Biomedical subjects

G D Snowder

Publications and source records attributed to G D Snowder.

41 records · Page 3Linked to original sources

PubMed1993

Growth and slaughter characteristics of ram and wether lambs implanted with zeranol.

Forty-nine Columbia ram and wether lambs born in April 1990 and 46 born in April 1991 were studied to determine the effects of zeranol implants on growth, difficulty of pelt removal, and carcass characteristics. Implanting ram and wether lambs once (1990) or twice (1991) with 12 mg of zeranol did not change live weight or ADG but gain/feed decreased (P < .05) in ram lambs slaughtered at approximately 50 kg. Testes weight was reduced approximately 50% by implanting. Two implants reduced (P < .05) the force needed to pull the pelt from the hind legs of ram lambs, but implanting tended to increase the force required to pull the pelt from wether lambs. Data for pelt weight, force required to pull the pelt, percentage of the carcass in the shoulder or splenius muscle, and Warner-Bratzler shear values showed that zeranol implants resulted in ram lambs becoming more like wethers and wether lambs becoming more like rams. Implanting with zeranol did not affect closure of the metacarpal growth plate in ram or in wether lambs. Difficulty of pelt removal can be reduced by implanting ram lambs with 12 mg of zeranol at approximately 114 d of age and reimplanting zeranol 28 d later.

Age Factors↗

PubMed1991

Simulation of lean lamb production systems.

A series of simulations were performed to evaluate the effects of mature size (WMA; 60, 70, 80 and 90 kg), slaughter weight (SW; 55, 60 and 65 kg) and three diets fed to feedlot lambs. Rations included a traditional diet (C2L) or placing weaned lambs on alfalfa for either 30 (A30) or 60 (A60) d before placing them on the C2L diet (A30-C2L and A60-C2L). Two lamb pricing schemes were used in the financial analysis of the biological results: sale price based on weight with or without adjustment for carcass fat. Placing lambs on alfalfa pasture increased ownership by 22 d on average compared to C2L. As WMA and SW increased, ownership increased from 3 to 11 d. Across nutritional treatments, fat decreased by 5.8 to 9.0% as WMA increased from 60 and 90 kg. When market lambs were priced on weight, net returns per lamb were greatest for A30-C2L or A60-C2L ($2.34 and $5.21, respectively above C2L) and for greater SW ($4.77 and $7.16 greater for SW 60 and 65 kg than for SW 55). The combination WMA of 90 kg, a SW of 65 kg and nutritional treatment of A60-C2L proved most profitable. However, when sale price was discounted for excessive fat content, the combinations WMA of 60 or 70 with a SW of 65 and A60-C2L were most profitable. The rank correlation between biological efficiency (weight gain/dry matter feed consumption) and net return, when sale price was based on weight, was found to be -.51. This was because lambs slaughtered at lighter weights had high biological efficiencies but low net returns due to a negative price margin. With negative price margins but positive feeding margins, net returns are greatest for heavier, fatter lambs fed longer.

Adipose Tissue↗

PubMed1991

Influence of breed, number of suckling lambs, and stage of lactation on ewe milk production and lamb growth under range conditions.

Milk production and lamb growth were characterized in 118 multiparous, 3- to 7-yr-old Rambouillet, Columbia, Polypay, and Suffolk ewes under spring sage range and high mountain meadow grazing from 28 to 98 d postpartum. Daily milk yield as measured by the lamb suckling weight differential technique did not differ (P greater than .05) among breeds, although milk production of Suffolk ewes tended to be higher than that of the other three breeds. Within the Rambouillet, Columbia, and Polypay breeds, total estimated yield of ewes with twins was 13 to 17% higher than that of ewes with singles, whereas in the Suffolk breed, suckling twins increased total milk yield 61% over that of ewes with singles. Twin lambs induced a larger differential in dam milk production in late lactation (70 to 98 d) than in earlier lactation (28 to 70 d). Number of lambs did not influence milk protein, Ca, or P content (P greater than .05). Fat levels in colostrum and 4-d milk were elevated 14 and 20%, respectively, in ewes suckling twins compared with ewes suckling singles. Under range conditions, Suffolk ewes suckling single or twin lambs lost more BW (12 and 21% of 4-d postpartum body weight, respectively) than Rambouillet (4 and 7%), Columbia (5 and 8%), or Polypay (8 and 8%) ewes. Correlation coefficients of milk production and lamb growth rate were positive and significant (P less than .05) up to 56 d of age. Growth rate was less closely associated with milk production for twin than for single lambs.

Animal Husbandry↗

PubMed1991

Effects of age, castration, and season on difficulty of pelt removal in lambs.

Sixty-four white-faced rams and wethers were dressed with the aid of a commercial pelt puller. The effects of age, castration, and season on difficulty of pelt removal and pelt damage were evaluated. Lambs were divided into two age groups (5 and 12 mo) within gender (ram and whether) and season (spring and fall). A greater force (P less than .05) was required to remove pelts from rams than from wethers in both 5- and 12-mo-old groups. Older lambs slaughtered in the fall required more force (P less than .05) to remove their pelts than did those slaughtered in the spring, but differences by season did not exist for 5-mo-old lambs. The difference between rams and wethers in percentage of live weight that was closely shorn pelt weight was not significant (P greater than .05). The area of grain crack in the flank expressed as a percentage of total area of the skin was lower (P less than .05) for skins from 5-mo-old lambs and ram lambs than it was for skins from 12-mo-old lambs and wether lambs, respectively. Factors involved in difficulty of pelt removal in ram lambs included crosscut shoulder weight, fat firmness, and carcass weight. Difficulty of pelt removal in wether lambs was best predicted by including crosscut shoulder weight and bodywall thickness in multiple regression equations.

Age Factors↗

PubMed1990

Prevalence and effect of subclinical ovine progressive pneumonia virus infection on ewe wool and lamb production.

The prevalence of infection with ovine progressive pneumonia (OPP) virus and its effects on ewe wool and lamb production were investigated in a flock of 2,976 ewes of 6 breed types (Rambouillet, Targhee, Columbia, Polypay, 1/4 cross Finnsheep, and 1/2 cross Finnsheep). Prevalence of seropositivity was significantly (P less than or equal to 0.01) lower among Rambouillet and Targhee breeds (44 and 42%, respectively), intermediate in Polypay, Columbia, and 1/4 cross Finnsheep (approximately 53%), and higher among 1/2 cross Finnsheep (62%). Seropositivity increased with age in all breed types from 11% at 1 year of age to 93% at greater than or equal to 7 years of age. Lateral disease transmission is indicated by linear increase of seropositivity prevalence with increasing age, including that in sheep greater than 6 years old. Subclinical infection with OPP virus had no apparent detrimental effect on number of lambs born, lamb viability, birth weight, number of lambs weaned, or growth rate of single and twin lambs, compared with findings for noninfected sheep in the same flock. Mature ewe body weight and grease fleece weight did not differ between subclinically infected seropositive and seronegative ewes. Subclinical infection with OPP virus does not appear to have an adverse economic effect on ewe wool and lamb production. Culling rate attributable to clinical manifestation of infection with OPP virus must be accurately determined before the true effects of virus infection on production can be determined and an eradication program can be recommended.

Age Factors↗