Time required to determine performance variables and production efficiency of lactating dairy cows.

Thirty-five lactating dairy cows throughout weeks of lactation (WOL) 16 to 30 were used to determine optimal time needed for reliable measurement of performance variables, and to classify the cows into high-, medium-, and low-efficiency groups. Individual performance variables [body weight (BW), dry matter intake (DMI), and milk production] were measured daily with a computerized monitoring system. Body condition was visually scored weekly and used to calculate retained or depleted body energy as a result of fat content change (REF). Milk composition was analyzed weekly. Body weight, DMI, and total recovered energy (RE), which represents energy in milk production plus REF, were summarized weekly. Efficiency was calculated as RE/DMI and as residual feed intake (RFI; i.e., the difference between actual and expected DMI), which was calculated from multiple linear regression of DMI dependence on BW(0.75) and RE. Unexpectedly, it was found that BW did not affect DMI and RE/DMI. Changes and relative changes in phenotypic coefficient of variation and correlations among data from shortened tests ranging from 1 wk (WOL 16) to a sequence of 15-wk tests were used to determine optimal test period durations for 5 traits: BW, DMI, RE, RE/DMI, and RFI. Traits were fitted into a mixed model with repeated measures. For each week, the traits were summarized as a sequence of cumulative data, starting from WOL 16 and cumulated over periods that increased in 1-wk steps up to WOL 16 to 29. Weekly cumulations were compared with those for entire test period (WOL 16 to 30). Consistency of each cow's efficiency classification as high, medium, or low was tested by the total-agreement procedure; the kappa index P-value was used. Throughout WOL 16 to 30, the effects of increasing test period duration on between-animal coefficient of variation differed with respect to the various performance variables and RE/DMI: it tended to change with respect to BW, did not change with respect to DMI, and decreased with respect to RE and RE/DMI. In conclusion, compared with a 15-wk study, a 2-wk study can classify RFI and RE/DMI to 3 efficiency levels, with an individual correlation coefficient of 0.6. When the study was carried out over 3 wk or more, the lowest significant index of the classification was P<0.004, the lowest individual correlation coefficient was 0.65, and its lowest significance was P<0.01. The current study indicated that the insignificant effect of the BW of dairy lactating cows on their DMI should be validated in more studies.

Effect of feeding cows in early lactation with diets differing in roughage-neutral detergent fiber content on intake behavior, rumination, and milk production.

This study measured the effects of including soyhulls as partial roughage replacement in total mixed rations (TMR) fed to 25 pairs of cows during early lactation, on the dry matter (DM) intake, particle kinetics, rumination, in vivo DM and NDF digestibility, milk and FCM yields, and BW changes. The 2 diets used in this study differed in the content of roughage and roughage NDF [23.5 vs. 35.0%, and 12.8 vs. 18.7% in the experimental (EXP) and control (CON) TMR, respectively]. The EXP TMR contained 20.5% less physically effective NDF than the CON TMR (11.7 vs. 14.1% of DM, respectively). These differences were expressed in a greater intake per meal (by 13.3%), a higher rate of meal intake (by 23.2%), a similar number of meals per day, a shorter daily eating duration (by 13%), and a higher total daily DMI (by 7.2%) in the EXP cows as compared with the CON cows. The in vivo DM and NDF digestibility was higher by 4.9 and 22.7%, respectively, in the EXP cows than in the CON cows. The rumination time for the TMR in the EXP cows was 12.7% (54.3 min/d) shorter than in the CON cows, and this was probably related to the difference of 12.4% in physically effective NDF intake between the 2 groups. Patterns of daily rumination and feed consumption throughout an average day showed a delay of approximately 1 to 2 h between the eating and rumination peaks. Particle flow from the rumen of the EXP cows was characterized by a longer rumen mean retention time (by 17.8%) and longer rumination time per kilogram of roughage ingested (by 23.5%) as compared with the CON cows. Thus, favorable conditions for NDF digestion were created in the rumen of the EXP cows, as reflected in their rumen pH values (6.67). The advantage of the EXP cows in intake and digestibility was reflected in a concomitant increase of 7.4% in milk production and of 9.2% in FCM yield as compared with the CON cows. No difference was found between the 2 groups with respect to efficiency of feed utilization for milk production and BW changes.

Consistency of feed efficiency ranking and mechanisms associated with inter-animal variation among growing calves.

This study investigated the possible mechanisms for explaining interanimal variation in efficiency of feed utilization in intact male Holstein calves. Additionally, we examined whether the feed efficiency (FE) ranking of calves (n = 26) changed due to age and/or diet quality. Calves were evaluated during three periods (P1, P2, and P3) while fed a high-quality diet (calculated mobilizable energy [ME] of 11.8 MJ/kg DM) during P1 and P3, and a low-quality diet (calculated ME of 7.7 MJ/kg DM) during P2. The study periods were 84, 119, and 127 d, respectively. Initial ages of the calves in P1, P2, and P3 were 7, 11, and 15 mo, respectively, and initial body weight (BW) were 245, 367, and 458 kg, respectively. Individual dry matter intake (DMI), average daily gain (ADG), diet digestibility, and heat production (HP) were measured in all periods. The measured FE indexes were: residual feed intake (RFI), the gain-to-feed ratio (G:F), residual gain (RG), residual gain and intake (RIG), the ratio of HP-to-ME intake (HP/MEI), and residual heat production (RHP). For statistical analysis, animals' performance data in each period, were ranked by RFI, and categorized into high-, medium-, and low-RFI groups (H-RFI, M-RFI, and L-RFI). RFI was not correlated with in vivo digestibility, age, BW, BCS, or ADG in all three periods. The L-RFI group had lowest DMI, MEI, HP, retained energy (RE), and RE/ADG. Chemical analysis of the longissimus dorsi muscle shows that the L-RFI group had a higher percentage of protein and a lower percentage of fat compared to the H-RFI group. We suggested that the main mechanism separating L- from H-RFI calves is the protein-to-fat ratio in the deposited tissues. When efficiency was related to kg/day (DMI and ADG) and not to daily retained energy, the selected efficient L-RFI calves deposited more protein and less fat per daily gain than less efficient H-RFI calves. However, when the significant greater heat increment and maintenance energy requirement of protein compared to fat deposition in tissue were considered, we could not exclude the hypothesis that variation in efficiency is partly explained by efficient energy utilization. The ranking classification of calves to groups according to their RFI efficiency was independent of diet quality and age.

"Chrono-functional milk": The difference between melatonin concentrations in night-milk versus day-milk under different night illumination conditions.

Pineal melatonin (MLT) is produced at highest levels during the night, under dark conditions. We evaluated differences in MLT-concentration by comparing daytime versus night time milk samples, from two dairy farms with different night illumination conditions: (1) natural dark (Dark-Night); (2) short wavelength Artificial Light at Night (ALAN, Night-Illuminated). Samples were collected from 14 Israeli Holstein cows from each commercial dairy farm at 04:30 h ("Night-milk") 12:30 h ("Day-milk") and analyzed for MLT-concentration. In order to study the effects of night illumination conditions on cows circadian rhythms, Heart Rate (HR) daily rhythms were recorded. MLT-concentrations of Night-milk samples from the dark-night group were significantly (p < 0.001) higher than those of Night-illuminated conditions (30.70 ± 1.79 and 17.81 ± 0.33 pg/ml, respectively). Interestingly, night illumination conditions also affected melatonin concentrations at daytime where under Dark-Night conditions values are significantly (p < 0.001) higher than Night-Illuminated conditions, (5.36 ± 0.33 and 3.30 ± 0.18 pg/ml, respectively). There were no significant differences between the two treatments in the milk yield and milk composition except somatic cell count (SCC), which was significantly lower (p = 0.02) in the Dark-Night group compared with the Night-Illuminated group. Cows in both groups presented a significant (p < 0.01) HR daily rhythm, therefore we assume that in the night illuminated cows feeding and milking time are the "time keeper", while in the Dark-night cows, HR rhythms were entrained by the light/dark cycle. The higher MLT-concentration in Dark-night cows with the lower SCC values calls upon farmers to avoid exposure of cows to ALAN. Therefore, under Dark-night conditions milk quality will improve by lowering SCC values where separation between night and day of such milk can produce chrono-functional milk, naturally rich with MLT.

Effects of fill volume of diets on digestive tract kinetics and fattening pattern of growing Holstein-Friesian bull calves.

Young Holstein-Friesian bull calves were tested in three trials for their performance and digestive tract kinetic responses to diets differing in their fill volume (FV) in the digestive tract. In Trial 1, a high ME (11.7 MJ/kg of DM) diet was compared with three medium ME (10.5 MJ/kg of DM) diets, one of high FV and two of low FV. In Trial 2, two silages (wheat and sorghum), differing in FV, were compared with or without poultry litter inclusion. All the diets in this trial had the same ME content of 10.5 MJ/kg of DM. Rate of gain, DM and ME intake, and depot fat percentage at slaughter were recorded. In Trial 3, two diets (high and low FV) and the same ME content of 10.4 MJ/kg of DM were compared in a short-term trial for digestive tract kinetics using a single dose of Cr-NDF and Co-EDTA as particulate and solute markers, respectively. Calves in Trial 1 fed medium ME and low FV diets had higher (not significant) DMI than high ME calves but similar ADG, whereas medium ME and high FV calves had the lowest DMI (P < .1) and ADG (P < .05). Low FV and medium ME calves were leaner (P < .05) at slaughter than the high ME calves and fatter (not significant) than the high FV and medium ME calves. In Trial 2, reduction of FV by silage replacement increased DMI (P < .01) and ADG (P < .05). Incorporation of poultry litter into the diets resulted in effects in the same direction (not significant). Such a reduction caused increased (P < .01 for both silage end poultry litter effects) deposition of cod fat in the carcass. Mean retention time estimations in Trial 3 indicated increased (P = .055) particle retention time in the low FV calves, compared to the high FV calves. This increase was due to a longer (P = .1) stay of particles in the lower parts of the digestive tract, and not in the rumen. Lowering the FV of medium ME diets increased DMI of calves to support ADG equal to that of a high ME diet, but with a lower fat accumulation.

Comparison of models estimating digesta kinetics and fecal output in cattle from fecal concentrations of single-dosed markers of particles and solutes.

Fecal concentrations of chromium and cobalt, following a single labeling dose of Cr-mordanted fiber and Co-EDTA to the rumen, were obtained from two experiments: one with beef cows fed two diets before and after parturition, and one with growing bull calves fed two diets of high and low fill volume. These data were used to compare three optional models that estimated the whole digestive tract kinetics of particles and solutes and fecal output, with a fourth model that estimated particle kinetics only. The first model (M1) assumes separate routes for particles and solutes, with two bypass fluxes (i.e., simultaneous fluxes from one pool to more than one other pool) in the particle route and one in the solute route. The second model (M2) is similar to M1, but allowance is made for some of the particles to pass to the solute route. The third model (M3) assumes that most of the kinetic variables in the solute route are identical to the correspondent variables in the particle route. The fourth model (M4) assumes an unspecified number of sequential compartments with constant increase of the outflow rate from each compartment to the next one, without allowance for any bypass fluxes. All the models could fit all the data sets. Goodness of fit was the best with M2 and the worst with M3. Goodness of fit of the particle curve with M2 was comparable to that of M4. Model M1 estimated the shortest and M3 estimated the longest total retention time (TRT) for particles (72.8, 85.0, and 91.2 h for M1, M2, and M3, respectively), and the partition of retention time between the different pools differed among models. There were no significant differences among models in their estimates of solute TRT (30.2, 31.5, and 30.8 h for M1, M2, and M3, respectively). Fecal output estimations were similar among models, all of them overestimating the predetermined measurements by 9.5 to 13%. The r2 of the linear regression of the estimated on the determined fecal output was .74, .75, and .70 for M1, M2, and M3, respectively.

Effect of diet energy concentration and of age of Holstein-Friesian bull calves on growth rate, urea space and fat deposition, and ruminal volume.

Holstein-Friesian bull calves were fed diets of three metabolizable energy concentrations: 11.7, 10.9, and 10.0 MJ/kg of DM, and the same content of CP, 145 g/kg. Two trials were carried out. Initial weights were 195 and 180 kg and final weights were 490 and 600 kg for Trials 1 and 2, respectively. The live weight gains (kg/d) were .93, 1.06, and 1.16 in Trial 1 and .98, 1.11, and 1.16 in Trial 2 on the low-, medium-, and high-energy diet, respectively. In Trial 2, measurements were made of ruminal fluid volume and urea space, which expresses the protein mass in the body. Ruminal fluid volume of young calves was high, exceeding 250 mL/kg live weight. Proportional to live weight, it tends to decrease from the age of 213 d to slaughter. It was higher on the lower-energy diet (P < .01). Rate of fat deposition between 250 and 600 kg body weight did not increase even on the diet with 11.7 MJ/kg, although these calves were fatter (P < .05) at slaughter than those on the low-energy diets. The ratios of depot fats (g of fat/kg of hot carcass) in both trials were close for each energy level, in spite of a 100-kg difference in live weight at slaughter. It was 24.0, 29.8, and 40.7 for calves fed low-, medium-, and high-energy diets, respectively, in Trial 1 and 27.7, 37.1, and 40.4, respectively, in Trial 2.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of recombinant bovine somatotropin on dietary energy level-related growth of Holstein-Friesian bull calves.

Our objective for this study was to assess the effect of recombinant bovine somatotropin (rbST) in overcoming the biological effects attributed to live weight increase and age on growth and fat deposition in male cattle. Holstein-Friesian bull calves (n = 56; 182.2 +/- 14.7 d old) were allotted to four subtreatments in a randomized complete block with a factorial arrangement of two levels of rbST: 0 and 500 mg of Posilac, every 2 wk, and two dietary metabolizable energy (ME) concentrations: low metabolizable energy (LME) and high metabolizable energy (HME); 10 vs 11.3 MJ/kg DM, respectively. The effect of rbST treatment on daily gain was expressed mostly on the HME diets. The rbST treatment had no effect on the animals fed the LME diets before the age of 240 d was reached. Dry matter intake and the effect of rbST treatment on DM intake were inversely related to the energy concentration of the diet. The degree of fatness of the animals was significantly reduced by rbST treatment and significantly increased by energy concentration of the diet. The major effect of rbST, under the experimental conditions, in regards to adipose tissue deposition, was on the fat depots and not on the intramuscular fat. The concentration of bST, IGF-I, and insulin in the plasma was increased (P < .001) owing to rbST treatment. Lower metabolizable energy supply led to a higher (P < .001) plasma bST concentration, nonsignificantly lower plasma IGF-I and thyroid hormone concentrations, and lower (P < .001) plasma insulin concentration. A trend (P = .065) toward an increase in PUFA was found in the muscle of the rbST-treated and the HME diet animals. At a young age, when the natural growth potential is high, rbST treatment will be efficient only when a diet allowing a high digestible energy intake is provided.

Estimation of energy expenditure from heart rate measurements in cattle maintained under different conditions.

We examined whether heart rate (HR) could be used to estimate energy expenditure (EE) in cattle. Six Hereford heifers (345 +/- 10.8 kg BW) 12 mo of age were implanted with HR radio transmitters and maintained in individual pens under the following treatments: 1) shade or sun exposure, 2) high- or low-energy diet, and 3) feeding in morning or afternoon. The HR of animals was measured every .5 h during 3 mo; measurements of oxygen consumption and HR were made simultaneously in the morning and in the afternoon while animals were resting and exercising. Average daily HR (52 +/- 4 beats/min) and average daily EE (380 +/- 9 kJ/kg(.75)) in animals on the low-energy diet were less than values in animals on the high-energy diet (94 +/- 4 beats/min and 653 +/- 9 kJ/ kg(.75), respectively). For each animal and within each diet, linear regressions best described the relationship between HR and EE in resting animals, whereas quadratic regressions best described this relationship for exercising animals. The quadratic equation for the exercising animals could also be used for resting animals. In addition, a constant value of EE per heart beat (EE pulse) for each individual resting animal was found and gave accurate estimations. This method was convenient because 1) no exercise equipment was needed to generate the regression equations and 2) EE pulse was less affected by diet than was EE estimated by regression equations. We conclude that HR, a relatively easy measurement, can be useful and accurate in estimating EE. To increase the accuracy of the estimation of EE by HR, the relationship of HR to EE should be established for each animal. In addition, the nutritional regimen for the animal in which EE is estimated should be used for the animal in establishing the relationship.

Dietary effects on fat deposition and fatty acid profiles in muscle and fat depots of Friesian bull calves.

Dietary effects on fat deposition, cholesterol level, and fatty acid profiles of muscle and fat depots in Friesian bull calves were evaluated in two trials. In Trial 1 (eight pens of seven Friesian bull calves), three levels of ME (10.4, 10.9, 11.7 MJ/kg of DM; diets L, M and H, respectively) were offered to three groups of calves throughout the entire experimental period. Calves of the fourth group were fed diet M for the first 80 d and diet L thereafter (Treatment ML). Calves were 185 +/- 15 d of age and 215 +/- 18 kg BW at the start of the trial and were slaughtered when they reached a predetermined equal degree of fatness, in a BW range of 480 to 580 kg, and an age range of 417 to 548 d. In Trial 2, four groups of calves (eight pens of seven Friesian bull calves) had free access to diets of the same ME (11.7 MJ/kg of DM) but that differed in either CP content (11.3 vs 13.4%) or had poultry litter substituted for part of soybean meal at the equivalent CP. Calves were 18o +/- 13 d of age and 240 +/- 19 kg BW at the start of the trial and were slaughtered after 232 +/- 11 d, at 508 +/- 22 kg BW. In both trials, dressing percentages and carcass percentages of kidney, pelvic, and cod fat depots were recorded at slaughter, and samples of the 12th rib longissimus muscle with its subcutaneous fat were obtained for lipid analyses. Increasing the ME concentration shortened the growing period and tended to increase carcass depot fat percentage.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of solar radiation, dietary energy, and time of feeding on thermoregulatory responses and energy balance in cattle in a hot environment.

Ten growing heifers were either exposed to or protected from solar radiation, offered a diet of either high (H) or low (L) ME, and fed either in the morning or afternoon during a hot summer. Heifers that consumed the H diet had a greater water intake, DMI, metabolizable energy intake, energy expenditure, and retained energy than heifers that consumed the L diet. Solar radiation did not have an effect on any of these variables. Furthermore, dietary energy and time of measurement had an effect on rectal temperature (Tr), respiration rate (RR), heart rate (HR), and rate of oxygen uptake (VO2); solar radiation had an effect on Tr and RR but not on HR and VO2; and time of feeding had an effect only on VO2. Heifers coped with greater heat loads by increasing RR and the difference in Tr between morning and afternoon. It seems that a lowered body temperature in the morning is a physiological mechanism used by animals to prepare for the heat load that develops during the day. Heat production (HP) and HR throughout the day were affected mainly by the time of feeding and not by the environmental heat load. Feeding in the afternoon increased HP in the cooler hours of the day when heat losses from the animal through conduction and radiation were more efficient. With a pending high heat load situation, reducing feed quality and(or) changing the time of feeding to the late afternoon could be beneficial to the animals in reducing their heat loads.

The effects of long-term administration of recombinant bovine somatotropin (Posilac) and Synovex on performance, plasma hormone and amino acid concentration, and muscle and subcutaneous fat fatty acid composition in Holstein-Friesian bull calves.

The effect of recombinant somatotropin (rbST), Synovex (Syn), and their combination (rbST+Syn) on intact male calves was examined in an experiment that lasted an average of 238 d. Holstein-Friesian bull calves were allotted to one of four subtreatments (n = 14/treatment) in a factorial arrangement. There were two levels of rbST (0; rbST) and two levels of the estrogenic growth promoter Synovex (0; Syn). The rbST was administered once every 2 wk as injections of 500 mg of Posilac. Synovex (C and S) was implanted at 90-d intervals. The animals were fed for ad libitum consumption a diet with a metabolizable energy concentration of 11.7 MJ/kg DM and 15% crude protein. The hot carcasses were weighed after the removal of kidney, pelvic, and cod fats, which were weighed separately. The 12th rib cut was saved for analysis. Average daily gain and feed conversion efficiency were increased by rbST treatment by 9% (P < .005) and 10% (P < .016), respectively. There was no significant effect of Syn treatment, nor was there a rbST x Syn interaction. The proportion of the fat of the large depots in the carcass was reduced by 34% (P < .0001) and in the longissimus muscle by 32% (P < .16) owing to the rbST treatment. The plasma concentrations of GH, insulin, and thyroxin were increased by rbST treatment (P < .001, P < .01, and P < .03, respectively). The concentration of IGF-I was not affected. Synovex had no effect on plasma hormone concentration. Plasma essential and nonessential amino acid concentrations were reduced by 14 and 9%, respectively, when rbST was injected. Concentrations of cholesterol and fatty acids in muscle and subcutaneous fat were not affected (P > .072) by the rbST treatment. Synovex increased the monounsaturated fatty acids (MUFA), and the combinaton of Syn with rbST reduced polyunsaturated fatty acid (PUFA) concentration in the longissimus muscle (at the 12th rib). The reduced muscle fat content of the rbST-treated animals was associated with a trend toward an increase in polyunsaturated fatty acids.

Acute maduramicin toxicity in calves.

A herd of 277 beef-breed calves in three age groups was mistakenly given the poultry coccidiostat maduramicin in a total mixed ration. It caused an acute toxicosis in which sudden death was the sole clinical finding in most cases. One group of 212 calves aged five to eight months suffered a mortality of 51 per cent in eight days and a total mortality of 56 per cent during the 40 days in which mortality was recorded. Mortality of only 3 per cent was recorded in two other groups of calves aged nine to 16 months in eight days and a total mortality of 11 per cent over the 40-day period.

Foraging behavior of two cattle breeds, a whole-year study: II. Spatial distribution by breed and season.

Spatial distributions of 22 mature large-framed Beefmaster × Simford (BS) cross cows and 16 mature small-framed Baladi (BA) cows were determined. Cows were allocated to the same paddock of a Mediterranean pasture and monitored during 6 consecutive seasons: spring (April 2006), summer (June 2006), autumn (September 2006), winter (February 2007), early spring (March 2007), and summer (June 2007). The locations of the cows were determined at 5-min intervals for 3 to 4 d during each season by using Global Positioning System (GPS) collars. The distances between consecutive locations and the average locations of each breed at each hour of the day in each season were calculated. The Lateral Foraging Index (LFI) was calculated as the ratio between the average distance per day travelled by the cows of each breed and the perimeter of the diurnal itinerary of that breed, which was calculated from its hourly average locations. The 2 breeds maintained similar diurnal patterns of foraging and resting, characterized by morning and afternoon foraging, and resting at midday and during the night. In summer this pattern was more distinctive, with longer resting periods and more intense foraging periods than in winter, when the noon rest was shorter and only partial. The diurnal routes differed (P < 0.001) between the breeds in all seasons, in their locations, their travelling time, or both. The BA cows were more active than the BS cows in all seasons: they travelled longer distances (P < 0.001) and foraged for more hours during the day (P < 0.001). For both breeds the LFI was numerically greater in winter and spring (February, and March) than in summer (June and September), and it was numerically greater for BA than for BS cows in most seasons.

Foraging behavior of two cattle breeds, a whole-year study: I. Heat production, activity, and energy costs.

The foraging behavior and energy costs of activity of 19 large-frame Beefmaster × Simford (BS) cross mature cows and 14 small-frame Baladi (BA) mature cows was determined. Cows were allocated to the same paddock of a Mediterranean pasture and were monitored during 5 seasons throughout 2006 and 2007: spring (April 2006), summer (June 2006), autumn (September 2006), winter (February 2007), and early spring (March 2007). Cows were given poultry litter (25% CP, DM basis) as supplemental feed during autumn only. The cows were fitted for 3 to 4 d in each season with global positioning system (GPS) monitors, activity monitors attached to 1 of their hind legs, and heart rate (HR) monitors harnessed to their chests. Oxygen consumption per heart beat was determined for each cow during each season to enable conversion of the diurnal HR patterns to heat production (HP) units. All GPS data of cattle locations and activity and the HR and HP data were synchronized to produce simultaneous 5-min interval records; step length also was calculated for each record. These records provided summaries of partitioning among activities: lying down, standing, foraging, and walking without foraging as well as horizontal and vertical distances walked per day and number of steps taken per day. These attributes were analyzed using multiple regression models to relate these activities to HP and to estimate specific HP costs per unit of each activity. Accordingly, the daily energy costs of activity were calculated for the 2 cattle types in each season as the product of the specific activity and the number of units of each activity per day. The HP level of the large-frame BS cows was greater than that of the small-frame BA cows in winter and lower in spring (P < 0.001); however, the respective HP levels were much closer in summer and autumn, with BA cows having values greater by 3% than those of BS cows. The BA cows were more active than the BS cows during all seasons: they foraged for more hours per day (P < 0.001) and walked longer distances (P < 0.001). The mean specific costs of activity of BA cows were 20% less than those of BS cows (P < 0.001). The BA cows took longer steps during foraging and walking idle compared with BS cows despite their much smaller frame. The BA cows were more efficient in conditions of low herbage quality whereas metabolic rate of BS cows was greater in conditions of high herbage quality.

Energy cost of activities and locomotion of grazing cows: a repeated study in larger plots.

We determined the energy costs associated with the activities of beef cows grazing on Mediterranean foothill rangeland covered with herbaceous vegetation. Our central aim was to compare the energy cost coefficients obtained in this study, using relatively large plots, with those obtained in a previous study conducted on smaller plots. Measurements were performed in 3 seasons: in March on nursing cows grazing a 135-ha plot of high quality herbage (11.4 MJ/kg of ME), and in May and September on nonlactating cows grazing a 78-ha plot of low quality herbage (6.2 MJ/kg of ME). Poultry litter manure was given as a supplement in September. Stocking rates on the respective plots were 2.25 and 1.95 ha/cow; 5, 5, and 7 cows were monitored in the respective months. Heat production was determined by continuous monitoring of the heart rate and measurement of the oxygen consumption per heartbeat. Animal location was tracked with global positioning system (GPS) collars equipped with motion sensors. Activity was determined for 5-min intervals using suitable calibration equations. Horizontal and vertical distances traveled were computed by integrating GPS data and plot maps in a geographic information system. Three models were used to estimate the energy cost coefficients of engaging in a given activity and locomotion. Total daily heat production ranged from 644 (September) to 1,014 kJ.kg of BW(-0.75).d(-1) (March; P = 0.04). Estimates of the energy cost coefficients for activity states (kJ.kg of BW(-0.75).d(-1)) ranged from 42.7 to 46.2 for standing, from 84.5 to 92.4 for walking idle, and from 89.4 to 103.2 for grazing; those for locomotion (kJ.kg of BW(-0.75).d(-1).km(-1)) ranged from 2.8 to 2.9 for horizontal locomotion and from 21.4 to 27.9 for vertical locomotion. Estimated cost coefficients of standing, grazing, and horizontal locomotion derived in the present study from animals on relatively larger plots were similar to those of the previous study based on data from smaller plots, but the energy costs of walking idle and of vertical locomotion were greater in the present study than in the previous one. The differences found are associated with the fact that cows in the present study walked for longer periods of time and traveled longer distances in single uninterrupted bouts of locomotion than those in the previous study.

Dynamics of offensive gas-phase odorants in fresh and aged feces throughout the development of beef cattle.

Livestock odors are largely caused by several groups of volatile organic compounds (VOC), including sulfur-containing compounds, VFA, and phenols and indoles. Throughout the growth stages of cattle in the nursery and feedlot, distinctly different diets are formulated to meet the changing requirements of the animal. Because diet composition and manure management are 2 major factors affecting odor emissions, it was assumed that changes in diet composition along the development of calves would affect VOC emissions from fresh and stored manure. In this study, the dynamics of gas-phase VOC in feces from 6 Holstein-Friesian bull calves were followed at 5 ages: 1 to 5 wk (stage I), 6 to 8 wk (stage II, before weaning), 9 to 14 wk (stage III, after weaning), and 15 to 36 wk (stages IV and V). The CP content of the formulated diet decreased from 23.0 to 13.9%. Samples of fresh feces were incubated under either aerobic or anaerobic conditions for 21 d. The VOC were analyzed from the feces headspace by solid-phase microextraction, followed by gas chromatography-mass spectrometry. Distinct changes in gas-phase VOC were observed in fresh and aged feces from calves at different ages. Semiquantitatively (based on comparative peak area counts), the following trends were observed: 1) S-containing compounds were the least dominant in fresh feces at the age of 2 wk (stage I), whereas VFA esters were the most dominant. 2) At the age of 7 wk (stage II), 1 wk before calves were weaned, feces seemed to be the most offensive, presumably because of the difficulty of synchronizing the requirements of the animal and the diet formulation during this stage of rapid development. 3) The VOC decreased during storage of feces under aerobic conditions but significantly increased at all 5 life stages during storage under anaerobic conditions. This study demonstrates that life stage and manure management affect odor emissions from beef fattening operations. Incorporation of the age and diet of calves in odor modeling could improve annoyance predictions.

Grazing behavior and energy costs of activity: a comparison between two types of cattle.

The grazing behavior, diet intake, and energy costs of activity of 2 types of cows grazing a Mediterranean pasture were compared. Fifteen large-frame Beefmaster x Simford (BM) cross cows and 13 small Baladi (Ba) mature cows were allocated to the paddock and monitored during 3 seasons throughout 2006; spring (April), summer (June), and autumn (September). Cows were not given supplemental feed during the spring and summer, but had free access to a poultry litter supplement (25% CP, DM basis) during the autumn. Fecal output and digesta kinetics and feed intake were estimated using indigestible double-marker technique. Cows were fitted for 3 to 4 d in each season with global positioning system (GPS) monitors, with activity monitors attached to one of their hind legs, and with heart rate (HR) monitors harnessed to their chests. Oxygen consumption per heart beat was determined for each cow during each season to enable conversion of the diurnal HR patterns to heat production (HP) units. All the GPS data of cattle locations and the activity, HR, and HP data were synchronized to produce a simultaneous record at 5-min intervals. Partition of time spent by the cows lying down, standing, grazing, and walking without grazing, the horizontal and vertical distances walked per day, and the number of steps taken per day were summed from these records. Multiple regression models were adjusted to refer these activities to the HP and to estimate the specific HP costs per unit of each activity. Accordingly, the daily energy costs of activity were calculated for the 2 cattle breeds on each season as the product of the specific activity and the number of units of each activity per day. Feed intake by Ba cows per unit of metabolic BW was greater (P < 0.001) than that of BM cows in both spring and summer and their apparent selection of greater-quality herbage in spring was greater (P < 0.1) than that of BM cows. The smaller framed Ba cows grazed more hours per day and walked longer distances than the BM cows among all seasons. The specific costs for locomotion were less for the Ba cows.

Heat production and retained energy in lactating cows held under hot summer conditions with evaporative cooling and fed two rations differing in roughage content and in vitro digestibility.

The objective of this study was to measure the effect of feeding two total mixed rations (TMRs), differing in their roughage content and in vitro dry matter (DM) digestibility, on the physiological response and energy balance of lactating cows. The partitioning of metabolizable energy intake (MEI) between heat production (HP) and retained energy (RE) of cows held under hot weather conditions and external evaporative cooling was measured. In all, 42 lactating cows were divided into two similar sub-groups, each of 21 animals, and were fed either a control (CON) ration containing 18% roughage neutral detergent fiber (NDF) or an experimental (EXP) TMR containing 12% roughage NDF and used soy hulls as partial wheat silage replacer. The in vitro DM digestibility of the CON and EXP TMR was 75.3% and 78.6%, respectively (P < 0.05). All cows were cooled by evaporative cooling for 2 adaptation weeks plus 6 experimental weeks under hot weather conditions. The EXP diet reduced rectal temperature and respiratory rate of the cows while increasing their DM intake (DMI) from 23.1 to 24.7 kg/cow per day, milk yield from 41.9 to 44.2 kg and yield of energy-corrected milk from 38.7 to 39.7 kg, as compared with the CON group. Cows fed the EXP TMR had increased RE in milk and body tissue, as compared with the CON group, but the diets had no effect on the measured HP that was maintained constant (130.4 v. 130.8 MJ/cow per day) in the two groups. The measured MEI (MEI = RE + HP) and the efficiency of MEI utilization for RE production were also similar in the two dietary groups.

Heart rate measurements as an index of energy expenditure and energy balance in ruminants: a review.

A major part of the ME consumed by ruminants (MEI) is dissipated as heat. This fraction, called heat production or energy expenditure (EE), is assayed largely by measuring O2 consumption (VO2). Conventional measurement of EE in controlled conditions in chambers does not reflect the complexity of natural, environmental, and social conditions of free-ranging animals. In mammals, most of the measured VO2 is transferred to the tissues through the heart; therefore, regression of heart rate (HR) against VO2 can be used to estimate the EE of free-ranging animals. The present article reviews the current knowledge on the use of HR for estimating EE. Energy expenditure can be determined from HR measurements, recorded daily over the course of several days, multiplied by the VO2 per beat. When an animal does not perform significant exercise, a constant value of VO2 per beat [O2 pulse (O2P)] measured over a short period (10 to 15 min) is used; during exercise, O2P increases, and the regression equation of VO2 against HR is used. Under extreme heat load, HR increases to improve heat dissipation, and O2P decreases; therefore, the effect of heat load on O2P needs to be taken into account. Cold stress that doubles heat production does not affect O2P. Heart rate and EE are highly correlated with MEI, but there is significant individual variation in the relationship; therefore, the daily change in the HR of individual animals can be used as an indicator of changes in the individual energy status of a ruminant, and the average HR of the group can serve in the estimation of the energy status of the group. When O2P is measured, the average group EE is an indication of the energy balance of the whole group. Because the MEI of nondraft animals is the sum of EE and retained energy (RE), the MEI of free-ranging ruminants can be determined by measurement of EE by the HR method and adding the RE. Similarly, the RE can be determined without slaughtering the animals from measurements of EE and MEI. Soon when devices for automatic HR monitoring of domestic ruminants become available at a reasonable price, continuous monitoring of HR might provide producers with a sensitive tool for identifying changes in the energy status of their animals. This will also significantly help to shorten the time needed to identify health problems of individual animals.