摘要:

The effects of evaluating milk yield in the first three lactations by a single-trait animal model or by a repeatability animal model instead of by the true multitrait animal model were investigated using stochastic simulation. The models were compared both in terms of how accurately they predicted genetic trend when applied to the same dataset and regarding difference in true genetic progress when selecting on breeding values predicted by these models. A breeding structure resembling the Icelandic dairy cattle population was used for the simulation.

ISSN:0906-4702    

DOI:10.1080/09064709509410907

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Average inbreeding coefficients were calculated for the Icelandic dairy cattle population, using pedigree records of 129 115 animals with the most remote ancestor born in 1902 and the youngest animals born in 1991. The average coefficient for animals born 1980 or later and with at least both parents and one grandparent known was 1.82%, but for animals with at least four ancestral generations known it was 2.70%. No significant trend in inbreeding was detected in the period after 1980 when considering animals with at least four ancestral generations known. The AI bulls were inbred by 2.39% on average and a significant increase in inbreeding of +0.08% per year was detected. The effects of inbreeding level on milk, fat and protein yields in each of the first three lactations were estimated by including inbreeding level in the multitrait animal model currently used for breeding value estimation of the breed. A large proportion (58.6%) of the cows with production records were inbred. Negative effects were detected, corresponding to a reduction of 0.22–0.39% of mean production per 1% increase in inbreeding. Inclusion of inbreeding level in the model did not affect the ranking of animals.

ISSN:0906-4702    

DOI:10.1080/09064709509410908

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Data from the Finnish milk recording system consisting of records for the first three parities from a total of 66 554 Ayrshire and 9664 Friesian cows were analysed using REML methodology and sire model. Factors with statistically significant effects on body weight were: year, age and season of calving and lactation stage. The influence of the random herd effect was also evident. Within-herd herit-abilities for body weight in the first three parities were from 0.29 to 0.41 in Ayrshires and from 0.21 to 0.34 in Friesians. Genetic correlations between body weight and 305-day milk, fat and protein yields varied from +0.09 to +0.34 in the Ayrshire data and from -0.06 to +0.28 in the Friesian. Phenotypic correlations were slightly larger and positive in both breeds. Genetic correlations between body weight and fat and protein percentages were negative and phenotypic correlations were near zero.

ISSN:0906-4702    

DOI:10.1080/09064709509410909

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The relationship between twice the adjusted daughter yield deviation (DYD) of the son and the average of the estimated breeding values (EBV) of his parents was investigated for milk and fat yield. Deviations from expectations of DYD minus the pedigree index and the regression of DYD on the EBV for each of the parents were estimated. The EBV of each bull dam was calculated in several ways using different combinations of pedigree information and their own records. In all, 1693 bulls (880 Black and White (BW), 418 Red Danish (RD) and 395 Danish Jersey (DJ)) with Direct Updating indices for milk and fat yield were included in the investigation. Mean discrepancies between estimated and observed genetic merit for kg of milk yield were −348 for BW, −213 for RD and −228 for DJ, when all of the bull dams' individual records were utilized in breeding value estimation. The corresponding mean discrepancies for kg of fat yield were −14.7, −11.5 and −11.9, respectively. The discrepancies were positively correlated with the number of lactation records included in the dams' EBVs. Regression coefficients of bull DYDs on bull dam breeding values were significantly lower than expected for RD and BW regardless of the number of individual lactation records included in the dams' indexes for milk and fat yield. For all three breeds, the regression coefficients were lowest for fat yield. The most probable cause of overestimation in bull dam EBVs is preferential treatment, particularly in second and later lactations. To avoid this bias, estimation of a bull dam's breeding value should be based on pedigree information and on records from only her first lactation.

ISSN:0906-4702    

DOI:10.1080/09064709509410910

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Alternative selection strategies in the bull dam path were investigated to reduce the magnitude of bias. The study's objective was to examine the effect of alternative strategies under the assumption of particular biases. Bias in the evaluation of bull dam estimated breeding values (EBVs) causes an estimated reduction of 32% in their genetic superiority, compared with the theoretical potential. Biased evaluations caused selection of too many bull dams from later lactations. Two alternative strategies were developed to account for existing bias. Results suggested that the influence of bias could be reduced. The estimated improvement in selection response was 11–13% higher than current practice. Problems with biased EBVs in conventional breeding schemes are discussed and a method to counteract bias from future breeding schemes is presented.

ISSN:0906-4702    

DOI:10.1080/09064709509410911

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The effects of level and degradability of rapeseed meal on ration digestibility, N balance, urinary purine derivatives excretion, milk production and milk composition in dairy cows were studied. A total of 24 multiparous lactating diary cows were selected from a production experiment and divided into two 12-cow groups according to their lactation stage (LG1, 14th-16th week of lactation; and LG2, 26th-30th week of lactation). Within lactation groups, cows were fed four different rations (3 cows per treatment). Four concentrate mixtures with two levels of protein (19% and 14% of CP on DM basis) and two different rumen degradabilities (72% and 52%) of the dominating protein feed rapeseed meal were fed to the cows together with pasture silage and hay. Apparent total tract digestibilities were not affected by the treatments. N balance was positive and similar between diets in both lactation groups. N partition data were similar between treatments on LG1, while on LG2 a tendency for a more efficient use of the dietary N was detected on lower protein degradability diets. Urinary excretion of purine derivatives remained unaffected by the treatments in LG1, but was higher in cows fed low-protein degradability diets on LG2 associated with a higher DM intake. A positive correlation was observed, in both lactation groups, between urinary purine derivative excretion and digestible organic matter intake. Milk production tended to increase with increasing protein intake in LG1, and with increasing DM intake in LG2. Milk composition was not significantly affected by the diets in any of the lactation groups.

ISSN:0906-4702    

DOI:10.1080/09064709509410912

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In a joint Nordic project, four experiments with a total of 880 growing pigs following the same outline were conducted in Denmark, Norway, Finland and Sweden. In three of these experiments the animals were fed individually. Five dietary treatments were investigated with respect to effects on performance, carcass composition and leg condition by entire or partial dissection. The treatments were: (1) restricted standard feeding as a reference in all experiments; (2)ad libitumfeeding with protein (amino acid) concentrations according to recommended allowances (RA); (3) as in (2) but RA increased by 10% (RA + 10%); (4) as in (2) but RA lowered by 10% (RA - 10%), or (5) the most common restricted feeding scale recommended in the individual countries, thus being different from experiment to experiment. Compared with the restricted standard feeding, for which daily feed intake and daily weight gain in the weight range 23–100 kg averaged 2.07 kg and 750 g, respectively (rel. value 100), the corresponding mean values for thead libitumfed animals were 119 and 120, respectively (P< 0.001).Ad libitumcompared with restricted feeding lowered carcass meat percentage by 1.5 percentage units (P< 0.05–0.01). Feeding regimen did not affect leg condition. In the weight range 23–60 kg, treatment RA - 10% resulted in a slight decrease in performance and also in a slightly lowered carcass quality at 100 kg. On restricted feeding, females and castrated males performed equally, but carcass meat percentage of the former exceeded that of the latter by 2.3 percentage units (P< 0.001). Daily feed intake and weight gain ofad libitumfed castrated males exceeded the values of females by 11% and 9%, respectively (P< 0.001). Sex did not affect feed efficiency ofad libitumfed animals. Castrated males showed a poorer hind leg condition than females (P< 0.01). Carcass meat percentage was higher in restrictedly fed than inad libitumfed animals. The difference was 0.7 and 1.8 percentage units for females and castrated males, respectively. A main conclusion is that the daily feed intake is a major factor in the control of the development of the animals and also for the extent of fat deposition.

ISSN:0906-4702    

DOI:10.1080/09064709509410913

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This investigation was performed to study the effects of restricted versusad libitumfeeding on carcass composition, on protein and fat accretion and on body development and organ weights. The carcass composition was evaluated on 168 pigs by serial slaughter at 20, 50, 80 and 110 kg LW. The chemical composition was examined in only 62 of these animals. The carcasses were partitioned into four cuts and dissected into lean meat, fatty tissue, rind and bones.Ad libitumfeeding resulted in daily weight gain exceeding restricted feeding in the three weight ranges by 42%, 17% and 7% and feed conversion ratios by 3%, 15% and 9%, respectively. Castrated males exceeded daily weight gains of females by 6%. At 20 kg the carcass moisture content was 65% for both sexes, which on average over feed regimens at 110 kg decreased to 56% and 52% for females and castrated males, respectively. Correspondingly, the carcass crude fat (CF) content increased from 13% to 24% and 30%, respectively. At 110 kg LW on restricted feeding the carcass meat content of females exceeded that of castrated males by 1.7, and onad libitumfeeding by 3.9 percentage units; correspondingly, carcass fatty tissue of castrated males exceeded those values for females by 0.5 and 3.9 percentage units, respectively. Daily carcass crude protein (CP) accretion onad libitumfeeding for females and castrated males for the interval 22–111 kg LW was, on average, 95 g. Daily caracass CF accretion onad libitumfeeding exceeded that on restricted feeding by 34%.Ad libitumfed castrated males and females showed daily CF accretion rates of 231 g and 158 g, respectively.Ad libitumfeeding increased weights of liver over restricted feeding by 12% (P< 0.01) and kidneys by 21% (P< 0.001). Feed regimen also influenced CF content of muscles. It is concluded that feed regimen influenced carcass CP content at slaughter only to a limited extent, but greatly influenced daily CP accretion. However, carcass CF content and daily CF accretion were largely influenced by feed regimen and sex. These differences became manifest after 50 kg LW. Feed regimen also influenced liver and kidney weights.

ISSN:0906-4702    

DOI:10.1080/09064709509410914

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The objective of this study was to create operational replacement guidelines under various conditions concerning reproductive performance, supply of replacement heifers and individual milk yield. Nine culling strategies were defined by three average insemination periods and by three discrimination policies between high- and low-yield cows. The effect of the nine culling strategies was analysed with combinations of heat detection rate and time of initiation of breeding after calving under two replacement heifer purchase policies: purchase (open herd) and no purchase (closed herd). The strategies were evaluated using a stochastic simulation model that simulated production and reproductive status in herds composed of dual-purpose cattle with additional young stock. The evaluation of the strategies was made in a situation without a milk quota under typical Danish conditions in 1993. Results showed that discriminating between high- and low-yield cows improved net revenue significantly in open herds but not in closed herds. Irrespective of the purchase policy, using longer insemination periods increased net revenue significantly in herds with poor reproductive performance; whereas net revenue in herds with good reproductive performance tended to increase by using shorter insemination periods. The culling rate is a poor figure when evaluating culling strategies and culling strategies should be assessed at herd level rather than per cow.

ISSN:0906-4702    

DOI:10.1080/09064709509410915

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Nutrient digestibilities were evaluated in comparative experiments with blue foxes and mink by using six diets differing in fat:carbohydrate (F:C) ratios. In mink, apparent digestibilities of N and amino acids decreased with decreasing F:C ratio. N digestibility, and most amino acid digestibilities, were higher in blue foxes than in mink (P< 0.01). Fat digestibility in mink, but not in blue foxes, declined as the F:C ratio decreased (P< 0.05). Fat digestibility was higher in blue foxes than in mink (P< 0.05). Carbohydrate digestibility was not affected by the F:C ratio, but high levels of carbohydrates were digested more completely by foxes than by mink. The use of mink digestibility values in feed evaluations for blue foxes will consequently underestimate digestibility. Thus, to evaluate feed correctly, separate digestibility determinations should be made for mink and foxes.

ISSN:0906-4702    

DOI:10.1080/09064709509410916

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor