The effects of dietary net energy on grow-finish performance and carcass characteristics of market gilts managed with immunological suppression of ovarian function and estrus (Improvest).

The objective was to determine the effects of net energy (NE) during the grow-finish period on live performance and carcass characteristics of market gilts managed with immunological suppression of ovarian function and estrus (Improvest®; IMP) compared with market gilts not managed with Improvest (CON). The 104-d study began when 1,008 gilts (11 wk old; average starting weight of 30.8 kg) were allocated by weight to 48 pens with 21 gilts/pen. Half of the pens were randomly selected to be managed with Improvest while the other half of the pens were not managed with Improvest. Three dietary programs differing in their NE were formulated over five dietary phases (according to standardized ileal digestible lysine requirements) to provide an average of 2,218 kcal/kg (low NE), 2,343 kcal/kg (medium NE), or 2,468 kcal/kg (high NE). The experiment was designed as a 2 × 3 factorial with main effects of Improvest management and NE. For the overall study period, there were no significant interactions (P ≥ 0.20) for average daily feed intake (ADFI), average daily gain (ADG), or Gain:Feed (G:F). There were also no significant interactions between Improvest management and NE (P ≥ 0.30) for carcass characteristics. However, IMP gilts consumed more feed (6.8% greater ADFI; P < 0.01), grew faster (5.0% greater ADG; P < 0.01), were less efficient (1.8% lower G:F; P < 0.01), heavier (3.5 kg hot carcass weight; P < 0.01), and fatter (1.9 mm greater backfat thickness and 1.26% less predicted lean carcass yield; P < 0.01). No difference (P = 0.21) in carcass dressing percentage between IMP and CON gilts was reported. For the overall study period, gilts fed low NE and medium NE diets consumed more feed compared with gilts fed high NE diets (6.8% more ADFI for low NE and 5.7% more for medium NE; P < 0.01), and gilts fed low NE diets grew 2.5% slower (P < 0.01) than gilts fed medium NE diets, while gilts fed high NE diets were intermediate and not different from the other NE treatments. This resulted in gilts fed Low NE diets being the least efficient (3.8% lower G:F than medium NE and 7.1% lower G:F than High NE; P < 0.01). Overall, these data indicate that typical Improvest response levels were sustained at each of the NE treatments evaluated in this study as there were no significant interactions for Improvest management and NE; however, consideration should still be provided to the known production impacts of low NE diets.

The effects of dietary net energy on grow-finish performance and carcass characteristics of male market pigs managed with immunological castration (Improvest).

The objective was to determine the effects of dietary net energy (NE) during the grow-finish period on live performance and carcass characteristics of intact male pigs managed with immunological castration (Improvest) compared with physically castrated (PC) male pigs. The 101-d study began when 1,008 pigs (504 intact male pigs and 504 PC male pigs; 10 wk old) were allocated by weight to 48 pens with 21 intact males or 21 PC males per pen. Three dietary NE treatments were fed to pigs using five dietary phases (dietary programs were formulated according to standardized ileal digestible lysine requirements of Improvest males or PC males) to provide an average of 2,212 kcal/kg (low NE), 2,337 kcal/kg (medium NE), or 2,462 kcal/kg (high NE). The experiment was designed and analyzed as a 2 × 3 factorial with main effects of Improvest management and NE. For the overall study period, there were no significant interactions between Improvest management and NE (P ≥ 0.19) for average daily feed intake (ADFI), average daily gain (ADG), or gain:feed (G:F). There were also no significant interactions between Improvest management and NE (P ≥ 0.06) for carcass characteristics. Improvest males consumed less feed (5.3% lower ADFI; P < 0.01), grew faster (5.1% greater ADG; P < 0.01), and were more efficient (11.2% greater G:F; P < 0.01) compared with PC males. Hot carcass weight (HCW) did not differ (P = 0.16) between Improvest males and PC males (attributed to 1.6 percentage unit lower dressing percentage for Improvest males; P < 0.01); however, Improvest males were leaner (0.9 mm less backfat and 0.65% greater predicted lean yield; P < 0.01) compared with PC males. For the overall study period, pigs fed low NE and medium NE diets consumed 7.5% and 4.6% more feed (P < 0.01) than pigs fed high NE diets, respectively, and pigs fed low NE diets grew 1.7% slower (P < 0.02) than pigs fed medium NE and high NE diets. This resulted in pigs fed low NE diets having 4.4% lower G:F compared with pigs fed medium NE and 8.6% lower G:F compared with pigs fed high NE diets (P < 0.01). Pigs fed low NE had 3.0 kg lighter (P < 0.01) HCW compared with medium NE, while high NE had intermediate HCW that did not differ from the other two treatments. Overall, typical Improvest response levels for live performance and carcass characteristics when compared with PC males were achieved for each of the NE treatments evaluated in this study.

Leptospirosis in beef herds from western Canada: serum antibody titers and vaccination practices.

One study described the frequency of pre-breeding vaccination for leptospirosis in 205 cow-calf herds from across western Canada and the prevalence of positive Leptospira antibody titers in unvaccinated, weaned calves from 61 of these herds. The percentages of herds vaccinated for leptospirosis were 13.7% in 2001 and 8.4% in 2002. Of 1539 calves examined, 13 (0.8%) had a positive antibody titer for a Leptospira serovar; the most common serovar detected was hardjo. A second study examined the prevalence of positive Leptospira antibody titers during the summer grazing season in 313 vaccinated and 478 unvaccinated cows from 40 cow-calf herds in southern Saskatchewan. Antibody titers for 7 Leptospira serovars were measured during the grazing season. Of the non-vaccinated cows, 9.6% were positive in the spring for serovar pomona, 6.7% for serovar grippotyphosa, and 6.1% for serovar icterohaemorrhagiae; the corresponding percentages for the fall were 5.5%, 3.0%, and 1.3%, respectively. Of 781 vaccinated and unvaccinated cows that were sampled twice, 11.3% of vaccinated cows and 2.3% of unvaccinated cows had increases in Leptospira antibody titers during the grazing season.

Associations between prebreeding serum micronutrient concentrations and pregnancy outcome in beef cows.

OBJECTIVE: To determine associations between serum concentrations of copper, molybdenum, selenium, vitamin A, and vitamin E measured in beef cows at the start of the community pasture breeding season and pregnancy status at the end of the season. DESIGN: Prospective cohort study. ANIMALS: 771 beef cows from 39 cow-calf herds. PROCEDURES: Serum micronutrient concentrations were measured in samples collected from cows on arrival at 5 different community pastures in Saskatchewan, Canada, in May 2008. Cows were palpated transrectally to determine pregnancy status in October 2008. Herd owners and professional herd managers were surveyed to collect individual data for cows (age, calving date, and history of exposure to bulls before the start of the breeding season) and information on herd and breeding management. Associations between animal-, herd-, and pasture-level variables and pregnancy status were examined. RESULTS: Serum concentrations of selenium, molybdenum, vitamin A, and vitamin E were not associated with pregnancy status after accounting for prebreeding body condition score, age, and calving-to-breeding interval. Serum copper concentrations were more commonly assessed as below adequate than were other micronutrients. Decreased serum copper concentrations were associated with increased odds of nonpregnancy in cows < 10 years of age. CONCLUSIONS AND CLINICAL RELEVANCE: Prebreeding micronutrient supplementation programs should be carefully managed in herds with poor reproductive performance in areas known to be copper deficient, and evaluation of serum copper concentrations from a subset of cows should be considered before the start of the breeding season.

Selenium status at the end of the grazing season, reproductive performance and degenerative myopathy in beef herds.

The objectives of this study were to describe the serum selenium (Se) concentrations of beef cows from herds with varying levels of reproductive success, to examine factors associated with the Se concentrations at the end of the grazing season, and to determine if there were any associations between serum Se and reproductive success or calf viability. In the fall of 2001, 781 serum samples from 66 herds were analyzed as part of a nested case-control study to investigate risk factors for fertility; 10.6% were deficient in Se (< 0.025 ppm) and 86.8% were less than adequate (< 0.08 ppm). Low serum Se was most common in thin cows where feed Se was < 0.2 ppm, and from areas with more precipitation or with black or gray soils. Serum Se at pregnancy testing was not associated with an increased risk of reproductive failure. Lower herd serum Se was associated with increased risk of identifying degenerative myopathy in the subsequent calf crop (P = 0.006).