pasture was grazed heavily (61-77% herbage use) yearlong; the other was grazed heavily (SO-67% use) from mid-April to 1 November. Deer diets were dominated yearlong by a mixture of browse (49.3~83.2%) and forbs (11.2-47.1%). Cattle consumed mostly grasses during spring and summer and 60 and 40% browse and herbage, during fall and winter, respectively. Cattle consumed more herbage on first-year burns. Dietary overlap under heavy yearlong grazing averaged 25.8, 11.8, 26.0, and 30.7% during spring, summer, fall, and winter, respectively. Overlap under heavy seasonal grazing averaged 18.5, 7.4, and 22.6% during spring, summer, and fall, respectively. Diets of both animals were diverse and overlap generally resulted from sharing small amounts of many plant taxa. Except on recent burns during summer, dietary overlap under heavy yearlong grazing was comparable to that observed under moderate yearlong grazing at half the cattle stocking rate. Moderate grazing (40-50% herbage removal) of similar range from late spring through early fall should have little negative impact on deer forage availability. Grazing during late fall and winter reduces an already limited supply of deer forage by reducing availability of evergreen browse and herbaceous winter rosettes. J. WILDL. MANAGE. 53(3):540-548 Most woodland grazing in the southern United States has been confined to the longleaf-slash pine (P. elliottid) type. Bluestem grasses dominate the herbaceous understory on about 2 million ha of this forest type in southern portions of Louisiana, Mississippi, and Alabama, and in northwest Florida. Substantial knowledge on integrated forestry and cattle management has been gathered, but questions of compatibility between catt le and wildlife, especial ly deer, have st i rred considerable debate but resul ted in l i t t le research until recently (Mitchell 1980, Thill 1984, Thill and Martin 1986). Early studies of cattle diets in the South perta in pr imari ly to the sparse ly forested bluestem and wiregrass (Aristidu stricta) ranges that developed fol lowing extensive c learcutt ing ear l ier this century. The heavy yearlong grazing and frequent (often annual) burning common earlier this century reduced availability of woody plants , which are general ly a major component of deer diets in southern states (Lay 1969). Consequently, it is not surprising that browse was generally a minor component of cattle diets in early studies (Thill 1985). Most of this cut-over range has been replanted with pines, and woody plants are now relat ively abundant as a result of less burning and grazing. Thus, early studies of cattle diets are generally not applicable to present conditions. Recent research in southern Mississippi showed that browse contributed from 2.5% of cattle diets during summer to 21.4% during winter (Mitchell 1980) . Catt le diets on rotat ional ly burned, moderately grazed pine-bluestem range in central Louisiana averaged 40.9% browse during winter, and dietary overlap between cattle and deer ranged from 8.6% during summer to 34.7% during winter (Thill and Martin 1986). Prescr ibed burning is an integral component of southern range management because it increases forage quality and production and aids in distributing cattle. Deer receive similar forage benefits and prefer recent burns (Lay 1967). Our study was conducted in 2 phases of 3 years each to evaluate dietary overlap between deer and cattle under prescribed rotational burning and several grazing treatments. In phase I, we studied deer and cattle diets in a pasture grazed moderately yearlong and deer diets only in an adjacent ungrazed pasture (Thill and Martin 1986). We also evaluated phase I treatment effects on deer nutrition (Thill et al. 1987). The object ive of this study was to quantify deer and cattle dietary overlap on pine-bluestem range under heavy seasonal and heavy yearlong grazing. We also compare phase I and phase II data. We thank W. R. Thacker and R. D. Herrick for their assistance with data collection. D. C. Guynn, Jr., R. J. Warren, J. G. Kie, and D. L.

Effects of energy and lasalocid on productivity of first-calf heifers.

One hundred forty-three crossbred, fall-calving first-calf heifers were used to determine the effects of two levels of energy and two levels of lasalocid on cow-calf productivity. Diets fed for approximately 110 d prepartum were calculated to provide a daily intake of 15.3 (LE) or 18.0 (HE) Mcal ME; diets fed for approximately 130 d postpartum were calculated to provide a daily intake of 17.8 (LE) or 21.0 (HE) Mcal ME. Two supplements were fed with each energy level to provide a calculated 0 (C) or 200 mg.hd-1.d-1 lasalocid (L). Heifers fed HE gained .06 kg more (P = .08) per day prepartum than LE heifers. There was an interaction (P less than .05) between treatment and prepartum days on trial for heifer weight approximately 2 wk prepartum and body condition at calving. Energy had no effect on heifer weight at 2 wk prepartum or condition score at calving when estimated and compared at 90 d on trial. However, regression estimates for 130 d on trial showed that HE heifers would have been 19 kg heavier (P less than .001) and would have had .4 unit higher condition score (P less than .01) than LE heifers. Energy and lasalocid had no effect (P greater than .05) on hip height or pelvic area at calving or on calf birth weight, calving ease score or gestation length. Cows fed HE weighed 17 kg more (P less than .05) and had .5 unit higher (P less than .001) condition score than LE cows at approximately 130 d postpartum. Lasalocid had little effect on postpartum changes in weight or body condition. Lasalocid supplementation to the LE diet tended to increase milk production and calf weight, whereas supplementation to the HE diet did not. Feeding the LE diet decreased (P less than .05) cycling activity by 18 percentage points and decreased (P less than .01) overall pregnancy rate by 25 percentage points. Lasalocid had no influence on reproductive performance.