High Plane Of Nutrition Research Articles

Puberty attainment and reproductive characteristics in ewe lambs of Chios and Karagouniki breeds raised on two planes of nutrition

Twenty ewe lambs from each of the two Greek breeds Chios (C) and Karagouniki (K) were assigned at random to high (H) and low (L) planes of nutrition. The level of feeding was adjusted weekly according to live weight so that at the time of expected puberty the animals of the H and L groups would reach 70 and 50%, respectively, of the mature ewe body weight estimated for the flock. The occurrence of oestrus was detected by ram presentation, and the ovarian activity was monitored by progesterone concentrations in blood samples collected twice weekly. Progesterone and oestradiol profiles around the second pubertal ovulation were also determined by blood sampling in twenty animals. Ovulation rate was assessed by laparoscopy at four defined oestrous cycles. Ewe lambs in the H group grew faster ( P<0.01) and were heavier ( P<0.01) at the beginning of the first breeding season than those on the L plane of nutrition. The Chios started to ovulate 12 days earlier ( P<0.05) and showed oestrus 9 days earlier than the Karagouniki ewe lambs. Chios showed breeding activity for 26 days ( P<0.01) longer than the Karagouniki ewe lambs, and animals in the H group 25 days ( P<0.01) longer than those in the L group. The duration of the breeding season and the number of oestrous cycles per ewe lamb were correlated with age at first ( r= −0.71 and r= −0.66. P<0.001) and last ovulation ( r=0.80 and r=0.82, P<0.001). Ewe lambs in the H feeding group showed a significantly higher ovulation rate than those in the L group. Ovulation rates during the second breeding season were affected by carry-over effects of the nutritional regime. The level of progesterone was higher while oestradiol was lower in Chios than in Karagouniki ewe lambs during the luteal phase of the first pubertal cycle. Ewes in the H group had a higher ( P<0.05) oestradiol concentration during the oestrous cycle than ewes in the L group, while the preovulatory peak was of the same magnitude for both feeding groups. The results indicate that the two breeds are different in terms of reproductive characteristics and that differences in growth rate and body weight, imposed by feed intake manipulation in early life, have significant effects on most pubertal reproductive characteristics of the ewes and carry-over effects in their second breeding season.

Subclinical parasitism in calves: Biochemical and serological evaluation of preventive treatment against gastroenteritis and husk

The use of the biochemical and serological parameters pepsinogen, gastrin and antibodies against Cooperia, Ostertagia and Dictyocaulus in an enzyme-linked immunosorbent assay was evaluated in diagnosing gastrointestinal parasitism and lungworm disease in seven oxfendazole pulse-release bolus (OPRB)-treated and seven non-treated first-season grazing calves. During the grazing season, no difference in growth rate was observed and the control animals showed no clinical symptoms. The Dictyocaulus antibody levels in the controls increased from turn-out, while in the treated animals the rise was postponed until August. The Cooperia antibody titres for both groups were comparable. At the end of the grazing season, the control group showed significantly higher pepsinogen and gastrin values, and Ostertagia antibody titres. It was concluded that these parameters are a useful tool in confirming subclinical parasitism and that preventive treatment with the OPRB in a low to moderately infected environment, together with a high plane of nutrition, provided little benefit to the farmer.

Effects of nutrition, sex of calf and breed type on response to zeranol: preweaning growth

An experiment was conducted to evaluate the effects of breed, sex and plane of nutrition on the growth response to zeranol in Angus and crossbred calves prior to weaning. Eighty-eight heifers and 118 steers received either a high or low plane of nutrition using a first and last grazing technique. Half of the calves in each nutrition group received a zeranol implant (36 mg) at an average age of 3.4 mo. Both zeranol and the higher level of nutrition increased (P less than .001) growth rate prior to weaning (7.4 mo of age). Zeranol did not affect hip height at weaning (P greater than .1), but calves on the higher plane of nutrition were taller (P less than .01) than calves on the lower plane of nutrition. The zeranol x nutrition interaction was not significant (P greater than .1) for growth rate or hip height. Steers grew faster (P less than .01) preweaning and were taller (P less than .01) at weaning than heifers. Crossbred calves gained more rapidly (P less than .001) preweaning and were taller (P less than .001) at weaning than Angus calves were. Neither sex nor breed interacted with zeranol to influence any of the traits examined. Based on these results we conclude that preweaning growth was affected by zeranol and this effect was consistent across sexes, breeds and planes of nutrition tested.

The effect of different distributions of the same total dietary between late pregnancy and early lactation on the performance of twin-bearing suckler cows

The advent of twinning in suckler cows, through the application of multiple ovulation and embryo transfer techniques has provided a means of increasing the biological efficiency of the suckled calf system of beef production. However, even with improvement in output the need remains for twin-bearing suckler cows to be fed economically. This can be achieved by making effective use of summer and autumn grazing which on most farms provides a high plane of nutrition and allows the cows to increase their body reserves. This generous level of feeding may be followed by more stringent and controlled feeding in winter and early spring, when conserved feeds, grain and by-products are fed. This restriction leads to a reduction in feed costs and also to a depletion of the accumulated resrves.

The direct and residual effects of the plane of nutrition of calves in early life on physical performance and gains in chemical composition

The direct, residual and overall effects of the plane of nutrition of calves in early life were investigated with a factorial arrangement of high, medium and low planes of nutrition (H, M and L respectively) imposed from 2 to 14 weeks of age (Period 1) and high and low planes of nutrition (H and L respectively) from 14 to 26 weeks (Period 2). A common high plane of nutrition was offered from 26 weeks of age until the mean slaughter live weight of 527 kg. The planes of nutrition were based on appropriate fixed allowances of concentrates and good quality silage offered ad libitum apart from the first half of Period 1 where appropriate allowances of milk substitute were offered and the roughage was hay. In addition to the final slaughter point, representative samples of three calves per treatment were also slaughtered at the start of the experiment and at the end of Periods 1 and 2 and crude protein, total lipid and ash were determined. Energy contents of the tissues were also estimated from protein and lipid analyses.

Effect of pre-mating nutritional status and post mating progesterone supplementation on early pregnancy in Large White gilts

A rising plane of nutrition prior to mating increases ovulation rate in pigs (Anderson and Melampy, 1972), but this potential for increased Utter size is negated by the subsequent detrimental effect of high plane feeding on embryo survival. The mechanism underlying this effect may involve an increased rate of steroid clearance from the liver in animals on a high plane of nutrition (Symonds and Prime, 1989). The resultant lower circulating steroid levels would be expected to elevate pituitary gonadotrophin levels and consequently increase ovulation rate. However, after mating, such low steroid (particularly progesterone) concentrations may compromise embryo survival.A further factor which may affect the ability of a gilt to carry a large number of fetuses to term is the spacing of fetuses within the uterus. Dzuik (1985) proposed that a uniform distribution of fetuses would optimise litter size, fetal growth and survival.

Effect of plane of nutrition and age on carcass maturity of sheep.

One hundred twenty ewe and wether lambs were fed high (76% TDN, 12.3% crude protein) or low (70.6% TDN, 16.1% crude protein) energy diets and slaughtered at average ages of 261, 356 or 469 d. High planes of nutrition for lambs at 356 or 469 d of age resulted in heavier carcasses, thicker fat depth and higher flank streaking scores compared to lambs fed low planes of nutrition. Rib bone, break joint and overall maturity scores were not influenced (P greater than .05) by diet. Metacarpal and metatarsal bones from lambs fed high planes of nutrition were slightly longer and heavier and required more force to break (P less than .05) compared with bones from lambs fed low planes of nutrition. The majority of the ewes fed high or low planes of nutrition had fused growth plates and possessed spool joints by 469 d; none of the wethers had spool joints. An additional 27 wethers were slaughtered at an average of 480, 578 or 662 d. Rib bone, break joint and overall maturity scores were not different (P greater than .05) for animals fed the high or low energy diets, but bone weight and shaft break force values were higher for those fed high energy diets. At 662 d of age, only 20% of the wethers on each dietary regimen possessed fused growth plates. Overall, plane of nutrition in market-weight lambs and yearlings had very little influence on the presence or absence of a break joint or on other bone maturity scores.(ABSTRACT TRUNCATED AT 250 WORDS)

Estimation of Cell Birth Rate in the Wool Follicle Bulb using Colchicine Metaphase Arrest or DNA Labelling with Bromodeoxyuridine

The birth rate of cells in the wool follicle cells (CBR) was measured in two experiments on sheep differing widely in wool growth rate as a consequence of differences in nutritional regime. In Experiment 1, CBR was determined in one sheep on a high and one on a low plane of nutrition by two methods: the colchicine-metaphase arrest method, or from the product of total cell number and cell cycle time (the latter determined by DNA labelling with 5-bromo-2'-deoxyuridine (BrdU) and analysis of the fraction of mitoses labelled curve). CBR by colchicine was 0.73 and 0.56 of that determined using BrdU for the low- and high-plane sheep respectively. Cell cycle times were 26.5 h (low nutrition) to 18.6 h (high nutrition). In Experiment 2, CBR was again measured by the colchicine method, and from the rate of increase in labelled cells following a pulse dose of BrdU, in sheep on two levels of nutrition (n = 4llevel) and with a 3.7-fold difference in wool growth rate. Again, CBR by colchicine was only 0.41 (high nutrition) to 0.74 (low nutrition) of estimates made using the BrdU method, this difference being statistically significant only for sheep on the high plane of nutrition. Nutrition significantly altered CBR determined by colchicine (Pc0.001) and by BrdU (Pc0.034). The rate of fibre growth per follicle measured on two separate occasions was closely related to CBR measured using colchicine (r= 0.83, P&lt; 0.01 and 0.8 1, P c 0.02) or BrdU (r= 0.73, P c 0.04 and 0.64, P&lt; 0.08). It is concluded that CBR is a major determinant of fibre growth, but that colchicine depresses CBR. Previous estimates of mitotic activity in wool follicle bulbs have been made using colchicine and are thus probably underestimated. The technique using BrdU labelling and the subsequent rate of increase in labelled cells appears to be a useful one for estimating follicle cell kinetics.

The effect of three planes of nutrition on natural coccidial infections in Awassi sheep yearlings

Faecal samples from three groups of yearling Awassi sheep fed three different nutritional planes were taken at 2-week intervals over a period of 3 months. Eimerian oocysts were found in 252 (80%) of the 315 samples collected. The species of Eimeria were identified and 30.2% of the samples contained three or four species, 27.3% had two species and 22.2% had one species. The prevalences in decreasing order were: E. pallida (37.1%); E. parva (28.9%); E. crandallis (17.8%); E. marsica (15.6%); E. bakuensis (syn. E. ovina) (13.7%); E. ovinoidalis (11.4%); E. intricata (11.1%); E. ahsata (9.2%); E. faurei (7.0%); E. granulosa (4.4%). The prevalence of E. bakuensis was significantly ( P < 0.05) higher in sheep fed the high and moderate planes of nutrition, while the prevalence of E. faurei was significantly ( P < 0.05) lower in sheep fed on the moderate plane. The numbers of E. marsica were also significantly higher ( P < 0.05) than other Eimeria species in the moderate plane group.

Ovarian follicular populations, steroidogenic capacity and physiological status in post-partum suckling beef cows in high and low body condition

Recent evidence indicates that body condition at calving has an important effect on the length of the post-partum anoestrous period in beef cows being longer in cows calving in low body condition (Richards et al, 1986, Wright et al, 1987). It is known that body condition affects baseline concentrations of LH (Rutter and Randel, 1984) and LH pulse frequency (Wright et al, 1987). However, the effect of body condition on ovarian follicles has not been studied.An experiment was designed to examine the effect of body condition score (BCS) at calving on follicle populations, follicular steroidogenic capacity, follicular histology and patterns of gonadotropin release at two different stages of the post-partum period (5 and 9 weeks after calving) in suckling beef cows.Thirty-eight suckling Blue-Grey cows with a mean live-weight of 567 ± 9.4 kg and mean BCS of 3.0 ± 0.05 at 110 days before calving to a synchronized insemination were differentially fed so that they achieved BCS of 2.83 ± 0.05 and 2.30 ± 0.05 for cows on a high (H) and low (L) plane of nutrition, respectively. After calving cows were fed a live-weight maintenance ration according to individual requirements. Cows of each BCS were ovariectomized at either 5 (w5) or 9 (w9) weeks after calving and follicles &gt; 3mm in diameter were dissected from the ovaries and incubated for 2 h in culture medium (Medium 199) at 37°C. Follicles were then kept in Bouin's solution until histological examination. Follicle incubates were assayed for progesterone, testosterone and oestradiol. Blood samples were taken 2 days before ovariectomy for 10 h every 15 minutes and were later assayed for LH (all the samples) and FSH (every third sample).

The circulating erythrocytes of rainbow trout ( Salmo gairdneri)

1. 1. Washed erythrocytes from rainbow trout maintained nonnoxically at near-optimum temperature (14°C) on a high nutritional plane and seasonally-neutral photoperiod (12L:12D) with minimum disturbance were separated by velocity sedimentation at unit gravity into 10 fractions. 2. 2. On the basis of constancy of mean cell hemoglobin content, 81.9% of circulating red cells were judged to be mature. 3. 3. What may have been postmature cells accounted for a further 7.5% of the total. The remainder, 10.6%, were presumed to be juvenile. 4. 4. The 11-membered hemoglobin isomorph system exhibited significant ontogenetic variations in the abundances of several minor, but no major isomorphs. 5. 5. Ultrastructural examination confirmed that cell elongation during maturation is correlated with development of the marginal band microtubule system. 6. 6. Hemoglobin formation appeared to be sequentially correlated with the appearance and complexity of the segregation apparatus, and the abundances of mitochondria and polysomes. 7. 7. The question of postmaturational hemoglobin synthesis was not resolved.

Effect of level of food intake in mid and late pregnancy on the performance of breeding ewes

ABSTRACTIn three experiments pregnant ewes (mean weight 72·5 kg) were subjected to different planes of nutrition on grass silage-based diets during mid pregnancy and, in factorial designed trials with ad libitum silage or ad libitum silage + concentrates in late pregnancy. The high plane of mid-pregnancy nutrition resulted in an average gain of 11·5 kg between weeks 7 and 14 of pregnancy while the low plane gave an average loss of 3·5 kg during this period. These differences did not affect lamb birth weight but ewes on the high plane were 7·2 kg heavier after lambing than those on the low plane. The effect of plane of nutrition during mid pregnancy on silage intake during late pregnancy was variable but there was some evidence of a greater reduction in intake during the last few weeks of pregnancy following the high plane of mid-pregnancy nutrition. The higher plane of nutrition in late pregnancy resulted in higher ewe live weights as well as higher lamb birth weights and highest lamb birth weights occurred following restriction in mid pregnancy and a high plane of nutrition in late pregnancy.Plasma 3-hydroxybutyrate levels were variable but there was little evidence of an effect of mid-pregnancy nutrition although levels appeared to be increased by the low plane of nutrition in late pregnancy.

The influence of high dietary intakes of energy and protein on third metacarpal characteristics of weanling ponies

The influence of high dietary intakes of protein and energy on bone development was described and the accuracy of radiographic photometry as an estimator of bone mineral content was determined. There were higher (P<.10) values for breaking strength and cortical area, and lower (P<.10) percentages of calcium and total mineral content in the bones of ponies on high planes of nutrition. These ponies developed at a faster rate than the normally fed ponies, suggesting that during accelerated growth bone mineral deposition may be reduced. Thus, high intakes of energy and protein appeared to increase the rate of skeletal growth while decreasing deposition of mineral into bone. These conditions may be related to bone failure from high compressive loads. Radiographic photometry was found to be an adequate predictor of bone mineral, calcium and phosphorus content in live ponies. However, care must be used in obtaining the radiographs to ensure the accurate estimation of mineral status.

Influence of nutritional status and oestradiol-17 beta on plasma growth hormone, insulin-like growth factors-I and -II and the response to exogenous growth hormone in young steers.

Plasma GH profiles and circulating concentrations of plasma insulin-like growth factors-I and -II (IGF-I and -II) were examined in 20 steers on either high (3% dry matter of body weight per day) or low (1% dry matter of body weight per day) planes of nutrition with or without an implant of oestradiol-17 beta. The response of plasma IGF-I and -II to a bolus injection of bovine GH (bGH) was also investigated. Reduced feeding significantly (P less than 0.01) increased the mean concentration, peak height and integrated area of plasma GH. Treatment of steers with oestradiol at low nutrition significantly increased baseline GH concentrations. Treatment of steers with oestradiol at high nutrition significantly (P less than 0.05) increased mean, baseline, peak height, and integrated area of plasma GH. GH pulse frequency was not changed by either nutritional plane or oestradiol treatment. Basal concentrations of plasma IGF-I were significantly (P less than 0.01) decreased by reduced feeding in both the oestradiol-treated and the control group. Treatment with oestradiol increased (P less than 0.01) basal plasma concentrations of IGF-I at both high and low levels of nutrition. After i.v. injection of bGH (0.1 mg/kg body weight), an increase in plasma IGF-I was observed only in steers at high nutrition. Basal concentrations of plasma IGF-II were not altered by nutritional manipulations but were significantly (P less than 0.001) increased by oestradiol treatment. After bGH infusion only steers at high nutrition showed an increase in plasma IGF-II.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of inbred and outbred sheep on two planes of nutrition 2. Responses to acute cold and heat exposure

AbstractFour groups each of 14 sheep aged 11 to 13 months comprising outbred (O) and inbred (I, inbreeding coefficient 0·37 or 0·5) sheep reared on either a low plane (L, maintenance) or on a high plane (H, ad libitum) of nutrition from the age of 6 months were exposed first to acute cold and 1 week later to heat. Exposures in climate chambers ended for each sheep when rectal temperature decreased to 36°C (in the cold) or increased to 42·5°C (in the heat) subject to a limit of 8 h. Throughout the experiment, sheep were kept in matched quartets comprising one sheep of each type.The average cold resistance times (min) were 161, 267, 348 and 381 for the LI, LO, HI and HO groups respectively, showing a significant effect of both inbreeding and plane of nutrition (P &lt; 0·01). Five sheep in the HO group lasted the full 8 h in the cold chamber with little or no reduction in rectal temperature. Skin temperature at the mid side was significantly higher in L than in H sheep throughout cold exposure, but there was no effect of inbreeding.Respiration rates were much higher before and during cold exposure in the H sheep, but there was no effect of inbreeding.The residual correlation of cold resistance with live weight was 0·58, but differences in live weight do not explain all the differences in cold resistance and particularly do not explain the rapid decrease in rectal temperature of the LI sheep. It was concluded that under cold exposure a high level of nutrition was able to compensate partly for the disadvantages of inbreeding, and that outbreeding was able to compensate partly for the adverse effects of poor nutrition.With heat exposure, there were no significant differences among the four groups in heat tolerance time, but within the 1st h, H sheep had slightly higher rectal temperatures and much higher respiration rates than L sheep. Inbreeding affected only the time taken to reach a respiration rate &gt; 200 per min, which was longer in I (131 min) than in O sheep (113 min) and longer in L (149 min) than in H animals (96 min).

The somatotrophic axis in young steers: influence of nutritional status and oestradiol-17 beta on hepatic high- and low-affinity somatotrophic binding sites.

The binding of bovine GH (bGH) to hepatic membranes obtained from steers on either high (3% dry matter of body weight per day) or low (1% dry matter of body weight per day) planes of nutrition with or without an oestradiol-17 beta implant was studied (n = 5 per group). Binding studies were performed on both crude membrane homogenates and on 100,000 g microsomal membrane fractions; identical results were obtained using both preparations. In all four groups of animals, linear Scatchard plots were obtained, but following pretreatment of the membranes with MgCl2 to remove endogenously bound hormone, curvilinear plots were obtained in the groups on the high plane of nutrition. Analysis of these curves suggested the presence of a high- and low-affinity binding site, the high-affinity site being fully occupied in the absence of MgCl2 pretreatment. The specific binding of bGH in MgCl2-pretreated crude membranes was greater (P less than 0.01) in well-fed steers (14.8 +/- 1.6%) than in poorly fed steers (9.8 +/- 0.9%). Scatchard analysis showed this to be due to the presence of a high-affinity site (dissociation constant (Kd) = 11.6 +/- 3.3 pmol/l) in the well-fed animals only. In addition, there was an increase (P less than 0.01) in the affinity, but not in the capacity, of the low-affinity site (Kd = 106.4 +/- 22.8 pmol/l in well-fed steers and 197.0 +/- 23.8 pmol/l in poorly fed steers).(ABSTRACT TRUNCATED AT 250 WORDS)

Residues in beef cattle accidentally exposed to commercial heptachlor.

The changes in concentration of heptachlor epoxide (HCE) and oxychlordane (OCD) were studied in the tissues of beef cattle that had previously grazed pasture contaminated with commercial heptachlor. In 25 cows and heifers monitored over 488 days, the mean concentration of HCE decreased from 22.0 to 0.08 mg/kg and of OCD from 5.68 to 0.18 mg/kg. The respective half-lives were estimated to be 66 and 92 days. In a controlled feeding experiment, nine steers were subjected to one of three dietary regimes; a high plane of nutrition for 81 days then a low plane for 140 days; a moderate plane of nutrition for the total period; and a low plane of nutrition for 81 days then a high plane for 140 days. Approximately five months later similar treatments were applied for 101 and 94 days. The rate of decline of HCE and OCD was consistently greatest in animals on the high plane of nutrition and lowest in those on the low plane. Lactation did not appear to have a major effect on the rate of decline in the tissue concentrations of these compounds. No significant (P greater than 0.05) relationships were found between the concentrations of HCE or OCD in the subcutaneous fat and either milk or blood at any stage of the experiment. At slaughter, from 18 to 24 months after the commencement of the experiments, significant correlations (P less than 0.05) were found among concentrations of HCE and OCD in subcutaneous fat, renal fat and fat from the bone marrow.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of high planes of nutrition on skeletal growth and development of weanling horses.

Effects of high dietary levels of energy, protein and Ca and deficient levels of Ca on skeletal growth and development in the equine were studied in two experiments. The weanlings were fed grain-based diets. In Exp. 1, Group 1 (Ctl) received all nutrients at NRC recommended levels for growth; Group 2 (HE) received 150% of their digestible energy (DE) requirement; Group 3 (LC) received 150% of DE and 35% of Ca requirements. In Exp. 2, Group 1 (Ctl) again received all nutrients at NRC recommended levels for growth; Group 2 (HEP) received 150% of DE and 275% of CP requirements; Group 3 (HEPC) received 150% of DE, 275% of CP and 500% of Ca requirements. In addition, all groups had access to pasture. The HE treatment resulted in greater (P less than .10) increases in BW and total cortical width. However, LC weanlings had lower (P less than .10) gains in third metacarpal length and radiographic bone density. Cumulative increases in BW and wither height were greater (P less than .10) for the HEP and HEPC weanlings than for the Ctl weanlings. Increases in third metatarsal length also were greater (P less than .10) for HEP weanlings than for Ctl weanlings. Higher planes of nutrition increased body weight gains and growth rate of several long bones. However, skeletal development (e.g., cortical area) may be compromised by a high rate of growth.

Relationships between plasma hormone concentrations, udder development and the production of early mammary secretions in twin-bearing ewes on different planes of nutrition.

Ewes carrying twin fetuses were maintained during late pregnancy on a uniformly high plane (well fed), a uniformly low plane (underfed) or a low plane rising to a high plane (refed) of nutrition. The maternal plasma concentrations of hormones concerned with udder development, colostrum production and milk secretion were measured in samples obtained during the last 32 d before and the first 18 h after birth. Udder weights were derived from their linear dimensions, the yields of mammary secretions by hand milking during the first 18 h after birth and the transition from colostrum to milk was indicated by changes in the concentrations of lactose, lipid and immunoglobulin G. Underfeeding reduced prenatal udder development and colostrum accumulation and delayed the post-natal transition to milk secretion. Refeeding previously underfed ewes to a high plane during the last 5 d before birth had no effect on udder growth, but it did return the secretory functions of udder tissue to the levels observed in well-fed ewes. Nutritional effects on the plasma concentrations of insulin, placental lactogen, prolactin, cortisol and oestradiol-17 beta were small or absent. The relative changes in the plasma concentrations of growth hormone and insulin were such that the growth hormone: insulin ratio increased markedly during the last 11 d before birth in the underfed and refed ewes but not in the well-fed ewes. These differences in the growth hormone: insulin ratio were associated with greater increases in udder growth rate in the underfed and refed ewes than in the well-fed ewes. The plasma concentrations of progesterone decreased before birth in all ewes, but the decrease was delayed by underfeeding and refeeding rapidly overcame this effect. The slower progesterone withdrawal in the underfed ewes was associated with a delay in lactogenesis. It is concluded that the nutritionally induced changes in the growth hormone: insulin ratio and in the progesterone concentrations were the most likely endocrine determinants of the observed differences in the rates of mammogenesis and lactogenesis, respectively, but possible independent effects of substrate supply to the udder remain to be clarified.

Effect of Plane of Nutrition from Starting to and Through the Breeder Period on Reproductive Performance of Hen Turkeys

Large - type breeder hens were given high (HP) and low (LP) planes of nutrition from day of age to 31 weeks of age. Rearing treatments were then divided, and each was fed HP and LP breeder feeds to 57 weeks. Protein and metabolizable energy (ME) levels of the HP feeds approximated NRC (1977) recommendations, while LP feeds largely involved substitution of corn, fat, and soybean meal for wheat, barley, and oats, such that ME/protein ratio and relative content of essential amino acids were similar between treatments, respective of age.The LP rearing regimen led to reduced hen body weight at 31 weeks. Combining the LP rearing with LP breeder regimen resulted in continuously lighter weights than occurred with the other three treatments to 57 weeks. Carcass fat based on finish grade of sample hens was lower after LP than HP rearing at both 31 and 57 weeks, while the breeder treatments were without effect. Experimental variables neither influenced egg production nor egg weight, but a reduction in the proportion of yolk occurred that was attributable to LP rearing and to a lesser extent the LP breeder feed. Apparent fertility improved with hens that had been LP reared, while feeding the LP breeder led to reduced pip losses, but only if eggs were set within 7 days of being laid. The converse occurred with eggs set after 7 days storage.