Litter Feed Intake Research Articles

HERITABILITY AND REPEATABILITY ESTIMATES OF MATERNAL PERFORMANCE TRAITS IN PUREBRED AND CROSSBRED DOES

Data on purebred doe (298 lillers) and combined purebred and crossbred doe (461 litters) produclion records were collected over a 2-year period (1990 and 1991) and analyzed separately to obtain heritability and repeatability estimates. Doe breed types were Californian (CAL), New Zealand White (NZW) and CAL x NZW. Litters were sired by bucks representing four breeds or lines - CAL, NZW, and control and selected synthetics. Maternal performance traits included doe body weight al parturition, gestalion length, litter size and weight al birth, 21 d, and weaning (28 d), doe production efficiency (litter weaning weighUdoe body weight), 1-21 d and 1-28 d total doe and litter feed intake, and neonatal and preweaning survival rates. A doe repeatability model was employed which consisled of fixed effects of year, season, parity, and doe breed type, and random direct additive genetic, permanent and residual effects. Sire breed and individual service sire of the litter were added to this model for the analysis of litter weaning weight. Heritability and repeatability estimates were reasonably similar for all traits studied between pooled purebred and combined purebred and crossbred data analyses. From pooled purebred doe data analysis, heritability (repeatability) eslimates for doe body weight, gestation length, and litter size al birth, 21 d, and 28 d were 0.53, 0.00, 0.13, 0.00, and 0.00 (0.72, 0.09, 0.23, 0.06, and 0.06), respectively. For doe produclion efficiency and litter weights al birth, 21 d and 28 d, heritabililies (repeatabilities) were 0.07, 0.14, 0.09, and 0.03 (0.07, 0.14, 0.09, and 0.03); however, when statislically adjusted for the corresponding litter size, heritabilities (repeatabilities) changed to 0.06, 0.00, 0.02, and 0.00 (0.06, 0.24, 0.30, and 0.28), respeclively. Heritabililies (repeatabilities) of 0.13 and 0.13 (0.30 and 0.21) were oblained for 1-21 d and 1-28 d total doe and litter feed intake. Lastly, neonatal and preweaning survival rates had herilability (repeatability) estimates of 0.13 and 0.00 (0.16 and 0.19). In summary, maternal performance traits tend to be lowly heritable (except for doe body weight) and lowly to moderately repeatable.

Correlated responses in maternal performance following divergent selection for heat loss in mice1

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.

Preweaning variables' influence on market traits in rabbits.

Influence of several preweaning variables on market trait determination was investigated using 338 fryer rabbits from 52 litters. Variables measured at 1, 8, and 15 d included litter size, individual kit body weight (BW), within-litter rank score for BW, and litter uniformity (coefficient of variation for BW among littermates; CV). Daily milk consumption in wk 1, 2, and 3 was used to determine average weekly dominance rank score and total weekly milk consumption. Market traits were individual average daily gain (ADG) and litter feed intake (FI) from 28 to 70 d, and 70-d BW (BW70), litter uniformity (CV70), litter size (LS70), and within-litter rank score for BW (RANK70). Market traits were analyzed separately by week involving preweaning variables and season of weaning as covariates. The week models provided the most accurate predictions of ADG, BW70, FI, and LS70 (R2 = .542, .712, .906, and .970, respectively). Prediction of CV70 and RANK70 was poor (R2 = .202 to .369). Season influenced ADG, BW70, and FI (partial R2 values of .285 to .435). Path analysis indicated that milk consumption and BW were more important in BW70 determination (28.4, 26.4, and 36.9% of total variation in wk 1, 2, and 3, respectively) than litter size (partial R2 < or = 2.0%). In wk 1, litter size plus dominance rank score primarily determined LS70 (direct and indirect contributions of 62.3 and 21.5%). Because of major seasonal influences, management should take measures to optimize feed intake and to improve doe milk yield and fryer gain performance.

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)

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.

Doe reproduction and preweaning litter performance of straightbred and crossbred rabbits.

Reproductive characters (N = 430 matings) of four doe genetic groups and preweaning performance of litters (N = 280) were evaluated in a 15-mo study. Doe genetic groups were New Zealand White (NN) and Californian (CC) straightbreds and Californian X New Zealand White (CN) and New Zealand White X Californian (NC) crossbreds. Does and litters were provided either a commercial control or a 74% alfalfa pelleted diet. Sires of litters included NN, CC and Flemish Giant (FG) straightbred bucks. The linear and quadratic regression on age of dam affected (P less than .01) litter birth weight. The NN does were heavier than CC does at first breeding at 154 d and produced heavier litters at birth and weaning (all P less than .01). Percentage survival of kits from birth to weaning and doe and preweaning litter feed intake and efficiency were greater from NN than CC does (all P less than .01). Numbers born and reared/litter to weaning at 28 d were likewise greater for NN vs CC straightbred does. Heterosis estimated from comparing litters of reciprocal crossbred vs straightbred does was significant for number born, litter birth and weaning weights and doe and preweaning litter feed intake. Reciprocal crossbred differences were observed (P less than .05) for doe breeding weight, number born and weaned per litter, litter birth and weaning weights and doe and preweaning litter feed intake, favoring CN does reared by NN straightbred dams over NC does. Diet, in consistent favor of the 74% alfalfa diet, significantly affected all traits studied with the exception of doe longevity, doe fertility percentage, and doe and litter feed efficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

Meat production from pigs which have farrowed. 3. The effect of weaning-to-slaughter interval on food utilization and carcass quality

SUMMARYTwenty-eight Landrace × (Landrace × Large White) young female pigs (gilts) were allocated to one of four treatment groups at about 75 kg live weight. The gilts were mated at second oestrus and suckled their piglets for 35 days. Gilts were slaughtered 14, 21, 28 or 35 days after weaning. The ‘effective’ food conversion ratios (i.e. total gilt plus litter feed intake (kg) divided by total gilt weight gain plus litter weaning weight) of the four groups were 5·22; 4·70; 4·62; and 4·56 respectively. The differences were not statistically significant.Neither carcass weights nor individual joint weights were significantly affected by treatment. Samples of 11 middle sections from the 14-, 21- and 28-day slaughter groups were boned and cured. Bacon produced from the streak blocks had poor colour, texture and moisture-holding capacity. It was concluded that streak blocks from gilts that had farrowed were unsuitable for curing as streaky bacon.