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J.p. Kent - One of the best experts on this subject based on the ideXlab platform.
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Birth sex ratios in sheep over six Lambing seasons
Behavioral Ecology and Sociobiology, 1992Co-Authors: J.p. KentAbstract:The birth sex ratio of a commercial flock of Suffolk × sheep, Ovis aries , were studied over six consecutive Lambing seasons. In all, data from 1820 lambs were recorded and analysed. The overall birth sex ratio was 49.56% male lambs. Significantly more males (56.23%) were born to ewes with single lambs than to ewes with like-sex twins (47.73%). Significantly more female lambs were born to ewes with triplet births (41.79% male). A significant difference in the birth sex ratio was observed between the first and second half of the Lambing season, among like-sex pairs of twin lambs. More males were born in the first half (51.43%) and significantly more females (43.59% male) in the second half of the Lambing season. The results are discussed with reference to the theory of Trivers and Willard (1973).
Marko Samardžija - One of the best experts on this subject based on the ideXlab platform.
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The effects of monthly air temperature and rainfall variations on the reproductive performance and Lambing distribution of the Jezersko-Solčava sheep
International Journal of Biometeorology, 2019Co-Authors: Dražen Đuričić, Miroslav Benić, Ivona Žura Žaja, Hrvoje Valpotić, Marko SamardžijaAbstract:The aim of this study was to investigate the effects of monthly air temperature and rainfall variations on the reproductive performance and Lambing distribution of the Jezersko-Solčava breed in northwestern Croatia during 7 years period from 2010 until 2016. At 11 medium-scale sheep farms, the sheep were kept on a pasture in a semi-intensive environment with access to the stables. The anomalies of rainfall observed on a monthly basis during monitoring were statistically significant. Non-parametric test showed that the percentages of Lambing differ among the months during the year ( P = 0.0001). By using regression analysis, it was found that the percentages of pregnant sheep were linearly associated with the sequential number of the month. The seasonal distribution of Lambings were 53.85% of ewes delivered in winter ( n = 1296), 21.13% in spring ( n = 509), 8.91% in summer ( n = 215) and 16.11% in autumn ( n = 387). Sexual activity was lowest during spring and early summer (from March to May) with a peak from the end of July to October. The conception rate during year 2011 was significantly lower (89.74%), and the litter size was the lowest (1.05) than in other years of the observation. Average conception rate was 92.85% and average litter size 1.21. Despite being a seasonally polyoestrous, the distribution of matings and Lambings of this breed of sheep was not uniform throughout the seasons. There were established a positive or negative correlations between the air temperature and rainfall precipitation variations with tested reproductive performances of Jezersko-Solčava breed sheep in the Northwestern part of Croatia.
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influence of season rainfall and air temperature on the reproductive efficiency in romanov sheep in croatia
International Journal of Biometeorology, 2019Co-Authors: Dražen đuricic, Miroslav Benic, Ivona žura žaja, Hrvoje Valpotic, Marko SamardžijaAbstract:The aim of this study was to investigate the influence of season, rainfall and air temperature on the reproductive efficiency in the Romanov breed of sheep in continental part of Croatia during five consecutive years (2012–2016). During this period, 5379 matings resulted in 5046 successful conceptions, i.e. Lambings at eight medium-scale Romanov breed sheep farms. The conception rate was 93.81%, fecundity was 195% and average preweaning mortality until 90 days of age was 12.41%. The seasonal distribution of Lambings was 47.64% for ewes that delivered in winter (n = 2422), 23.37% in spring (n = 1179), 18.82% in summer (n = 950) and 9.81% in autumn (n = 495). Sexual activity was lowest during spring and early summer when air temperatures were above average (very and extremely warm), and sexual activity peaked from August to September, especially during extremely wet and very wet seasons. Litter size was greater during winter than in other seasons (1.70 vs. 1.54) and was significantly different as compared to each of selected years of the study period. There was a statistically significant difference in the number of pregnant ewes between mating seasons. Most female Romanov lambs born during winter and early spring mated in late summer or autumn and delivered at the age of 1 year or earlier. The seasonal distribution of matings and Lambing was not uniform throughout the seasons over five consecutive years. Thus, it can be assumed that air temperature and rainfall during different seasons could affect the reproductive efficiency in Romanov breed of sheep in continental part of Croatia.
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seasonal Lambing distribution of the romanov breed in northwestern croatia during five consecutive years
Abstract book of the 30th World Buiatics Congress Sapporo Japan, 2018Co-Authors: Dražen đuricic, Ivona žura žaja, Hrvoje Valpotic, Romana Turk, Silvijo Vince, Juraj Grizelj, Branimira Spoljaric, Ivan Folnožic, Ivan Butkovic, Marko SamardžijaAbstract:Objectives. The aim of this study was to investigate the Lambing distribution of the Romanov breed in northwestern Croatia during five consecutive years. Most European breeds of sheep are seasonal breeders in the moderate climate region ; however, the Romanov breed is a meat breed that is aseasonally polyoestrous. Romanov sheep are considered to be highly fertile, with a fecundity rate of 230% or more. In Croatia, the Lambing season is primarily in the winter and spring for seasonal breeders. Materials and methods. During five consecutive years (December 2011 to November 2016) at eight medium-scale sheep farms in northwestern Croatia, there were 5379 mattings with 5046 successful conceptions i.e. Lambings. Ewes were kept at pasture, which primarily provided area for exercise, with access to stables during the night, in a semi-intensive environment. According to standard farming practices, animals had free access to good quality meadow hay (about 1.8 kg per doe daily), adequate concentrate and drinking water. Results. Fertility was 93.81%. The seasonal distribution of Lambings in this study was: 47.64% of ewes delivered in winter (n=2422), 23.37% in spring (n=1179), 18.82% in summer (n=950) and 9.81% in autumn (n=495). The winter season refers to the period of December to February. Sexual activity was lowest was during spring and early summer (March to June) with a peak of sexual activity from August to October. Litter size was greater during spring and winter than in other seasons (1.67 vs.1.36) though birth weight was lower in larger than in smaller litters (2.64±0.65 vs. 2.87±0.61). Conclusions. More lambs during Lambing season and a higher percentage of multiple births (triplets, quadruplets, etc.) was expected during the optimal breeding season, as seen in most European sheep breeds. Despite being aseasonally polyoestrous, the distribution of mating and Lambing was not uniform through the seasons for the Romanov breed.
J. G. Mulholland - One of the best experts on this subject based on the ideXlab platform.
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Annual Lambing performance of crossbred ewes in out-of-season and accelerated lamb production systems
Animal Production Science, 2013Co-Authors: N M Fogarty, J. G. MulhollandAbstract:The average annual lamb production of 1182 crossbred ewes was evaluated in three lamb production systems over 4 years at two sites (Cowra and Wagga Wagga). The lamb production systems were: accelerated 8-monthly joinings with two flocks joined 4 months apart (Ac8), spring joining with an autumn back-up joining (SpB), and annual autumn joining (AuA). The Ac8 and SpB systems were evaluated at Cowra and the SpB and AuA systems were evaluated at Wagga Wagga. Two genotypes of ewes, Border Leicester × Merino (BLM) and Hyfer (Dorset × Merino composite), were used at both sites, with natural joinings to Dorset, Suffolk or Hyfer rams. Four traits were analysed separately at each site to evaluate the average performance per ewe joined per year: number of Lambings, number of lambs born, number of lambs weaned and total weight of lamb weaned. Analyses were also undertaken using only spring joining data. At Cowra ewes in the Ac8 system had more Lambings (1.23 vs 0.87), lambs born (1.88 vs 1.28), lambs weaned (1.47 vs 1.00) and weight of lamb weaned (31.1 vs 21.5 kg) than ewes in the SpB system (P < 0.01). At Wagga Wagga the AuA system had significantly more lambs born (1.37 vs 1.13), lambs weaned (1.08 vs 0.95) and weight weaned (26.1 vs 21.9 kg) than the SpB system (P < 0.01). The system × breed interaction was significant for all traits because the BLM ewes were greater than Hyfer ewes in the AuA, but the reverse in the SpB system. At both sites the advantage of the back-up joining over only joining in spring was greater for the BLM than the Hyfer ewes. The relative performance of the various lamb production systems for each ewe breed is presented. An accelerated Lambing system is likely to be more successful using ewes that have an extended breeding season and good out-of-season breeding performance.
D R Notter - One of the best experts on this subject based on the ideXlab platform.
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opportunities for genetic evaluation of reproductive performance in accelerated Lambing systems
Livestock Science, 2012Co-Authors: H B Vanimisetti, D R NotterAbstract:Data from a Polypay sheep flock managed in an accelerated Lambing system were used to estimate means, heritabilities, and genetic correlations for ewe lamb fertility (ELF); age at first, second, and third Lambing (AGE1, AGE2, and AGE3, respectively); first and second Lambing interval (INT1 and INT2); and number of Lambings by 38 month of age (LAMB3). Summer matings had lower fertility than autumn and winter matings. Heritabilities of ELF, AGE1, AGE2, AGE3, and LAMB3 were 0.14, 0.39, 0.28, 0.36, and 0.27, respectively (P<0.01) but heritabilities for INT1 and INT2 were only 0.00 and 0.09, respectively. The quantity AGEACC=[(age in months at ith Lambing)—12i] was proposed to compare observed ages at Lambing to those expected in an annual Lambing system using a repeated-measures analysis and had heritability of 0.31 and repeatability of 0.90. Genetic correlations of ELF with AGE1, AGE2, and LAMB3 were −0.89, −0.91, and 0.89, respectively (P<0.01). Genetic correlations of LAMB3 with AGE1 and AGE2 were −0.49 and −1.00, respectively. Genetic correlations of ELF and LAMB3 with direct genetic effects on WW were approximately −0.70, but correlations with maternal genetic effects on WW were 0.88 (P<0.10) and 0.58, respectively. Litter size was independent of ELF and LAMB3. Initial selection on ELF, augmented by additional selection on ewe ages at subsequent Lambings, may allow prediction of genetic merit for reproductive performance and increase the frequency of Lambing in accelerated Lambing systems.
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effects of ewe age and season of Lambing on prolificacy in us targhee suffolk and polypay sheep
Small Ruminant Research, 2000Co-Authors: D R NotterAbstract:Factors affecting ewe prolificacy (number of lambs born per ewe Lambing) were evaluated using records on 9705 Targhee, 12,721 Suffolk, and 7231 Polypay Lambings from flocks participating in the US National Sheep Improvement Program. Factors considered were ewe age and season of Lambing. Prolificacy was affected by age of the ewe (P 8-year-old) ewes was consistently reduced by 0.17-0.20 lambs relative to adult ewes. Within the 1-year-old age class, age in months further affected prolificacy of Suffolk and Polypay but not Targhee ewes. For these two breeds, prolificacy of 15-month-old ewes averaged 0.21 lambs more than that observed for 12-month-old ewes. Seasonal differences in prolificacy were large for Targhee and Polypay (P<0.001) but not for Suffolk (P=0.23) and the distribution of Lambings among seasons differed (P<0.001) for all breeds. 22% of adult Polypay ewes, but only 1% of Targhee and Suffolk ewes lambed in summer and autumn. Prolificacy was highest in winter and spring Lambings (December through May) and did not differ importantly among months within this period. Average prolificacy of 3- to 6-year-old ewes Lambing in winter and spring was 1.75 for Targhee, 1.91 for Suffolk, and 2.13 for Polypay. For age groups with at least 10 observations, prolificacy in autumn (September through November) was reduced by an average of 0.14 lambs in Suffolk and 0.24 lambs in Polypay (very few Targhee lambed in autumn). Prolificacy in summer (June through August) was reduced by an average of 0.18 lambs in Targhee and 0.31 lambs in Polypay (very few Suffolks lambed in summer). Adjustment of prolificacy records for effects of ewe age is therefore necessary in genetic evaluation programs. Seasonal effects on prolificacy are probably best handled by placing ewes that lamb in different seasons in different contemporary groups.
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response to selection for fertility in a fall Lambing sheep flock
Journal of Animal Science, 1997Co-Authors: S A Alshorepy, D R NotterAbstract:Selection for fertility in a fall Lambing system was applied for 5 yr (1.45 generations) in a crossbred sheep population. Three flocks were involved: a fall-Lambing selected (S) flock of 125 ewes and 10 rams, a fall-Lambing environmental control (EC) flock of 55 ewes and five rams, and a spring-Lambing genetic control flock of 45 ewes and five rams used to produce replacements for EC. Estimated breeding values for fertility (ewes Lambing per ewe exposed) were calculated for animals mated in each year of the study using a single-trait animal model and increased more rapidly in S (.0138/yr) than in EC (.0067/yr). After accounting for genetic drift, EBV of ewes mated in S in the final year of the study averaged .070 +/- .032 (P = .08). A correlated response of .0087 lambs/yr was observed in S for fall litter size Genetic trends in all body weights were positive in EC, likely because of supplemental selection on body size in ram lambs used in EC. Ninety-day weight, maternal effects on weaning weight, and 90-d scrotal circumference increased in S, but direct effects on birth and weaning weights declined. In order to focus on realized selection response in fertility, EBV for fertility of 330 replacement ewe lambs from S and EC were calculated using only data collected after their birth. These realized EBV were then regressed on pedigree EBV calculated at the time the ewe lambs were born. The regression was significant when all relationships were used to calculate both EBV (.20 +/- .08) but only approached significance (.13 +/- .07) when only records of the ewe lambs themselves, their descendants, and their paternal half-sibs were used to calculate realized EBV. Also, EBV for all ewes were calculated at the start of each breeding season and were higher (P < .01) for ewes that subsequently lambed than for open ewes. These results suggest that selection can be used to improve fertility in fall-Lambing sheep flocks.
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ewe fertility in the star accelerated Lambing system
Journal of Animal Science, 1996Co-Authors: R M Lewis, D.e. Hogue, D R Notter, B H MageeAbstract:Effects of environmental factors such as ewe age, season of exposure, and time from Lambing to exposure on fertility were evaluated using records on 1,084 Dorset ewes in the STAR accelerated Lambing system. The STAR program consisted of five 30-d concurrent breeding and Lambing periods per year beginning on January 1, March 15, May 27, August 8, and October 20. Fertility in the flock changed in a cyclic and predictable fashion during the year. Changes in prolificacy were less consistent but also tended to show cyclic variation. Matings that occurred within the typical breeding season (August, October, and January) were more fertile than those occurring in March and June. However, fertility also varied with the age of the ewe and the time since the ewe's last Lambing. Except in June, fertility at the first postpartum mating increased as ewes aged. In March and June matings, adult ewes that had just weaned lambs were less fertile than ewes that had failed to conceive in the previous season and therefore had longer postpartum intervals. However, in October and January, ewes that had just weaned lambs were more fertile. A matrix of expected pregnancy rates, or probabilities of fertility, was constructed using a mixed GLM to describe the combined effect of season, ewe age, and time since Lambing on ewe fertility in accelerated Lambing.
Andrew S Peregrine - One of the best experts on this subject based on the ideXlab platform.
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a longitudinal study on the effect of Lambing season on the periparturient egg rise in ontario sheep flocks
Preventive Veterinary Medicine, 2013Co-Authors: L C Falzon, Paula I Menzies, K P Shakya, Andria Jonesbitton, John A Vanleeuwen, J Avula, Jocelyn Jansen, Andrew S PeregrineAbstract:Abstract The epidemiology of the periparturient egg rise (PPER) of gastrointestinal nematodes (GINs) in sheep remains unclear, and may be influenced by the Lambing season. This longitudinal study was performed to determine the effect of out-of-season Lambing on the PPER in ewes in Ontario, and whether total plasma protein (TPP) and packed cell volume (PCV) were associated with the PPER. Six farms that practiced out-of-season Lambing were enrolled, and sampled for three consecutive Lambing seasons (winter, spring and autumn). For each Lambing season, all farms were visited five times. On the first visit for each Lambing season, 15–20 pregnant ewes and 15–20 non-pregnant/early gestation ewes were randomly selected. At each visit, fecal samples were collected from all selected animals and processed individually to measure GIN fecal egg counts (FECs). Blood samples were collected on three visits in each Lambing period and processed to measure TPP and PCV. The ewes were classified into one of five production stages (maintenance [i.e. not pregnant], early or late gestation [
