Influence of undegraded intake protein on intake,digestion, serum hormones and metabolites,and nitrogen balance in sheep

In Exp. 1, 20 ewes of mixed breeding were fed grass hay : straw mixtures, assigned to one of four supplemental treatments and evaluated during six collection periods. Supplemental treatments were control (no supplement), and low, medium, and high levels (5.2%, 22.1%, and 41.3% of DM, respectively) of undegraded intake protein (UIP). Supplements were formulated to be similar in degraded intake protein (DIP; 21%). Digestibilities of DM, OM, and CP were increased (P < 0.10) with protein supplementation and in medium and high compared with low UIP supplemented ewes. Digestibility of CP also was increased (P < 0.10) in ewes on high compared with medium treatments. Serum insulin was not influenced (P > 0.10) by UIP treatment, except in collection period four. In contrast, serum glucose and growth hormone were not influenced (P > 0.10) by UIP treatment. In Exp. 2, four wether lambs fed the same treatments as in Exp. 1, were used in two 4 × 4 Latin squares trials. In trial 1 lambs received a grass hay diet (6.7% CP) and in trial 2 lambs were fed 40 : 60 blend (6.6% CP) of grass hay and spring wheat straw. In both trials, N intake, urinary N, N digestion, apparent N absorption, and N retention were increased (P < 0.10) with protein supplementation. In addition, in trial 1, urinary N, N digestion, and apparent N absorption were increased (P < 0.10) in medium and high compared with low UIP and also in high compared with medium UIP treatments. In trial 2 of Exp. 2, total feed intake (g/kg BW), digestibility of DM and OM, BW, and fecal N were increased (P < 0.10) with protein supplementation. Organic matter digestion, BW, N intake, and N retention were increased by medium and high compared with low UIP. Fecal N, BW, N intake, and N retention were increased (P < 0.10) in high compared with medium UIP. These data indicate that increasing levels of UIP supplementation increases DM, OM, and CP (N) digestibility, serum urea N concentration, and N retention in sheep fed low quality forage.     

Nutrition-induced differences in body composition, compensatory growth and endocrine status in growing pigs

In this experiment, we assessed the effect of amino acid (AA) intake restriction in entire male Yorkshire pigs between 15 and 38 kg BW (restriction phase) on BW gain, body composition and plasma levels of blood urea nitrogen (BUN), cortisol, insulin-like growth factor I (IGF-I), growth hormone (GH) and leptin during the subsequent re-alimentation phase. During the restriction phase, 36 pigs were allotted to one of two dietary treatments: adequate AA intake (control) or AA-limiting diets (AA-30%). Thereafter, pigs were fed common non-limiting diets up to 110 kg BW. Throughout the experiment, pigs were scale-fed at 90% of the estimated voluntary daily digestible energy intake. At the end of the restriction phase, pigs on AA-30% had lesser BW gain (650 v. 784 g/day; P < 0.001), loin area (LA; 12.2 v. 14.2 cm2; P < 0.001), BUN (4.6 v. 6.3 mg/dl; P < 0.02), lesser plasma levels of IGF-I (440 v. 640 ng/m; P < 0.001) and cortisol (8.2 v. 19.2 μg/dl; P < 0.001), greater backfat thickness (BF; 7.56 v. 6.56 mm; P < 0.02), and greater plasma levels of leptin (2.7 v. 1.8 ng/ml; P = 0.027) and GH (3.3 v. 2.0 ng/ml; P = 0.05) than pigs on control. During the re-alimentation phase, previously restricted pigs showed full compensatory growth (CG) in terms of BW gain (1170 v. 1077 g/day; P < 0.002), whole-body protein deposition (Pd) (179 v. 163 g/day; P < 0.001) as well as physical and chemical body composition (whole-body lipid to body protein mass ratio, LB/PB; 1.14 v. 1.15; P > 0.10). Besides GH at 45 kg BW (4.2 v. 2.4 ng/ml; P = 0.066), there were no effects of previous AA intake restriction on leptin, IGF-I and BUN during the re-alimentation phase (P > 0.10). Plasma cortisol and IGF-I levels may act as an indicator of AA-induced restriction in Pd in growing pigs. Plasma BUN level does not appear as a sensitive indicator for compensatory Pd. Plasma leptin and GH levels allow for the involvement of the brain in controlling chemical body composition. Full CG was observed during the energy-dependent phase of Pd in growing pigs and might be driven by a target LB/PB, possibly mediated via plasma leptin, IGF-I and GH levels.     

Effects of prepartum lipid supplementation on FSH superstimulation and transferable embryo recovery in multiparous beef cows

The objective of this experiment was to determine the effect of prepartum lipid supplementation on the number and quality of embryos recovered following ovarian super-ovulation in postpartum suckled beef cows. Mature cows (n = 40) were assigned to one of two treatments (lipid versus. no lipid) and supplemented for approximately 40 days prior to calving. Supplements provided to cows were isocaloric and isonitrogenous. The treatment group was fed 1.6 kg hd(-1) per day of whole soybeans (WSB; 19.8% ether extract, and 41.8% crude protein) and the control group received a supplement consisting of 1.8 kg hd(-1) day of a soybean meal and soy-hull combination (SBS; 2.15% EE and 36.81% CP). Cows were synchronized using a GnRH [Cystorelin((R)) 100 microg im]-GnRH-PGF(2alpha) [Lutalyse 25 mg im] protocol. Cows were administered two injections of GnRH seven days apart and PG seven days after the second GnRH injection. Twenty-eight cows (WSB, n = 15; SBS, n = 13) responded to estrus synchronization and were superstimulated. Super-ovulation was initiated on day 8-10 of the synchronized cycle by twice-daily injections of pFSH (Pluset) over four days in decreasing doses using a total of 608.4 IU per cow. Prostaglandin F(2alpha) was administered 96 and 108 h after super-stimulation was initiated with FSH. Days postpartum (WSB = 59 days; SBS = 57 days) at initiation of FSH treatments were similar (P > 0.10) for both treatments. Cows were monitored for estrus activity by the HeatWatch Estrus Detection System. Twenty-seven cows (WSB, n = 15; SBS, n = 12) exhibited estrus after FSH and inseminated at 0, 12, and 24 h after the onset of estrus with 1, 2, and 1 units of semen, respectively. Embryos were recovered and evaluated 7-8 days later. Only cows that responded to FSH and that were inseminated were used for statistical analysis. Data were analyzed using the General Linear Models Procedure of SAS. Body condition scores did not differ (P > 0.10) between treatments when cows were evaluated at the initiation of the experiment, two weeks prior to calving, and at initiation of superovulation with FSH. Estrous cyclicity prior to the initiation of estrus synchronization did not differ (P > 0.10) between treatments. There was no difference (P > 0.10) between treatments in recovery of total embryos (WSB, 14.7 +/- 3.5; SBS, 17.5 +/- 3.0), transferable embryos (WSB, 10.3 +/- 2.5; SBS, 13.6 +/- 2.6), degenerate embryos (WSB, 3.3 +/- 1.1; SBS, 1.6 +/- 1.7) or unfertilized ova (WSB, 1.1 +/- 0.5; SBS, 2.3 +/- 1.2). Cows that were supplemented with whole soybeans prior to parturition failed to produce an increased total number of ova or transferable embryos following super-ovulation.     

Postpartum anoestrus is reduced by increasing the within-day milking to suckling interval in dual purpose cows

In the dual purpose milk/beef production system practised in Mexico, the cows are milked once a day in the presence of the calf and then the calf suckles for the next 1-8 h. It was hypothesised that the imposition of milking and suckling in close succession contributes to the long postpartum anoestrous periods experienced by cows in this system. Therefore, separating these two inhibiting factors, by delaying the start of suckling after milking would lower the impact on the hypothalamus-hypophysial axis and allow it to recover more readily. This hypothesis was tested in two experiments using Bostaurus x Bosindicus cows which weighed 541.3 +/- 12.7 kg (mean +/- S.E.M.; experiment 1) and 537.8 +/- 10.6 kg (experiment 2) and had a body condition score of 5-6 (scale 1-9) at calving. The cows and calves were maintained on separate pastures and the cows were offered concentrate supplements. Experiment 1 was conducted in the dry season and cows were offered a daily supplement of 3 kg of 17% crude protein (CP) concentrates plus 1 kg molasses per cow. Experiment 2 was conducted during the wet season and the nutritional supplement consisted of only 1 kg of 17% CP plus 1 kg molasses per cow per day. Each experiment lasted for the first 100 days postpartum and the cows were not mated during this time. Cows were hand-milked once a day in the presence of the calf to stimulate milk let-down. In experiment 1, 30 multiparous cows were assigned at random by date of calving, to one of three treatments: controlled suckling (CS; n = 10), delayed suckling (DS; n = 10) and prolonged delayed suckling (PDS; n = 10). The suckling period on all treatments lasted for 2 h and started at 0 h (CS), 4 h (DS) or 8 h (PDS) after milking. In experiment, 34 multiparous cows were assigned at random to three treatments: CS (n = 11), PDS (n = 11) or prolonged delayed short suckling (PDSS; n = 12), in this last treatment the suckling period was reduced to only 30 min. In both experiments, one quarter of the udder of cows on treatment CS was not milked but all the udder was milked on the other treatments. Body weights of cows and calves and cow milk yields were recorded. Weekly blood samples were collected for plasma progesterone assay to detect the first postpartum corpus luteum. Data were analysed by ANOVA and chi-square test. Cows in experiment 1 had similar weight changes during the first 100 days postpartum. Milk production was higher for DS (8.0 +/- 0.7 kg per day) and PDS (7.0 +/- 0.5 kg per day) cows than for CS (5.2 +/- 0.7 kg per day) cows (P < 0.01). Calf daily gain was greater (P < 0.05) for PDS (827 +/- 35 g per day), than CS (702 +/- 26 g per day) or DS (715 +/- 29 g per day). The proportion of cows ovulating during the first 100 days postpartum were 50.0, 70.0 and 100.0%, for CS, DS and PDS, respectively (P < 0.05). The intervals from calving to first significant rise in progesterone were 70.4 +/- 1.6, 72.1 +/- 1.3 and 64.6 +/- 1.5 days for CS, DS and PDS (P > 0.05), respectively. In experiment 2, cow body weight during the first 100 days postpartum did not differ between treatments. Milk production was not significantly different between CS (7.3 +/- 1.0 kg per day) and PDSS (6.8 +/- 1.0 kg per day), but was higher (P < 0.05) for CS than PDS (5.2 +/- 1.0 kg per day). Calf daily gain was lower for CS (576 +/- 31 g per day; P < 0.05) than PDS (779 +/- 38 g per day) and PDSS (780 +/- 20 g per day). The proportion of cows ovulating was higher (P < 0.05) for treatments PDS (100%) and CS (81.8%) than PDSS (50%). Calving to first ovulation interval was shorter (P < 0.05) for PDS (57.3 +/- 4.5 days) and PDSS (49.7 +/- 3.0 days) cows than CS (72.1 +/- 3.5 days) cows. It is concluded that delaying suckling for 8 h after milking, increases the proportion of cows ovulating within 100 days of calving, shortened the calving to first ovulation interval and improved calf performance without adversely affecting cow milk yield or body weight change.     

Effects of diets containing free gossypol on follicular development, embryo recovery and corpus luteum function in Brangus heifers treated with bFSH

Thirty 2 yr old Brangus heifers were randomly assigned to 1 of 3 dietary treatments: Control, 0 g of free gossypol (FG) per head per day (FGHD) from corn and soybean meal (SBM); 5 g of FGHD from cottonseed meal (CSM); and 15 g of FGHD from whole cottonseed (WCS). Blood samples were collected weekly for serum progesterone (P(4)) and later quantified by RIA. Whole blood was collected on Days 1, 28, 42, 56 and 70 for erythrocyte fragility (EF) analysis. Following 65 d on dietary treatments and estrus detection, the heifers received bovine-FSH (bFSH) once daily on Days 10, 11 and 12 postestrus, and PGF(2alpha) on Day 12 postestrus. Fifteen of the thirty heifers were randomly selected, and 12 h following PGF(2alpha), the ovaries were removed and follicular diameters, ovarian weight and stromal weights were recorded. Follicular fluid was analyzed for steroid content by RIA. The remaining fifteen heifers were artificially inseminated. Embryos were recovered non-surgically on Day 7 postestrus and graded, and the recovery efficiencies were calculated. Following embryo collection, both ovaries were removed, the number of CLs was recorded, and CL P(4) content was determined by RIA. By Day 42 of treatment, heifers receiving CSM had elevated (P < 0.04) EF compared with the Controls, and remained elevated above that of Controls throughout the study. At Day 70, the CSM heifers tended to have higher (P < 0.07) EF than the WCS group, which in turn tended to be higher (P < 0.06) than the Controls. The Control and CSM heifers gained weight during the 70 d treatment period, while heifers consuming WCS lost weight (P < 0.05). Ovarian and stromal weights did not differ (P > 0.10) among treatment groups. Heifers receiving CSM had fewer (P < 0.05) follicles > 5 mm than WCS or Control heifers. Follicular fluid weights and steroid content did not differ (P > 0.10) among treatments. Both CL weight and the number of CLs per heifer were similar (P > 0.10) among treatments. Heifers receiving CSM or WCS had a higher (P < 0.003) CL P(4) content per gram of CL tissue than the Controls. Progesterone content per CL was greater in WCS heifers (P < 0.003) than in CSM heifers, while both the CSM and WCS heifers had a higher CL P(4) content than the Control heifers. Weekly and Day 7 postestrus serum concentrations of P(4) were similar (P > 0.10) among treatments. The number of embryos recovered, number of degenerated embryos, embryo grades and recovery efficiencies were not affected (P > 0.10) by dietary treatments. To standardize heifers relative to the number of degenerated embryos, the percentage of degenerated embryos recovered was calculated and tended to be greater (P < 0.06) in heifers consuming CSM than in either the Control or WCS groups. While most ovarian, follicular and embryo characteristics were not affected by dietary free gossypol, these results suggest that differences in the availability of free gossypol and/or dietary components between CSM and WCS may influence weight gain, CL P(4) content and embryo viability.     

Effect of low-protein amino acid-supplemented diets on the growth performance, gut morphology, organ weights and digesta characteristics of weaned pigs

A 21-day study was conducted to determine whether isoleucine might limit the performance of piglets fed low-crude protein (CP), amino acid (AA)-supplemented diets and to investigate the potential benefits of low-CP diets on gastrointestinal health in weaned pigs. Ninety-six piglets (initial BW = 6.44 ± 0.14 kg), housed four per pen, were randomly assigned to one of four diets, resulting in six replicate pens per diet. Dietary treatments were as follows: (1) 210 g/kg CP diet, (2) 190 g/kg CP diet deficient in isoleucine, (3) 190 g/kg CP diet supplemented with crystalline isoleucine up to the level in the 210 g/kg CP diet and (4) 170 g/kg CP diet supplemented with isoleucine and valine on the ideal protein ratio basis (60% and 70% relative to lysine, respectively). Pigs were allowed to adapt to the new environment for 4 days before the experiment commenced. Overall, pigs fed the 210 g/kg CP diet had higher (P < 0.05) average daily gain and lower (P < 0.05) feed : gain ratio compared with those fed the other diets. The faecal consistency score of pigs fed the 210 g/kg CP diet was higher (P < 0.05) than those fed the other diets. Pigs fed the 170 g/kg diet had lower (P=0.02) small intestine weight than those fed the 210 g/kg CP diet. Pigs fed the 210 g/kg CP diet had deeper (P < 0.05) crypt in the duodenum and ileum and higher (P < 0.05) ammonia N concentration in caecal digesta than those fed the other diets. There were no effects of diet on microbial population and volatile fatty acid concentration in the caecal digesta except for propionic acid whose concentration was higher (P < 0.05) for pigs fed the 170 g/kg diet than those fed the 190+isoleucine and the 210 g/kg CP diets. The results indicate that the low-CP, AA-supplemented diet reduced crypt hypertrophy, ammonia N concentration in the caecal digesta, small intestine weight and the performance of piglets. Also, the results of the current study were inconclusive with respect to whether isoleucine may limit the performance of pigs fed a low-CP, AA-supplemented diet.     

Declining fertility in the lethal yellow mouse is related to progressive hyperleptinemia and leptin resistance

Mice possessing the lethal yellow mutation (C57BL/6J A(y)/a) become obese and develop hyperleptinemia and leptin resistance as they age. To determine the relationship between altered leptin physiology and reproductive function in these mice, we compared body weight (BW), serum leptin concentration, ovulation rate, and in vitro blastocyst development among 120- and 180-d-old lethal yellow and black non-mutant (a/a) mice. Estrous female yellow and black mice were mated with fertile black males. Oviducts were flushed approximately 36 h after mating and the recovered embryos were cultured for 96 h. BW, serum leptin levels, and the leptin:BW ratio differed among groups as follows: 180-d yellow > 120-d yellow > 180-d black = 120-d black. Ovulation rate was similar among 120-d yellow and black, and 180-d black mice. Among 180-d yellow mice, five of twelve mice failed to ovulate, but the other seven mice ovulated a similar number of oocytes as their black counterparts (8.4 +/- 0.9 versus 8.0 +/- 1.3). Non-ovulators had higher (P < 0.05) leptin levels (56.6 +/- 1.8 ng x mL(-1)) than ovulators (46.2 +/- 3.5), but BW did not differ significantly. Fewer embryos from 180-d yellow mice reached the blastocyst stage in culture than did the embryos from black mice (55% versus 83%, P < 0.05). Moreover, blastocyst development in 180-d old yellow mice negatively correlated with leptin levels (r = -0.797, P = 0.032) and leptin:BW ratio (r = -0.847, P = 0.016), but not with BW. Declining reproductive function in lethal yellow mice appears to be related to increasing levels of leptin and progression of leptin resistance.     

Age, body weight and backfat thickness at first observed oestrus in crossbred Landrace x Yorkshire gilts, seasonal variations and their influence on subsequence reproductive performance

The objective of the present study was to investigate puberty attainment in crossbred Landrace x Yorkshire (LY) gilts reared under tropical conditions and their subsequent reproductive performance. This study was carried out in a 2400-sow herd over a 1-year period. A total of 696 crossbred LY replacement gilts were included. Faecal samples from 214 gilts were collected to determine the faecal progesterone profiles around the time of first oestrus. Solid-phase 125I-radioimmunoassay was used to determine the progesterone concentrations in the faecal extract. The gilts entered the herd at an average age of 177.5 +/- 12.6 days, 95.7 +/- 10.2 kg body weight (BW) and a backfat thickness (BF) of 12.0 +/- 2.9 mm. On average, the gilts expressed first standing oestrus at 195 days of age, 106 kg of BW and a BF of 13.0 mm. The interval from entry to the gilt pool to the first observed oestrus (EOI) was 24.4 +/- 18.0 days (range 0-88 days). The hormonal profile indicated that the gilts that actually ovulated during the first observed oestrus was 34% (group A), the gilts that had ovulated before the first observed oestrus was 21% (group B) and the gilts that did not ovulate during the first observed oestrus was 45% (group C). During summer the proportion of group A gilts was significantly lower than during the winter and the rainy seasons (P < 0.05). The BW of gilts at entry significantly correlated with the BF at entry (r = 0.31, P < 0.001), the age at entry (r = 0.47, P < 0.001), the BW at first oestrus (r = 0.65, P < 0.001) and the BF at first oestrus (r = 0.33, P < 0.001). An increase of BW at entry of 1 kg resulted in a decrease of EOI of 0.28 days. The age, BW and BF of gilts at the first observed oestrus significantly influenced the total number of piglets born per litter (TB) and the number of piglets born alive per litter (BA) in the first three parities. Gilts expressing their first oestrus between 181 and 200 days had a significantly larger TB than gilts that expressed first oestrus between 150 and 180 days (P = 0.03) and between 201 and 220 days (P = 0.003). Gilts that showed first oestrus between 110.1 and 120.0 kg had a larger TB and BA than gilts that showed first oestrus between 80.0 and 100.0 kg (P < 0.05). Gilts that showed first oestrus with a BF between 13.1 and 15.0 mm had a larger TB and BA than gilts that showed first oestrus with a BF between 11.1 and 13.0 mm (P < 0.05). Group A gilts had a significantly larger TB than group B (10.5 piglets/L versus 9.4 piglets/L, P = 0.02), while farrowing rate (FR) did not differ significantly among groups A, B and C (78.1, 76.9 and 77.6%, respectively). Gilts that farrowed in the summer had a larger TB and BA than gilts that farrowed in the winter (TB, P = 0.03; BA, P = 0.09) and the rainy season (TB, P = 0.006; BA, P = 0.003). In conclusion, LY gilts reared under tropical conditions expressed first standing oestrus at 195 days of age, 106 kg BW and a BF of 13.0 mm. Under field conditions, 21% of the gilts with an observed oestrus had ovulated. The proportion of gilts that showed first oestrus and ovulated normally was lowest during the summer. The age, BW and BF at first observed oestrus influenced subsequent reproductive performance over the first three parities. The mean litter size (TB and BA) in the first three parities were highest in gilts that had a first observed oestrus between 181 and 200 days with 110.1-120.0 kg BW and 13.1-15.0 mm BF.     

Bull exposure and an increased within-day milking to suckling interval reduced postpartum anoestrus in dual purpose cows

It is hypothesized that the combined effects of suckling and milking in the dual purpose cows is one of the main suppressors of reproductive efficiency in this production system. The experiment described here examined whether managing the interval between milking and suckling could reduce the postpartum anoestrous period and whether the presence of a teaser bull could enhance the effects of these managements. The experiment involved 39 Bos taurus x Bos indicus cows which had an average weight of 523.0 +/- 12.8 kg (mean +/- S.E.M.) and body condition score of 5-7 (scale 1-9) at calving. The cows and calves grazed separate pastures and the cows were supplemented with 2 kg 17% CP concentrates and 1 kg molasses per cow per day. The experiment was conducted over the first 100 days postpartum. Cows were hand-milked once per day in the presence of the calf to stimulate milk release. The factors in the 2 x 2 design were the milking to suckling interval (0 h, control suckling; CS versus 8 h prolonged-delay suckling; PDS) and no exposure versus exposure to a teaser bull (B). Cows were assigned at random within calving date to the four treatments: CS (n = 10), PDS (n = 10), CS-B (n = 9) and PDS-B (n = 10). Cows on treatments CS and CS-B had three-quarters of the udder milked and one-quarter was not milked. The entire udder was milked on those treatments where there was an interval between milking and suckling. The bull was introduced 7 days after calving in treatments where the cows were exposed to a teaser bull. Body weights of cows and calves and cow milk yield were recorded. Weekly blood samples were collected for plasma progesterone assay. Data were analyzed by ANOVA in a 2 x 2 factorial design and by chi(2)-test. There were no statistically significant differences between treatments in cow body weight at calving and at 100 days postpartum, nor in milk yield (overall mean 6.0 +/- 1.1 kg per day). Calf daily gain was 598 +/- 25 g for treatments CS and CS-B in which suckling immediately followed milking and 833 +/- 24 g for treatments PDS and PDS-B (P < 0.001). The proportion of cows ovulating was CS 80.0%, PDS 100.0%, CS-B 88.8% and PDS-B 100.0%. The difference between CS and PDS or PDS-B was significant (P < 0.05). CS-B did not differ significantly from the other three treatments. The calving to first ovulation interval was not improved when the interval between milking and suckling was increased from 0 h (56.5 +/- 5.0 days) to 8 h (64.8 +/- 4.5 days). Exposure to a teaser bull, however, significantly (P < 0.001) reduced this interval from 77.0 +/- 2.7 days (no bull exposure) to 44.4 +/- 2.7 days (exposure to teaser bull). Exposure to a teaser bull significantly reduced the calving to first anoestrus interval. Delaying the start of suckling after milking did not improve the reproductive performance of the cows or alter the effect of bull exposure, however, delaying suckling after milking improved the performance of the calves without affecting milk yield.     

食物水平和初始体重对杂交罗非鱼生长和个体生长分化的影响

将72尾杂交罗非鱼分别养在12个水槽内,每个水槽内养6尾大小不同的鱼(A、B、C、D、E、F),其中鱼A的初始体重为62．69±1．46g,B为56．48±1．30g,C为50．75±1．19g,D为35．56±1．18g,E为31．05±0．88g,F为27。35±0．95g(平均值±标准误)．在4周实验中,实验鱼分别被停食或每天按体重1．5％、3．0％和饱食水平投喂．鱼的特定生长率(SGR)和食物效率(FE)先随食物水平增加而增加,当食物水平超过鱼体重的3．0％后,继续增加投喂量,SGR不再升高而FE明显下降．按体重1．5％投喂的鱼SGR和终体重个体间变异较大．对鱼A而言,食物水平超过体重1．5％后对其SGR无显著影响,但对鱼F而言,食物水平对SGR影响较大．结果表明,杂交罗非鱼的生长和个体生长分化与食物条件和初始体重有关,当食物水平超过体重的3．0％后,鱼的SGR较高,个体生长分化相对较轻．     

Effects of body weight loss on serum progesterone concentrations of non-lactating dairy cows

The objective was to evaluate serum concentrations of nonesterified fatty acids (NEFA), cortisol, insulin, and progesterone (P4) of dairy cows maintaining or mobilizing body weight (BW). Eleven non-lactating, non-pregnant, and ovariectomized Gir × Holstein cows were stratified by BW and body condition score (BCS), and randomly assigned to: 1) BW loss (six cows; LOSS) and 2) BW maintenance (five cows; MAINT). Treatments were achieved through a grazing schedule using three pastures. From Days −7 to 1 of the study, all cows were maintained in Pasture A (12 kg of dry matter/cow daily). From Days 2 to 30, LOSS cows were maintained in Pasture B (less than 1.0 kg of dry matter/cow daily), whereas MAINT cows were maintained in Pasture C (12 kg of dry matter/cow daily). However, from Days 3 to 30 of the study, cows from both treatments were regrouped daily into Pasture A from 0600 to 1200 h to allow LOSS cows to consume, on average, 4.5 kg/d of forage dry matter. On Day −66 of the study, all cows received an intravaginal drug releasing device containing 1.9 g of P4 (replaced every 14 d and removed on Day 3). Cow BW and BCS were assessed on Day 0 and 30 and blood samples were collected daily from Days 0 to 30 at 0600 and 1200 h. Changes in BW and BCS were greater (P ≤ 0.05) in LOSS cows compared to MAINT cows. Within samples collected at 0600 h, serum NEFA concentrations were often greater (P < 0.05) in LOSS cows compared to MAINT after Day 14. Serum P4 concentrations were greater (P < 0.05) on Days 21 and 22, and tended (P < 0.10) to be greater on Days 16, 23, and 24 of the study in LOSS cows compared to MAINT. In conclusion, BW loss was associated with increased circulating concentrations of P4 in non-lactating ovariectomized dairy cows; this was mainly attributed to fat mobilization and consequent release of P4 stored in adipose tissues.     

Effects of increasing crude protein concentrations on performance and carcass characteristics of growing and finishing steers and heifers

A 2 × 3 factorial design was utilized to ascertain the effects of three dietary crude protein (CP) concentrations on performance, carcass characteristics, and serum urea nitrogen (SUN) concentration in steers and heifers. Animals were blocked by gender (n = 9) and body weight (BW; n = 3/gender), randomly assigned to a diet containing 110, 125 or 140 g/kg dietary CP (n = 6), subjected to a growing period of 56, 84 or 112 d, depending on start BW, and a finishing period of 84 d. Animals were weighed and bled at 28 d intervals and daily dry matter intake (DMI), average daily gain (ADG), and gain to feed (G:F) were calculated and SUN was analyzed as a repeated measure throughout the study. Following slaughter, carcass data was collected for hot carcass weight (HCW), dressing percent (DP), kidney, pelvic and heart fat (KPH), 12th rib backfat (BF), loin muscle (LM) area, marbling score (MS), and yield grade (YG). Growing steers and heifers were programmed to gain 1.02 and 0.91 kg/d, respectively. Therefore, heifers consumed less than steers and steers gained more than heifers (P<0.01) with no differences in feed efficiency. Dietary CP treatment did not effect DMI, but did result in a quadratic (P=0.04) increase in ADG; thereby quadratically (P=0.06) and linearly (P=0.08) increasing final BW, and G:F, respectively. Finishing heifers consumed and gained less than steers (P<0.01), had lighter HCW (P<0.01) and greater DP (P=0.01) and LM area (P=0.01) than steers. DMI (P=0.02), ADG (P=0.05), HCW (P=0.08), and DP (P=0.06) reacted quadratically with increasing dietary CP. HCW (P=0.02) increased linearly with increasing dietary CP. G:F, KPH, BF, LM area, MS and YG was not affected by dietary CP concentration and G:F, KPH, BF, MS, and YG did not differ between genders. However, there was a gender × dietary CP interaction (P=0.01) for G:F. Steers were the most efficient at 125 g/kg dietary CP, while heifers were most efficient at 140 g/kg dietary CP. Gender had no effect on SUN concentrations, but SUN increased linearly (P<0.01) with increasing dietary CP concentrations. In conclusion, quadratic responses in DMI and ADG indicate that a 125 g/kg dietary CP concentration is optimal for either steers or heifers during the finishing period.     

Serum thyroid hormones and reproductive characteristics of Rambouillet ewe lambs treated with propylthiouracil before puberty

Twenty-four Rambouillet ewe lambs (average weight=43.7+/-1.2 kg, approximately 6 months of age) were used to examine the effect of thyroid suppression before the onset of puberty on serum thyroid hormones, body weights (BW), and reproductive performance. Beginning in early September, ewe lambs were randomly assigned to three treatments (n=8 lambs/treatment). All animals remained in a single pen (4 x 12 m) with access to salt, water, shade and alfalfa hay (2.5 kg per animal per day) throughout the experiment. Beginning on Day 0 (first day of treatment), all ewe lambs received daily treatments (gavage) for 15 days consisting of 0, 20, or 40 mg 6-N-propyl-2-thiouracil(PTU)/kg BW per day. Beginning on Day 15, the 20 and 40 mg treatments were lowered to 10 and 20 mg PTU/kg BW, respectively. All animals were treated for 28 days. Ovarian cyclicity was determined by twice weekly progesterone (P(4)) analysis. Thyroxine (T(4)) concentrations were similar on Day 0 (61.6, 54.8 and 56.9+/-2.5 ng/ml, P=0.17) in ewe lambs receiving 0, 20 and 40 mg PTU/kg BW, respectively. By Day 7, both PTU-treated groups had T(4) values less than 20 ng/ml (9.0 and 15.4+/-2.5 ng/ml) compared with 78.5 ng/ml in controls (P<0.01). By 7 days after termination of PTU treatment, serum T(4) had risen to 29.1 and 26.9 (+/-2.9)ng/ml in the 20/10 and 40/20 PTU groups, respectively. On Day 66, control ewes had 55.0 ng T(4)/ml compared with 43.1 and 39.0 (+/-2.6 ng/ml) for ewes in the 20/10 and 40/20 groups, respectively (linear, P<0.01). Serum triiodothyronine (T(3)) followed a similar pattern to that observed for T(4). Ewe lamb BW were similar (P>0.50) among groups throughout the treatment period. However, following the treatment, PTU-treated ewes tended (P<0.10) to weigh less than controls. Average Julian day of puberty was also similar (P>0.50) among treatments (286, 288 and 288+/-5 days; control, 20/10 and 40/20, respectively). Control ewes had a pregnancy rate of 75%, while both PTU-treated groups had pregnancy rates of 88% (P>0.20). The administration of PTU resulted in a rapid decline in serum T(4) and T(3) but neither time of puberty nor pregnancy rates were affected by lowered thyroid hormones.     

Synchronization of parturition in beef cattle with prostaglandin and dexamethasone

The effectiveness of dexamethasone and prostaglandin in combination for induction and synchronization of parturition in cattle was evaluated in 100 pregnant Angus, Hereford, Charolais and Simmental cows. Cows were distributed equally by breed, day of gestation and cow age to one of three treatments: 1) Control, 2) Dexamethasone (25 mg) plus prostaglandin F(2alpha) (25 mg) or 3) Dexamethasone (25 mg) plus fenprostalene (1 mg). Hormones were administered simultaneously from 275 to 283 d of gestation. Gestation length at calving for control cows differed significantly (P < 0.01) among breeds: Angus, 278.5 +/- 0.9; Hereford, 283.1 +/- 1.1; Charolais, 283.2 +/- 1.5; and Simmental, 285.4 +/- 1.2 d. For hormone-treated cows, 80% of the calves were born between 30 and 46 h after the hormone injections; overall mean was 37.6 +/- 1.1 h. Calving response did not differ (P >0.1) between cows treated with prostaglandin F(2alpha) versus fenprostalene (36.5 +/- 1.6 vs 38.6 +/- 1.6 h) or among cow age, day of gestation, or breed. Also, duration of labor, calving difficulty and calf viability did not differ between calves born at an induced or spontaneous parturition. The incidence of placenta retained for >24 h was higher for induced than spontaneous parturition (21.0 vs 0.0%), but it did not differ (P >0.1) between cows treated with prostaglandin F(2alpha) or fenprostalene (19.2 vs 22.6%). An acceptable degree of synchrony of parturition was attained by the administration of prostaglandin F(2alpha) or fenprostalene in combination with dexamethasone. The higher incidence of retained placenta in treated than control cows did not affect subsequent fertility. The longer biological half-life for fenprostalene than for prostaglandin F(2alpha) provided no improvement in increasing synchrony of parturition or decreasing frequency of retained placenta.     

Effects of various supplements on voluntary intake and performance by growing cattle consuming forage moderate to high in crude protein∗

Growing cattle were supplemented with substances to lessen or increase ruminai ammonia level to determine if consumption of moderate‐ to high‐crude protein (CP) forage is limited by high ruminai ammonia absorption. In Experiment 1 (5 × 5 Latin square), five Holstein steers (198 kg) had ad libitum access to alfalfa cubes (17% CP) without supplementation or with com at 0.25 or 0.75% body weight (BW) alone (LC or HC) or with 0.06% BW of zeolite (chabazite; LC‐Z and HC‐Z). Total daily organic water (OM) intake was not affected by treatment (6.08, 6.14, 6.11, 6.19 and 6.09 kg for control, LC, LC‐Z, HC and HC‐Z, respectively; SE 0.25). In Experiment 2, Simmental crossbred beef calves grazed fescue‐clover paddocks in the srping (clipped forage: 21 to 27% CP) for 84 days and were supplemented with 0.25 or 0.75% BW com alone or with added zeolite (0.06% BW) or lasalocid (0.5 mg/kg BW). Daily gain did not differ among treatments (1.24 to 1.31 kg/day). In Experiment 3 (6×6 Latin square), six Holstein steer calves (168 kg) had ad libitum access to medium‐quality, orchardgrass‐clover hay (15% CP). Steers received one of the following six treatments: no supplement (Control), 0.35% BW ground com (C), com plus 0.049% BW urea (C‐U), 0.35% BW soybean meal (S), 0.205% BW feather meal (F) or 0.103% BW feather meal, 0.052% BW blood meal and 0.067% BW com gluten meal (F‐BG). Total daily OM intake was 5.00, 5.14, 5.00, 5.11, 4.84 and 4.70 kg for control, C, C‐U, S, F and F‐BG, respectively (SE 0.13). In Experiment 4 (6 × 6 Latin square), six Holstein steer calves (226 kg) were fed 0.75% BW of alfalfa cubes (19% CP) plus ad libitum access to medium‐ to high‐quality orchardgrass hay (16% CP). Steers received one of the following six treatments: no supplement (Control), corn at 0.25% BW alone (c) or mixed with 0.12% BW peanut skins (C‐PSK), a mix of high‐CP feedstuffs high in ruminai escape protein (0.029% BW blood meal, 0.038% BW com gluten meal and 0.028% BW feather meal; C‐REP), 0.139% soybean meal (C‐S) or soybean meal plus peanut skins (C‐PSK‐S). Total daily OM intake was 6.16, 6.25, 6.13, 6.52, 6.50 and 6.60 kg for control, C, C‐PSK, C‐REP, C‐S and C‐PSK‐S, respectively (SE 0.10). In conclusion, with forages moderate to high in CP, high ruminai ammonia absorption did not appear to affect feed intake.     

Plasma progesterone response following ACTH administration during mid-gestation in the pregnant Brahman heifer

Previous reports of adrenal progesterone (P4) contributions during late gestation in cattle, and ACTH-induced P4 responses in the non-pregnant heifer, prompted a retrospective investigation to evaluate the plasma P4 response and the relative ratio of plasma cortisol (CT) to P4 following ACTH administration during mid-gestation in pregnant Brahman heifers. Twenty-three pregnant (139.0 +/- 5.0 days of gestation) Brahman heifers received one of the following treatments: 0 (saline; n = 5), 0.125 (n = 4), 0.25 (n = 5), 0.5 (n = 4), or 1.0 (n = 5)IU of ACTH per kg BW. Blood samples were collected at -15 and -0.5 (time 0), 15, 30, 45, 60, 75, 105, 135, 165, 195, and 255-min post-ACTH challenge. Plasma P4 and CT were quantified by RIA. Pre-ACTH P4 did not differ (P > 0.10) among ACTH treatment groups (pooled, 12.1 +/- 0.6 ng/mL). Among peak P4 values at 15-min post-ACTH infusion, control P4 (9.6 +/- 1.2 ng/mL) tended to be lower (P < 0.07) than 0.5 IU ACTH-treated heifers (13.3 +/- 1.1 ng/mL); and were lower (P < 0.02) than 0.25 and 1.0 IU ACTH-treated heifers (14.7 +/- 1.1 and 22.2 +/- 3.7 ng/mL, respectively). During the primary P4 response period (0 to 75-min post-ACTH), the area under the curve (AUC) was greater (P < 0.05) for 1.0 IU ACTH-treated heifers than all other groups. The CT:P4 ratios were lower (time x treatment, P < 0.01) for control heifers than all ACTH-treated heifers. Among ACTH-treated heifers, CT:P4 ratio response and CT:P4 ratio AUC were similar (P > 0.10) following ACTH challenge. In conclusion, acute increases in ACTH elevated plasma P4, likely of adrenal origin, in mid-gestation pregnant heifers, while the CT:P4 ratio (relative output) remained constant irrespective of ACTH dose (0.125-1.0 IU). Whether ACTH-induced increases in P4 in pregnant animals are of physiological significance (e.g., an accessory role in the maintenance of pregnancy during periods of acute stress) remains to be determined.     

交联脲酶聚集体的制备和初步应用

为提高游离脲酶的稳定性,将游离脲酶用硫酸铵沉淀下来后,以戊二醛作为交联剂对其进行化学交联,制备新型的固定化脲酶交联脲酶聚集体,并对其酶学性质进行研究。交联脲酶聚集体的最适pH、最适温度和K_m值分别为：pH 8.0、70℃和0.021 mol/L。在对交联脲酶聚集体的热稳定性,储存稳定性,和对抗蛋白水解酶的能力的研究中,交联脲酶聚集体均显示了比游离脲酶更高的稳定性。为考察其使用效果和稳定性,将其与包醛氧淀粉联合,用于慢性肾衰动物模型的口服治疗。以腺嘌呤灌胃法(每天300mg/kg, 共30d)制备慢性肾衰动物模型,将23只大鼠随机分为模型对照组(每天以10mL/kg蒸馏水灌胃)、单纯包醛氧淀粉组(给予含包醛氧淀粉饲料,10mL/kg蒸馏水灌胃)和包醛氧淀粉+交联脲酶聚集体组(给予含包醛氧淀粉饲料,交联脲酶聚集体悬浮液10mL/kg灌胃),经2周治疗后, 模型对照组、治疗对照组和治疗组实验前后的肌酐含量均有小幅下降,但差异不显著(P值分别为0.922、0.972和0.225＞0.05)。模型对照组的尿素氮含量变化不明显(P=0.211＞0.05)。治疗对照组和治疗组实验前后的尿素氮含量均明显下降(P值分别为0.004和小于0.001,均小于0.01)。治疗对照组和治疗组实验前后的尿素氮含量下降量比较,有显著性差异(P=0.016＜0.05)。治疗组尿素氮含量下降更明显。说明交联脲酶聚集体和包醛氧淀粉联合使用时,对尿素的清除效率比单纯使用包醛氧淀粉更高。     

Growth response, reproductive activity, and serum growth hormone in fine-wool ewe lambs treated with triiodothyronine

Forty-four 6-mo-old, fine-wool ewe lambs were randomly allotted to one of three triiodothyronine (T(3)) treatment groups (14 or 15 ewe lambs/group). Treatments (0, 200, and 400 mug T(3)) were administered daily by subcutaneous injection during a 30-d treatment period in September. Following the treatments, ewe lambs were allowed to mate with Debouillet rams during a 34-d breeding season. Animal weights did not differ (P > 0.10) among treatment groups throughout the study. However, ewe lambs receiving 400 mug T(3)/d gained less (P < 0.05) during the treatment period than did those receiving 200 mug T(3)/d or controls. Grease fleece weights (6-mo clip) were similar (P > 0.10) among treatment groups. Serum growth hormone (GH) values in blood samples collected on Days 7 and 28 of the 30-d treatment were similar (P > 0.10) before treatments were administered and on Day 7 after treatments were administered. However, on Day 28 after treatments were administered, serum GH was lower (P < 0.01) in ewe lambs receiving 400 mug T(3)/d (1.5 ng/ml) than in those receiving 200 mug/d (2.1 ng/ml) or controls (2.2 ng/ml). Ovarian cyclicity was determined by monitoring serum progesterone. Forty percent of control ewe lambs were determined to have cycled during treatment compared with 20% of those receiving 200 mug T(3)/day and none of those receiving 400 mug T(3)/d (P < 0.10). Pregnancy rates were lower (P < 0.10) in ewe lambs receiving 400 mug T(3)/d (29%) compared with those receiving 200 mug T(3)/d (60%) or controls (66.7%). Day of conception, lambs born/ewe exposed, lambs born/ewe lambing, and lambs weaned/ewe lambing did not differ (P > 0.10) among treatments. Preweaning performance of offspring was not altered by maternal treatment with 200 or 400 mug T(3)/d (P > 0.10). These data indicate that 200 and 400 mug T(3)/d will not enhance GH production or improve reproductive performance of ewe lambs.     

Peas (Pisum sativum L.) as an alternative protein source in lamb diets: growth performances,and carcass and meat quality

Thirty weaned Barbaresca lambs were divided into three groups and fed diets that differed in their protein supplement source; the main protein source was soybean meal in SBM diet treatment, totally or partially replaced by peas in P39 and P18 diet treatments, respectively. Soybean meal and peas were present in the diets in the following proportions (on as fed basis): 16:0% (SBM), 0:39% (P39), 9:18% (P18).The diets were of different crude protein content: higher in SBM diet (16.96% DM) than in P39 (14.27% DM) and P18 (15.37% DM). Soluble protein was higher in P39 diet than in the other treatments (36.2, 27.4 and 23.14% CP in P39, P18 and SBM treatments, respectively) while the B₂-protein fraction was lower. The NDF-bound nitrogen was 17.36, 16.87 and 15.06% of crude protein in P39, P18 and SBM diet, respectively. The NDF content was similar among the diets. Growth and slaughter performances were similar among groups (250 g per day versus 219 and 218 g per day respectively in P18, P39 and SBM groups). Carcass fatness was comparable among treatments. Meat pH, colour parameters and cooking losses were comparable among groups. Drip losses were significantly higher (P<0.001) in meat from P39 and P18 than from SBM group. In the present trial, the replacement of soybean meal with peas did not significantly affect growth and slaughter performances and preserved meat quality.     

Reproductive, hormonal and milk characteristics in ewe lambs treated with ovine growth hormone before breeding

One month before a fall breeding season, 30 6-mo-old fine-wool ewe lambs were allotted to one of three treatment groups consisting of either 0, 2.5 or 5 mg ovine growth hormone (oGH) daily for 10 d and then, on alternate days, for an additional 20 d. Five ewes from each treatment group were bled at hourly intervals for 8 h on Days 0 (first day of treatment), 9, 19 and 29. Milk yield and composition were examined on Day 21 post partum. Neither feed intake nor ewe weights differed (P > 0.20) among treatments. Serum insulin did not differ (P > 0.20) among treatments before or during the 5 h following treatment on Day 0 or 29; however, 6, 7 and 8 h after oGH administration, a linear, dose-dependent increase (P < 0.10) in serum insulin was noted. On Day 9, serum insulin differed linearly (P < 0.10) before and after treatment. On Day 19, serum insulin differed (P < 0.10) among the groups 2, 3, 6, 7 and 8 h following oGH treatment. One hour after treatment on Day 0, serum GH increased linearly (P < 0.01) among groups. Serum GH continued to rise 3 h after treatment and remained elevated through Hour 8 in ewes receiving oGH. Serum GH was increased (P < 0.01) before and after oGH administration on Days 9, 19 and 29 in GH-treated ewes. Percentage of ewes that cycled during treatment or breeding as determined by serum progesterone was similar (P > 0.20) among groups. Pregnancy rates did not differ (P > 0.20) in ewe lambs receiving 0 (70%), 2.5 (80%) and 5 (60%) mg oGH. No differences were detected (P > 0.40) in milk yield or composition among treatments. In fine-wool ewe lambs treated with 2.5 or 5 mg of exogenous oGH for 30 d before breeding, neither reproductive performance nor subsequent milk production were enhanced; however, these treatments increased serum GH and insulin.