Effects of breed, parity, day of lactation and number of kits on milk production of rabbits

Lactation records (n = 86) from 60 does of four breeds (Californian, New Zealand White, Palomino and White Satin) were analyzed to assess the effects of breed, parity, day of lactation and number of kits on milk production. Breed of doe tended (P less than .07) to be important for mean milk yield according to ANOVA results. Californian does had numerically higher production than did does of the other breeds. Doe body weight, litter size born alive and weaned and litter weaning weight, likewise, were not influenced (P greater than .05) by breed of doe. Significant linear and quadratic relationships were found between milk production vs day of lactation, and milk production vs number of kits. However, breed x days and breed x number of kits interactions (P less than .05) indicated that the individual breeds responded differently to two of these effects. Peak lactation occurred at approximately 20 d after kindling. As kit number increased, milk yield also increased to a predicted maximum when 12 kits were suckling. Parity tended (P less than .10) to influence lactation yield in a curvilinear manner, increasing steadily through the seventh parity and declining thereafter. A nonsignificant residual correlation (.34) between milk production and doe body weight was observed. Corresponding correlations between milk production were high for litter size born alive and weaned (r = .62 and .87, respectively) and litter weaning weight (r = .86). Although lactation curves are unique to each particular breed, milk yield is influenced by several factors.     

Breed and heterotic effects on postweaning traits in Altex and New Zealand White straightbred and crossbred rabbits

Postweaning data from 1,111 straightbred and reciprocally crossbred rabbits were analyzed to evaluate Altex and New Zealand White (NZW) breeds for individual growth and litter traits. The Altex is a recently developed sire breed, whereas the NZW is a popular commercial dam breed. Individual fryer growth traits were weaning (28 d; WW) and market (70 d; MW) weights and ADG. Litter traits included litter size (LSW) and total weight of litter at weaning (LWW), 28 to 70 d total feed intake (LFI), feed efficiency (LFE = total litter gain/LFI), survival rate, and within-litter MW uniformity. Least squares models consisted of fixed effects of sire breed, dam breed, season of weaning, doe parity, two- and three-way interactions, and random effects of sire within sire breed, litter within sire x dam breed, and(or) residual error (depending on whether an individual or a litter trait was analyzed). Crossbreeding parameters (direct breed additive, maternal breed, and individual heterosis) were estimated. Altex sires increased WW, ADG, and MW by 40 g (P < 0.10), 2.5 g/d, and 152 g (P < 0.001), respectively. Individual growth traits were not significantly influenced by the maternal breed effect. Litter size at weaning and LWW means were numerically similar for Altex and NZW dams. Direct heterosis increased ADG (1.7 g/d; P < 0.01) and MW (66 g; P < 0.10). In straightbred Altex compared to NZW fryers, ADG and MW were increased by 3.6 g/d and 216 g, respectively (P < 0.001). In Altex (sire) x NZW (dam) crossbred compared to NZW straightbred fryers, WW and MW were heavier (55 and 218 g; P < 0.10 and < 0.001) and ADG was more rapid (4.2 g/d; P < 0.001). For litter traits, Altex compared to NZW sires increased LFI by 1.28 kg (P < 0.10). Individual crossbreeding parameters did not affect (P > 0.05) other litter traits. No relationship existed between breed type of fryer and survival status (chi2 = 2.81; P > 0.25). For litter traits, straightbred Altex had significantly greater LFI by 2.45 kg and increased LFE by 0.015 units relative to NZW. Combined direct breed additive and heterosis effects increased LFI by 1.84 kg (P < 0.05) in Altex (sire) x NZW (dam) crossbreds compared to NZW straightbreds. Also, 25% more Altex (sire) x NZW (dam) crossbred fryers were marketable (body weight > or = 1.8 kg) by 63 d of age than NZW straightbred fryers. These data suggest that crossing Altex bucks to NZW enhanced breeding efficiency of fryer growth performance.     

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。     

Prediction and causation of litter market traits from preweaning and weaning characteristics in commercial meat rabbits

Market data on 1,315 rabbits from 201 litters from Californian (CAL), New Zealand White (NZW), CAL X NZW and NZW X CAL dams bred to CAL, NZW and Flemish Giant sires were subjected to multiple regression and path analyses. Market traits observed in litters at 56 d included average kit weight (A56W), litter size (LS56), total litter weight (L56W) and within-litter uniformity in individual weights (LCV). Preweaning variables as covariates included in the model were dam metabolic body weight (DMW), litter born (LSB), litter birth weight (LBW), milk yield from 1 to 21 d (MY) and feed intake from 1 to 28 d of the dam and litter (FI). Results from multiple regression analyses indicated linear and quadratic effects (P less than .20) due to LSB and MY for all four market characters. The LBW influenced (P less than .05) LS56 and L56W, and FI affected (P less than .05) LS56, L56W and LCV. Separate analyses were conducted involving 28-d weaning and feed intake variables as covariates: litter size weaned (LSW), litter weaning weight (LWW) and litter feed intake from 28 to 56 d (LFI). The three weaning covariates were important (P less than .05) for all market traits except LS56 (LWW was not significant). The most accurate regression equations were obtained from the weaning model for prediction of L56W and LS56 (R2 = .68 and .78). Path analyses revealed that preweaning covariates generally had direct rather than indirect effects on market traits. Both direct and indirect effects of weaning covariates were important for market traits. Results suggest that litter market traits of size and weight can be predicted with a reasonable degree of accuracy.     

Comparison of rabbit breed types for postweaning litter growth, feed efficiency, and survival performance traits

Postweaning data on 643 rabbits from 122 litters representing four breed types, New Zealand White (NZW) and Californian (CAL) purebreds, CAL X NZW (CXN), and Flemish Giant (FG) crossbreds (the latter group was a collection of FG X CAL, FG X Champagne D'Argent [CHA], and 1/2 FG X 1/4 CAL X 1/4 CHA), were gathered over five seasons and compared for growth, feed efficiency, and survival-related performance traits. Evaluation criteria included litter size and weight at weaning (28 d); 28- to 70-d litter feed intake, weight gain, feed efficiency, and mortality rate; and litter and average market weight (70 d). The least squares model included main effects of breed type, season of birth of the litter and parity of dam, litter size at weaning as a linear covariate, and the random error. Breed-type differences were not detected for litter size and weight at weaning and feed efficiency. Purebred NZW and CAL litter trait performances were comparable (P greater than .05). Purebred NZW litters consumed less feed than CXN and FG crosses, gained weight less rapidly than FG crosses, and weighed less per fryer at 70 d than CXN and FG crosses (P less than .05). Feed intake was lower and average market weight was lighter for CAL purebred litters than for CXN and FG crossbred litters (P less than .05). The CXN and FG crossbreds only differed (P less than .05) for average market weight (2,078 vs 2,192 g). Mortality rate was lower (P less than .05) in CXN crossbred litters than in CAL purebred litters.(ABSTRACT TRUNCATED AT 250 WORDS)     

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)     

Evaluating response to selection and nutritional needs in a three-way cross of rabbits

An experiment was carried out to evaluate the response obtained in a three‐way cross of rabbits when the lines involved had undergone within‐line selection for litter size or postweaning daily gain. The interaction between the level of nutrition and genetic level of the crossbreds was also studied. Using frozen embryos, old (H1) and current (H2) crossbred does and young were compared contemporarily. Does were fed a standard diet or a diet having high digestible energy and protein. The difference in the number of generations between lines used to produce both crosses were: 13 or 0 for the maternal lines, and 12 for the paternal line. The traits studied in the crossbred does were: daily feed intake during gestation, during the first 3 weeks of lactation and during the last week before weaning; doe weight at mating and at kindling; litter weight at birth and at weaning; total litter size, number born alive and litter size at weaning. The recorded traits for the young were: individual weight at weaning and at 63 days; individual daily gain after weaning; daily feed intake and feed conversion index. The last two traits were recorded as averages per cage. A total of 1161 litters from 190 does were involved. Significant differences in litter‐size traits, between H1 and H2 does, were observed and were higher than the expected from the within‐line response. The doe effect was not significant for other doe traits, adjusted to a constant litter size. The estimated difference in postweaning daily gain between H1 and H2 young was significant and in favour of H2, but the value was considerably lower than expected. The effect of type of feed and the interaction with the type of doe was not significant for any doe trait. The type of feed consumed by the doe was significant for postweaning daily gain, and the interaction with the type of crossbreds was significant for this trait and for individual weight at 63 days.     

Genetic parameters for total lactation yields of milk,fat, protein,and somatic cell score in New Zealand dairy goats

The aim of this study was to estimate genetic parameters for lactation yields of milk (MY), fat (FY), protein (PY), and somatic cell score (SCS) of New Zealand dairy goats. The analysis used 64,604 lactation records from 23,583 does, kidding between 2004 and 2017, distributed in 21 flocks and representing 915 bucks. Estimates of genetic and residual (co) variances, heritabilities, and repeatabilities were obtained using a multiple‐trait repeatability animal model. The model included the fixed effects of contemporary group (does kidding in the same flock and year), age of the doe (in years), and as covariates, kidding day, proportion of Alpine, Nubian, Toggenburg, and “unknown” breeds (Saanen was used as the base breed), and heterosis. Random effects included additive animal genetic and doe permanent environmental effects. Estimates of heritabilities were 0.25 for MY, 0.24 for FY, 0.24 for PY, and 0.21 for SCS. The phenotypic correlations between MY, FY, and PY ranged from 0.90 to 0.96, and the genetic correlations ranged from 0.81 to 0.93. These results indicate lactation yield traits exhibit useful heritable variation and that multiple trait selection for these traits could improve milk revenue produced from successive generations of New Zealand dairy goats.     

Heterosis and recombination effects in Hampshire and Landrace swine: I. Maternal traits.

Hampshire and Landrace sows and crossbreds of the two breeds were used to determine heterosis and recombination effects for milk production, milk composition, and litter traits at birth and d 21. Twelve mating types were represented in this study: two purebred, two F1, two F2, two F3, and four backcross. Information was gathered on a total of 358 litters over four farrowing seasons. Milk production was measured at d 10 and 20 of litter age according to the weigh-suckle-weigh procedure. Milk samples were collected at d 10 and 20 of litter age and evaluated for percentages of fat (PCFA), protein (PCPR), lactose (PCLA), and solids-not-fat (PCSN). The model used to evaluate litter traits at birth included main effects of mating type, parity, and farrowing season. The model used for milk production and milk composition traits included these main effects and number of pigs nursed as a covariate. Estimates of maternal genetic effects showed that Landrace females were superior to Hampshire females for number born (NB), number born alive (NBA), litter birth weight (LBW), adjusted 21-d litter weight (ALW), and milk production at d 10 of litter age (WT10). Hampshires were superior to Landrace for PCPR at d 10 of litter age and PCSN at d 10 and 20 of litter age. Heterosis effects were significant (P less than .05) for NBA (.97) and LBW (1.46 kg). Maternal heterosis effects were significant for LBW (3.94 kg; P less than .01). Epistatic recombination losses in the offspring were significant for LBW (6.80 kg; P less than .05). Differences in maternal performance of reciprocal F1 dams were generally not significant. Heterosis and recombination effects were not significant for milk production or milk composition.     

不同分娩季节对齐卡新西兰兔产仔性状的影响

为探讨分娩季节对母兔产仔性能的影响,利用2010-2013年度665只齐卡新西兰母兔共计1 649窝次的产仔性能记录,按不同分娩季节进行了比较分析.结果表明：分娩季节极显著影响齐卡新西兰母兔的产仔性状（P＜0.01）,其中春季产仔数、产活仔数、初生窝重以及初生个体重均为最高,秋季产仔数和产活仔数较低,夏季初生窝重和初生个体重最小.由于产仔数是繁殖性能最重要的衡量指标,研究表明,齐卡新西兰母兔繁殖的最佳季节为春季.     

Correlated responses in maternal performance following divergent selection for heat loss in mice

Divergent selection in mice was applied in 3 independent replicates for high (maintenance high; MH) and low (maintenance low; ML) heat loss for 16 generations. An unselected control (maintenance control; MC) was also maintained in all replicates. Selection ceased for 26 generations; heat-loss measurement and selection resumed at generation 42. Lactation performance, dam weight, dam feed intake, and efficiency of production of pup weight were recorded or calculated for MH and ML dams in all 3 replicates at generation 46 or 47 with the objective of determining whether selection for heat loss has created correlated responses in maternal performance. One-half of the dams reared their own litters, and one-half reared cross-fostered (across lines) litters. Between 10 and 12 litters were used from each replicate-line-rearing class. Litter size was recorded, and litters were standardized to 8 pups within 24 h of birth. For cross fostering, MH litters were matched to ML litters born within 24 h of each other, and MH-ML litter pairs were cross-fostered at 3 d of age. A weigh-suckle-weigh protocol was used to obtain milk production estimates over a 2-h suckling period at 6, 9, 12, and 15 d. Dam (plus litter) feed intake was also recorded at these times and was calculated as the disappearance of feed over 3-d intervals. Dams of the MH selection tended (P < 0.11) to have greater litter size than those of the ML selection; litter size of MC dams was intermediate. Line of dam affected milk production (P = 0.04) and dam feed intake (P < 0.03) as MH dams produced more milk and consumed more feed than ML dams. Average milk production for the 2-h measurement period was 1.70 +/- 0.07 and 1.41 +/- 0.07 g, and average 3-d feed consumption was 50.8 +/- 1.2 and 45.2 +/- 1.2 g for MH and ML dams, respectively. Cross-fostering had no effect (P > 0.86) on milk production. Line of dam tended to affect 21-d litter weight (P = 0.15) with litters reared by MH dams weighing more than those reared by ML dams, but there was no difference (P > 0.86) in 21-d dam weights. Efficiency of producing litter weight (litter 15-d weight: dam plus litter feed intake from d 6 to 15) was greater (0.49 vs. 0.46, SE = 0.009; P = 0.03) for ML than for MH dams. Selection for reduced heat loss (lower maintenance feed intake in the ML line) resulted in reduced milk production and feed intake in dams and greater efficiency of litter weight production.     

Direct and maternal genetic differences between lines of mice selected for body weight and litter size: traits of dams

Genetic differences in performance of dams were estimated by linear contrasts using means of two selected lines of mice and reciprocal F1's, F2's and backcrosses. The lines were selected for increased 6-wk body weight (W) or increased litter size (L). Genetic differences estimated were direct average (gD), direct heterosis (hD), maternal average (gM), progeny average (gP), and progeny heterosis (hP). For dam weight and feed consumption from 12 to 21 d postpartum (pp), gD was the largest genetic difference and favored line W. For litter size, litter weight at birth, litter efficiency (litter weight gain/dam feed consumption) from birth to 12 d pp and within litter mortality from 1 to 21 d pp, gD favored L and, except for hD in litter efficiency, was the most important genetic difference for these traits. Direct heterosis was the only significant difference for litter weight at 21 d pp, litter efficiency from 12 to 21 d pp and within litter mortality at parturition. The gM were larger in W than in L for dam weight and feed consumption, and for litter size and weight at birth, but they were usually of smaller magnitude than gD. The gP were significant only in litter traits measured before 12 d pp and favored W. For no trait measured was hP of consequence. Line differences in dam and litter weight accounted for genetic differences in dam feed consumption. Genetic differences in litter size at birth were not due to line differences in dam weight. The lower mortality within litters nursed by crossbred dams was responsible for hD on litter weight and litter efficiency. Within but not among lines, higher mortality rates were associated with larger litters.     

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.     

Effect of parental genotypes and paternal heterosis on litter traits in crossbred goats.

The effect of parental genotype and paternal heterosis on litter size (LS), total litter birth weight (TLW) and average litter birth weight (ALW) was analysed utilizing data from a crossbreeding programme involving the exotic German Fawn goats and local Katjang goats in Malaysia. In this study, these traits were regarded as traits of the litter to consider the effect of service sire genotype. The results revealed that LS was significantly influenced by the genotype of sire. The genotypes of sire and dam had significant effects on TLW and ALW. Estimates of crossbreeding parameter showed significant and negative influence of paternal heterosis on TLW and ALW while there was no significant effect of paternal heterosis on LS. The results of this study stress the need to reconsider the use of local males in the tropics.     

Postpartum performance in a diallel cross among lines of mice selected for litter size and body weight

Postpartum dam performance was studied in a complete diallel design involving five lines of mice. The selection criterion in each line was: large litter size at birth (L+); large 6-wk body weight (W+); an index for large litter size and small 6-wk body weight (L+W-); the complementary index (L-W+) and random (K). Females from the five lines and 20 reciprocal F1 crosses were mated to sires of a randomly selected control line (CC). Correlated responses in average direct genetic and average maternal genetic effects for dam body weight and litter size at parturition persisted throughout lactation, indicating important pleiotropic effects. Major correlated responses occurred for litter weight, feed intake and litter feed efficiency, primarily due to average direct genetic effects. Using general combining ability and net line effects as criteria for choosing among lines, L+ had a distinct advantage if the objective was to increase litter size in a crossing program. If the objective was to maximize litter weaning weight, then W+ would be favored for net line effects, while L+ and W+ would be about equivalent for general combining ability. None of the lines had an advantage for litter feed efficiency. Direct heterosis for dam weight at 12 and 21 d of lactation averaged 2.7 and 1.9%, while for litter size the respective averages were 7.4 and 7.3%. The W+ X L+W- cross exhibited overdominance for litter size. Direct heterosis was moderate for feed intake and litter weight, but was negligible for litter feed efficiency because of the mathematical relationship among the three traits. Maternal heterosis for preweaning progeny growth was suppressed because of heterosis for litter size in the dam. Grand-maternal effects on growth of the young were small and would not be an important consideration in choosing among these lines in a crossbreeding program.     

家兔选育性状典型相关分析

选择日本大耳白和新西兰两个品种家兔的生长、繁殖、以及体尺3组共17个性状，应用多元统计方法进行了典型相关分析，结果表明；日本大耳白兔的初生重、初生窝重、21日龄重、泌乳力、胸围等5个性状，新西兰兔的产活仔数、初生重、21日龄重、泌乳力、断奶窝重、母兔体重等6个性状为主要性状。     

Tolerance of New Zealand White and Californian doe rabbits at first parity to the sub-tropical environment of Egypt

Tolerance of New Zealand White (NZW) and Californian (Cal) doe rabbits at the first parity to the sub-tropical environmental conditions of Egypt was evaluated. The study included 1090 parturitions: 601 NZW and 489 Cal. The does used were 5 months of age and 3.1 ± 0.10 kg mean body weight. The study was carried out during the different seasons of the year. The results showed that the effects of breed on the traits studied were not significant except on the doe kindling weight. However, the traits studied were, in general, higher in NZW than in Cal. The estimated temperature–humidity index (THI) average values were 19.8, 18.0, 23.7 and 25.7 during autumn, winter, spring and summer, respectively, indicating absence of heat stress during autumn and winter (less than 22.2) and exposure to severe (more than 23.3) and very severe heat stress (more than 25.6), during spring and summer, respectively. The effects of season of kindling were highly significant (P < 0.001 or 0.01) on conception rate, gestation period, kindling weight, litter weight at birth (live and total), 21 days of age and at weaning and kit weight at birth. The values were, in general, the lowest (P < 0.05) during the very severe heat stress in summer, while the kindling interval and pre-weaning mortality were the highest in summer. Adaptability was estimated (during the four seasons of the year) to be 93.3% and 95.1% for NZW and Cal, respectively. No interactions were observed in the analysis.     

Heterosis and recombination effects on pig reproductive traits

The objective was to estimate breed, heterosis, and recombination effects on pig reproductive traits in two different four-breed composite populations. Breeds included Yorkshire, Landrace, Large White, and Chester White in Exp. 1 and Duroc, Hampshire, Pietrain, and Spot in Exp. 2. Data were recorded on purebred pigs, two-breed cross pigs, and pigs from generations F1 through F6, where F1 pigs were the first generation of a four-breed cross. Litter traits were considered a trait of the gilt. There were 868 first parity litters in Exp. 1 and 865 in Exp. 2. Direct heterosis significantly increased sow weight at 110 d of gestation and litter weight at 14 and 28 d (weaning) in both experiments. Direct heterosis significantly increased number of nipples, weight at puberty, lactation weight loss, litter size, and litter birth weight in Exp. 2. Gestation length in Exp. 1 and age at puberty in Exp. 1 and Exp. 2 were significantly decreased by direct heterosis. Maternal heterosis significantly increased age at puberty in Exp. 2 and decreased sow weight at 110 d of gestation in Exp. 1. Recombination significantly increased sow weight at 110 d of gestation and tended to increase total number born and litter birth weight in Exp. 1. Recombination significantly decreased age at puberty in Exp. 2. Litter heterosis significantly increased number of pigs at 14 and 28 d; litter weights at birth, 14, and 28 d; and tended to increase lactation weight loss in Exp. 1. Litter heterosis decreased litter size in Exp. 2. Maternal heterosis and recombination effects had a sampling correlation of -0.97 in Exp. 1 and -0.91 in Exp. 2 for number of fully formed pigs. Therefore, maternal heterosis and recombination effects were summed, and their net effect was tested. This net effect tended to increase number of nipples, lactation weight loss, and litter birth weight and significantly increased number of fully formed pigs in Exp. 1. Direct, maternal, and litter heterosis and recombination effects significantly influenced reproductive traits.     

Value of raw soybeans and soybean oil supplementation in sow gestation and lactation diets: a cooperative study

A cooperative study using 215 sows during two parities (349 litters) was conducted at six stations to determine the effect of raw soybeans in gestation and lactation diets on sow and litter performance. Sows were bred and allotted to fortified corn diets containing either soybean meal (control) or raw soybeans. A corn-soybean meal-soybean oil diet, isocaloric to the raw soybean diet, was included as a third treatment at three stations. All diets contained 14% CP. These diets were fed during both gestation and lactation through two parities. The daily gestation feed intake ranged from 1.8 to 2.3 kg/sow, depending on station. During lactation, the sows were allowed ad libitum access to their respective diets. Gestational weight gain was not influenced by diet, but sows fed raw soybeans consumed less (P less than .01) feed during lactation and had greater (P less than .01) lactational weight loss and their pigs were lighter in weight (P less than .05) both at 21 d and at weaning (varied between 3 and 5 wk of age). Sows fed the diet with supplemental oil had reproductive and lactational performance similar to those fed the control diet. Milk obtained at d 10 to 14 of lactation from sows fed raw soybeans had lower (P less than .05) protein content than milk from sows fed the other two diets, but fat content of the milk tended to be increased by raw soybeans or by added soybean oil. Return to estrus was not affected by diet.(ABSTRACT TRUNCATED AT 250 WORDS)     

Growth Performance and Reproductive Traits at First Parity of New Zealand White Female Rabbits as Affected by Heat Stress and Its Alleviation under Egyptian Conditions

Exposing growing and adult New Zealand White (NZW) female rabbits to severe heat stress (temperature–humidity index = 28.9) during summer adversely affected their growth and reproductive traits. The traits that declined significantly (p<0.01) were the live body weight, daily weight gain and feed intake of growing rabbits, and the litter size and litter weight at weaning (p<0.05) and the pre-weaning weight gain of pups (p<0.01) for adult females. The conception rate declined considerably with heat stress. The declines in the values of the digestibility coefficients due to heat stress were 7.9% (p<0.05) for dry matter (DM), 8.1% (p<0.05) for crude protein (CP) and 1.0% for crude fibre (CF). The traits that increased significantly (p<0.01) due to heat stress were water intake, water/feed ratio and rectal temperature in growing rabbits and pre-weaning mortality for adult females.Alleviation of heat stress in the growing and adult female NZW rabbits was more efficient with drinking cool water (10–15°C; between 10:00 and 17:00) than with supplementation with palm oil (as a source of energy) or natural clay (as a natural enhancer to growth and milk production). Supplying the animals with cool drinking water gave the highest body weight and weight gain, conception rate, litter size and weight and digestibility coefficients for DM and CP and the lowest rectal temperature, respiration rate and pre-weaning mortality.The loss in rabbit production pertaining to heat stress estimated from the percentages of decline in conception rate×pre-weaning mortality×litter weight at weaning was 73.0%. The provision of cool water restored 11/12 of heat loss.