摘要:

Crossbreeding effects on beef production characteristics, growth, carcass and meat quality traits were registered on a total of 162 purebred Norwegian (NRF) dual‐purpose and crossbred bulls obtained from mating (AI) NRF dams with NRF, Aberdeen Angus, Hereford and Charolais sires. The offspring were reared in commercial farms until slaughter. Data were analysed by mixed models and adjusted to either constant carcass weight (305 kg), slaughter age (19.5 mos.) or carcass fat level (6% fat) end points. Improvements in beef production traits obtained by crossbreeding were highly dependent on the choice of sire beef breed. NRF × Charolais crossbreds had the highest daily carcass gain and carcass quality (fleshiness grading) at all end points. Crossbreeding with Aberdeen Angus and Hereford gave no growth advantages, an intermediate increase in carcass fleshiness grading and an increase in weight constant carcass fat level compared to purebred NRF.

ISSN:0906-4702    

DOI:10.1080/09064709809362405

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Plasma levels of insulin, somatostatin, gastrin and oxytocin, rumen volatile fatty acid (VFA) composition and content oftrans‐C18:1 fatty acids in milk fat were studied in relation to milk fat content in 12 dairy cows. Half of the cows were fed restrictedly according to Swedish standards (R) and half were fed ad libitum (AL). In the previous lactation three cows from each treatment had a high milk fat content (HF) and three had a low fat content (LF). Blood and rumen samples were taken in lactation weeks (lw) 8 and 21. In lw 21, the AL cows had a lower proportion of acetate in the rumen VFA, a higher plasma level of gastrin and a different diurnal pattern of insulin compared with the R cows. The LF cows had a higher plasma level of insulin after feeding than the HF cows in lw 21. Correlation analysis showed that the plasma level of somatostatin was positively related to milk fat content both in lw 8 and in lw 21. In addition, the milktrans‐C18:1 fatty acids were inversely related to milk fat content in lw 8, whereas the proportion of butyrate in rumen VFA was positively related and the proportion of propionate was inversely related to milk fat content in lw 21. A route by which somatostatin could regulate milk fat synthesis is discussed.

ISSN:0906-4702    

DOI:10.1080/09064709809362406

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The present energy evaluation systems of pig feeds are described and evaluated with reference to their scientific basis and practical performance. The different energy evaluation systems are assessed with regard to (i) the definitions and determinations of nutrient fractions in the feed, (ii) the methods for determination of digestible nutrient fractions, (iii) the expression of energy value, (iv) the methods for determination of specific energy coefficients for the different nutrient fractions, and (v) the adequacy of using energy as the sole property in the feed value. It is concluded that present feed evaluation might generally be imprecise due to limitations in the principles of current energy evaluation systems, which oversimplify the nutritional value of the feed and ignore variations in the actual values.

ISSN:0906-4702    

DOI:10.1080/09064709809362407

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A new nutrient‐based evaluation system for feedstuffs and pig diets is proposed. The proposed system is based on (i) an identification of those organic nutrient fractions that, according to their absorption, metabolism and utilization, are relevant for determining the value of the feed, and (ii) biochemically‐based calculations of the potential physiological value of these fractions. The system is further based on a flexible stepwise evaluation in which the fundamental properties of the feed are related to its utilization in actual situations.Step 1is characterized by single feedstuffs according to the digestible amounts of those nutrient fractions which are relevant for feed formulation, i.e. essential amino acids, other N‐compounds, ileal digestible carbohydrates, fermentable carbohydrates, fatty acids and other lipid compounds.Step 2involves complete diets with three complementary properties, measured according to their potential value for the pig: protein value (i.e. amount of digestible ideal protein), “fat value”; (i.e. amount of digestible triacylglycerols) and the “complemental energy value”; (i.e. potential metabolic energy generated directly from the residual digestible nutrient fractions).Step 3predicts the production value, either a standardized value determined by standard mathematical equations, or the actual value determined by the use of computerized pig models.

ISSN:0906-4702    

DOI:10.1080/09064709809362408

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The possible relationship between performance, behaviour and immune capacity was studied in pigs reared for slaughter as siblings or in mixed groups in 2 x 5 pens of 9–10 pigs in each, i.e. 48 and 49 individuals, respectively. Kilogram feed per kg weight gain was lower (4%) and daily weight gain was higher (3%) for the siblings, which also showed the lowest level of agonistic interactions, as compared with the mixed groups. No direct relationships between agonistic interactions, plasma cortisol and measures of “immune capacity”; (total and differential leukocyte counts, mitogen‐induced proliferation and interleukin‐2 production in vitro) were found. The order of voluntarily leaving a pen and entering a scale were correlated to individual intra‐pen weight ranking class; this ranking could be predicted by an x‐matrix of the blood variables when subjected to partial least square analysis. Thus, a linkage between weight ranking class and physiological variables could be observed.

ISSN:0906-4702    

DOI:10.1080/09064709809362409

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Effects of dietary arginine levels of 1.2%, 1.7% and 2.2% of dry matter (DM) (4.8 g/16 g N, 6.4 g/16 g N and 8.0 g/16 g N, respectively) and excess dietary lysine (6.5% in DM, 22 g/16 g N) were investigated in male mink kits fed low‐protein diets supplemented with a mixture of amino acids in the growing period during 4 weeks in July‐August. Urinary excretion of orotic acid, growth performance, feed consumption, plasma concentrations of ammonia (NH3), orotic acid, urea and glucose were studied. The results showed that arginine is an essential nutrient for mink kits in the growing period and that excess dietary lysine antagonizes arginine. An arginine supply of 2.2% of DM (8.0 g/16 g N) resulted in minimum urinary excretion of orotic acid and a supply of 1.7% of DM (6.4 g/16 g N) prevented increased plasma concentrations of NH3. Growth performance was negatively affected by the low protein level in all diets. The plasma concentrations of orotic acid, urea and glucose were not affected by the dietary levels of arginine.

ISSN:0906-4702    

DOI:10.1080/09064709809362410

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Pelage development was compared in male blue foxes born in early May (E) and in early June (L) (4/group). Guard hair and underfur hair cycles were studied histologically on series of skin samples taken from the hip, between August and December. The winter guard hair cycles were similar but there was a shift in time of several weeks between the groups. The difference evened out in mid‐November, when 97% of guard hairs were mature. The growth cycle of winter underfur hairs in group L was more synchronized than in group E. The mean count of mature (telogen) underfur hairs per bundle differed slightly between the groups on 1 December but the mean total hair counts (anagen and telogen hairs) were similar. The natural adjustment of the pelage cycle in blue foxes of different age is modified by the duration of the resting period of summer hair follicles, which probably is mediated via melatonin.

ISSN:0906-4702    

DOI:10.1080/09064709809362411

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0906-4702    

DOI:10.1080/09064709809362404

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor