Associations between feed efficiency,sexual maturity and fertility-related measures in young beef bulls

The beef industry has emphasized the improvement of feed utilization, as measured by modeling feed intake through performance traits to calculate residual feed intake (RFI). Evidence supports an inverse relationship between feed efficiency and reproductive function. The objective of this study was to determine the relationship of reproductive assessments and RFI unadjusted (RFI_Koch) or adjusted for body composition (RFI_us) and the relationship among fertility-related parameters. In total, 34 crossbred bulls were housed together for 112 days of performance evaluation, followed by assessment of scrotum IR imaging, scrotal circumference, testes ultrasonography and semen quality parameters at 377±33.4 days of age. Bulls were slaughtered at 389±34.0 days of age, and analyses of carcass composition, biometrics and histomorphometry of the testis and epididymis were conducted. Bulls were grouped into two subpopulations based on divergence of RFI, and within each RFI model either by including 50% of the population (Halves, high and low RFI, n=17) or 20.6% extremes of the population (Tails, high and low RFI, n=7). The means of productive performance and fertility-related measures were compared through these categories. Pearson’s correlation was calculated among fertility-related measures. In the Halves subpopulation of the RFI_us, sperm of low-RFI bulls had decreased progressive motility (47.30% v. 59.90%) and higher abundance of tail abnormalities (4.30% v. 1.80%) than that of high-RFI bulls. In the Tails subpopulation of the RFI_Koch, low RFI displayed less variation in the scrotum surface temperature (0.62°C v. 1.16°C), decreased testis echogenicity (175.50 v 198.00 pixels) and larger (60.90 v. 56.80 mm²) but less-developed seminiferous tubules than high-RFI bulls. The evaluation of fertility-related parameters indicated that a higher percentage of immature seminiferous tubules was correlated with occurrence of sperm with distal droplets (r=0.59), a larger temperature variation at the top of the scrotum was correlated with improved sperm progressive motility (r=0.38), a lower occurrence of sperm loose head abnormalities was correlated with larger temperature variation at the lower part of the scrotum (r=−0.43), and a lower minimum testis echogenicity (r=−0.59) and smaller scrotal circumference (r=0.72) were correlated with age. The adjustment for body composition (RFI determination) enabled distinct biological inferences about reproduction and feed efficiency when compared with the non-adjusted model. However, both RFI models and the correlation analysis supported the hypothesis that feed-efficient bulls have features of delayed sexual maturity. Overall, the assessment of fertility-related measurements is important to avoid the improvement of feed efficiency at the expense of reproductive function in young bulls.     

Digestibility contributes to between-animal variation in feed efficiency in beef cows

Residual feed intake (RFI) is an alternative measure of feed efficiency (FE) and is calculated as the difference between actual and expected feed intake. The biological mechanisms underlying animal-to-animal variation in FE are not well understood. The aim of this study was to investigate the digestive ability of beef cows selected for RFI divergence as heifers, using two contrasted diets. Fifteen 4-year-old beef cows were selected from a total of 69 heifers based on their RFI following the feedlot test. The selected heifers were ranked into high-RFI (+ 1.02 ± 0.28, n = 8) and low-RFI (−0.73 ± 0.28, n = 7), and a digestibility trial was performed after their first lactation. Both RFI groups were offered two different diets: 100% hay or a fattening diet which consisted of a DM basis of 67% whole-plant maize silage and 33% high starch concentrates over four experimental periods (two per diet). A diet effect was observed on feed intake and apparent digestibility, whereas no diet × RFI interaction was detected (P > 0.05). Intake and apparent digestibility were higher in cows fed the fattening diet than in those fed the hay diet (P < 0.0001). DM intake (DMI) and organic matter apparent digestibility (OMd) were repeatable and positively correlated between the two subsequent periods of measurements. For the hay and fattening diets, the repeatability between periods was r = 0.71 and r = 0.73 for DMI and r = 0.87 and r = 0.48 for OMd, respectively. Moreover, both intake (r = 0.55) and OMd (r = 0.54) were positively correlated (P < 0.05) between the hay and fattening diets. Significant differences between beef cows selected for divergence in RFI as heifers were observed for digestive traits (P < 0.05), DM and organic matter (OM) apparent digestibility being higher for low-RFI cows. Overall, this study showed that apparent digestibility contributes to between-animal variation in FE in beef cows.     

Vertical transmission of Anaplasma marginale in cattle

Ten Hereford heifers in the third trimester of gestation and negative for Anaplasma marginale complement fixing (CF) antibody titers were used in this study. Six of the 10 heifers were inoculated with blood from a known anaplasma carrier animal. Four heifers served as uninoculated controls. Four fetuses from the principal heifers and 3 from control heifers were surgically recovered. All fetuses were alive at the time of surgical recovery. One inoculated heifer delivered a dead autolyzed fetus and one delivered a live healthy calf. One control heifer delivered a live healthy calf. Blood from 4 fetuses and 1 calf recovered from the inoculated heifers was subinoculated into splenectomized CF negative calves. Two of 5 subinoculated calves developed anaplasmosis. This study provides evidence of vertical (transplacental) transmission of Anaplasma marginale in pregnant heifers in the last trimester of gestation.     

Grazed grass herbage intake and performance of beef heifers with predetermined phenotypic residual feed intake classification

Data were collected on 85 Simmental and Simmental × Holstein–Friesian heifers. During the indoor winter period, they were offered grass silage ad libitum and 2 kg of concentrate daily, and individual dry matter intake (DMI) and growth was recorded over 84 days. Individual grass herbage DMI was determined at pasture over a 6-day period, using the n-alkane technique. Body condition score, skeletal measurements, ultrasonic fat and muscle depth, visual muscularity score, total tract digestibility, blood hormones, metabolites and haematology variables and activity behaviour were measured for all heifers. Phenotypic residual feed intake (RFI) was calculated for each animal as the difference between actual DMI and expected DMI during the indoor winter period. Expected DMI was calculated for each animal by regressing average daily DMI on mid-test live weight (LW)^0.75 and average daily gain (ADG) over an 84-day period. Standard deviations above and below the mean were used to group animals into high (>0.5 s.d.), medium (±0.5 s.d.) and low (<0.5 s.d.) RFI. Overall mean (s.d.) values for DMI (kg/day), ADG (kg), feed conversion ratio (FCR) kg DMI/kg ADG and RFI (kg dry matter/day) were 5.82 (0.73), 0.53 (0.18), 12.24 (4.60), 0.00 (0.43), respectively, during the RFI measurement period. Mean DMI (kg/day) and ADG (kg) during the grazing season was 9.77 (1.77) and 0.77 (0.14), respectively. The RFI groups did not differ (P > 0.05) in LW, ADG or FCR at any stage of measurement. RFI was positively correlated (r = 0.59; P < 0.001) with DMI during the RFI measurement period but not with grazed grass herbage DMI (r = 0.06; P = 0.57). Low RFI heifers had 0.07 greater (P < 0.05) concentration of plasma creatinine than high RFI heifers and, during the grazed herbage intake period, spent less time standing and more time lying (P < 0.05) than high RFI heifers. However, low and high RFI groups did not differ (P > 0.05) in ultrasonic backfat thickness or muscle depth, visual muscle scores, skeletal size, total tract digestibility or blood hormone and haematology variables at any stage of the experiment. Despite a sizeable difference in intake of grass silage between low and high RFI heifers during the indoor winter period, there were no detectable differences between RFI groupings for any economically important performance traits measured when animals were offered ensiled or grazed grass herbage.     

über den Einfluß von Diäthylstilboestrol und anderer Wirkstoffe auf den Stoffwechsel männlicher Ratten

The presented study aimed at investigating the residual feed intake (RFI) of Sahiwal calves, nutrient utilisation as affected by RFI and its relationship with methane (CH₄) emissions and some blood metabolites. Eighteen male Sahiwal calves (10–18 months of age; mean body weight 133 kg) were fed ad libitum with a total mixed ration. After calculating RFI for individual calves (?0.40 to +0.34 kg DM/d), they were divided into three groups with low, medium and high RFI, respectively. Dry matter intake (DMI) was higher (p < 0.05) in Group High RFI, whereas digestibility of all nutrients except crude protein and ether extract was significantly higher in Group Low RFI. Nitrogen balance was also significantly higher in Group Low RFI (20.2 g/d) than in Group High RFI (17.0 g/d). Average daily gain and feed conversion ratio were similar among the groups. With exception of glucose, concentrations of all measured blood metabolites were higher in Group High RFI (p < 0.05). Compared with Group High RFI, the CH₄ emission of Group Low RFI was significantly lower (on the basis g/d and g/kg DMI by 11% and 19%, respectively). Furthermore, the CH₄ emission [g/d] was significantly correlated with RFI (r = 0.77). Because higher feed efficiency and less CH₄ production were observed in Group Low RFI, it was concluded that RFI can be used as a measure of feed efficiency, which has a potential to select Sahiwal calves for lowered CH₄ emissions.     

Differential hepatic oxidative status in steers with divergent residual feed intake phenotype

Oxidative stress occurs when oxidant production exceeds the antioxidant capacity to detoxify the reactive intermediates or to repair the resulting damage. Feed efficiency has been associated with mitochondrial function due to its impact on cell energy metabolism. However, mitochondria are also recognized as a major source of oxidants. The aim of this study was to determine lipid and protein oxidative stress markers, and gene and protein expression as well as activity of antioxidant enzymes in the liver of steers of divergent residual feed intake (RFI) phenotypes. Hereford steers (n = 111) were evaluated in post-weaning 70 days standard test for RFI. Eighteen steers exhibiting the greatest (n = 9; high-RFI) and the lowest (n = 9; low-RFI) RFI values were selected for this study. After the test, steers were managed together under grazing conditions until slaughter when they reached the slaughter body weight. At slaughter, hepatic samples were obtained, were snap-frozen in liquid nitrogen and stored at −80°C until analyses. Hepatic thiobarbituric acid reactive species and protein carbonyls were greater (P = 0.05) and hepatic 4-hydroxynonenal protein adducts tended (P = 0.10) to be greater for high- than low-RFI steers. Hepatic gene expression glutathione peroxidase 4, glutamate–cysteine ligase catalytic subunit and peroxiredoxin 5 mRNA was greater (P ≤ 0.05) and glutathione peroxidase 3 mRNA tended (P = 0.10) to be greater in low- than high-RFI steers. Hepatic protein expression and enzyme activity of manganese superoxide dismutase and glutathione peroxidase enzyme activity tended (P ≤ 0.10) to be greater for low- than high-RFI steers. High-efficiency steers (low-RFI) probably had better hepatic oxidative status which was strongly associated with greater antioxidant ability near to the oxidant production site and, therefore, reduced oxidative stress of the liver. Decreased hepatic oxidative stress would reduce maintenance requirements due to a lower protein and lipid turnover and better efficiency in the use of energy.     

Nutrient utilisation,growth performance and blood metabolites in Murrah buffalo calves (Bubalus bubalis) divergently selected for residual feed intake

The aim of this study was to evaluate differences in efficiency of feed utilisation between buffalo calves with low and high residual feed intake (RFI) by comparing feed intake, nutrient digestibility, growth traits and blood metabolites. Eighteen male Murrah buffalo calves (aged 4–6 months; 70 ± 1.0 kg body weight) were fed ad libitum with a total mixed ration for 120 d. Based on linear regression models involving dry matter intake (DMI), average daily gain (ADG) and mid-test metabolic body size, calves were assigned into low and high RFI groups. The RFI varied from ?0.33 to +0.28 kg DM/d with an average RFI of ?0.14 and 0.14 kg DM/d in low and high RFI calves, respectively. Calves had a mean DMI of 1.9 and 2.4 kg/d and an ADG of 0.5 and 0.6 kg/d in low and high RFI groups, respectively. Low RFI calves ate 19.0% less DM each day and required significantly less metabolisable energy for maintenance compared with high RFI calves (12.5 vs. 16.7 MJ/d). Nutrient digestibility and nitrogen balance did not differ among low and high RFI calves. In more efficient animals (low RFI calves) higher (p < 0.05) plasma level of growth hormone, insulin-like growth factor-1 (IGF-1), triiodothyronine (T₃) and lower concentration of thyroxin hormone were detected. No significant differences in levels of insulin, hydroxyproline, plasma and urine creatinine, total protein and albumin between high and low RFI groups were found. Blood metabolites showed significant (p < 0.05) differences at initial and final stages of study in both groups. At final stage of study, RFI showed negative correlations with growth hormone, IGF-1, T₃, urine creatinine and albumin. Low RFI buffalo calves are more efficient in feed utilisation and the differences in blood metabolites are probably due to differences in feed intake and body metabolism.     

A possible dominant white gene in Jersey cattle

A white heifer ("Snow") was born in 1991 from coloured registered Jersey parents. She produced six calves sired by coloured Jersey bulls: three white bull calves, two white heifer calves, and one coloured bull calf. One of the white bull calves was mated with 40 Hereford × Friesian yearling heifers (white face, predominantly black body with some white patches). The 38 resulting calves included 16 white and 22 coloured calves. Twelve of the 16 white calves were heifers and four were bulls. Red or black spotting was recorded on some white calves. The results are consistent with an autosomal dominant mutant causing the white phenotype. The mutation appears to have arisen spontaneously in Snow, then passing to her white progeny and white grand-progeny. The white individuals varied from entirely white in a few cases, to most having some residual small areas of red or black pigmentation in patterns not typical of other reported white spotting patterns of cattle.     

Effects of reduced in utero and post-weaning nutrition on milk yield and composition in primiparous beef cows

Development and long-term retention of replacement beef females in a semi-arid environment are of a major concern for extensive livestock producers. Furthermore, the demand of not only producing a thriving, healthy calf, but having sufficient milk to support that first calf is essential. To address this issue, we conducted a 3-year study measuring milk production and milk constituent yields in primiparous beef heifers (n=48; 16/year reared under two different feeding regimens) raising steer calves. Cows received 1.8 or 1.2 kg/day winter supplementation for ~80 day before parturition and their heifer calves were then randomly assigned to heifer development treatments that provided ad libitum (AL) or 80% (less than ad libitum (LAL)) of ad libitum feed post weaning. Heifers developed on the AL treatment also received 1.8 kg/day winter supplementation for life, whereas heifers developed on the LAL treatment received 1.2 kg/day winter supplementation for life. Milk production of primiparous cows was measured with a portable milking machine every other week from days 27 to 125 postpartum. Milk yield for the 125-day lactation period was calculated from area under the lactation curve approximated by trapezoidal summation. The ANOVA model included in utero winter nutrition, post-weaning heifer development treatment, year and their interaction. Heifers subjected to the AL treatment reached peak milk yield ~12.3 day later (P=0.02) than heifers receiving LAL treatment. In addition, an in utero nutrition×post-weaning heifer treatment×year interaction existed (P⩽0.04) for milk peak yield, average daily milk yield (kg/day) and nutrient composition (protein, lactose, fat, solids non-fat, g/day). These interactions manifest as changes in magnitude and rank across the 3 years of the study. Livestock production in extensive environments is subject to variations in seasonal precipitation patterns and quality and quantity of grazeable forage and these fluctuations have a large impact on milk yield. In summary, the gestational nutritional environment of a heifer’s mother may interact with the heifer’s nutrient consumption during post-weaning growth and the current year to trigger variation in year-to-year milk production.     

Induction of LH surges with 17β estradiol in prepuberal beef heifers: An age dependent response

Twenty-four crossbred heifer calves were used to determine the age at which the endocrine mechanisn involving the stimulatory action of estradiol on luteinizing hormone (LH) release becomes competent to function in prepuberal beef heifers.Twelve calves were studied at 3 months of age at an average body weight of 113 kg; and 12 were studied at 5 months of age at an average body weight of 171 kg. Half of the heifers in each age group were injected with 500 μg of estradiol-17β (E₂) in corn oil and half were injected with corn oil (controls). Acute release of LH did not occur in any control heifers of either age nor in any 3-month-old, E₂-treated heifers but did occur in four of the six heifers treated at 5 months of age.The acute release, lasting for 6 to 8 hr, was initiated between 12 and 14 hr after injection of estradiol with LH peaks ranging from 39 to 146 ng/ml. These results suggest that the hypothalamic-hypophyseal mechanism responsible for estradiol-stimulated LH release becomes functional between 3 and 5 months of age in calves that do not ovulate until 12 to 16 months of age.     

Assessing feed efficiency in beef steers through feeding behavior, infrared thermography and glucocorticoids

A better understanding of the factors regulating feed efficiency and their potential as predictors of feed efficiency in cattle is needed. Therefore, the potential of three classes of traits, namely, feeding behavior characteristics: daily time at feeder (TF; min/day), time per meal (TM; min), meal size (MS; g DM), eating rate (ER; g DM/min), number of daily meals (NM) and daily visits to the feeder (VF); infrared (IR) thermography traits (°C): eye (EY), cheek (CK), snout (SN), ribs (RB) and hind area (HA); and glucocorticoid levels: fecal cortisol metabolites (FCM; ng/g) and plasma cortisol (PC; ng/ml) as predictors of efficiency were evaluated in 91 steers (436 ± 37 kg) over 2 years (Y1 = 46; Y2 = 45). Additionally, the individual traits of each of these three classes were combined to define three single traits. Individual daily feed intake of a corn silage and high-moisture corn-based diet was measured using an automated feeding system. Body weight and thermographs were taken every 28 days over a period of 140 days. Four productive performance traits were calculated: daily dry matter intake (DMI), average daily gain (ADG), feed to gain ratio (F : G) and residual feed intake (RFI). Steers were also classified into three RFI categories (low-, medium- and high-RFI). Among the feeding behavior characteristics, MS and ER were correlated with all efficiency traits (range: 0.26 to 0.75). Low-RFI (more efficient steers) had smaller MS, lower ER and fewer VF in comparison to high-RFI steers. Less efficient steers (high-RFI) performed more VF during the nocturnal period than more efficient steers. More efficient steers had lower CK and SN temperatures than less efficient steers (28.1°C v. 29.2°C and 30.0°C v. 31.2°C), indicating greater energetic efficiency for low-RFI steers. In terms of glucocorticoids, PC was not correlated with efficiency traits. In contrast, more efficient steers had higher FCM in comparison to less efficient steers (51.1 v. 31.2 ng/g), indicating that a higher cortisol baseline is related to better feed efficiency. The overall evaluation of the three classes of traits revealed that feeding behavior, IR thermography and glucocorticoids accounted for 18%, 59% and 7% of the total variation associated with RFI, respectively. These classes of traits have usefulness in the indirect assessment of feed efficiency in cattle. Among them, IR thermography was the most promising alternative to screen cattle for this feed efficiency. These findings might have application in selection programs and in the better understanding of the biological basis associated with productive performance.     

Mitochondrial abundance and function in skeletal muscle and liver from Simmental beef cattle divergent for residual feed intake

Cellular mitochondrial function has been suggested to contribute to variation in feed efficiency (FE) among animals. The objective of this study was to determine mitochondrial abundance and activities of various mitochondrial respiratory chain complexes (complex I (CI) to complex IV (CIV)) in liver and muscle tissue from beef cattle phenotypically divergent for residual feed intake (RFI), a measure of FE. Individual DM intake (DMI) and growth were measured in purebred Simmental heifers (n = 24) and bulls (n = 28) with an initial mean BW (SD) of 372 kg (39.6) and 387 kg (50.6), respectively. All animals were offered concentrates ad libitum and 3 kg of grass silage daily, and feed intake was recorded for 70 days. Residuals of the regression of DMI on average daily gain (ADG), mid-test BW^0.75 and backfat (BF), using all animals, were used to compute individual RFI coefficients. Animals were ranked within sex, by RFI into high (inefficient; top third of the population), medium (middle third of population) and low (efficient; bottom third of the population) terciles. Statistical analysis was carried out using the MIXED procedure of SAS v 9.3. Overall mean ADG (SD) and daily DMI (SD) for heifers were 1.2 (0.4) and 9.1 (0.5) kg, respectively, and for bulls were 1.8 (0.3) and 9.5 (1.02) kg, respectively. Heifers and bulls ranked as high RFI consumed 10% and 15% more (P < 0.05), respectively, than their low RFI counterparts. There was no effect of RFI on mitochondrial abundance in either liver or muscle (P > 0.05). An RFI × sex interaction was apparent for CI activity in muscle. High RFI animals had an increased activity (P < 0.05) of CIV in liver tissue compared to their low RFI counterparts; however, the relevance of that observation is not clear. Our data provide no clear evidence that cellular mitochondrial function within either skeletal muscle or hepatic tissue has an appreciable contributory role to overall variation in FE among beef cattle.     

Divergence for residual feed intake of Holstein-Friesian cattle during growth did not affect production and reproduction during lactation

Residual feed intake (RFI) is the difference between actual and predicted dry matter intake (DMI) of individual animals. Recent studies with Holstein-Friesian calves have identified an ~20% difference in RFI during growth (calf RFI) and these groups remained divergent in RFI during lactation. The objective of the experiment described here was to determine if cows selected for divergent RFI as calves differed in milk production, reproduction or in the profiles of BW and body condition score (BCS) change during lactation, when grazing pasture. The cows used in the experiment (n=126) had an RFI of −0.88 and +0.75 kg DM intake/day for growth as calves (efficient and inefficient calf RFI groups, respectively) and were intensively grazed at four stocking rates (SR) of 2.2, 2.6, 3.1 and 3.6 cows/ha on self-contained farmlets, over 3 years. Each SR treatment had equal number of cows identified as low and high calf RFI, with 24, 28, 34 and 40/11 ha farmlet. The cows divergent for calf RFI were randomly allocated to each SR. Although SR affected production, calf RFI group (low or high) did not affect milk production, reproduction, BW, BCS or changes in these parameters throughout lactation. The most efficient animals (low calf RFI) lost similar BW and BCS as the least efficient (high calf RFI) immediately post-calving, and regained similar BW and BCS before their next calving. These results indicate that selection for RFI as calves to increase efficiency of feed utilisation did not negatively affect farm productivity variables (milk production, BCS, BW and reproduction) as adults when managed under an intensive pastoral grazing system.     

Predicting dystocia in heifers

The relationship of heifer size, calf size and sire on dystocia was studied in approximately one thousand Angus, Hereford X Angus and Charolais heifers bred to Angus, Hereford and Charolais bulls. Heifers were weighed and pelvic measurements taken 35 days post breeding, at midgestation, and on a random group of 135 heifers two weeks prior to calving. Dystocia score, calf birth weight, calf body length, calf hip width and calf sex were recorded at calving.Correlation coefficients for calf traits indicate that birth weight and birth weight to body measurement ratios were the most highly correlated variables with dystocia score. For traits of the dam, pelvic area was the most highly correlated variable to dystocia score, while dam weight had a low and nonsignificant correlation.Sires experiencing a higher than average incidence of dystocia had calves that were larger for all measures of body size. Individual sire differences for dystocia indicate a large number of calves and an accurate randomization of heifers bred to each bull is necessary to make precise judgements as to a bull's potential for siring easy-calving offspring.Calf size measurements were positively correlated with heifer weight and pelvic area; however, correlations tended to be low. Breed of calf, sire, heifer weight I and II and pelvic area I, II and III accounted for only 23.6% of the variation in calf birth weight.Charolais calves were larger (P<.05) and had more dystocia (P<.05) than Hereford or Angus sired calves. Hereford sired crossbred calves were larger (P<.05) and had more dystocia than Angus crossbred or straightbred calves. Angus crossbred calves were larger (P<.05) but had no more dystocia than Angus straightbred calves.Heritability estimates for calf body length (0.35) and calf hip width (0.42) indicate calf skeletal measurements were more heritable than calf birth weight (0.28).Pelvic area measurements were correlated (P<.01) with heifer weight; however, heifer weight I and II accounted for only 37% and 30% of the variability in pelvic area I and II, respectively. Average pelvic area was largest in Charolais heifers, followed by Crossbred and Angus heifers. Pelvic area growth was .275 cm²/day in Angus, .254 cm²/day in Crossbred, and .250 cm²/day in Charolais heifers.Dystocia score was most highly related to calf size and pelvic area I. Pooled over all breeds, a regression analysis showed 37% of the variability in dystocia score being accounted for by the ratio of calf birth weight to calf body length and pelvic erea I. Very little increase in the R² value occurred by the addition of the other independent variables.Histogram analyses demonstrates that a constant level of dystocia can be maintained only if pelvic area increases in proportion to calf size. However, regardless of the size of calf, heifers that had very small pelvic openings had a high rate of dystocia, just as heifers having very large calves experienced high rates of dystocia even when they had large pelves.     

Social dominance affects intake rate and behavioral time budget in pre-pubertal dairy heifers allocated in continuous competitive situations

In intensive feeding systems, competition may be high and social dominance may affect animal performance by changing dry matter intake (DMI) and behavioral time budgets. If competition level is maintain over time, the strategies developed by heifers of different social status are expected to differ. Thus, the aim of this study was to compare individual DMI, intake rate and eating, ruminating, lying and standing behaviors in dominant (DOM) and subordinate (SUB) pre-pubertal dairy heifers in a model study implying continuous competitive situations. A total of 16 Holstein and Jersey×Holstein pre-pubertal heifers (251±10 days old, weighing 208±14 kg; mean±SEM) were allocated into eight homogeneous dyads. Each dyad was maintained during 120 days (day 0=beginning of measurements) in pens, and received a total mixed ration from one feeder/dyad. The DOM and SUB heifers was determined (day 0, twice during the first month of the experiment and every month afterwards) by observation of the winner in agonistic interactions in each dyad after the feed was supplied. The general activity pattern (eating, ruminating, lying and standing) of each heifer was recorded by direct instantaneous scan-sampling, every 10 min for 12 h, in 7 days (days 1, 21, 35, 60, 75, 100 and 120). Individual DMI was estimated with the double marker technique, in three intervals (I=days 17-26; II=days 78-87 and III=days 112-120), while estimated intake rate (kg/min) was calculated for each interval as the DMI per total eating time. After the experiment was concluded, data of the first 5 and the last 6 h of the 12 h scan-sampling (related to the moment the feed was supplied) was grouped according to the moments of greater and lesser competition for feed on each day. During the first 5 h, where competition was expected to be highest, no differences in eating behavior were found between heifers of different social status, but DOM heifers spent more time ruminating and lying than SUB heifers, while SUB spent more time standing than DOM heifers. No differences were found on DMI between DOM and SUB, but SUB ate at a faster rate on interval II compared with DOM heifers. In conclusion, in this model study of heifer dyads, SUB heifers had greater intake rate with no differences in feed intake, spent less time ruminating and lying, and more time standing than DOM heifers during the first hours after feed delivery.     

Impacts of stocking density on development and puberty attainment of replacement beef heifers

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

Biological mechanisms related to differences in residual feed intake in dairy cows

Residual feed intake (RFI), defined as the difference between an animal’s actual feed intake and expected feed intake over a specific period, is an inheritable character of feed conversion efficiency in dairy cows. Research has shown that a lower RFI could improve the profitability of milk production. This study explored variation in RFI by comparing the differences in body size, milk performance, feeding behavior, and serum metabolites in 29 Holstein cows in mid lactation. The cows were selected from a total of 84 animals based on their RFI following feedlot tests. Selected cows were ranked into high RFI (RFI >1 SD above the mean, n=14) and low RFI (RFI<1 SD below the mean, n=15). The low RFI cows (more efficient) consumed 1.59 kg/day less dry matter than the high RFI group (P<0.01), while they produced nearly equal 4% fat-corrected milk. The milk : feed ratio was higher for the low RFI group than for the high RFI group (P<0.05). The levels of milk protein (P<0.01), total solids (P<0.05), and nonfat solids (P<0.05) were also higher for the low RFI group, whereas milk urea nitrogen was lower (P<0.01). The daily feeding duration was shorter for the low RFI group than for the high RFI group (P<0.01). No significant differences were found in levels of glucose, β-hydroxybutyrate, prolactin, insulin, IGF-1, growth hormone or ghrelin, but the level of neuropeptide Y was higher (P<0.01) and levels of leptin and non-esterified fatty acid (P<0.05) were lower for the low RFI group than for the high RFI group. There were substantial differences between cows with different RFI, which might affect the efficiency of milk protein metabolism and fat mobilization.     

Serum biochemical profile of Mizoram strain female Mithun (Bos frontalis) at different age and season

The present investigation aimed at generating baseline biochemical profile of Mizoram strain female mithun (Bos frontalis) at the age groups of calves (6 months to 1 year), heifer (1 to 3 years) and adult (above 3 years) during monsoon, winter and spring of a year. Glucose level was significantly (p ≤ 0.01) highest in heifers during monsoon season and lowest in adults in all the seasons. Protein level was significantly (p ≤ 0.01) highest during monsoon season in heifers and lowest in calves. Albumin level was significantly (p ≤ 0.01) highest in heifers and lowest in calves. Globulin and A: G ratio showed non-significant variation with age. Calves (23.05 ± 4.20) and heifer (23.13 ± 4.88) have significantly (p ≤ 0.01) higher urea concentration during winter and in adult (38.66 ± 1.35) during spring season. Creatinine level was highest in calves during monsoon which decreased significantly (p ≤ 0.01) with age in this season. Direct bilirubin level significantly (p ≤ 0.01) decreased as age increases and the highest concentration was observed during spring season. Total cholesterol, HDL-cholesterol and triglyceride level increased significantly (p ≤ 0.01) with age in all seasons with the highest values observed during winter season.     

The effects of estrogen,its antagonist ICI 182, 780, and interferon-tau on the expression of estrogen receptors and integrin alphaV beta 3 on cycle day 16 in bovine endometrium

We have shown previously that downregulation of intercaruncular stromal integrin α_vβ₃ in bovine endometrium on day 16 of the estrous cycle coincided with the antibody recognition of estrogen receptors (ER) in the luminal epithelium. In pregnancy, these changes were not observed. Our hypothesis was that on day 16 of the estrous cycle, estrogen from the dominant follicle causes a reduction in integrin α_vβ₃ and affects ERα in the luminal epithelium. The pregnancy recognition protein, interferon-τ (IFN-τ), may prevent downregulation of integrin α_vβ₃ and suppress ERα expression in the luminal epithelium. On days 14 to 16, heifers received uterine infusions of the anti-estrogen ICI 182, 780, estradiol 17β, IFN-τ or the saline control. On day 16, reproductive tracts were collected for analysis of integrin α_vβ₃ and ERα. Estrogen receptor α immunoreactivity was largely restricted to the luminal epithelium in control animals. Using anti-ERα recognizing the amino terminus, estrogen-treated animals showed reactivity in the stroma, shallow and deep glands and myometrium as is typical of estrus, whereas ICI 182, 870 treated heifers showed little or no reactivity. In contrast, carboxyl terminus-directed antibodies showed a widespread distribution of ERα with reactivity detected in the uterine epithelium, stroma and myometrium of both estrogen and ICI 182, 780 treated animals. Heifers treated with IFN-τ had low ERα reactivity overall. Control and IFN-τ treated heifers had lower intercaruncular stromal expression of integrin α_vβ₃ in comparison to estrogen and ICI 182, 780 treatments. Overall, the results suggest that on day 16 of the estrous cycle, estrogen effects on integrin α_vβ₃ are indirect and do not directly involve ERα in the luminal epithelium. During pregnancy, interferon-tau may block ERα in the luminal epithelium but likely does not rescue integrin α_vβ₃ expression.     

Post-weaning feed efficiency decreased in progeny of higher milk yielding beef cows

Current trends in the beef industry focus on selecting production traits with the purpose of maximizing calf weaning weight; however, such traits may ultimately decrease overall post-weaning productivity. Therefore, the objective of this study was to evaluate the effects of actual milk yield in mature beef cows on their offspring’s dry matter intake (DMI), BW, average daily gain, feed conversion ratio (FCR) and residual feed intake (RFI) during a ~75-day backgrounding feeding trial. A period of 24-h milk production was measured with a modified weigh-suckle-weigh technique using a milking machine. After milking, cows were retrospectively classified as one of three milk yield groups: Lower (6.57±1.21 kg), Moderate (9.02±0.60 kg) or Higher (11.97±1.46 kg). Calves from Moderate and Higher milk yielding dams had greater (P<0.01) BW from day 0 until day 75 at the end of the backgrounding feeding phase; however, day 75 BW were not different (P=0.36) between Lower and Moderate calves. Body weight gain was greater (P=0.05) for Lower and Moderate calves from the day 0 BW to day 35 BW compared with Higher calves. Overall DMI was lower (P=0.03) in offspring from Lower and Moderate cows compared with their Higher milking counterparts. With the decreased DMI, FCR was lower (P=0.03) from day 0 to day 35 in calves from Lower and Moderate milk yielding dams. In addition, overall FCR was lower (P=0.02) in calves from Lower and Moderate milk yielding dams compared with calves from Higher milk yielding dams. However, calving of Lower milk yielding dams had an increased (P=0.04) efficiency from a negative RFI value compared with calves from Moderate and Higher milking dams. Results from this study suggest that increased milk production in beef cows decreases feed efficiency during a 75-day post-weaning, backgrounding period of progeny.