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1.
    
The aim of this trial was to assess the effects of the administration of different combinations of mycotoxins in naturally contaminated maize grains on dairy heifer growth, blood measurements and puberty onset. A total of 35 Friesian female heifers were randomly allotted to three experimental groups from 18–21 to 42–45 weeks of age. During the 24-week experimental period (EP), heifers were fed the same diet, but with maize meal derived from three differently contaminated lots: very low contamination, as control (C); medium–low aflatoxin-contaminated (A); and mixed aflatoxin–fumonisin contaminated (A-F). At the end of the EP, they returned to a common diet without contaminated maize, and they were monitored for an additional period of 12 weeks (post-experimental period, PEP). BW, wither height, hip height, body length and heart girth were measured every 4 weeks from the beginning of EP to the end of PEP. At the same time, body condition score was evaluated and blood samples were taken from the jugular vein to be analysed for haematological, serum protein and metabolic profiles. Age at puberty was assessed by measuring weekly plasma progesterone levels from 40 to 52 weeks of age. Body growth measurements were processed both by ANOVA of average daily gain of EP and PEP separately, and by the analysis of growth curve parameters. Haematological, serum protein and metabolic profile were evaluated using a mixed model, taking into account the repeated measurements in time on each animal. Heifers’ growth was delayed both in A and A-F groups during EP, as evidenced by the different linear coefficients of the BW growth curve in the three groups. Differently contaminated diets did not affect the haematological profile, so that it can be concluded that these levels of mycotoxin contamination do not determine any specific effect on haematopoiesis and immunity in growing heifers. The main blood marker of mycotoxin chronic toxicity was the γ-glutamyl transferase activity level in plasma, which appeared to be altered even after the removal of mycotoxins. During EP, plasma glucose was lower in the groups fed contaminated diet compared with C. The joint actions of an altered nutritional status and a long-lasting liver damage were probably the causes of the delay in puberty attainment in A and, particularly, in the A-F group. The results from this trial evidenced that a chronic aflatoxin–fumonisin contamination in diets of dairy heifers can determine an important delay in the reproductive career of these animals.  相似文献   

2.
    
In an effort to better understand the consequences of early weaning (EW) for replacement beef heifers, a two-phase experiment was conducted investigating the impact on metabolic function and documenting reproductive characteristics. In phase 1, Angus×Simmental heifers (n=35) were stratified by BW and sire, and randomly assigned to either a normal weaning (NW, n=18) or EW (n=17) treatment. EW heifers were weaned at 107±3 days of age and provided access to a concentrate-based ration ad libitum with limit-fed mixed grass hay. NW heifers remained with their dams until 232±3 days of age, at which point heifers from both treatments were comingled and grazed on mixed summer pasture. Following NW, weekly blood samples were collected from all heifers for progesterone analyses used to determine the onset of puberty. Pelvic and ovarian size was measured before breeding. All heifers were subjected to an estrous synchronization protocol with timed artificial insemination (AI) at 437±4 days of age. During phase 2 of the experiment, a subset of pregnant heifers (n=16) were divided into two replicates and subjected to a glucose tolerance test, epinephrine challenge and progesterone clearance analysis. Neither age nor BW at puberty differed between EW and NW heifers. Likewise, no differences in pelvic area or ovarian size were observed. Thus, it appears that the reproductive maturity of EW and NW heifers was similar. Heifers studied during phase 2 of the experiment were restricted to those that had become pregnant to their first AI. Within this cohort, EW heifers tended to have lower overall circulating progesterone concentrations than those that were NW (P=0.14). Aspects of glucose and insulin dynamics were also altered, as EW heifers tended to have lower baseline glucose concentrations (P=0.10) despite similar baseline insulin concentrations. Compared with NW heifers, EW heifers had lower insulin area under the curve (P<0.05), which was partly the result of a tendency for lower peak insulin concentrations (P=0.11). Results of the glucose tolerance test indicate that a lesser insulin response was necessary to properly clear the glucose in the EW heifers, suggesting enhanced insulin sensitivity. Collectively, these results indicate that EW is not detrimental for the growth or reproductive development of replacement beef heifers, although some differences in glucose and insulin dynamics persist into adulthood.  相似文献   

3.
A cross-sectional study (n = 99) was made of male baboons (Papio cynocephalus) aged 3 weeks to > 10 years. Serum testosterone and testicular size were compared with body weight and crown-rump length. Pubertal onset in baboons occurs at 3–4 years of age; data were analyzed, therefore in three groups: 0–3 years; 3–4 years; and greater than 4 years. Testicular volume index increased minimally prior to 3 years of age. Between 3 and 4 years of age, there was an increase (P < .05) in testicular growth, which was followed after 4 years of age by a return to the prepubertal rate. Plasma testosterone decreased from birth to 3 years of age. Between 3 and 4 years of age, there was an increase (P < .05) in testosterone. The levels of which remained unchanged after 4 years of age. A linear increase in body weight was observed for the first 3 years which was followed by an increase (P < .05) in the rate of weight gain between 3 and 4 years of age. After 4 years of age, body weight continued to increase but at a rate less than those of the two earlier periods. A linear increase in crown-rump length was observed over the first 3 years. Between 3 and 4 years of age there was a slight increase (P > .06) in crown-rump length, which approached zero after 4 years of age. These data demonstrate many similarities between the pubertal development of male baboons and humans. Male baboons appear to be appropriate for the study of reproductive and endocrine development and the factors involved in the pubertal growth spurt of the human male.  相似文献   

4.
    
The objective of the study was to assess the post-weaning growth response of Sahiwal calves reared on four different pre-weaning dietary regimens. The four diets were: (a) whole cow's milk, starter ration (SR; CP = 20%, total digestible nutrients (TDN) = 72%) and Berseem hay (H; Egyptian clover; CP = 21%, TDN = 63%); (b) whole cow's milk + H; (c) milk replacer (MR; reconstituted to supplier specification; Sprayfo®) + SR + H; and (d) MR + H. The protein and fat percentages of reconstituted MR were 2.22 and 1.84, respectively. Milk or MR were fed at the rate of 10% of the calves’ body weight (BW) until 56 days of age, and then withdrawn gradually until weaned completely by 84 days of age. The average initial BW of calves in groups A, B, C and D were 56.3 ± 1.0, 47.5 ± 1.0, 40.4 ± 1.0 and 30.3 ± 1.0 kg, respectively. Initially, there were 12 calves in each group with six of each sex; however, one male calf died from each of groups B and C and were not replaced. During the post-weaning period, 13 to 24 weeks, the calves were fed a single total mixed ration ad libitum based on maize, canola meal, wheat straw and molasses containing 16% CP and 70% TDN. Daily feed intake and weekly BW gains were recorded. The data were analyzed by MIXED model analysis procedures using the statistical program SAS. The intake of calves as percent of their BW, feed conversion ratio and cost per kg of BW gain were not different (P > 0.05) across treatments. The daily gain at 24 weeks of age for the pre-weaning treatments A, B, C and D were 746 ± 33, 660 ± 33, 654 ± 33 and 527 ± 33 g/day and the final liveweights of calves were 119 ± 4.2, 102 ± 4.2, 95 ± 4.2 and 75 ± 4.2 kg, respectively. Gains were influenced significantly (P < 0.05) by pre-weaning treatments. The calves fed MR and H only during the pre-weaning period were unable to catch up post weaning with calves on other dietary treatments. The calves fed whole milk from birth at the rate of 10% of liveweight together with concentrates had higher weaning weight and superior growth rate post weaning as well. Thus, pre-weaning feeding was important for higher weaning weights and superior growth rates post weaning.  相似文献   

5.
    
The aim of this study was to investigate the effect of dietary replacement of soya bean meal (SBM) with faba bean (FB) and a blend of non-starch polysaccharide (NSP) degrading enzymes on the gastrointestinal function, growth performance and welfare of young turkeys (1 to 56 days of age). An experiment with a 2×2 factorial design was performed to compare the efficacy of four diets: a SBM-based diet and a diet containing FB, with and without enzyme supplementation (C, FB, CE and FBE, respectively). In comparison with groups C, higher dry matter content and lower viscosity of the small intestinal digesta were noted in groups FB. The content of short-chain fatty acids (SCFAs) in the small intestinal digesta was higher in groups FB, but SCFA concentrations in the caecal digesta were comparable in groups C and FB. In comparison with control groups, similar BW gains, higher feed conversion ratio (FCR), higher dry matter content of excreta and milder symptoms of footpad dermatitis (FPD) were noted in groups FB. Enzyme supplementation increased the concentrations of acetate, butyrate and total SCFAs, but it did not increase the SCFA pool in the caecal digesta. The enzymatic preparation significantly improved FCR, reduced excreta hydration and the severity of FPD in turkeys. It can be concluded that in comparison with the SBM-based diet, the diet containing 30% of FB enables to achieve comparable BW gains accompanied by lower feed efficiency during the first 8 weeks of rearing. Non-starch polysaccharide-degrading enzymes can be used to improve the nutritional value of diets for young turkeys, but more desirable results of enzyme supplementation were noted in the SBM-based diet than in the FB-based diet.  相似文献   

6.
    
BW of replacement heifers is rarely measured on commercial farms, making it difficult to evaluate the success of management practices related to calf growth. Our aims were to describe variability among commercial farms in Holstein heifer BW, determine how BW differences varied with management and propose a method of estimating calf growth based upon single measurement. Heart girth circumference was used to estimate BW of 576 heifers 48 to 70 weeks of age on 33 different farms (on average 11±6 heifers/farm) in British Columbia, Canada. Regression analysis showed a linear relationship of BW with age (BW (kg)=116+5×age (weeks)). Residuals from this regression were averaged across heifers within each farm to identify farms where heifers were heavier or lighter than would be predicted on the basis of their age; farm average residuals ranged from −54 to 72 kg. Farms with heifers showing the highest residual BW also had the highest rates of gain for pre-weaned calves. These results indicate that farms able to rear faster growing calves before weaning were also rearing faster growing heifers at breeding, and suggest that management of milk-fed calves is a particularly important component of replacement heifer management.  相似文献   

7.
Ontogeny refers to every aspect of the development of an individual. In this respect growth and sexual maturation are useful life-history parameters that can be correlated with developmental features of social behavior. In this paper, I analyze body-weight growth and sexual maturation in captive gray-cheeked mangabeys (Cercocebus albigena). I also describe the development of external morphological characteristics, used as “physical markers.” Body-weight growth is analyzed in 15 males and 7 females. Individual weight velocity curves for animals of both sexes showed an, early peak around 2 years of age. Males had a later growth spurt, peaking between 4 and 6 years of age. Females showed no clear second growth acceleration (spurt), but they experienced an interruption of their weight growth deceleration between 3 and 5 years of age, which is generally coincident with puberty. In females there is a close relationship between weight and the occurrence of the first swelling of their sexual skin. These developmental parameters are compared to those described in baboons and macaques.  相似文献   

8.
The characteristics of 7-day-old embryos non-surgically collected from 35 repeat breeder heifers (RBH) and 24 virgin heifers (VH) were compared by repeated observations within each animal. A higher incidence of the embryos collected from the VH was classified as normal and had reached a more advanced developmental stage than embryos from the RBH. Nearly all VH yielded normal (N) embryos, but morphologically deviated (MD) or degenerated embryos (D) appeared occasionally in many VH. The RBH group contained three subgroups of animals. One group of RBH yielded a high percent of N embryos. A second group yielded mostly MD or D embryos with an occasional N embryo, and the third group only D embryos or no embryos. Heifers from which no embryos were recovered on day 7 yielded uncleaved ova, apparently retarded embryos or no embryos when slaughtered three days after insemination. It is concluded that retarded embryonic development may be a common factor for most RBH. The embryo morphology and the degree of retardation differ among animals and between oestrous periods in the same animal.  相似文献   

9.
    
Objective: To examine whether there is an association between the timing of the development of obesity and children's growth. Research Methods and Procedures: This study investigated 141 prepubertal obese children (76 girls) and 72 healthy non‐obese children (39 girls). The target height standard deviation score (SDS), the percentage weight for height, and the height SDS (H‐SDS) at presentation and at the age of 2 years were calculated. Patients were classified, according to whether obesity developed before or after the age of 3 years, as presenting with early‐onset or late‐onset obesity, respectively. Results: Mean age (±SD) at presentation was 9.4 (2.1) years. At the age of 2 years, the H‐SDS of the children with early‐onset obesity was 1.3 (1.0) vs. 0.9 (1.3) for the late‐onset obese (p > 0.5) and 0.4 (1.0) for controls (p < 0.001), and the children with late‐onset obesity were also significantly taller than controls (p < 0.005). At presentation, children with early‐onset obesity were significantly taller than children with late‐onset obesity [1.1 (0.8) vs. 0.6 (1.0); p < 0.001] and controls [0.2 (0.8); p < 0.001]. There was no increase in H‐SDS after the age of 2 years in the late‐onset obese children (p > 0.05). H‐SDS values were below average in 21% of the children with late‐onset obesity and in only 4% of the children with early‐onset obesity. Discussion: These findings indicate that late development of obesity is not associated with increased stature in prepubertal children; however, it may be preceded by growth acceleration in the early years of life. Growth acceleration in early life may be a predictor for future obesity.  相似文献   

10.
    
This study investigated the relationship between the size, condition, year class, family, and sexual maturity of Atlantic salmon (Salmo salar) using data collected in an aquaculture selective breeding programme. Males that were sexually mature at 2 years of age (maiden spawn) have, on average, greater fork length and condition factor (K) at 1 year of age than their immature counterparts. For every 10-mm increase in fork length or 0.1 increase in K at 1 year of age, the odds of sexual maturity at 2 years of age increased by 1.48 or 1.22 times, respectively. Females that were sexually mature at 3 years of age (maiden spawn) have, on average, greater fork length and K at 2 years of age than their immature counterparts. For every 10-mm increase in fork length or 0.1 increase in K at 2 years of age, the odds of sexual maturity at 3 years of age increased by 1.06 or 1.44 times, respectively. The family explained 34.93% of the variation in sexual maturity among 2-year-old males that was not attributable to the average effects of fork length and K at 1 year of age and year class. The proportion of variation in sexual maturity among 3-year-old females explained by the family could not be investigated. These findings suggest that the onset of sexual maturation in Atlantic salmon is conditional on performance (with respect to energy availability) surpassing a threshold, the magnitude of which can vary between families and is determined by a genetic component. This could support the application of genetic selection to promote or inhibit the onset of sexual maturation in farmed stocks.  相似文献   

11.
木麻黄逆境生理研究进展(综述)   总被引：2，自引：0，他引：2  
本文综述水分、盐分、重金属和酸雨等逆境条件对木麻黄生长发育及生理生化等方面的影响,指出木麻黄造林的主要逆境因素是水分和盐分,并对今后的研究工作提出建议。  相似文献   

12.
    
The effects of dietary nucleotide supplementation from 9 days of age until the end of post-weaning on piglets hormonal and immune responses and on growth performance were investigated. During lactation (days 9 to 21) and post-weaning (days 22 to 55) 10 [HBI Fomeva11 × (Large White × Landrace)] litters (n = 108 piglets) had ad libitum access to two standard diets, both supplemented with 0% (T0 group) or 0.1% (T1 group) of yeast extract nucleotides. BW of piglets at days 21 (P < 0.10), 35 and 55 (P < 0.05) was greater in T1 compared with T0. Feed intake was not different between groups (P > 0.05). Cortisol content was lower in T1 than in T0 at days 28 and 35 (P < 0.05), whereas growth hormone was lower at day 35 (P < 0.05). Levels of IGF-1 were similar across groups (P > 0.05). Nucleotide-supplemented diets increased lymphocyte subpopulation CD4-CD8+high at days 21 and 35 (P < 0.05), whereas CD4+CD8- cells were higher in T1 than in T0 at day 21 (P < 0.05). Peripheral blood mononuclear cells cytokine expression was influenced by dietary nucleotide supplementation. At weaning, interleukin (IL)-6 and IL-1β expression was lower (P < 0.05) in T1 compared with T0, whereas the expression of interferon (IFN)-γ and IL-10 was higher (P < 0.05). At day 28, piglets in T1 showed higher values of tumor necrosis factor (TNF)-α expression than T0 and lower values of IL-10 expression (P < 0.05). Dietary nucleotide supplementation had a suppressive effect on IL-6 and IL-10 expression (P < 0.05) at day 35. On the contrary, the expression of IFN-γ, TNF-α and IL-1β was enhanced (P < 0.05). In conclusion, these results suggest that starting a dietary nucleotide supplementation before weaning can improve the adaptive capabilities of weaned piglets to the stressors, enhancing the growth performance.  相似文献   

13.
    
This experiment evaluated the impacts of supplementing a yeast-derived product (Celmanax; Church & Dwight Co., Inc., Princeton, NJ, USA) on productive and health responses of beef steers, and was divided into a preconditioning (days 4 to 30) and feedlot receiving phase (days 31 to 69). In all, 84 Angus × Hereford steers were weaned on day 0 (BW=245±2 kg; age=186±2 days), and maintained in a single group from days 0 to 3. On day 4, steers were allocated according to weaning BW and age to a 21-pen drylot (4 steers/pen). Pens were randomly assigned to (n=7 pens/treatment): (1) no Celmanax supplementation during the study, (2) Celmanax supplementation (14 g/steer daily; as-fed) from days 14 to 69 or (3) Celmanax supplementation (14 g/steer daily; as-fed) from days 31 to 69. Steers had free-choice access to grass-alfalfa hay, and were also offered a corn-based concentrate beginning on day 14. Celmanax was mixed daily with the concentrate. On day 30, steers were road-transported for 1500 km (24 h). On day 31, steers returned to their original pens for the 38-day feedlot receiving. Shrunk BW was recorded on days 4, 31 and 70. Feed intake was evaluated daily (days 14 to 69). Steers were observed daily (days 4 to 69) for bovine respiratory disease (BRD) signs. Blood samples were collected on days 14, 30, 31, 33, 35, 40, 45, 54 and 69, and analyzed for plasma cortisol, haptoglobin, IGF-I, and serum fatty acids. Preconditioning results were analyzed by comparing pens that received (CELM) or not (CONPC) Celmanax during the preconditioning phase. Feedlot receiving results were analyzed by comparing pens that received Celmanax from days 14 to 69 (CELPREC), days 31 to 69 (CELRECV) or no Celmanax supplementation (CON). During preconditioning, BRD incidence was less (P=0.03) in CELM v. CONPC. During feedlot receiving, average daily gain (ADG) (P=0.07) and feed efficiency (P=0.08) tended to be greater in CELPREC and CELRECV v. CON, whereas dry matter intake was similar (P⩾0.29) among treatments. No other treatment effects were detected (P⩾0.20). Collectively, Celmanax supplementation reduced BRD incidence during the 30-day preconditioning. Moreover, supplementing Celmanax tended to improve ADG and feed efficiency during the 38-day feedlot receiving, independently of whether supplementation began during preconditioning or after feedlot entry. These results suggest that Celmanax supplementation benefits preconditioning health and feedlot receiving performance in beef cattle.  相似文献   

14.
    
In all, 60 Angus×Hereford heifers were ranked by age and BW (210±2 days and 220±2 kg) on day 0, and assigned to: (a) one of three drylot pens (10×14 m pens; 10 heifers/pen) resulting in a stocking density of 14 m2/heifer (HIDENS; n=3), or (b) one of three pastures (25 ha pastures; 10 heifers/pasture), resulting in a stocking density of 25 000 m2/heifer (LOWDENS; n=3). Pastures were harvested for hay before the beginning of this experiment, and negligible forage was available for grazing to LOWDENS heifers during the experiment (days 0 to 182). All heifers received the same limited-fed diet, which averaged (dry matter basis) 4.0 kg/heifer daily of hay and 3.0 kg/heifer daily of a corn-based concentrate. Heifer shrunk BW was recorded after 16 h of feed and water withdrawal on days −3 and 183 for BW gain calculation. On day 0, heifers were fitted with a pedometer behind their right shoulder. Each week, pedometer results were recorded and blood samples were collected for puberty evaluation via plasma progesterone. Plasma samples collected on days 0, 28, 56, 84, 112, 140, 161 and 182 were also analyzed for cortisol concentrations. On days 0, 49, 98, 147 and 182, hair samples were collected from the tail switch for analysis of hair cortisol concentrations. On days 28, 102 and 175, blood samples were collected for whole blood RNA isolation and analysis of heat shock protein (HSP) 70 and HSP72 mRNA expression. Heifers from LOWDENS had more (P<0.01) steps/week compared with HIDENS. No treatment effects were detected (P=0.82) for heifer BW gain. Plasma cortisol concentrations were greater (P⩽0.05) in LOWDENS compared with HIDENS heifers on days 84, 140, 161 and 182 (treatment×day interaction; P<0.01). Hair cortisol concentrations were greater (P<0.01) in HIDENS compared with LOWDENS heifers beginning on day 98 (treatment×day interaction; P<0.01). Heifers from LOWDENS had greater (P=0.04) mean mRNA expression of HSP72, and tended (P=0.09) to have greater mean mRNA expression of HSP70 compared with HIDENS. Heifers from HIDENS experienced delayed puberty attainment and had less (P<0.01) proportion of pubertal heifers on day 182 compared with LOWDENS (treatment×day interaction; P<0.01). In summary, HIDENS altered heifer stress-related and physiological responses, and delayed puberty attainment compared with LOWDENS.  相似文献   

15.
    
The adolescent growth spurt in linear dimension in humans is considered to be unique among mammals, but few comparative studies have been done, even on chimpanzees. Growth of the summed length of crown to rump, thigh, and leg was studied longitudinally in 12 chimpanzees. We took body weight growth and reproductive maturation into consideration. Reproductive maturation was monitored by the swelling of sexual skin and menarche in females, and by testicular development in males. We applied two relationships found in humans between body length growth and the environment to the chimpanzees. The first relationship was the robustness of the growth spurt, meaning that the spurt is absent only in individuals under the most severe environmental pressure. Subjects maturing in a favorable or even mediocre environment are anticipated to show the growth spurt. The second relationship was catch-up growth, where, when the environment is ameliorated, growth may be accelerated to attain the target size. Catch-up growth at the end of the juvenile period may mimic the adolescent growth spurt. Results showed that subjects living under favorable conditions did not exhibit a growth spurt, and that it was only the subjects who had delayed growth in the juvenile period that showed a spurt in adolescence, the period when reproductive maturation occurred. Although we have concluded that chimpanzees do not have an adolescent growth spurt, except in cases of catch-up growth, this does not mean that they have a different growth pattern from that of humans. The absence of a growth spurt may be associated with adaptations to chimpanzee patrilineal society, where adolescent males are incorporated into the adult hierarchy at a low rank.  相似文献   

16.
    
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17.
    
The presence of breeding tubercles (BTs) on the pectoral fins has been investigated as a typical male secondary sexual characteristic (SSC) that distinguish males from females in adult zebrafish. Nonetheless, the earliest occurrence of these tubercles and its association with puberty onset and body growth remain unclear. In this study, using morphological, histological and statistical analyses, the authors examined the first appearance of BTs and puberty onset in male zebrafish, with particular emphasis on the potential impact of body growth on them. The results of this study revealed that BTs distributed along the first five branched pectoral fin rays were the earliest manifestation of male SSCs, which is significantly strongly correlated with body weight (R2 = 0.9609, P < 0.001), and could be used as a “gold standard” for the earliest sex distinction (<0.1 g in weight). Using the first appearance of BTs (<0.20 mm2) as a metric, the authors established that male puberty commenced at a body weight of c. 0.056 ± 0.015 g or a standard length of 10.99 ± 1.051 mm (mean ± S.D. ). In this study, the authors thus established a simple method that can be used to sex live zebrafish at the pubertal stage and provides the first evidence for the relationship of BTs and male puberty initiation with body growth. These findings will accordingly lay a foundation for exploring mechanisms of the SSCs and male puberty onset in zebrafish and other teleost fish.  相似文献   

18.
Oryzalin (3,5-dinitro-N4,N4-dipropyl-sulfanilamide) and BAS 083 (l,l-dimethylpiperdinium chloride) reduced root-knot infection in tomato roots when respectively applied as a soil drench at 20 ppm and 10,000 ppm. Oryzalin reduced knot counts with various intervals between treatment and inoculation. BAS 083 reduced knot counts only when applied before inoculation. Oryzalin was shown not to be a contact nematicide, and BAS 083 was only a weak one. Neither compound reduced penetration by infective larvae. Postinfection reduction in knot counts by Oryzalin and BAS 083 resulted, in part, from activation of natural defense mechanisms of the host. Giant-cell development in cotton roots inoculated with nematodes was inhibited by Oryzalin. Lateral root development was inhibited by BAS 083.  相似文献   

19.
    
The objective of this meta-analysis was to develop empirical equations predicting growth responses of growing cattle to protein intake. Overall, the data set comprised 199 diets in 80 studies. The diets were mainly based on grass silage or grass silage partly or completely replaced by whole-crop silages or straw. The concentrate feeds consisted of cereal grains, fibrous by-products and protein supplements. The analyses were conducted both comprehensively for all studies and also separately for studies in which soybean meal (SBM; n=71 diets/28 studies), fish meal (FM; 27/12) and rapeseed meal (RSM; 74/35) were used as a protein supplement. Increasing dietary CP concentration increased (P<0.01) BW gain (BWG), but the responses were quantitatively small (1.4 g per 1 g/kg dry matter (DM) increase in dietary CP concentration). The BWG responses were not different for bulls v. steers and heifers (1.4 v. 1.3 g per 1 g/kg DM increase in dietary CP concentration) and for dairy v. beef breeds (1.2 v. 1.7 g per 1 g/kg, respectively). The effect of increased CP concentration declined (P<0.01) with increasing mean BW of the animals and with improved BWG of the control animals (the lowest CP diet in each study). The BWG responses to protein supplementation were not related to the CP concentration in the control diet. The BWG responses increased (P<0.05) with increased ammonia N concentration in silage N and declined marginally (P>0.10) with increasing proportion of concentrate in the diet. All protein supplements had a significant effect on BWG, but the effects were greater for RSM (P<0.01) and FM (P<0.05) than for SBM. Increasing dietary CP concentration improved (P<0.01) feed efficiency when expressed as BWG/kg DM intake, but decreased markedly when expressed as BWG/kg CP intake. Assuming CP concentration of 170 g/kg BW marginal efficiency of the utilisation of incremental CP intake was only 0.05. Increasing dietary CP concentration had no effects on carcass weight, dressing proportion or conformation score, but it increased (P<0.01) fat score. Owing to limited production responses, higher prices of protein supplements compared with cereal grains and possible increases the N and P emissions, there is generally no benefit from using protein supplementation for growing cattle fed grass silage-based diets, provided that the supply of rumen-degradable protein is not limiting digestion in the rumen.  相似文献   

20.
Weekly measurements of fruit growth, fruit respiration and shoot extension growth were made in the field on early (June Lady) and late (O'Henry) maturing cultivars of peach ( Prunus persica L. Batsch). The seasonal patterns of fruit growth and respiration for the two cultivars were very similar except that the early maturing cultivar bloomed a few days earlier than the late cultivar and had a shorter intermediate stage (Stage II) of fruit growth. Maximum rates of fruit respiration per unit weight at 20°C were similar for both cultivars during the first two stages of fruit growth but higher for the early cultivar during the final stage of fruit growth. Maximum fruit growth rates within any particular stage of fruit growth were similar for both cultivars, but the mean fruit weight of the late cultivar was greater at the end of Stage II, because of the extended length of this stage compared to the early cultivar. The final stage of most rapid fruit growth and respiration coincided with the period of most rapid shoot extension growth in the early maturing cultivar but occurred after this period in the late maturing cultivar. Genetic selection for early fruit maturity in peach has apparently had little effect on timing of shoot growth and this may result in increased competition between vegetative and reproductive sinks during peak periods of fruit growth in early maturing cultivars.  相似文献   

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