Calf Gender Research Articles

Evaluation of the Criollo breed Romosinuano as purebred and crossbred cows with Brahman and Angus in Florida. II. Maternal influence on calf traits, cow weight, and measures of maternal efficiency1,2,3

The objectives of this work were to compare the Criollo breed Romosinuano as straightbred and crossbred cows with Angus and Brahman in subtropical Florida and to estimate heterosis for size traits of their calves, their own weight, and maternal efficiency traits. Cows (n = 404) were born from 2002 to 2005. After their first exposure to bulls as young cows, crossbred cows were bred to bulls of the third breed, and straightbred cows were bred in to bulls of the other 2 breeds. Calves were spring-born from 2005 through 2011. Evaluated calf (n = 1,254) traits included birth weight and weight, ADG, BCS, and hip height at weaning. Cow weight (n = 1,389) was recorded at weaning. Maternal efficiency traits evaluated included weaning weight per 100 kg cow weight, weaning weight per calving interval, and weaning weight per cow exposed to breeding (n = 1,442). Fixed effects and their interactions were investigated included sire and dam breed of cow, sire breed of calf, cow age, year, calf gender, and weaning age as a linear covariate (calf traits at weaning). Direct and maternal additive genetic effects were random in models for calf traits; only direct additive effects were modeled for cow traits. Cows sired by Angus bulls from outside the research herd had calves that were heavier at birth and weaning and greater ADG, BCS, and hip height (P < 0.05). Estimates of heterosis for weaning weight, BCS, and ADG ranged from 1.3 to 13.2% for all pairs of breeds (P < 0.05). Estimates of heterosis for birth weight (3.2 to 8.2%) and hip height (2.3%) were significant for Romosinuano-Angus and Brahman-Angus. Heterosis for cow weight was 65 ± 8 kg for Brahman-Angus (P < 0.001), and estimates for other pairs of breeds were approximately one-half that value. Heterosis for weaning weight/100 kg cow weight was 3.4 ± 0.75 kg for Romosinuano-Angus. Heterosis estimates for weaning weight/calving interval (P < 0.001) ranged from 0.08 ± 0.01 to 0.12 ± 0.01. Heterosis for weaning weight/cow exposed were 31.6 7.7, 36.9 ± 7.4, and 59.1 ± 7.5 kg for Romosinuano-Angus, Romosinuano-Brahman, and Brahman-Angus, respectively (P < 0.001). Most aspects of Romosinuano crossbred maternal performance were acceptable; maternal performance of Brahman-Angus cows excelled.

A new application of pelvis area data as culling tool to aid in the management of dystocia in heifers1

Although fetomaternal disproportion is the major cause of dystocia in heifers, pelvis area (PA) is not recommended as a culling tool due to its relatively low importance and genetic correlation with calf birth weight (BWT), the most important factor associated with dystocia. The objective of this observational study of 484 limited bred yearling beef heifers was to compare the effects of different methods of adjustment of PA data for culling to select against dystocia. Multivariable analyses were used to determine predictors of PA, calf BWT, and dystocia. Hypothetical culling rates of 10 and 20% were then applied after ranking heifers by each of the following: unadjusted PA, PA adjusted to 365 d of age by subtracting 0.27 cm(2) per day of age difference between each heifer's age and 365 d (APA), PA:prebreeding BW ratio (PA:BW), PA adjusted to the median BW of the group using the regression coefficient of PA on BW within age group (BWPA), and PA similarly adjusted to the median lean BW (LBWPA). Dam parity, sire, prebreeding age, prebreeding BW, and prebreeding BCS were associated with PA whereas dam parity, sire, own BWT, PA, AI bull, and calf gender were associated with calf BWT (P < 0.05). Dam parity, calf BWT, and either BWPA or LBWPA were the only independent predictors of dystocia (P < 0.05). Adjusting PA to BW or lean BW (LBW) improved the sensitivity and specificity to predict dystocia. After hypothetical culling by PA, retained heifers were heavier and had a higher calving rate and calves tended to be heavier at birth compared to culled heifers, but dystocia rates were not different. Culling by APA resulted in similar effects, except that dystocia rate tended to be lower in retained heifers. Culling by PA:BW resulted in lower dystocia rate in retained than in culled heifers, but retained heifers had lower prebreeding BW than culls. Culling by BWPA and LBWPA resulted in lower proportions with dystocia and a tendency towards higher calving rates in the retained heifers, without affecting the prebreeding BW or calf BWT. It is concluded that pelvimetry is a useful culling tool to aid in the management of dystocia in yearling heifers and that adjustment of PA to median BW or LBW within age group improves its accuracy and avoids the undesirable side effects.

A cross-classified and multiple membership Cox model applied to calf mortality data

A cross-classified and multiple membership Cox model was applied to calf mortality data from Western Canada, where 23,409 calves from 174 herds were followed for up to 180 days after calving. The herds were cross-classified by 49 veterinary clinics and 9 ecological regions and in a multiple membership relation to the veterinary clinics, resulting in a 3-level cross-classified and multiple membership data structure. The model was formulated in a mixed-effects Poisson model framework with normally distributed random effects, and was fitted to the data by Bayesian Markov Chain Monte Carlo (MCMC) estimation. Important fixed effects included whether the calf was a twin, calf gender, assistance at calving, cow age, average temperature the first week after calving, the percentage of the herd that had already calved, whether calf shelters were provided, whether cow-calf pairs were moved to a nursery area, and whether any animals were purchased into the herd at or near the time of calving. The analysis demonstrated a greater variation among herds than among both ecological regions and veterinary clinics. Further, a simulation study for a setting similar to the real data gave evidence that the used approach provides valid estimates.

Maternale en omgevingsfactoren die significant geassocieerd zijn met het geboortegewicht van holsteinkalveren

In deze studie werden de factoren onderzocht die significant geassocieerd zijn met het geboortegewicht van een holsteinkalf. De hier beschreven retrospectieve dwarsdoorsnedestudie bij 1594 holstein-friesiankalveren en hun moederdieren werd van 2011 tot 2013 uitgevoerd op vier melkveebedrijven in België en één in Duitsland. Bij de primipare moederdieren hadden het geslacht van het kalf, de drachtduur, het afkalfseizoen, de afkalfleeftijd en de grootte van het moederdier bij het afkalven (borstomtrek, schofthoogte, diagonale lengte) een significante invloed op het geboortegewicht (GG). Het GG was significant lager bij vaarzen die op zeer oude leeftijd afkalfden (25,5-37,3 maanden) (P &amp;lt; 0,001). Bij het afkalven tussen 22 en 23,5 maanden was het GG hoger dan bij vaarzen die tussen 20,3 en 22 maanden of tussen 23,3 en 25,5 maanden afkalfden (P&amp;lt;0,001). Bij de multipare moederdieren hadden het geslacht, het afkalfseizoen, de drachtduur, de pariteit, de lengte van de droogstand en de melkproductie tijdens de dracht (MDRACHT) een significante invloed op het GG (P &amp;lt; 0,001). Het GG van kalveren was respectievelijk 0,97 en 1,11 kg zwaarder bij koeien met een lage (1.400 tot &amp;lt; 5.400 kg) en een hoge (6.500 tot &amp;lt; 7.200 kg) MDRACHT dan bij koeien met een zeer hoge (7.200 tot &amp;lt; 11.600 kg) MDRACHT. De negatieve invloed van een vroege of late eerste partus bij vaarzen en van de zeer hoge melkproductie tijdens de dracht bij koeien op het geboortegewicht kan de basis zijn voor verder onderzoek naar de invloed van nutritionele en andere maatregelen tijdens de dracht op de productie en gezondheid van de nakomelingen op lange termijn.

Factors influencing social organization in postpartum Angus cows under confinement. Effect on cow–calf weight change

The objective was to determine factors influencing social organization in postpartum Angus cows and its effect on variation of cow–calf weight after 90d. Postpartum Angus cows (N=90) with no history of puerperal problems, a calf suckling, and body condition score (BCS) no less than 3 were allocated into 3 groups of 30 (A, B, and C) according to parity (P) and cow body frame (CF). Using the agonistic interactions recorded during the study, a raw dominance value with subsequent Arc-sin conversion (Arc-sin DV) was calculated to generate a linear social dominance order (DO) with 3 social categories (dominant—D-, intermediate—I-, and subordinate—S-cows). The effects of postpartum body weight (PPBW), BCS, CF, and P on Arc-sin DV were statistically analyzed using ANOVA. Similar procedure was applied to analyze the effects of group, P, CF, and DO on cow body weight at 90d (CW90), and the effects of DO of dams, P, group, calf gender (CG), and sire within breed (SWB) on calf body weight at 90d (CFW90). Cows with larger CF and heavier PPBW obtained greatest (P<0.0005) Arc-sin DV. The youngest and the oldest cows tended (P<0.10) to obtain the lowest Arc-sin DV. After 90d of trial, D cows were heavier than I (P<0.002) and S cows (P<0.0001). Calf birth weight was influenced by SWB (P<0.03) and P (P<0.05), and D cows had heavier (P<0.05) calf at birth than S cows. At 90d, calf body weight was influenced by P (P<0.03) and DO of dam (P<0.008). Thus, calf weight at 90d increased with DO of dams. In conclusion, CF, PPBW, and to a less extent P, influenced DO. Parity and CF influenced PPBW. Variation of CW90 was influenced by DO. Calf birth weight was influenced by SWB, P, DO of cow, and CG. Meanwhile, CFW90 was influenced by P and DO of cow. Interactions among social organization, management strategies, calf growth, and reproductive aspects need more attention.

Cool-season annual pastures with clovers to supplement wintering beef cows nursing calves

In December of 3 years, 87 beef cows with nursing calves (594 ± 9.8 kg; calving season, September to November) at side were stratified by body condition score, body weight, cow age, and calf gender and divided randomly into 6 groups assigned to 1 of 6 cool-season annual pastures (0.45 ha/cow) that had been interseeded into a dormant common bermudagrass (Cynodon dactylon [L.] Pers.)/bahiagrass (Paspalum notatum Flugge) sod. Pastures contained 1 of the following 3 seeding mixtures (2 pastures/mixture): 1) wheat (Triticum aestivum L.) and ryegrass (Lolium multiflorum Lam., WRG), 2) wheat and ryegrass plus red clover (Trifolium pretense L., WRR), or 3) wheat and ryegrass plus white (Trifolium repens L.) and crimson clovers (Trifolium incarnatum L., WRW). All groups had ad libitum access to grass hay (12% crude protein; 58% total digestible nutrients). The second week in December, cow estrous cycles were synchronized and artificially inseminated. In late December, a bull was placed with each group for 60-d. Data were analyzed with an analysis of variance using a mixed model containing treatment as the fixed effect and year as the random effect. Body weight and condition scores did not differ (P ≥ 0.27) among cows between February and June. Calf birth weights or average daily gain did not differ (P ≥ 0.17) among treatments; however, calves grazing pastures with clovers did tend (P = 0.06) to weigh more than calves grazing grass only. Weaning weight per cow exposed to a bull was greater (P = 0.02) for WRR and WRW than WRG. Cows grazing winter-annual pastures containing clovers tended to wean more calf body weight per cow exposed to a bull than cows grazing the grass only pastures.

Effect of timing of artificial insemination after synchronization of ovulation on reproductive performance in Holstein dairy cows

The objective of this study was to determine the effect of timing of artificial insemination on pregnancy rates, calving rates, abortion rates, twinning rates, and calf gender ratio after synchronization of ovulation with Ovsynch protocol in Holstein dairy cows. The ovulation of 219 lactating Holstein dairy cows was synchronized using the Ovsynch protocol. Therefore, cows received an injection of GnRH followed by an injection of prostaglandin F(2α) 7 days later and a second treatment with GnRH 2 days later. Cows were artificially inseminated at 0, 12, or 24 h after the second injection of GnRH. Reproductive performance did not differ between cows inseminated at 0 h (n = 82), 12 h (n = 66), or 24 h (n = 71) after the last injection of GnRH (pregnancy rate: 0 h 48 %, 12 h 47 %, 24 h 52 %; abortion rate: 0 h 5 %, 12 h 0 %, 24 h 11 %; calving rate: 0 h 43 %, 12 h 47 %, 24 h 41 %; twinning rate: 0 h 2 %, 12 h 0 %, 24 h 0 %; calf gender ratio (F/M): 0 h 61:39 %, 12 h 48:52 %, 24 h 39:61 %; P > 0.05). Pregnancy rates for cows inseminated in postpartum times of 50-75, 76-100, and >100 days within the first and ≥ 3 parities were statistically similar (P > 0.05), but pregnancy rates for cows inseminated at different postpartum times of 50-75, 76-100, and >100 days within the second parity were different (P < 0.01). In general, pregnancy rates of cows inseminated at different postpartum times (P < 0.01) and parities (P < 0.001) differed. The findings of the current study showed that rates of pregnancy, abortion, calving, and twinning of Holstein dairy cows subjected to artificial insemination at different times after synchronization were similar. These results also indicate that the timing of artificial insemination after synchronization did not influence calf gender ratio. Furthermore, pregnancy rates of Holstein dairy cows inseminated after synchronization were significantly influenced by postpartum time and parity number.

Influence of Predator Harvest, Biological Factors, and Landscape on Elk Calf Survival in Idaho

ABSTRACT We evaluated survival of elk (Cervus elaphus) calves on 2 contrasting study areas in north‐central Idaho, USA, from 1997 to 2004. Recruitment was modest (&gt;30 calves:100 F [calves of either sex: F elk 1 yr old]) and stable on the South Fork study area and low (&lt;20 calves:100 F) and declining on the Lochsa study area. The primary proximate cause of calf mortality on both study areas was predation by black bears (Ursus americanus) and mountain lions (Puma concolor). We experimentally manipulated populations of black bears and mountain lions on a portion of each study area. Black bear harvest (harvest density/600km2) initially doubled on the Lochsa treatment after manipulating season bag limits. Mountain lion harvest also increased by 60% but varied widely during the manipulation period. Harvest seasons were closed for black bears and mountain lions on the treatment portion of the South Fork study area. Using the Andersen—Gill formulation (A‐G) of the Cox proportional hazards model, we examined effects of landscape structure, predator harvest levels, and biological factors on summer calf survival. We used Akaike's Information Criterion (AICc) and multimodel inference to assess some potentially useful predictive factors relative to calf survival. We generated risk ratios for both the best models and for model‐averaged coefficients. Our models predicted that calf survival was influenced by biological factors, landscape surrounding calf locations, and predator harvest levels. The model that best explained mortality risk to calves on the Lochsa included black bear harvest (harvest density/600 km2), estimated birth mass of calves, and percentage of shrub cover surrounding calf locations. Incorporating a shrub X time interaction allowed us to correct for nonproportionality and detect that effect of shrub cover was only influential during the first 14 days of a calf's life. Model‐averaging indicated that estimated birth mass of calves and black bear harvest were twice as important as the next variables, but age of calves at capture was also influential in calf survival. The model that best explained mortality risk to calves on the South Fork included black bear harvest, age of calves at capture, and gender of calves. Model‐averaging indicated that age at capture and black bear harvest were twice as important as the next variable, forest with 33–66% canopy cover (Canopy 33–66). Risk to calves decreased when calves occupied areas with more of this forest cover type. Model‐averaging also indicated that increased mountain lion harvest lowered calf mortality risk 4% for every 1‐unit increase in lion harvest (harvest density/600 km2) but was lower (&lt;25%) in importance compared to age at capture and black bear harvest. Our results suggest that levels of predator harvest, and presumably predator density, resource limitations expressed through calf birth mass, and habitat structure had substantial effects on calf survival. Our results can be generalized to other areas where managers are dealing with low calf elk recruitment. However, because factors vary spatially, a single management strategy applied in different areas will probably not have the same effect on calf survival.

Dietary Protein During Gestation Affects Circulating Indicators of Placental Function and Fetal Development in Heifers

The influences of nutritional protein during the first and second trimesters of pregnancy on placental hormones and fetal growth were determined in composite beef heifers. At artificial insemination, heifers were stratified by weight within each composite genotype into 4 treatment groups: High High (HH=1.4kg crude protein (CP)/day for first and second trimesters of gestation; n=16), High Low (HL=1.4kg CP/day for first trimester and 0.4kg CP/day for second trimester; n=19), Low High (LH=0.4kg CP/day for first trimester and 1.4kg CP/day for second trimester; n=17) or Low Low (LL=0.4kg CP/day for first and second trimesters; n=19). Maternal plasma bovine pregnancy associated glycoprotein (bPAG) and progesterone (P4) were determined at gestation day (gd) 28, 82, 179 and 271 (mean gestation length 286 days) in addition to P4 at term. Estrone sulphate (ES) and bovine placental lactogen (bPL) concentrations were measured at gd 124, 179, 236 and 271 and at term in addition to ES at gd 82. Low dietary protein increased placental function as indicated by increased bPAG (P<0.001) and ES (P=0.02) concentrations in first trimester and increased bPL concentrations (P=0.01) in the second trimester of gestation. In the third trimester, when dietary treatment had ceased, placental function was no longer associated with previous dietary treatments. Dam genotype affected placental function as measured by bPL (P<0.001) and ES concentrations (P=0.02). Calf gender, heifer age and maternal insulin-like growth factor (IGF)-I, -II and leptin did not affect hormonal indicators or circulating markers of placental function. Enhanced placental function during the third trimester, as measured by ES, was associated with increased calf birth weight (P=0.003).

Efectos del medio y la herencia sobre los pesos al nacimiento, al destete y a los 16 meses de edad en terneros de la raza criolla Romosinuano

Mediante el procedimiento general de modelos lineales (Proc Glm) del paquete estadístico SAS®, fueron analizados 1.877 registros de pesos al nacimiento, al destete y a los 16 meses de edad de terneros de la raza criolla colombiana Romosinuano nacidos en el Centro de Investigación Turipaná de Corpoica en Cereté (Córdoba) entre los años 1980 y 2001. Los pesos promedio al nacimiento, al destete y a los 16 meses de edad fueron en su orden de 30,65 ± 3,79 kg; 182,77 ± 29,35 kg y 247,18 ± 33,81 kg. Los efectos del año de nacimiento y el sexo del ternero fueron significativos (P&lt; 0,01) para los tres momentos de pesaje. Por su parte, el efecto del número de partos de la vaca fue significativo (P&lt; 0,01) sólo para los pesos al nacimiento y al destete; el mes de nacimiento afectó (P&lt; 0,01) los pesos al destete y a los 16 meses de edad. Las estimaciones de los parámetros genéticos se obtuvieron a través de los componentes de varianza y covarianza del programa Mtdfreml mediante un modelo animal. Las heredabilidades directas (h2) estimadas para los tres momentos de pesaje fueron de 0,17 ± 0,06 (nacimiento), 0,14 ± 0,05 (destete) y 0,13 ± 0,05 (16 meses). Las h2 estimadas para el efecto materno sobre los pesos al nacimiento y al destete fueron de 0,087 ± 0,03 y 0,12 ± 0,03, respectivamente. Las correlaciones genéticas, fenotípicas y ambientales entre los pesos al nacimiento, al destete y a los 16 meses fueron bajas en términos generales; no obstante, entre el peso al destete y a los 16 meses, fueron altas y positivas.

Effect of restricting silage feeding prepartum on time of calving, dystocia and stillbirth in Holstein-Friesian cows

A study was carried out to investigate the effect of restricting silage feeding on time of calving and calving performance in Holstein-Friesian cows. In the treatment group (n = 1,248 cows, 12 herds) silage feeding commenced in the evening (17:00 to 20:00 h), after a period of restricted access (2 to 10 h) while in the control group ad-libitum access to silage was provided over the 24 h period (n = 1,193 cows, 12 herds). Daytime and nighttime calvings were defined as calvings occurring between the hours of 06:30 and 00:29 and between 00:30 and 06:29, respectively. Restricting access to silage resulted in less calvings at night compared to cows with ad-libitum access to silage (18 vs 22%, P < 0.05). Cows with restricted access to silage had a higher percentage of difficult calvings (11 vs 7%, P < 0.001) and stillbirths (7 vs 5%, P < 0.05) compared to cows in the control group. The percentage of calvings at night was lower (13%) when access to silage was restricted for 10 h compared to 2, 4 or 6 h (22, 18, 25%, respectively) (P < 0.001). Calf sire breed, calf gender or cow parity did not influence time of calving. In conclusion, offering silage to pregnant Holstein-Friesian cows in the evening, after a period of restricted access, reduced the incidence of nighttime calvings, but increased the incidence of dystocia and stillbirth.

Impacts of Dystocia on Health and Survival of Dairy Calves

The objectives of this study were to determine incidence of stillbirths and heifer-calf morbidity and mortality, and their association with dystocia on 3 Colorado dairies. A total of 7,380 calvings produced 7,788 calves on 3 Colorado dairy operations between October 1, 2001, and November 5, 2002. Dystocia score and calf status (alive vs. dead) were recorded at calving. Calves that were born alive, but died before 24h of age, also were recorded as stillborn. Heifer calves were monitored for 120 d to evaluate morbidity and mortality. More than half (51.2%) of calves born to primiparous dams, compared with 29.4% of calves born to multiparous dams, required assistance during calving. A larger percentage of bull calves (40.0%) required assistance compared with heifer calves (33.0%). Proportion of stillborn calves was 8.2% overall, with bull calves, twin calves, calves born to primiparous dams, and those born to dams having dystocia having a larger stillbirth percentage compared with heifer calves, singletons, calves born to multiparous dams, and unassisted calvings, respectively. Multiple logistic regression models were constructed to evaluate stillbirths and heifer health while accounting for the clustering of calves within dairy. The models included dystocia score, parity, and season of calving as explanatory variables for heifer events and also calf gender, and single or twin birth for the stillbirth models. Heifer calves born to dams having severe dystocia had greater odds of stillbirth [odds ratio (OR) = 20.7] and treatment of respiratory disease (OR = 1.7), digestive disease (OR = 1.3), and overall heifer mortality (OR = 6.7). Calf gender and dam parity interacted with calving ease to affect stillbirths. For calves having severe dystocia, heifer calves and calves born to multiparous dams were at increased risk of stillbirth compared with bull calves and calves born to primiparous dams, respectively. Survival analysis demonstrated that severe dystocia was associated with stillbirths and deaths up to 30 d of age. Relatively simple interventions have the potential to significantly reduce the impact of dystocia on calf mortality and morbidity on dairy farms. Education of farm management and personnel in strategies to reduce dystocia and its effect on calf health should be a priority according to the results of this study.

Evaluación fenotípica y genética para características de crecimiento en la raza criolla colombiana Costeño con Cuernos

Se establecieron componentes de varianza, así como parámetros fenotípicos y genéticos, respecto de las variables ‘peso al nacimiento’, ‘peso al destete’ (ajustado a los 270 días) y ‘peso a los 480 días’ en un hato del ganado criollo colombiano Costeño con Cuernos. Se analizaron 2.281 registros de pesos al nacer, 1.722 de pesos al destete y 1.086 de pesos ajustados a los 480 días utilizando la metodología de máxima verosimilitud restringida (DFREML). También se ajustó un modelo animal que incluyó efectos genéticos directos, maternos y de ambiente permanente, asumiendo como efectos fijos el año de nacimiento, el sexo del ternero y el número de partos de la madre; finalmente, se estimaron los parámetros genéticos ‘heredabilidad’, ‘repetibilildad’ y se establecieron correlaciones genéticas y fenotípicas. Se reportan bajas estimaciones de heredabilidad de los efectos directos, que varían entre 0,17 ± 0,001 y 0,21 ± 0,074 para los pesos al nacer y al destete, respectivamente; así mismo, fue baja la heredabilidad de los efectos genéticos maternos con relación al peso al nacimiento, aunque estos estimados aumentaron respecto de los pesos al nacer y al destete. Las correlaciones entre efectos directos y maternos fueron negativas, pero el mayor valor se encontró para el peso al nacimiento (-0,89). La contribución del ambiente permanente como proporción de la varianza fenotípica total fue baja y disminuyó a medida que aumentó la edad del animal.

The effect of paragenetic factors on reproductive traits of simmental cows

The examination was made on the effect of systematic factors (parturition group, calving season, birth type, calf gender, and birth type-calf gender interaction) and age at first conception on the expression of reproductive traits (gestation length, service period, fertility intensity and calf birth weight) in 143 Simmental cows. The overall mean (?) for gestation length, service period, intercalving period and calf birth weight was 284.14 days, 153.82 days, 416.92 days and 35.40 kg, respectively. The parturition group effect on all fertility traits was highly significant (P&lt;0.01). The calving season statistically significantly (P&lt;0.05) affected the intercalving period and calf birth weight. Birth type induced very significantly longer gestation (P&lt;0.01) and higher calf birth weight in singles (P&lt;0.01) and significantly longer service period in twins (P&lt;0.05). Calf gender had a very significant effect (P&lt;0.01) only on calf birth weight, and the interaction between birth type and calf gender significantly affected gestation duration only (P&lt;0.05). The regression effect of age at first conception on all fertility traits was not significant (P&gt;0.05).

Using Adjusted 205-d Weight Ratios to Predict Beef Cow-Calf Performance12

Eighteen cow-calf herds were used to determine beef cow performance predictability over time to evaluate the effectiveness of Cooperative Extension recommendations on increasing calf preweaning growth performance, and to assess cooperators’ implementation of these recommendations. The data set included 8928 cow records, of which 4379 and 1958 cows had performance records for 2 and 3 consecutiveyr, respectively. For each cow herd, adjusted 205-d BW and ratios were calculated within calf gender. Cows within herds were ranked in descending order based on calf-adjusted 205-d weight ratios and then divided into three groups (top, middle, and bottom thirds). When comparing the cows’ consecutive years’ rankings, year and cow age were not significant (P> 0.10). Of the cows that ranked in the top one-third inyr 1, 33% ranked in the top one-third for the next 2 consecutiveyr, and 71% ranked in the top one-third at least 1yr of the next 2yr. Among the cows ranking in the bottom one-third inyr 1, 27% ranked in the bottom one-third for the next 2 consecutiveyr, and 63% ranked in the bottom one-third at least once in the next 2 consecutiveyr. The correlations between dam’s BW and weaning BW efficiency and metabolic efficiency across herds were all negative and ranged from -0.70 to -0.45 and -0.61 to -0.21, respectively. These results support the practice of culling cows, even first-calf heifers that rank in the bottom one-third of the herd, based on calf preweaning growth performance after 1yr.

Evaluation of age of dam effects on maternal performance of multilactation daughters from high- and low-milk EPD sires at three locations in the southern United States.

Angus bulls (n = 16) selected for either high- or low-milk EPD but similar growth EPD were mated within location at random to Angus cows. Daughters were bred to calve at 2 yr of age and annually until 6 yr of age. Milk yield was measured four times during lactation with a portable milking machine to estimate 12-h milk yield. Milk was collected for analysis of the percentage of fat and protein. A mixed model procedure was used to analyze the weaning weight, milk yield, and milk component data. The model for weaning weight included location, genetic line of sire, gender of calf, and age of dam. Calf age at weaning was used as a covariate. The model for the milk yield and components included location, genetic line of sire, gender of calf, period, and age of dam. Random effects for all models included sire of dam nested within line, sire of calf, and year. Genetic line was a significant source of variation for milk yield (P < 0.01) and weaning weight (P < 0.01) but not for percentage of fat or protein. Location was significant for milk yield (P < 0.01), fat (P < 0.01), protein (P < 0.01), and weaning weight (P < 0.01). The interaction of line with location was not significant except for percentage of protein (P < 0.01). Age of dam was significant for milk yield (P < 0.01), weaning weight (P < 0.01), and percentage of protein (P < 0.01), but not for percentage of fat (P = 0.29). Line difference for mean weaning weight was 18.1 kg, which is similar to the difference between lines for milk EPD (19 kg). Weaning weights from high-milk EPD line daughters were heavier (P < 0.01) than low-milk EPD line daughters at each age of dam evaluated. Cows nursed by males had higher milk yields (4.33 kg/12 h) than cows nursed by heifers (4.0 kg/12 h). The difference in yields for gender was significant for 2-, 3-, and 5-yr-old cows, but not for 4- (P < 0.052) and 6-yr old (P < 0.15) cows. Correlation coefficients between weaning weight and weaning EPD, milk EPD, and total maternal EPD were greater than zero (P < 0.01) (0.76, 0.65, and 0.89, respectively). Daughters of sires with high-milk EPD produced more milk at each age and weaned heavier calves than daughters of sires with low-milk EPD. These results confirm the value of milk EPD for improvement of weaning weights in beef cattle and also validate age of dam effects on milk yield and the associated effects on weaning weights.

Dinoprost Versus Cloprostenol

This factorial study was conducted to determine the reproductive performance of402 dairy cattle treated with either dinoprost (25 mg) or cloprostenol (500 pg), intravenously (IV) or intramuscularly (IM), for synchronization of estrus in a randomized clinical trial. Breeding, conception and pregnancy rates were analyzed with multivariate logistic regression. The model included the treatments (2 types of prostaglandins and 2 routes of injection) as well as eight clinically-relevant covariables. Interactions between treatments were not significant and comparisons were made on the main effect. Comparisons between types of prostaglandins (PGF2a) showed similar breeding rates (82.6 vs 83.0%; P=0.93), but lower conception rate (38.6 vs 46.6%; P=0.13) and pregnancy rate (31.4 vs 39.2%; P=0.14) for dinoprost versus cloprostenol. When comparing routes of injection, a similar breeding rate (84.1 vs 81.4%; P=0.45), but lower conception rate (38.7 vs 46.7%; P=0.13) and pregnancy rate (32.5 vs 38.1%; P=0.23) were noted for IM versus IV injections. The statistical power of the study was 19%, which allowed detection (P&lt;0.05) of a 5% difference or more in pregnancy rate between the main effect of treatments (200 animals per sample).Gender of calves was recorded on 117 calves and analyzed with univariate logistic regression. Overall, the male calf rate was not different from the expected population value (57.3 vs 53.0%; P=0.36). There was a greater proportion of male calves when using dinoprost compared to cloprostenol (72.3 vs 47.1%; P&lt;0.01), when using IV rather than IM injections (66.1 vs 49.2%; P=0.07) and when inseminating cattle 4 days or later after PGF2 injection instead of earlier (69.4 vs 51.9%; P=0.08). It is concluded that the type of PGF2a used and the route of injection might affect conception rate and hence, pregnancy rate, and that the statistical power of the study was too weak to detect any significant differences. It is also concluded that the interval (days) from PGF2a injection to breeding, the type of PGF2a and the route of injection might influence the sex ratio of calves.

Evaluation of maternal performance of daughters from high and low milk EPD sires.

Angus bulls (n = 24) were selected for either high or low milk EPD, but with similar growth EPD and mated within location (n = 6) at random to Angus cows. Daughters from these matings were bred to calve first at 2 yr of age to common reference sires across locations. Lactation records for 192 daughters were used to evaluate 12-h milk yield, percentage of milk fat and protein, and weaning weight of offspring. Milk production was measured four times during the lactation at regular intervals within location. Dams were separated from their calves the night before milking and milked with a portable milking machine the next morning to estimate 12-h milk yield. A sample of the milk was collected from each cow and analyzed for percentages of milk fat and protein. Data were analyzed as repeated records of the dam. Fixed effects were location, genetic line of sire, gender of calf within location, and milking period, with postpartum interval used as a covariate. Fixed effects and the random effects of sire of dam nested within line, sire of calf, and year were estimated by REML. Genetic line was an important source of variation for milk yield (P < 0.01) and percentage of milk fat (P = 0.03) but not for percentage of milk protein (P = 0.49). Location was significant for all three milk variables (P < 0.01), but the interactions between line and location were not significant. Gender of calf was significant for milk yield (P = 0.04) but not for percentage of milk fat or protein. Line (P = 0.02), location (P = 0.01), calf gender (P = 0.01), and age at weaning (P = 0.01) were significant sources of variation for weaning weight but the interaction of line and location was not (P = 0.69). The correlation coefficient between the sire's milk EPD and 12-h milk yield was significantly different from zero (r = 0.56). The difference between the least squares means for high and low lines for milk yield was 0.66 kg/12 h and the difference was 15.3 kg for weaning weight. The results indicate that there was not evidence for a genotype by environment interaction in milk production for daughters from divergent sires selected for high or low milk EPD.

Effect of Nutrition during Pregnancy on Calf Birth Weights and Viability and Fetal Membrane Expulsion in Dairy Cattle.

The objectives of this study were to show changes of blood parameters for nutrition during pregnancy and to examine the relationships between the blood parameters and calf birth weights, calf viability, time required for expulsion of fetal membrane, and the fetal membrane weights. Forty-one Holstein Friesian pregnant cows were used. The duration of the dry period was 74 ± 2 (SEM) days. The average milk yield (4% FCM) per cow per lactation for 305 days was 9,795 ± 146 kg. Mean gestation length, body weight of cows at parturition, and cotyledonary weight were 283.7 ± 0.5 days, 761 ± 11 kg, and 1562 ± 33g, respectively. Mean birth weights were 47.4 ± 1.1 kg for female, and 49.8 ± 0.8 kg for male calves. Of the 41 cows, 10 had weak calves and 13 had retained fetal membranes (RFM). No significant effects of parity, bull, lactation length, milk yield, gestation length, cows' body weights, and gender of calves on the cotyledonary and calf birth weights, incidences of neonatal weakness and RFM were shown. Cows showing low plasma glucose and TP concentrations in mid and late lactation periods had lower calf birth weights and cotyledonary weights, and a higher incidence of neonatal weakness. Likewise, cows with low glucose, cholesterol and Ca concentrations in plasma during the late dry period had a higher incidence of RFM. The results indicate that low intake of energy and protein during late lactation and early dry periods adversely affects feto-placental development, leading to neonatal weakness and RFM. Low intake of energy and Ca during the dry period may also cause RFM.

Utility of maternal serum total testosterone analysis for fetal gender determination in Asian elephants ( Elephas maximus)

It has been shown in some species that fetal testes produce testosterone early in gestation. This study investigated the possibility that fetal testosterone may be reflected in maternal serum levels in the Asian elephant ( Elephas maximus). Weekly serum samples were collected from seventeen pregnant captive Asian elephants and analyzed via radioimmunoassay (RIA) for total testosterone levels. Nine of the cows carried male fetuses and eight carried female fetuses. A non-random pattern over time ( P<0.01) was observed in cows carrying either a male or female fetus. Mean maternal serum total testosterone was significantly higher in cows carrying male versus female fetuses ( P<0.01). Mean trimester values indicate that first trimester values are not significantly different among male versus female groups. The second and third trimester values of cows carrying male fetuses were higher than cows carrying female fetuses, ( P<0.01 and <0.05, respectively). The results of this study show that it is possible via RIA of maternal serum for total testosterone to determine the gender of calves during gestation.