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Biomedical subjects

J W Wilton

Publications and source records attributed to J W Wilton.

10 recordsLinked to original sources
PubMed1992

Contribution of breed, cow weight, and milk yield to the traits of heifers and cows in four beef breeding systems.

Measurements were taken on 216 cows with 469 calvings for weight at weaning, condition at weaning, milk yield, milk fat percentage, milk lactose percentage, milk protein percentage, dry period feed intake, lactation period feed intake, total feed intake, first-service pregnancy rate, pregnancy rate, and days to pregnancy. Measurements were also taken on 183 heifers for first-service pregnancy rate, days to pregnancy, and age at first calving. The data spanned the years 1980 to 1988; animals belonged to one of four breeding systems: Hereford, small rotation (Angus, Gelbvieh, Pinzgauer, Tarentaise), large rotation (Charolais, Maine Anjou, Simmental), and Angus-large rotation (cows with Angus sires and large-rotation dams). Maine Anjou-sired cows had lower annual feed intake and Charolais-sired heifers lower first-service pregnancy rate than the other large-rotation breeds. Gelbvieh-sired cows had lower milk lactose and protein percentages than the other small-rotation breeds. Within breeding system neither cow weight nor milk yield were significantly associated with reproductive traits of cows. No differences among breeding systems in associations between feed intakes and weights or milk yields were detected.

Adipose Tissue↗
PubMed1992

Effects of source and level of dietary neutral detergent fiber on feed intake, ruminal fermentation, ruminal digestion in situ, and total tract digestion in beef cattle fed pelleted concentrates with or without supplemental roughage.

The effects of source and level of dietary NDF on intake, ruminal digestion in situ, ruminal fermentation, and total tract digestion were evaluated in Hereford steers using a replicated 5 x 5 Latin square design. Diets contained 62 to 64% TDN and included 1) 80% control concentrate (contained pelleted ground grains) and 20% timothy hay (traditional diet), 2) 80% control concentrate and 20% alfalfa cubes, 3) 90% control concentrate and 10% cubes, 4) a completely pelleted diet using corn cobs as the primary NDF source, and 5) 80% textured (rolled instead of ground grains) concentrate and 20% hay. Dry matter intake differed (P less than .05) between the traditional and cube diets due to limited acceptance of alfalfa cubes. Increased (P less than .05) ruminal osmolality, total VFA, and NH3 N and lower (P less than .01) ruminal pH in steers fed corn cob and cube diets relative to steers fed the traditional diet were due to preferential consumption of concentrate over supplemental roughage and the resultant rapid fermentation of concentrates. Potentially degradable DM in the traditional diet exceeded (P less than .06) all other diets, resulting in the increased (P less than .10) extent of DM disappearance despite a slower (P less than .05) rate of DM disappearance. Rate of NDF disappearance and all in situ starch disappearance parameters were similar between the traditional, corn cob, and cube diets. All ruminal digestion parameters involving NDF disappearance were similar between hay diets and between cube diets, whereas rate and extent of starch disappearance differed (P less than .05) between hay diets. Although formulation of diets with different sources of dietary NDF did not affect total tract digestion of nutrients, nutrient availability and ruminal fermentation were altered due to dietary differences in sources of dietary NDF and preferential selection of feedstuffs by steers.

Ammonia↗
PubMed1992

Effects of source of dietary neutral detergent fiber on chewing behavior in beef cattle fed pelleted concentrates with or without supplemental roughage.

Ten 394-kg, ruminally fistulated Hereford steers were used in a replicated 5 x 5 Latin square design to evaluate the effects of source and level of dietary NDF on chewing activities during eating and rumination. Diets contained 62 to 64% TDN and included 1) 80% pelleted concentrate (control; contained ground grains, fibrous byproducts, molasses, and protein, vitamin, and mineral supplements; 36% NDF, 16% CP) and 20% long timothy hay (67% NDF, 8% CP), 2) 80% control concentrate and 20% alfalfa cubes (56% NDF, 15% CP), 3) 90% control concentrate and 10% alfalfa cubes, 4) a completely pelleted diet using corn cobs as the primary NDF source (40% NDF, 17% CP), and 5) 80% textured (coarse instead of ground grains; 42% NDF, 15% CP) concentrate and 20% hay. Diets were formulated to be similar in NDF content, and dietary protein satisfied NRC recommendations. Chewing during eating did not differ (P greater than .10) between diets containing supplemental roughage but decreased (P less than .001) with the corn cob diet. Rumination chewing decreased (P less than .001) with the corn cob and cube diets. The number of chews per day during eating corrected for NDF intake/BW.75 decreased (P less than .05) in the corn cob diet. Rumination periods and duration increased and latency before rumination decreased in hay diets. Steers fed the corn cob diet tended to be more (P less than .10) consistent in time spent eating across 4-h intervals than steers fed the traditional diet. Replacement of long hay with the completely pelleted corn cob diet decreased rumination activity.

Animal Feed↗
PubMed1991

Productivity and profitability of twin births in beef cattle.

Data from 1,277 single and 85 twin calvings, occurring in both spring and fall from 1980 through 1987, were used to examine the productivity and profitability associated with twin births in beef cattle. Pregnancies in pure and crossbred cattle resulted from both AI and embryo transfer. Cows and calves were confinement-housed. Cows were individually fed to specification. Calves were given ad libitum access to creep feed and those born in 1986 and 1987 were fed to slaughter. The influence of birth number of gestation length, total calf birth and weaning weights, lactation yield, and cow fed intake during both the dry and lactating periods were examined. Twin-bearing cows had their gestation length shortened by 6.4 d (2%); yielded 25.5 (59) and 186.0 kg (73%) more weight of calf at birth and weaning, respectively; had lactation yield and lactation feed intake increased by 25 and 20%, respectively; and had precalving (dry) period feed intake no different from their single-bearing counterparts (P = .12). Postweaning growth was not different for single and twin calves (P = .50); twin gain, relative to initial size, was higher. Feedlot feed intake of twins was 85% of that for singletons (P = .20). Twins were 90% of singleton live weight at slaughter and yielded 93% of singleton hot carcass weight (P = .12). Twins were slightly older and significantly leaner at slaughter. Returns less feed costs showed twin births to be associated with increased profit for cow-calf programs. Returns less feed and overhead costs were higher for twin calves than for singles in the feedlot.

Adipose Tissue↗
PubMed1990

Feed intake, weaning weight and net returns comparisons for four breeding systems.

Feed intake, weaning weight and direct and maternal contributions to weaning weight were estimated for four breeding systems using data collected between 1979 and 1986 from 773 cow-calf pairs at the Elora Beef Research Centre. Breeding systems included purebred Hereford (HE), small rotational dual purpose (SR) (a four-way rotational crossing system utilizing Tarentaise, Angus, Gelbvieh and Pinzgauer breeds), large rotational beef (LR) (composed of Maine-Anjou, Simmental and Charolais) and Angus-sired large rotational beef (AL) utilizing Angus as the sire breed and LR as the maternal breed. Large rotational dams had the highest feed intakes for both dry (8.9 kg DM/d) and lactation (11.5 kg DM/d) periods. Conversely, HE calves consumed the greatest amounts of creep feed (309 kg DM), followed by AL, SR and LR. The large rotational system had the highest weaning weights (265 kg) and direct (12.3 kg greater than average of observations) and maternal (9.6 kg greater than average of observations) contributions to weaning weight, followed by AL, SR and HE for all three traits. An equation was derived for net returns that included parameters for feed intake and direct and maternal weaning weight. A linear programming model was designed to incorporate this equation as the objective function and determine the breeding system(s) that maximized net returns under various production conditions. In general, LR produced the greatest net returns, followed by SR and either AL or HE, depending on specific resource constraints (limited feed supply or herd size) included in the model.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Influence of variations in biological and economical parameters on beef production net returns.

Net returns were defined as a function of the monetary returns (revenue) generated by the outputs less the monetary costs generated by the variable inputs. Outputs included total weaning weights of steers and heifers, weight of cull cows and weight of open heifers. Inputs included both feed and nonfeed costs. The net returns equation was incorporated as the objective function in a linear programming model. By maximizing the objective function, the breeding system that generated the highest net returns could be identified considering certain resource constraints. Breeding systems included purebred Herefords; small rotational dual purpose (SR), utilizing the breeds Angus, Pinzgauer, Gelbvieh and Tarentaise; large rotational (LR), a three-way rotational cross with the breeds Charolais, Simmental and Maine-Anjou; and Angus-sired terminal (AL) utilizing Angus as the sire breed and LR heifers as the maternal breed. Large rotational generally produced the greatest net returns, followed by SR and either AL or HE, depending on specific resource constraints (limited feed supply or herd size), calving rates, management systems, environment, beef to feed price ratios and purchased or farm-produced (inexpensive) feed utilized. Only under the conditions of a herd size constraint and farm-produced feed did AL exceed SR in net returns. Hereford had larger net returns than LR only when the two breeding systems were evaluated in an environment assumed to be reproductively stressful to LR. Ranking of breeding systems were dependent on specific conditions and indicated that one must consider each resource constraint and environment in which cattle are expected to produce before making breeding system recommendations.

Animal Feed↗
PubMed1986

Prediction of traits at constant finish for performance-tested beef cattle.

The relationships of performance in time-constant intervals to that in the full feedlot phase of production and of bulls to steers were studied. Monthly records on 43 bulls and 48 steers for gain, ultrasonic backfat, weight and hip height were collected in the period postweaning to an estimated 6 to 7 mm subcutaneous backfat. Information gathered in the first 140 d (performance test) was used to predict feedlot performance to Canada grade A1 finish (7 mm backfat). Traits predicted were days to market finish (DM), weight at market finish (WM), relative growth rate (RGR) and economic rate of maturing (Ke). Economic maturing rate was derived as an estimator of growth relative to weight at fixed body composition (7 mm backfat). Prediction equations were developed by stepwise regression which explained 91, 92, 83 and 79% of the variation in DM, WM, RGR and Ke, respectively. Ratios for steer to bull values for DM and WM were .901 and .928, respectively. It was concluded that accurate prediction of DM, WM, RGR and Ke is possible from information on weight and backfat measurements as currently gathered in many test stations. Prediction of RGR and Ke could be improved by inclusion of heart girth measurements. Differences among animals in Ke are easier to estimate than are differences in rate of maturing, and may be of greater relevance for the genetic improvement of livestock.

Adipose Tissue↗
PubMed1985

Selecting mating pairs with linear programming techniques.

Mate selection can increase progency merit if overall merit is nonlinear for one or more component traits. An index of expected progeny merit could be calculated for all possible mating pairs, and the set of pairs with the highest progeny mean could be selected. There are serious computational problems for more than a few males and females. To select and mate f, females, and m, males, from n of each, with k0 females per male, would require (nf)(nm)f!/(k0!)m evaluations. Linear programming algorithms can determine the optimal strategy efficiently by considering only a subset of these possibilities. Let pi ij be the index of progency merit of the ith sire mated to the jth dam and Xij be the decision variable for that mating (restricted to 0 or 1). Then the problem of selecting mating pairs can be stated as: maximize sigma i sigma j pi ij Xij, subject to sigma i Xij less than or equal to 1, sigma j Xij less than or equal to k0, sigma i sigma j Xij = f, and Xij = 0 or 1. By including an artificial sire and an artificial dam and choosing appropriate merit values for the artificial matings, this problem can be solved by efficient "transportation" algorithms. These algorithms could be used to develop rational mating packages for dairy artificial insemination studs provided that an objective evaluation of progeny merit could be formulated, provided that merit is not simply additively inherited.

Animal Husbandry↗