Interrelationships among voluntary intake, eating and ruminating behavior and ruminal motility of heifers fed corn silage

Six heifers (1/4 Brahman X 1/4 Jersey X 1/2 Angus, 290 kg average weight) with ruminal, duodenal and ileal cannulae given ad libitum access to corn silage with or without 100 mg monensin X head-1 were used to determine interrelationships among behavior, ruminal motility and intake. Voluntary intake was positively related (P less than .001) to eating time, duration of the main morning meal and daily mastication time. Intake was negatively related to unitary times [min X g dry matter-1 X (kg body weight X 75)-1] of eating (P less than .05), rumination (P less than .001), mastication (P less than .001), unitary number of rumination boli (P less than .001), and latency time between termination of morning meal and onset of rumination (P less than .05). Both daily and unitary eating and ruminating time were positively related (P less than .001) to daily and unitary mastication time and unitary number of strong cranio-dorsal ruminal contractions. Positive relationships (P less than .01) were found between mean duration of daily meals, main evening meal and unitary eating time, and between mean duration of rumination periods and unitary ruminating time. Daily and unitary number of rumination boli and mean duration of one bolus were positively related (P less than .01) to unitary ruminating time. Interrelationships between intake, eating and ruminating activities and associated cranio-dorsal ruminal motility were all influenced (P less than .01) by individual heifer, which indicates potential in identifying individuals with better than average mastication behavior and ruminal motility.(ABSTRACT TRUNCATED AT 250 WORDS)     

Site and extent of neutral detergent fiber digestion, efficiency of ruminal digesta flux and fecal output as related to variations in voluntary intake and chewing behavior in heifers

Six heifers (1/4 Brahman x 1/4 Jersey x 1/2 Angus, 290 kg avg wt) with ruminal, duodenal and ileal cannulas were given ad libitum access to a corn silage-based diet with or without 100 mg monensin.hd-1.d-1 in a two-period crossover design. There was no significant effect of monensin on voluntary intake (VI), flow of NDF to the abomasum, fecal output or the efficiency of transfer of NDF to the duodenum (unitary fluxes of NDF through the reticulo-omasal orifice, number.g NDF.(kg BW.75)-1). Monensin increased extent of NDF digestion (NDFD) in the dorsal (P = .07) and ventral (P = .09) ruminal sac. As a fraction of the total tract NDFD, NDFD increased progressively in dorsal rumen (.214), ventral rumen (.548) and duodenal (.818) sites. The VI among individual heifers was negatively related to unitary fluxes of NDF through the reticulo-omasal orifice (P = .001) and to the extent of digestion of potentially digestible NDF (PDNDFD) in the ventral rumen (P = .006) and duodenum (P = .032), but not in the dorsal rumen (P = .720) or in the total tract (P = .785). Fecal output of NDF was negatively related to unitary times of eating (P = .027), ruminating (P = .001), masticating (P = .001) and unitary number of rumination boli (P = .001). These relationships all were influenced (P = .001) by individual heifer.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of monensin on voluntary intake, eating and ruminating behavior and ruminal motility in heifers fed corn silage

Eating and ruminating behavior and associated ruminal motility of six heifers (1/4 Brahman X 1/4 Jersey X 1/2 Angus, 290 kg average weight) given ad libitum access to corn silage with or without 100 mg monensin X head-1 X d-1 were examined according to a two-period crossover design. There was no effect (P greater than .05) of monensin on level of intake, daily and unitary eating, ruminating and masticating times [min X g dry matter-1 X (kg body weight X 75)-1], duration or number of these activity periods, duration of main meals or latency time for onset of rumination following cessation of main eating activities. With the monensin treatment, daily numbers of normal boli and total boli were decreased (P less than .05) and mean duration of one rumination bolus cycle was longer (P less than .05). Analysis of covariance indicated relationships between intake of corn silage and duration of the main morning meal, duration or number of rumination boli and total ruminal contractions were affected (P less than .01) by monensin. Frequency and unitary number of strong cranio-dorsal ruminal contractions were similar for both treatments. During eating, number of contractions per minute was about twice (2.55/min) that during idling and rumination activity (1.43/min and 1.22/min, respectively). The unitary daily number of contractions was negatively (P less than .05) related to level of intake. Total daily ruminal contractions were slightly reduced (-3.96%, P greater than .05) by monensin. Results are interpreted to suggest that monensin indirectly affects rumination through a lowered motility and thereby affects turnover, gut fill and intake.     

Effects of time of day and monensin on the size distribution of particles in digestive tract sites of heifers fed corn silage

Effects of time of day and dietary monensin in the distribution of size of digesta particles in different digestive tract sites and their intersite relationships were examined in six heifers (290 kg BW) with ruminal, duodenal and ileal cannulas given ad libitum access to corn silage, with or without 100 mg monensin.head-1.d-1, in a two-period crossover design. Ingestive masticate and digesta of corn silage were collected via esophageal, ruminal or intestinal cannulas. The distribution of particulate matter retained on sieves with apertures larger than 20 microm was determined by wet-sieving. The cumulative distribution of particulate matter on a series of sieves was regressed on retaining sieve aperture to estimate the sieve aperture that would retain 50% weight of the particulate matter (median retaining aperture, MRA). The MRA of masticate was 6,494 microm. The MRA of digesta particles decreased (P less than .05) from ventral rumen (1,847 microm) to dorsal rumen (1,797 microm) to duodenum (346 microm), but increased to the rectum (359 microm). The MRA was lower (P = .044) for the monensin treatment only in feces. The MRA of particulate matter in the dorsal and ventral rumen, duodenum and rectum all changed (P less than .05) over 24 h. An inverse pattern between the MRA of ruminal and duodenal digesta occurred, presumably the result of a nycterohemeral pattern of eating and ruminating activity. Across sampling times, an inverse relationship existed between MRA of ventral rumen and duodenal digesta. This relationship suggests that a ruminal digesta raft composed of larger particles (immediately following major meals) is more effective than a raft of smaller particles (prior to such meals) in preventing flux of large particles to the duodenum.     

圈养条件下小尾寒羊成年母羊春秋季昼夜行为节律分析

2011年3—5月及8—10月,以山东省临沂市兰山区众合牧业有限公司小尾寒羊种羊场圈养的成年母羊为研究对象,利用24h监控系统,采用目标动物取样法和全事件记录方法,研究了小尾寒羊成年母羊昼夜行为节律。结果显示,小尾寒羊昼夜反刍、卧息、取食、运动、站立与观望、修饰行为及其他行为持续时间依次减少。对小尾寒羊0：00—24：00各时段行为变量分析表明,其取食与反刍行为有2个高峰期,卧息全天都表现比较高的行为持续时间,而高峰期则发生在12：00—14：00。小尾寒羊观望行为有2个高峰期,分别在8：00—10：00及18：00—20：00。按照春秋季节规律特点,以06：00—18：00为白昼,其余时间为夜间。以Mann-Whitney U检验进一步分析圈养条件下小尾寒羊春秋季行为节律特点,结果表明,春秋季节,昼间小尾寒羊母羊在取食与其他行为上存在极显著差异,而夜间在取食、观望与其他行为上存在显著或极显著差异。在春季和秋季昼间与夜间行为对比分析表明,春季除卧息与运动行为外,另外5种行为均存在显著或极显著差异。秋季除卧息、修饰和其他行为外,其余4种行为均存在显著或极显著差异。对春秋季24h行为节律分析发现其取食行为存在极显著差异,运动行为与其他行为存在显著差异。对春秋季小尾寒羊成年母羊昼夜行为节律的研究可为认识圈养条件下小尾寒羊习性、改善小尾寒羊饲养管理与福利条件提供基础资料。     

Heifer development systems: a comparison of grazing winter range or corn residue

Two experiments at 2 Nebraska locations evaluated effects of heifer development system on growth and pregnancy rate. In Exp. 1, heifers (n=270, BW=225 ± 2 kg) grazed winter Sandhills range (WR) or west central Nebraska corn residue (CR) with a supplement (0.45 kg/animal; 31% CP; 80 mg·animal(-1)·d(-1) of monensin). In Exp. 2, heifers (n=180, BW = 262 ± 3 kg) grazed eastern Nebraska WR or CR with a supplement (0.45 to 0.90 kg/d; 31% CP; 80 to 160 mg·animal(-1)·d(-1) of monensin). The CR heifers tended to have less (P=0.10) ADG compared with WR heifers before breeding in Exp. 1; however, prebreeding ADG was similar (P=0.77) in Exp. 2. Prebreeding BW, percentage of mature BW at breeding, and pregnancy determination BW were similar (P ≥ 0.14) for CR and WR in both experiments. Percentage of heifers pubertal at breeding, AI conception, and AI pregnancy rate (Exp. 2) and final pregnancy rate in both experiments were also similar (P ≥ 0.27) for CR and WR heifers. Precalving BW, percentage of calves born in the first 21 d, calf birth date, calf birth BW, and dystocia score were all similar (P ≥ 0.21) for CR and WR heifers in both experiments. Cow BW at weaning, calf weaning BW, adjusted 205-d calf BW, and second season pregnancy rates were not affected (P ≥ 0.16) by treatment. Heifer development system did not affect (P ≥ 0.56) the cost of producing 1 pregnant heifer in Exp. 1 or 2. Development on CR may reduce ADG before breeding, but did not affect pregnancy rate. Heifer development using CR or WR postweaning resulted in similar reproductive performance and development cost.     

圈养条件下梅花鹿初夏昼间行为节律

2006年4月3日至5月27日,以江苏省扬州市瘦西湖景区平山堂养殖场圈养梅花鹿（sikadeer）为研究对象,采用扫描取样法（Scansampling）和全事件记录方法（All-occurrence recording）,研究了34只梅花鹿行为节律。结果表明：初夏昼间梅花鹿取食、卧息、观望、反刍、移动、修饰行为频次依次减少,取食和卧息行为频次占昼间行为的68%。昼活动节律中,取食频次有两个高峰期,分别在7：30和17：30左右。而反刍和卧息行为频次高峰期在11：00～14：00之间。对公鹿、母鹿和幼鹿群体取食和卧息行为频次分析表明,在11：30～12：30、13：30～14：30和15：30～16：30三个时间段内,公鹿取食频次和母鹿、幼鹿取食频次差异显著,在8：30～9：30和11：30～12：30及15：30～17：30连续时间段内,公鹿的卧息行为频次与母鹿和幼鹿卧息行为频次差异显著。本结论可为梅花鹿饲养管理和遗传选育提供基础理论依据。     

Effects of dietary nonstructural carbohydrates and protein sources on feeding behavior of tethered heifers fed high-concentrate diets

To describe the feeding behavior of growing heifers fed high-concentrate diets with different sources of protein and nonstructural carbohydrates, and to explain the ruminal fermentation pattern, 4 ruminally fistulated Holstein heifers (BW = 132.3 +/- 1.61 kg) were assigned to a 4 x 4 Latin square design with a 2 x 2 factorial arrangement of treatments. Two non-structural carbohydrate sources (barley and corn) and 2 protein sources [soybean meal (SBM) and sunflower meal (SFM)] that differ in their rate and extent of ruminal degradation were combined, resulting in a synchronized, rapid fermentation diet (barley-SFM), a synchronized, slow fermentation diet (corn-SBM), and 2 unsynchronized diets consisting of a rapidly and a slowly fermenting component (barley-SBM and corn-SFM). The corn-SFM diet resulted in a lower frequency of feeding (P < or = 0.05), longer meal length (P < or = 0.043), and larger meal size (P < or = 0.037) than the other 3 diets. Dietary treatment had no effect (P > or = 0.09) on the daily percentages of posture and behaviors. In general, heifers spent 9.97 +/- 0.83% of the day eating, 2.11 +/- 0.42% drinking, 25.13 +/- 1.36% ruminating, 16.97 +/- 1.42% in other activities such as social behavior and self-grooming, and the rest of the day (45.82 +/- 2.55%) resting or doing no chewing activities. Eating, drinking, and social behaviors were performed while standing (P < or = 0.01), whereas resting and ruminating occurred mainly while lying (P = 0.001). Eating took place mainly in the first 4 h after feeding (P = 0.001), whereas ruminating occurred mainly at night (P = 0.001). When chewing activities (eating and ruminating) were expressed per kilogram of DM or NDF from roughage intake, more time (P = 0.004) was spent chewing per kilogram of DMI for barley-based diets, and per kilogram of NDF from roughage intake for barley- (P = 0.01) and SFM- (P = 0.002) based diets. Tethered heifers fed the more fermentable and rapidly synchronized diet (barley-SFM) reduced intake and increased chewing time. With these high-concentrate diets, time spent chewing was inversely related to roughage intake.     

Bovine saccocystosis: patholgic features of naturally occurring infection with Sarcocystis cruzi.

Naturally occurring bovine sarcocystosis caused death and illness in eight dairy heifers. Clinical disease was characterized by cachexia, peripheral lymph node enlargement, and anemia. Increased amounts of serum enzymes and anti-Sarcocystis antibody titers were present in affected animal. Macroscopic findings in two heifers at necropsy included emaciation and serous atrophy. Necropsied heifers (No. 1 and 2) contained different developmental stages of Sarcocystis cruzi; each stage was characterized by specific histopathologic findings. Heifer 1 had vascular endothelial schizonts in various soft tissues, with mild mononuclear cell infiltration, alveolar capillary fibrinous thrombi, and multifocal splenic necrosis. Heifer 2 had developing young S cruzi cysts, in myofibrils of cardiac and skeletal muscles, with a concurrent multifocal degenerative myositis. Marked lymphoid hyperplasia occurred in both heifers.     

Effects of Prenatal Androgenization and Implantation on the Performance and Carcass Composition of Lactating Heifers in the Single-Calf Heifer System

Two experiments were conducted to evaluate feedlot performance of heifers and calves and the lactational characteristics and carcass composition and quality of heifers while in the single-calf heifer (SCH) system. In Exp. 1, 24 lactating Angus × Holstein heifers were slowly adapted to an 85% concentrate diet, and one-half of the heifers were implanted with Finaplix-H®, both at 11 wk postpartum. Heifer-calf pairs were then placed in feedlot pens, equipped with pinpointer feeding devices, and fed an 85% concentrate diet for 102 d. The control (C) and implanted (I) heifers had similar (P=0.27) daily gains and similar (P=0.30) DMI; however, I heifers consumed 8.9% less (P<0.05) DM as a percentage of BW. Pair efficiency of feed conversion tended to be higher (P<0.09) for I heifers than for C heifers. Hot carcass weight tended to be higher (P<0.10) for the I heifers. Ribeye area was 13% greater (P<0.05) and marbling score was 8.7% lower (P<0.01) for the I heifers than for the C heifers. In Exp. 2, 26 lactating Angus × Simmental heifers were used in the SCH system. Heifer adaptation to a high concentrate diet began 3 to 4 wk prepartum. Two to 3 d postpartum, 16 control (C) and 10 prenatally androgenized (PA) heifer-calf pairs were weighed, and eight C and five PA heifers were implanted with Synovex-H®. They were then placed in feedlot pens equipped with pinpointer feeding devices. By 1 wk postpartum, all heifers were adapted to an 85% concentrate diet and fed until they possessed approximately 1.1 cm s.c. fat cover over the 12th and 13th ribs. Heifers were slaughtered 12 h postweaning. The PA heifers tended to consume more (P<0.11) DM than C heifers. Gain:feed (G:F) was similar (P=0.35) for the C and PA heifers; however, the C heifers tended to have an improved (P<0.08) pair G:F. Heifer G:F and pair G:F were both similar (P=0.53) for the I and nonimplanted heifers. Most carcass measurements were unaffected by treatment; however, the I heifers tended to have higher marbling scores (P<0.07).     

Characterizing rumination patterns of dairy cows using spectral analysis

Spectral analysis techniques were used to characterize the cyclical variation in rumination behavior of cows. Four Holstein cows were fed twice daily a diet of 60% high-moisture shelled corn-based concentrate, 15% first-cut alfalfa-grass hay and 25% second-cut alfalfa silage. The number of minutes that each cow spent ruminating was determined for 15-min intervals during six consecutive days. Rumination data then were characterized using Fourier harmonic analysis to decompose the total sum of squares into 288 orthogonal components due to different rumination wavelengths. Rumination patterns for all cows consisted mainly of wavelengths that were harmonics of a 24-h cycle, indicating a circadian pattern of rumination. Differences in rumination patterns between cows occurred mainly at wavelengths of less than 2 h. Rumination patterns of two of the four cows were more complex, and consisted of high-frequency, non-24-h harmonic wavelengths in addition to the circadian pattern. Spectral analysis can be used to identify the component cycles of rumination patterns of individual animals, which can then be used to determine the effects of dietary or other manipulations on rumination behavior.     

Effect of copper source and level on performance and copper status of cattle consuming molasses-based supplements

Two studies were conducted to evaluate the availability of dietary Cu offered to growing beef cattle consuming molasses-based supplements. In Exp. 1, 24 Braford heifers were assigned randomly to bahiagrass (Paspalum notatum) pastures (two heifers/pasture). Heifers were provided 1.5 kg of TDN and 0.3 kg of supplemental CP/heifer daily using a molasses-cottonseed meal slurry. Three treatments were randomly assigned to pastures (four pastures/treatment), providing 100 mg of supplemental Cu daily in the form of either CuSO4 (inorganic Cu) or organic-Cu. A third treatment offered no supplemental Cu (negative control). Heifer BW was collected at the start and end of the study. Jugular blood and liver samples were collected on d 0, 29, 56, and 84. In Exp. 2, 24 Brahman-crossbred steers were fed the same molasses-cottonseed meal supplement at the same rates used in Exp. 1. Steers were housed in individual pens (15 m2) with free-choice access to stargrass (Cynodon spp.) hay. Four Cu treatments were assigned to individual steers (six pens/treatment) providing 1) 10 ppm of Cu from an organic source; 2) 10 ppm Cu from Tri-basic Cu chloride (TBCC); 3) 30 ppm of Cu from TBCC; or 4) 30 ppm of Cu, a 50:50 ratio of TBCC and organic Cu. Body weights and jugular blood and liver samples were collected on d 0, 24, 48, and 72. In Exp. 1, liver Cu concentrations did not differ between heifers supplemented with inorganic and organic Cu. Each source resulted in increased (P < 0.05) liver Cu concentrations compared with the unsupplemented control. Plasma ceruloplasmin concentrations were higher (P < 0.05) for Cu-supplemented heifers, independent of Cu source. Heifer ADG tended (P = 0.11) to increase with Cu supplementation compared with the unsupplemented control. In Exp. 2, liver Cu was greater (P < 0.05) on d 24, 48, and 72 for steers consuming 30 vs. 10 ppm of Cu. Steers supplemented with organic Cu had lower DMI than steers supplemented with 10 or 30 ppm of TBCC. These data suggest that the inorganic and organic Cu sources evaluated in these studies were of similar availability when offered in molasses supplements. A dietary Cu concentration greater than 10 ppm might be necessary to ensure absorption in beef cattle fed molasses-based supplements.     

Fragmentation and ruminal escape of particles as related to variations in voluntary intake, chewing behavior and extent of digestion of potentially digestible NDF in heifers

The distribution of particles of differing sizes in ruminal, duodenal and fecal samples, the efficiency of particle breakdown and ruminal escape and their relationships to voluntary intake, chewing behavior and extent of digestion of potentially digestible NDF were examined in six heifers (290 kg average BW) with ruminal, duodenal and ileal cannulas. Animals had ad libitum access to corn silage, with or without 100 mg monensin head-1.d-1, in a two-period crossover design. Variations in voluntary intake by individual animals were positively related to size of digesta particles (median retaining aperture, MRA) in the dorsal rumen (P = .07) and rectum (P = .08), but not to MRA of particulate matter from the ventral rumen and duodenum. No significant relationships existed among eating or ruminating activities and distribution of particles of differing sizes in digesta from any of the digestive sites. The MRA of particulate matter in duodenal and rectal digesta were negatively related (P = .08 and P = .10) to extent of digestion of potentially digestible NDF (PDNDF) at these sites. Voluntary intake was related positively to efficiency of ruminative degradation of digesta particles appearing at the duodenum (P = .09) and to duodenal DM digesta flow per opening of the reticulo-omasal orifice (ROO; P = .02), the latter being negatively related to extent of digestion of PDNDF in duodenal digesta (P = .09). These results suggest that animals with higher intake capability are more efficient ruminators and can partially override constraining factors of particle size and byoyancy and thereby achieve a larger amount of DM flowing per opening of the ROO.     

Effect of induction of late embryonic mortality on plasma profiles of pregnancy associated glycoprotein 1 in heifers

Inoculation with Actinomyces pyogenes and administration of prostaglandin (PG)F(2alpha) were used to induce late embryonic mortality (LEM) in heifers (n=8) on Days 30-38 of pregnancy in order to compare the profile for bovine pregnancy associated glycoprotein 1 (PAG1), progesterone and 15-keto-13,14-dihydro-PGF(2alpha) (PGFM). Two pregnant heifers were used as controls. Inoculation into the uterine body caused LEM, as established by ultrasonography in each heifer within 24h of treatment. When the inoculum was injected into the first part of the cervix, LEM occurred in one of two heifers (Heifer A) between 48 and 72 h after treatment. Similarly, PGF(2alpha) treatment caused LEM in three of four heifers. In six of eight heifers, PAG1 started to decrease steadily when it was accompanied by the subsequent death of the embryo. Inoculation through the cervix caused luteolysis in three of four heifers within 6-10 days after induction. After induction of LEM, PGFM concentrations showed a two to 3.8 fold increase in three of four heifers during the following six days, and from that time changed within normal ranges. The results of this study indicate that a PAG1 assay may provide an alternative method to ultrasonography for determining LEM in the cow.     

Effects of tribasic copper chloride versus copper sulfate provided in corn-and molasses-based supplements on forage intake and copper status of beef heifers

The objective of this study was to investigate the effect of supplemental tribasic copper chloride (Cu(2)(OH(3))Cl; TBCC) vs. Cu sulfate (CuSO(4)) on Cu status and voluntary forage DMI in growing heifers. Two 90-d experiments were conducted using 48 non-pregnant, crossbred heifers (24 heifers/experiment; 355 +/- 10.7 and 309 +/- 9.9 kg for Exp. 1 and 2, respectively). In each experiment, 3 supplemental Cu treatments were randomly allocated to heifers in individual pens consisting of (1) 100 mg of Cu/d from CuSO(4), (2) 100 mg of Cu/d from TBCC, or (3) 0 mg of Cu/d. The 2 experiments differed by the form of supplement used to deliver the Cu treatments (corn- vs. molasses-based supplements for Exp. 1 and 2, respectively). Supplements were formulated and fed to provide equivalent amounts of CP and TDN daily but differed in their concentration of the Cu antagonists, Mo (0.70 vs. 1.44 mg/kg), Fe (113 vs. 189 mg/kg), and S (0.18 vs. 0.37%) for corn- and molasses-based supplements, respectively. All heifers were provided free-choice access to ground stargrass (Cynodon spp.) hay. Jugular blood and liver biopsy samples were collected on d 0, 30, 60, and 90 of each experiment. Heifer BW was collected on d 0 and 90. Heifer ADG was not affected by Cu treatment (average = 0.22 +/- 0.11 and 0.44 +/- 0.05 kg for Exp. 1 and 2, respectively; P > 0.20). In Exp. 1, heifers provided supplemental Cu, independent of source, had greater (P < 0.05) liver Cu concentrations on d 60 and 90 compared with heifers provided no supplemental Cu. In Exp. 2, average liver Cu concentrations were greater (P = 0.04) for heifers receiving supplemental Cu compared with heifers receiving no Cu; however, all treatments experienced a decrease in liver Cu concentration over the 90-d treatment period. Plasma ceruloplasmin concentrations did not differ in Exp. 1 (P = 0.83) but were greater (P = 0.04) in Exp. 2 for heifers receiving supplemental Cu compared with heifers receiving no Cu. In Exp. 1, voluntary forage DMI was greater (P < 0.05) for heifers provided supplemental Cu, independent of source, compared with heifers provided no Cu. In contrast, voluntary forage DMI was not affected (P > 0.10) by Cu supplementation in Exp. 2. These data imply that CuSO(4) and TBCC are of similar availability when offered to growing beef heifers in both corn- and molasses-based supplements. However, corn- and molasses-based supplements appear to affect Cu metabolism differently. These impacts may affect voluntary forage DMI in growing beef heifers.     

Ultrasonographic evaluation of reticular motility during rest, eating, rumination and stress in 30 healthy cows

A 3.5 MHz linear transducer was used to assess the motility of the reticulum in 30 healthy, standing, non-sedated cows while they were at rest, eating, ruminating and under stress. The ultrasonographic examinations were made over periods of nine minutes and video recorded for analysis. The reticulum contracted in a biphasic pattern while the cows were resting, eating or stressed. The first contraction was incomplete and was followed by a period of incomplete relaxation. A complete second contraction occurred immediately afterwards, followed by an interval of complete relaxation and the return of the organ to its original position. When the cows were ruminating, a regurgitation contraction, which was incomplete, occurred immediately before the biphasic contraction. The number of reticular contractions in a nine-minute period was largest when the cows were eating (13.9 contractions, or approximately 1.5 per minute) and smallest when they were stressed (9.3 contractions, or approximately 1 per minute). The duration of the first reticular contraction was shortest during rumination (2.4 seconds) and longest when the cows were eating (3.0 seconds). The interval between two biphasic contractions was shortest when the cows were eating (31.6 seconds) and longest when they were stressed (53.8 seconds).     

Characteristics of protein-protease inhibitors, 17-beta estradiol and progesterone in the blood of heifers returning to estrus following LH/FSH-RH treatment]

Tests were performed to study the inhibitive capacity of protein-protease inhibitors, 17-beta estradiol, and progesterone in the blood serum of 21 heifers returning to oestrus which had been treated intramuscularly with 400 microgram LH/FSH-RH. Four selected heifers were examined as to the relationships between the concentrations of 17-beta estradiol, progesterone and the inhibitive capacity of the serum. Heifer no. 1 had low concentrations of 17-beta estradiol and higher concentrations of progesterone (average levels 7.8 and 657.4 pg ml-1 of serum). On the other hand, heifer no. 4 was found to have higher concentration of 17-beta estradiol and lower values of progesterone (average levels 28.3 and 325 pg ml-1 of serum). Having shown heat, the heifers were fertilized and remained in calf. Heifer no. 2 with a low concentration of progesterone (292 pg ml-1 of serum) and 17-beta estradiol (12.4 pg ml-1 of serum), as well as heifer no. 3 with a high concentration of both (830 pg ml-1 of serum and 22.7 pg ml-1 of serum, respectively) showed no heat and they were not mated. Heifers with significant differences in the concentrations of progesterone and 17-beta estradiol and with low values of protein-protease inhibitory capacities remained in-calf, whereas heifers with lower progesterone and 17-beta estradiol values, or adversely, with higher inhibition values, showed no heat. Synthetic LH/FSH-RH was found not to increase the amount of protein-protease inhibitors in heifer serum, as distinct from the cervical mucus of breeding cows treated with gestagens in heat synchronization.     

Oviposition patterns and plasma melatonin rhythms in response to manipulations of the light: Dark cycle

1. In 2 experiments with Single Comb White Leghorn hens, the effects of different light:dark cycles (LD-cycles) upon oviposition patterns and plasma melatonin rhythms were studied. In experiment 1, a 28-h ahemeral LD-cycle (12L:16D) was used. In experiment 2, a normal 24-h LD-cycle (16L:8D) was applied and the effects of a sudden 8-h forward or backward shift of the 8-h dark period (that is phase-advanced or phase-delayed LD-cycle) were studied. 2. The oviposition patterns as well as the plasma melatonin rhythms were fully synchronised with both LD-cycles (24-h or 28-h). The 2 rhythms were gradually re-synchronised after phase shifts, and the melatonin response phase-led the oviposition response by 2 cycles. Thus, the change of the melatonin rhythm coincided with the change of the (presumed) open period for LH-release. 3. In the unchanged 24-h LD-cycle, ovipositions occurred almost exclusively (98.9%) during light hours, whereas in the 28-h LD-cycle, ovipositions occurred primarily (84.5%) during the last 9 h of the dark period. 4. In both LD-cycles and after changes of the LD-cycle, light always suppressed plasma melatonin, regardless of previous light history. During dark periods, concentrations were elevated but, interestingly, only if darkness had also been experienced during the same time period 24 h earlier. This indicates that light has a direct inhibiting effect upon pineal melatonin release, while actual melatonin release during darkness is controlled by an endogenous clock.     

苜蓿干草切割长度对荷斯坦育成母牛采食与反刍行为和营养物质消化的影响

试验以3头8～10月龄、平均体重(300±22.4)kg的荷斯坦育成母牛为试验动物,采用3×3拉丁方试验设计,对2、4cm和自然全长3种理论切割长度的苜蓿干草对育成母牛采食与反刍行为和日粮营养物质消化的影响进行了研究。结果表明:随着苜蓿干草长度的增加,苜蓿干草采食时间、日粮采食时间、反刍时间、咀嚼时间明显增加(P<0.05);每日采食次数和每次采食的干物质采食量明显降低(P<0.05)。除苜蓿干草以外的日粮其他组分的采食时间、日粮采食时间与反刍时间的比例、日粮常规营养物质的消化率基本不受苜蓿干草长度的影响(P>0.05)。     

重复超排对育成牛繁殖力影响的研究

实验探讨了重复超排对育成牛繁殖力的影响。结果表明:(1)经1～3次重复超排后14～16月龄育成荷斯坦牛自然发情后人工授精(3次以内),超排1次组、超排2次组和超排3次组妊娠率分别为96.25%、91.67%和95.29%,与对照组(未超排组)妊娠率为94.74%均无显著差异(P>0.05)(;2)超排处理后恢复期为5～10d组的妊娠率为50.0%,低于恢复期为30～40d组66.67%和恢复60～80d组60.47%的移植妊娠率,但差异不显著(P>0.05);(3)不同超排次数胚胎移植妊娠率分别为超排1～2次组63.27%、3～4次组61.11%、5～6次组57.14%,差异不显著(P>0.05)。重复超排后奶牛胚胎移植妊娠率随超排次数的增加有下降趋势,但与对照组(未超排组)62.50%的妊娠率无显著差异。