Characterization of straightbred and crossbred rabbits for milk production and associative traits

Two hundred twenty-five lactation and litter performance records from 82 does representing four genetic groups and two diets were analyzed to quantify breed, heterosis, reciprocal F1 cross and diet effects for milk production and associative traits. Doe genetic groups were New Zealand White (NN) and Californian (CC) straightbred and Californian X New Zealand White (CN) and New Zealand White X Californian (NC) reciprocal crossbreds. Pelleted diets fed to does and litters were either a commercial control or a 74% alfalfa diet. Three sire breeds of litters included NN, CC and Flemish Giant (FG) straightbreds. Doe genetic group and diet were important sources of variation (P less than .05) for all traits examined except for litter milk efficiency (litter gain/milk intake) and doe feed efficiency (milk yield/feed intake). The sire breed of litter effect did not influence (P greater than .05) lactational performance of does nor associative preweaning traits. Straightbred NN does were heavier at kindling, yielded more milk, reared a heavier litter by 21 d and were more efficient in converting feed into milk than were straightbred CC does (P less than .01). Significant heterosis was detected for milk production and for litter size and weight at 21 d. Reciprocal differences between crossbred doe groups were observed (P less than .05) for litter milk efficiency and doe feed intake. The 74% alfalfa diet was superior to the commercial control diet for effects on milk production and litter size and weight at 21 d, although doe feed intake was increased.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reproductive and health traits among Boer, Kiko, and Spanish meat goat does under humid, subtropical pasture conditions of the southeastern United States

Boer (n = 132), Kiko (n = 92), and Spanish (n = 79) straightbred does were studied across 6 yr to assess doe fitness on southeastern US pastures. Does were exposed to Boer, Kiko, and Spanish bucks in a complete 3-breed diallel mating scheme each fall for spring kidding in March or May. A total of 1,041 doe-yr units were observed with does (ranging from 2 to 8 yr of age) managed together in a semi-intensive manner. The proportion of buck-exposed does delivering at least 1 live kid was less (P < 0.01) for Boer does (80%) than for Kiko (96%) and Spanish does (94%). Litter size and litter weight at birth were not affected (P > 0.15) by breed of dam. By weaning at 3 mo, the proportion of available does weaning at least 1 kid was less (P < 0.01) for Boer does (53%) than for Kiko (84%) and Spanish does (82%). For does weaning kids, litter size at weaning was greater (P = 0.01) for Spanish does (1.74 kids) than for Kiko (1.59 kids) and Boer does (1.47 kids). Litter weaning weight was lighter (P < 0.01) for Boer dams (23.0 kg) than for Kiko (27.2 kg) and Spanish dams (26.5 kg). The efficiency ratio of litter weight to dam weight at weaning differed (P < 0.05) among all 3 dam breeds: Boer = 51%; Kiko = 62%; Spanish = 68%. Annual rates of lameness, endoparasitism, and attrition, respectively, were greater (P < 0.01) for Boer does (69, 53, and 28%) than for Kiko (32, 24, and 10%) and Spanish does (42, 22, and 11%). Postpartum fecal egg counts for endoparasite loads were less (P < 0.05) for Spanish dams (346 eggs/g) than for Kiko (524 eggs/g) and Boer does (675 eggs/g). Whole-herd annual doe productivity based on all available does was less (P < 0.01) for Boer does (11.7 kg weaned/doe) compared with Kiko (22.0 kg weaned/doe) and Spanish does (21.1 kg weaned/doe). Boer does expressed substantially decreased levels of fitness compared with Kiko and Spanish does when semi-intensively managed on humid, subtropical pasture. Kiko and Spanish should be preferred as maternal breeds in meat goat production systems under conditions reflective of this study.     

Evaluation of Dorset, Finnsheep, Romanov, Texel, and Montadale breeds of sheep: I. Effects of ram breed on productivity of ewes of two crossbred populations

Effects of Dorset, Finnsheep, Romanov, Texel, and Montadale breeds for performance as sires were estimated in the initial phase of a comprehensive evaluation of these breeds as contributors to sheep crossbreeding systems. Objectives were to evaluate the effects of ram breed, ewe breed, season of mating, and two-way interactions. Rams from the five breeds were single-sire-mated with ewes from two breed types to produce lambs over a 3-yr period. Ewes were assigned to one of three distinct 35-d mating seasons initiated each year in August, October, and December. A different sample of six rams per breed was used each year across all three seasons, and each ram was penned with ewes of both breeds. Traits evaluated and number of ewe records were conception rate and litter weaning weight per ewe exposed (n = 3,261) and number born, litter birth weight, average birth weight, number weaned, and litter weaning weight per ewe lambing (n = 2,751). Ram breed and ewe breed interacted (P < .01) for conception rate and litter weaning weight per ewe exposed, implicating mating preferences, particularly of Romanov rams. In mixed groups of ewes exposed to Romanov rams, conception rate was 12.7% lower and litter weight weaned was 8.4 kg lower in the ewe breed presumably less preferred for mating by the rams. On a per ewe exposed basis, Romanov-sired litters produced either the largest or the smallest values for litter weaning weight, depending on the breed of ewe. Effects of ram breed on number born and litter birth weight interacted (P < .05) with season of mating. The largest litters within each ram breed were associated with the October mating season. Montadale and Romanov rams sired larger and heavier litters from August matings than from December matings, whereas the opposite was true for Dorset-sired litters. Texel- and Finnsheep-sired litters were similar in size and weight from August and December matings. Breed of ram differences affected per ewe lambing productivity measurements (P < .01). Differences between ram breeds for ewe productivity were noted, with increased number born and improved survival of crossbred progeny to weaning for Romanov-sired litters. These results may have implications for using these ram breeds as sires in different crossbreeding systems. Structured mating systems or the creation of new composite populations involving these breeds could be used to match the resources, environment, and market of specific production situations.     

品种对肉兔断奶后窝生长性状的影响

本研究旨在明确影响肉兔断奶后窝生长性状和料肉比的重要因素。利用一般线性模型分析了来自5个不同肉兔品种(新西兰白兔,加利福尼亚兔,比利时兔,青紫蓝兔和福建黄兔)的909只173窝肉兔断奶后窝生长和料肉比性状。结果表明,品种和断奶数对断奶窝重(5周龄窝重),窝增重,窝上市体重(10周龄窝重),个体平均上市体重,窝采食量和料肉比的影响极显著(P<0.01)。出生月份对窝采食量影响极显著(P<0.01),对断奶窝重和窝上市体重的影响显著(P<0.05)。比利时兔的断奶窝重、窝增重、窝上市体重、窝采食量和平均上市体重显著高于其他品种,而福建黄兔的上述5项指标显著低于其他品种(P<0.05)。断奶数与断奶窝重、窝采食量、窝增重、窝上市体重和料肉比的回归系数为正且显著。品种、断奶数和出生月份是影响肉兔断奶后窝性状和料肉比的重要因素。本研究的结果为将比利时兔作为杂交的终端父本提供重要依据。     

Interval to first postweaning estrus and causes for leaving the breeding herd in Large White, Landrace, Yorkshire and Chester White females after three parities

Three hundred and five Large White (LW, 93), Landrace (L, 92), Yorkshire (Y, 69) and Chester White (CW, 51) gilts produced at the Roman L. Hruska U.S. Meat Animal Research Center over 3 yr with 15 to 41 gilts per breed group per year were housed in total confinement and mated to farrow at 1 yr of age. After 28 to 30 d lactation, piglets were weaned and all females were observed for estrus daily for 30 d. During the year that each gilt initially farrowed, she was mated to produce a second and third litter if she returned to estrus within 30 d after piglet removal. Interval from weaning (d 0) to estrus and reason for leaving the breeding herd were recorded for each animal. Interval from weaning to estrus was influenced by breed (P less than .01), parity (P less than .01) and interaction between breed and parity (P less than .01). Intervals from weaning to estrus, in first parity females which exhibited estrus, were 7.8, 6.6, 9.3 and 14.0 d for the LW, L, Y and CW breeds. Intervals for all females after the second litter were 6.8, 4.9, 8.0 and 9.1 d, and after the third litter 6.4, 5.2, 8.3 and 10.1 d for the LW, L, Y and CW breeds. Breed, parity and year (P less than .01) affected the number of females not exhibiting estrus. Percentages of females not exhibiting estrus were 6.5, 18.7, 37.7 and 23.5 for the LW, L, Y and CW breeds and 16.1, 2.3 and 2.0 for sows after the first, second and third parities.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lifetime parental productivity in twenty-seven crosses of mice. II. Weaning traits reflecting reproduction and lactation

Twenty-seven crosses of mice derived from three random-mating, unselected strains (SWO, J. PGH) with 16 matings/pureline or cross were cohabited continuously and monogamously for a 365-d reproduction period to evaluate lifetime reproductive performance of the parents. Data from 3,249 litters born (2,792 surviving to weaning) were analyzed to study the effects of parity (number of litters) and type of cross (pureline, two-way, backcross, three-way) on certain traits measured at weaning (21 d). The traits evaluated were 1) weaning to weaning interval (WWI), 2) litter size at weaning (LSW), 3) fraction alive at weaning (FAW)-the ratio of LSW to number born alive, 4) total litter weight at weaning (LWT), 5) pup weight at weaning (PWT), 6) weaning weight per pup observed alive at birth (WPP), 7) parental feed consumption per day (FPD) and 8) parental costs (PCT). Cost per live weanling animal was estimated as the ratio of cumulative parental costs to cumulative number weaned. Cost per unit of weaning weight was defined as the regression of cumulative parental costs on cumulative litter weight. Parity effects were important (P less than .01) for all traits measured. Type of cross effects were noted for LSW, LWT, PWT, WPP, FPD (P less than .01) and PCT (P less than .05). A parity X cross-type interaction was expressed for WWI, LSW, PWT, WPP, FPD (P less than .01) and FAW (P less than .05). Three-way crosses were more productive than backcrosses, two-way crosses and pureline matings for all traits studied. Three-way crosses displayed the smallest cost per animal weaned and smallest cost per unit of weaning weight. The influence of parity on traits measured at weaning was less than for traits measured at birth. Weight per pup born alive (WPP) was found to be a better indicator of reproduction and lactation ability than LWT because WPP accounts for preweaning mortality.     

乳头数对母兔繁殖力的影响

按照母兔乳头数为１０和８分为试验Ａ组和试验Ｂ组，每组１６只。测定哺乳前三（组）周，每组母兔的泌乳量、仔兔每天的平均吮乳量等。试验结果表明：哺乳前三周，母兔的泌乳量、仔兔每天平均吮乳量、仔兔日增重、断奶窝重及断奶成活率，试验Ａ组分别为３１３８．６２克、２１．９８克／天、只、１４．１８克／日、５２４９．６８克和９３．９７％，分别比Ｂ组高８．３０％、１２．４３％、７．３４％、４．２７％和１０．５５％。经ｔ检验和Ｘ２检验后发现，除断奶窝重在Ａ、Ｂ两组之间差异不显著外，其它各项指标在Ａ、Ｂ两组之间均差异显著（Ｐ＜０．０５）。由此可以得出结论：有较多乳头数的母兔能哺乳更多的仔兔，其繁殖力较强     

Effect of dietary crude protein level on the reproductive performance and growth of New Zealand white rabbits

An experiment utilizing 391 preweaning and 187 postweaning litter records from 145 does was conducted for 12 mo to determine the effect of dietary crude protein level on performance of commercial New Zealand White rabbits. Does and their litters were fed alfalfa-based pelleted diets containing either 17.5, 19 or 20.5% crude protein (CP). In a separate experiment, the 17.5 and 20.5% CP diets were fed during lactation to 10 does to determine nitrogen (N) digestibility and retention. Body weights of does fed 17.5% CP were lower (P less than .01) than for the other treatments after 21 and 28 d of lactation. No differences (P greater than .10) were observed for doe weight at kindling, percentage fertility, litter size, preweaning litter mortality, 1- to 21-d consumption, preweaning feed efficiency and 28- to 56-d average daily consumption, average daily gain and average weight. Total born tended to be higher (P = .07) on higher protein levels but percentage born alive was greatest (P less than .01) on the 17.5% CP diet. Does fed 19% CP tended to have a greater number of parities (P = .06). Other significant differences observed for preweaning litter traits were between 17.5 and 19% CP groups. Does fed 19% CP had heavier litters at birth (P less than .01), at 21 d (P = .05) and 28 d (P = .06) and had greater 1- to 21-d litter gains and 21- to 28-d consumption (P = .05) than those fed 17.5% CP. For postweaning performance, feed efficiency values were lowest and mortality was highest for litters fed 20.5% CP. When litters were switched to different diets after weaning, mortality tended to be higher (P = .07) for animals that were fed 20.5% CP before weaning. The month of experiment effect did not influence any of the characters studied (P greater than .05). Parity number was important for percentage fertility, percentage born alive, litter birth weight and doe weight at 21 and 28 d (P less than .05). Does at first parity showed the poorest performance for all traits (except percentage fertility). Fertility fluctuated throughout the first four parities and then steadily declined. Does fed 20.5% CP had greater apparent dry matter and acid detergent fiber digestibilities and N intakes (P less than .05) and retained 90% more N during lactation (P = .22) than does fed 17.5% CP. Milk production and CP digestibility did not differ between the two diets tested.(ABSTRACT TRUNCATED AT 400 WORDS)     

Usefulness of subjective ovine milk scores: II. Genetic parameter estimates

Genetic parameters for a subjective milk score given to ewes within 24 h of parturition were estimated to determine the usefulness of milk score as a selection trait to improve milk production, which influences total litter weight weaned. Heritability of milk score and the genetic correlation of milk score with litter weight weaned were estimated by REML separately for four sheep breeds, Rambouillet (n = 1,731), Targhee (n = 1,638), Columbia (n = 1,731), and Polypay (n = 1,129). Litter weight weaned was the total weight of lambs weaned at approximately 120 d of age under a western range production system. Observed heritability estimates for milk score at first parity were moderate and similar among breeds, ranging from 0.18 to 0.32. Heritability estimates adjusted for a binomial distribution of milk scores at first parity were high (Columbia, 0.43; Polypay, 0.35; Rambouillet, 0.50; Targhee, 0.84). Estimates of observed heritability for second-parity milk score were moderate to high, ranging from 0.23 to 0.46. Milk score at first or second parity was genetically correlated with milk score records at maturity (third parity and greater), with estimates ranging from 0.69 to 1.00. Milk score and litter weight weaned were genetically correlated at first or second parity in Rambouillet (r(g) = 1.00) and Targhee breeds (r(g) = 1.00 and 0.61, respectively), but not in the Columbia and Polypay breeds. Estimates of heritability for lifetime records for milk score ranged from 0.16 to 0.26 across breeds. Estimates of genetic correlations of annual lifetime milk score records with litter weight weaned were high (Columbia, 1.00; Polypay, 0.81; Rambouillet, 1.00; and Targhee, 0.77). Repeatability estimates for milk score were similar across breeds, 0.23 for Columbia, Rambouillet, and Targhee ewes and 0.28 for Polypay ewes. Milk score measured at first or second parity may be a good predictor of future potential milking ability. Further, milk score can be used as a selection trait to improve maternal ability for increasing litter weight weaned. The need for increasing ewe milking performance and lamb growth rate at first parity in commercial range sheep production systems may be addressed by selection for milk score at first parity.     

Effects of genetic line and supplemental dietary fat on lactation performance of Duroc and Landrace sows.

A total of 124 Duroc and 99 Landrace primiparous and multiparous sows were assigned, within breed and contemporary group, to control (N) or 10% added fat (F) diets on d 105 of gestation based on parity and genetic line (control or selected for improved sow productivity), to determine the effects of genetic line and fat addition to the lactation diet on sow and litter performance. Weekly feed intake was not affected (P greater than .10) by genetic line for Duroc and Landrace sows but feed intake was reduced (P = .08) during wk 1 to 4 for Duroc sows and during wk 1 and 4 for Landrace sows (P less than .05) when they were fed diet F compared with diet N. Select (S)-line Duroc and Landrace sows lost more weight during lactation (P less than .01) than did control (C)-line sows. Select-line Landrace sows lost more backfat during lactation (P less than .05) than did C-line sows. Landrace sows lost less weight during lactation (P less than .05) when fed diet F than when fed diet N. The total number of pigs born, born alive, and alive at 21 d and at weaning were higher (P less than .01) for S-line Duroc sows, and litter size at 21 d and at weaning was higher (P less than .01) for S-line Landrace sows than for C-line litters within each breed. Pig survival from birth to weaning was increased (P = .07) for Duroc sows fed diet F but not for Landrace sows.(ABSTRACT TRUNCATED AT 250 WORDS)     

胎次对杜洛克、长白和大白母猪繁殖性能的影响

为了研究胎次对杜洛克、长白和大白母猪繁殖性能的影响,根据江苏省某国家级生猪核心育种场2009-2011年出生的繁殖母猪资料,分别选取128头杜洛克、681头长白和610头大白母猪共7280窝生产数据,统计分析不同胎次母猪的总产仔数、产活仔数、断奶仔猪数、初生窝重及校正21日龄窝重。此外,依据胎次将母猪分为3个繁殖阶段（1～2胎、3～6胎及7～8胎）来探究品种差异对母猪繁殖性能的影响。结果表明：胎次对母猪繁殖性能有显著影响（P<0.05）,母猪1～4胎的总产仔数、产活仔数、断奶仔猪数及初生窝重随胎次呈增加趋势,第4胎达到高峰,且显著高于其他胎次（P<0.05）;3～6胎繁殖性能较好,7胎之后出现迅速下降趋势;除在第4胎略有下降外,其他胎次的校正21日龄窝重随胎次递增。品种对母猪繁殖性能的影响显著（P<0.05）,长白和大白母猪的繁殖性能均极显著高于杜洛克母猪（P<0.01）;长白母猪的产活仔数和校正21日龄窝重显著高于大白母猪（P<0.05）,2个品种其他繁殖性能无显著差异（P＞0.05）。综上所述,杜洛克、长白和大白母猪的最佳繁殖胎次为3～6胎,长白猪的繁殖性能总体上优于大白猪,就本试验所在的育种场而言,长白猪可能更适合作为二元母猪生产中的母本。     

The effect of litter size before weaning on subsequent body development, feed intake, and reproductive performance of young rabbit does

An experiment was performed to study the effect of litter size before weaning on subsequent body development and composition, feed intake, and reproductive performance of young rabbit does with the objective to improve reproductive performance. Litter size (LS) before weaning (treatment) was 6, 9, or 12 kits. After weaning (30 d), 58 female kits per treatment (in two successive replicates) were reared and fed for ad libitum intake to 14.5 wk of age (end of rearing). At 14.5 wk of age, receptive does were inseminated. Nonreceptive and nonpregnant does were inseminated at 17.5 wk of age. The experiment ended when the second litter was weaned. Part of the animals was slaughtered to determine body composition at the end of the experiment (replicate one) and at the end of rearing (replicate two). At weaning, BW differed among treatments (P < 0.05; 855, 773, and 664 +/- 15 g for LS6, 9, and 12, respectively). Compensatory growth was observed. At the end of rearing, LS12 does were smaller (P < 0.05) than LS9 and LS6 does (3,524, 3,778, and 3,850 +/- 48 g, respectively). After first lactation, no difference in BW among treatments was found. Compared with LS6, empty body weight (BW minus gut, bladder, and uterus content) of LS12 contained more (P < 0.05) nitrogen (32.5 vs 31.1 +/- 0.3 g/kg), more (P < 0.05) ash (30.7 vs 28.3 +/- 0.6 g/kg), and less (P < 0.05) fat (168.6 vs 200.2 +/- 8.6 g/kg). No differences in body composition among treatments were found at the end of the experiment. During rearing, LS12 had the lowest (P < 0.05) daily feed intake (152, 164, and 169 +/- 2 g/d for LS12, 9, and 6, respectively). During the reproductive period, no differences in feed intake among treatments were found. Kindling rate (the number of kindlings per number of inseminations) was not influenced by treatment. In the first parity, total litter size (number of alive and stillborn kits) was lower (P < 0.10) for LS12 than for LS9 (6.4 vs 8.6 +/- 0.5, respectively). When first mating was delayed by 3 wk, an increased (P < 0.05) total litter size was found regardless of treatment (7.5 and 9.4 +/- 0.3 for 14.5, and 17.5 wk, respectively). Decreasing litter size before weaning from nine to six kits did not alter future reproductive performance. Based on results of this study, it seems advisable to perform a limited standardization level (at nine kits) after kindling and postpone first mating to an older age (17.5 wk) to improve reproductive performance.     

Effects of a novel carbohydrate and protein source on sow performance during lactation

Ninety-one primiparous and multiparous sows and their pigs were used to evaluate the effects of a novel carbohydrate- and protein-based feed ingredient (Nutri-Pal, NP) on sow and litter performance during lactation. Nutri-Pal is a feed supplement for sows that consists of a blend of milk chocolate, brewer's yeast, whey products, and glucooligosaccharides. The dietary treatments consisted of a corn-soybean meal control and a corn-soybean meal plus 5% NP fed from d 110 of gestation to weaning. The diets were formulated to be equal in total Lys and ME. Sows were allotted to treatment based on parity, body weight, and the date of d 110 of gestation. There were 46 and 45 sows per treatment over four farrowing groups. Litters were standardized to 10 pigs and weighed within 1 d of farrowing, and all sows weaned at least 8 pigs at an average age of 21 d. Sows were weighed on d 110 of gestation, d 1 postfarrowing, and at weaning. Sows were fed three times daily during lactation. Sows were checked twice daily after weaning for signs of estrus. The weaning weight of sows fed NP was increased (P < 0.10) compared with those fed the control diet. Sows fed the control diet tended (P = 0.11) to lose more weight per day from d 110 of gestation to weaning than the sows fed NP. Otherwise, sow response variables (sow weight on d 110 of gestation and d 1 postfarrowing, d 110 of gestation to d 1 postfarrowing and lactation weight change per day, d 110 of gestation to d 1 postfarrowing, lactation, and total feed intake, days to estrus, pigs born alive or dead, and litter and average pig birth weight) were not affected (P > 0.10) by diet. There were no effects (P > 0.10) of diet on litter performance response variables (pigs weaned, litter and average pig weaning weight and gain, and survival percent). The NP feed ingredient had minor effects on sow productivity, but it did not affect litter productivity indices.     

Biological type effects on gestation length, calving traits and calf growth rate

Gestation length, birth weight calving difficulty, calf mortality rate at birth, calf mortality rate from birth to weaning, preweaning calf growth rate and calf 200-d weight were evaluated in a biological type study in which four sire breeds were bred by AI to Hereford dams. Angus and Red Poll sires represented breeds of medium size, and Pinzgauer and Simmental sires represented large breeds. Angus and Pinzgauer represented breeds with medium milk production, and Red Poll and Simmental represented breeds with high milk production. Dams mated to large sire breeds had longer (P less than .01) gestation lengths (.95 d) and higher calving difficulty scores than dams mated to medium-sized sire breeds. Calves from large sire breeds had heavier birth weight (P less than .01) and 200-d wt (6.1 kg; P less than .01) than calves from medium-sized sire breeds. Calf death loss and ADG to weaning were similar (P greater than .10) for all breeds of sire. Calves from the higher milk level sire breeds exceeded the medium-milk breeds in birth weight (1.3 kg; P less than .01) but did not (P greater than .10) in other traits. Calves from the higher milk level sire breeds exceeded the medium-milk breeds in birth weight (1.3 kg; P less than .01) but not (P greater than .10) in other traits. Interaction between size and milk production of sire breed existed for gestation length, birth weight, ADG from birth to weaning and 200-d calf weight (P less than .01). In general, mature size of sire breed was a good indication of expected performance traits not easily influenced by environment. Not all differences, however, could be explained by size and milk production of the size breed.     

Usefulness of subjective ovine milk scores: I. Associations with range ewe characteristics and lamb production

Range ewes are commonly evaluated for milking ability by producers to determine the ewe's ability to rear lamb(s). The U.S. Sheep Experiment Station has subjectively scored (low, average, high) a ewe's milking ability within 24 h of lambing for many years. The relationship of subjective milk scores with lamb production was investigated using lambing records of Columbia (n = 1,731), Polypay (n = 1,129), Rambouillet (n = 1,704), and Targhee (n = 1,638) ewes. The incidence of high milk scores increased from less than 10% at first parity to 29 to 40% at second and greater parities. At maturity, Columbia ewes (38%) had the highest percentage of high milk scores. A positive association existed between ewe BW and her milk score at third and later parities. Ewes with high milk scores gave birth to heavier lambs (P < 0.05), whereas ewes with low milk scores were associated with lighter (P < 0.05) lambs at birth. Ewes with low milk scores weaned less (P < 0.05) total weight than ewes with better milk scores across all age groups for all breeds. Lighter weaned litter weights from ewes with low milk scores were linked to lighter birth weights and fewer weaned lambs. Differences for litter weight weaned between ewes with average and high milk scores were generally observed at 2 and 3 yr of age, when litter weights were heavier among ewes with high milk scores (P < 0.05) for all breeds. Between the ages of 1 and 3 yr, Columbia, Polypay, Rambouillet, and Targhee ewes with an average milk score weaned heavier (P < 0.05) litters (average differences of 10, 9, 13, and 12%, respectively) than ewes with low milk scores. For all breeds at all ages, individual lamb weaning weights were heavier (P < 0.05) when they were reared by ewes with high milk scores compared to lambs reared by ewes with low milk scores. Results suggest that milk score is an economically important trait in these four breeds and should be considered in management and breeding objectives; at a minimum, the incidence of low milk scores should be kept as small as possible.     

Examination of the relationship between the estrogen receptor gene and reproductive traits in swine

The relationship between estrogen receptor (ESR) genotype and reproductive traits in a population of Yorkshire, Large White, and crossbred animals was studied. Reproductive tract and litter data were analyzed for associations with ESR genotype, parity, and breed. Forty-six Yorkshire, 31 Large White, and 70 crossbred females from the above population were mated to Hampshire boars and slaughtered at 75 d of gestation. Data collected included ovulation rate, uterine horn length, number of fetuses, fetal weight, uterine weight, number of mummies, fetal sex, fetal placement, fetal survival, and fetal space. Data were analyzed using a model that included the fixed effects of ESR genotype, breed, parity, and all significant two-way interactions. Litter data representing 212 litter records were analyzed in a model that included the fixed effects of ESR genotype of dam, parity, farrowing month, dam breed, sire breed, and all significant two-way interactions. The ESR genotype was significantly associated with the total litter weight of piglets born and total litter weight of piglets born alive. Dams with the AA genotype had significantly (P = 0.04) heavier litters at birth (14.44 +/- 0.36 kg) than dams with the BB genotype (13.43 +/- 0.47 kg). Ovulation rate was significantly (P < 0.05) different between animals of parity 1 (17.22 +/- 0.41) and parity > or = 3 (19.92 +/- 0.85). Significant breed effects were observed for fetal weight, with purebred Large White animals having a greater fetal weight per horn (3,909 +/- 114 g) than purebred Yorkshire animals (3,553 +/- 92 g). Notable, but nonsignificant, trends with respect to ESR genotype were also observed for number of piglets alive at weaning and total litter weight at weaning. The ESR gene is positively associated with several previously uninvestigated reproductive traits.     

Effect of bee pollen levels on productive, reproductive and blood traits of NZW rabbits

Forty New Zealand White (NZW) rabbit does were equally divided among four groups feeding the same commercial diet and receiving a water solution containing, respectively, 0 (control), 100, 200 and 300 mg bee pollen/kg body weight (BW), 1 week before and after mating during moderate (October-February) and hot seasons (May-September) for three consecutive mating in each season. Does were mated with non-treated adult NZW male rabbits 11 days after kindling. Body weight of does, number of service per conception, conception rate, feed intake, litter size, milk production, blood constituents, weight of kits from birth up to weaning and survival rate were determined. For each season, 80 weaned rabbits originated from the does of the control group (untreated does) were equally divided into four groups (0, 100, 200 and 300 mg/kg BW) of bee pollen, given as a water solution twice per week from 4 to 12 weeks of age. The kit of the does given 100, 200 and 300 mg/kg BW did not receive bee pollen during the growing period (4-12 weeks of age). The effect of bee pollen on growing rabbit's performance was studied from 4 to 12 week of age. Bee pollen at 200 mg significantly (p < 0.01) increased body weight of does, conception rate, milk yield, litter size; improved biochemical profiles of blood and helps outstanding of does during both seasons. The same dose of bee pollen significantly increased kit growth and their survival rate until weaning. Growth and feed conversion ratio (FCR) of kits from the treated does during 4-8 weeks of age were significantly better than growth of kits from the untreated does that administrated bee pollen during 4-12 weeks of age. Meanwhile, during the following period (8-12 weeks of age) growth and FCR of kits given bee pollen from the untreated does were significantly better than that of treated does.     

Breed effects on crossbred cow-calf performance

Effects of seven breeds of cow's sire and 12 breeds of cow's maternal grandsire on preweaning performance of crossbred cows and their calves were examined in data from two experiments conducted at the Roman L. Hruska U.S. Mean Animal Research Center. Data included 1,836 records over three to five parities for 516 cows by 143 sires and by 307 maternal grandsires. The statistical model fitted effects of calf sex, parity, cow birth-breeding year or cow-calf birth year, the breed effects and their interactions. Deviations of breed of sire or equivalent grandsire effects on each trait from the mean for Hereford x Angus cows ranged from -1.6 to 5.5 kg (P less than .001) for calf birth weights, -15 to 1% (P less than .001) for calving difficulty, nonsignificant for preweaning calf mortality and -2 to 27 kg (P less than .001) for calf weaning weight. Deviations were nonsignificant for conception rate and calves weaned per cow exposed to breeding, but -2 to 40 kg (P less than .001) for calf weight weaned per cow exposed for breeding, -7 to 78 kg (P less than .001) for cow weight and -20 to 2% (P less than .001) for body condition score. The advantages of Holstein and Brahman cross over Hereford x Angus cows of 23 and 13% in weight of calf weaned/cow-breeding exposure must be compared with the expected greater feed requirements from 7 or 8% heavier cows and at least 50% higher milk production, which emphasizes the need to include input measures and costs in breed evaluation schemes.     

大白猪、长白猪和杜洛克猪催乳素受体基因多态性及其与繁殖性能的关系

本试验通过PCR-RFLP技术对大白猪、长白猪和杜洛克猪的催乳素受体(prolactin receptor,PRLR)基因第10外显子AluⅠ酶切位点进行多态性分析,并对各基因型母猪的第1至第3胎次产仔数、产活仔数、断奶仔猪数、初生窝重、21日龄窝重及断奶成活率进行测定,进而分析PRLR基因多态性与繁殖性能的关系。结果表明,PRLR基因在3个品种中均存在多态位点,且AA基因型都是其优势基因型。关联分析结果表明,大白猪AA基因型个体第1、2和3胎各繁殖性状均呈现出高于AB和BB基因型的趋势。在繁殖性能已经稳定的第3胎次AA基因型个体产仔数、产活仔数、断奶仔猪数、初生窝重及断奶成活率比BB基因型个体平均分别高出0.31头、0.63头、0.02头、0.65 kg和0.43%,但差异均不显著(P>0.05)。     

The effects of branched-chain amino acids on sow and litter performance

Sows (n = 306; PIC, Line C-19; average parity 2.1) were used to evaluate the interrelationship between valine, isoleucine, and leucine on sow and litter performance. Our objective was to determine whether the increase in litter weaning weight associated with added dietary valine is specific for valine or a result of the total branched-chain amino acid (i.e., isoleucine and[or] leucine) concentration of the diet. Eight dietary treatments (36 to 41 sows/treatment) were arranged as a 2 x 2 x 2 factorial with two levels of valine (.80 and 1.20%), isoleucine (.68 and 1.08%), and leucine (1.57 and 1.97%). This provided total branched-chain amino acid levels of 3.05, 3.45, 3.85, and 4.25%. The lowest level of each branched-chain amino acid was similar to that in a .90% lysine corn-soybean meal diet containing .15% L-lysine HCl. Amino acids other than valine, isoleucine, and leucine met or exceeded their suggested estimates relative to lysine using ratios derived from the National and Agricultural Research Councils. Average number of pigs on d 2 of lactation was 11.2, and average lactation length was 20.9 d. Number of pigs weaned (x = 10.6), sow ADFI (x = 5.85 kg), and sow weight loss (x = 4.25 kg) were not affected by dietary treatment (P > .10). Sow backfat loss (P < .02), litter weaning weight (P < .04), and litter weight gain from d 2 to weaning (P > .05) increased as dietary valine increased. Litter weight at weaning and litter weight gain were not affected by dietary isoleucine (P > .80) or leucine (P > .60). Sixteen or 17 sows per treatment (129 total) were milked manually on d 14 to 16 of lactation. Increasing dietary valine tended to increase milk urea N (P < .07) but did not affect milk DM, CP, fat, lactose, or ash. Increasing dietary isoleucine or leucine had no effects on milk composition. These results confirm the importance of dietary valine for increased litter weaning weight, independent of either additional dietary leucine or isoleucine.