Thermoregulation of nutrient-restricted hair ewes subjected to heat stress during late pregnancy.

In summers with severe hot environmental temperatures, thermoregulation is expected to be critical during the last third of gestation of hair ewes, and this effect can be overstated by suboptimal feeding conditions. Twenty-four multiparous hair sheep ewes with approximately 100d of pregnancy were randomly assigned to two treatments to evaluate the effects of nutritional restriction (NR) during late gestation on some serum metabolites, physiological variables, and thyroid hormone concentrations under intense heat load (maximum temperature 42-45°C). Treatments were as follows: (1) control, ewes fed free choice wheat straw plus a concentrate at a rate of 500g/d, and (2) nutritionally-restricted (NR) ewes, which were offered wheat straw only ad libitum. Body weight of NR ewes dropped 5.1kg (P<0.05), while control ewes gained 4.7kg during the study period. Rectal temperature was not affected (P>0.05) by feeding regime either in the morning or afternoon hours. Respiration rate was greater (P<0.05) in control ewes (20 and 40breaths/min higher in the day and night, respectively) on d 130 and 145 of pregnancy compared to NR ewes. Skin temperatures during the morning and afternoon were affected (P<0.05) by feeding regime at d 130 and 145 of pregnancy. In the morning, NR ewes presented greater (P<0.05) head and rump temperature at day 145 of gestation, and lower (P<0.05) udder temperatures at d 130 and 145 than control ewes. In the afternoon, skin temperatures of NR ewes were higher (P<0.05) in head and right flank on d 130 and 145 of pregnancy, and in udder at day 145 compared to control ewes. Serum glucose was higher (P<0.05) in NR ewes than control animals at day 145 of pregnancy. Serum cholesterol, triglyceride and thyroid hormones were not affected by nutritional restriction. Overall, it was found that nutritionally restricted ewes were less affected by intense heat loads than well-fed ewes, apparently due to the lower metabolic heat produced by this underfed animals. Also, it was apparent that the lower respiration rate of NR ewes was compensated by a greater body surface temperature.

Physiological and productive responses of multiparous lactating Holstein cows exposed to short-term cooling during severe summer conditions in an arid region of Mexico.

Heat stress generates a significant economic impact for the dairy industry in arid and semi-arid regions of the world, so that heat abatement is an important issue for dairy producers. The objective of this study was to evaluate effects of two short-term cooling periods on physiological and productive status of lactating Holstein cows during hot ambient temperatures. Thirty-nine multiparous cows were blocked by milk yield and assigned to one of three treatments including: control group (C), cows cooled before milking time (0500 and 1700 h daily, 1 h cooling); AM group, cows cooled at 1000 h and before milking (2 h cooling); and AM + PM group, cows cooled at 1100, 1500 and 2200 h, as well as before milking (4 h cooling). The cooling system was placed in the holding pen which the cows were moved through for cooling. Respiratory rate, and temperatures of thurl and right flank, were lower (P < 0.05) in cows from the AM + PM group than AM and C cows during the morning and afternoon. However, udder temperature was higher in the AM + PM group compared to AM and C groups during the afternoon, although lower than the AM group during the morning. Rectal temperature was similar in all groups. Thyroxin concentrations tended (P < 0.10) to be lower in AM + PM relative to the AM and C groups. The AM + PM group had higher (P < 0.05) milk production than C (18.70 vs. 17.43 kg, respectively), and AM + PM cows had a trend (P < 0.10) to increased milk energy output vs. the C and AM groups (13.75 vs. 13.18 and 13.15 Mcal, respectively). Protein and fat in milk, body condition score, glucose, cholesterol, triglycerides and triiodothyronine were similar among the groups. Four hours of cooling with spray and fans during severe summer temperatures only modestly improved milk yield of lactating Holstein cows.

Evaluation of the efficacy of Grofactor, a beta-adrenergic agonist based on zilpaterol hydrochloride, using feedlot finishing bulls.

Beta-adrenergic agonists (ß-AA) have been shown to positively impact finishing performance and some carcass traits of feedlot cattle. Our objective was to evaluate the efficacy of a ß-AA on the basis of zilpaterol hydrochloride (Grofactor, Laboratorios Virbac México, Guadalajara, Mexico) on growth and DMI, carcass characteristics, and meat quality of finishing bulls. Forty-five bulls (75% 25% ) initially weighing 448.7 ± 2.58 kg were blocked by BW and randomly assigned to 1 of 3 diets, using pens of 3 animals, in a randomized complete block design: 1) daily feeding without ß-AA in the basal diet (Control), 2) daily feeding with 0.15 mg/kg BW of Grofactor added to the basal diet (ZHG), or 3) daily feeding with 0.15 mg/kg BW of Zilmax (MSD Salud Animal México, Mexico City, Mexico) added to the basal diet (ZHZ). The duration of the feeding period was 30 d with a subsequent 4-d withdrawal period. Compared with Control bulls, the group fed ZHG had a 12% better ( < 0.025) G:F ratio, and their final BW ( 0.094) and ADG ( 0.084) tended to be enhanced. Feedlot performance of ZHG and ZHZ bulls was similar, although the DMI was ∼4% lower ( 0.05) in ZHG bulls vs. the ZHZ and Control groups. The HCW ( 0.001) and dressing percentage ( 0.015) were higher by 20 kg and 3%, respectively, in ZHG bulls vs. Control bulls. The KPH fat was lower ( 0.007) in bulls fed ZHG than in nonsupplemented bulls, but other carcass characteristics were not different in the ZHG and ZHZ bulls, and noncarcass components were not affected by ZHG or ZHZ supplementation. At 48 h postmortem, ZHG bulls had lower ( 0.007) water holding capacity and trended toward ( 0.06) increased chroma and reduced pH ( 0.09) compared to Control bulls. However, compared to ZHZ bulls, ZHG bulls had higher ( 0.02) chroma and a trend ( 0.08) toward increased hue angle. At 14 d postmortem, meat quality variables did not differ between the 3 groups of bulls. Supplementation of ZH Grofactor improved feedlot performance and some carcass characteristics of finishing bulls without affecting meat quality. The effects of Grofactor on feedlot performance, carcass traits, and meat quality were similar to those of Zilmax.

Effect of zilpaterol hydrochloride on feedlot performance, nutrient intake, and digestibility in hair-breed sheep.

Twelve Dorper × Pelibuey wether lambs (26.8 ± 1.6 kg initial BW, 5 mo of age) were used to evaluate effects of zilpaterol hydrochloride (ZH) on feedlot performance, and effects of ZH and ZH supplementation period (15 and 30 d) on nutrient intake and digestibility. Lambs were blocked by initial BW, and assigned randomly within BW blocks to 1 of 2 treatments: i) control (no ZH), and ii) supplemented with ZH (10 mg ZH/wether lamb daily). Measurements of intake and digestibility were performed on d 9 to 15 and 24 to 30. Feedlot performance data were analyzed as a randomized complete block design, and nutrient intake and digestibility data were analyzed as a randomized complete block design with a 2 × 2 factorial arrangement of treatments. Final BW, ADG, total BW gain, and G:F were greater (P ≤ 0.04) for ZH than for control lambs. No treatment × feeding duration interaction for nutrient intake and apparent total tract digestibility were observed (P > 0.05). Intake of DM, OM, CP, and GE were less (P ≤ 0.03) for ZH than for control. Lambs fed for 30 d had greater (P ≤ 0.04) NDF and GE intake compared with those fed for 15 d. Total tract digestibility of DM, OM, CP, EE, and ADF (P ≤ 0.03) was less for ZH than control. Furthermore, calculated DE, ME, and TDN intake decreased (P < 0.01) with ZH supplementation. Also, DM, CP, and ether extract(EE) digestibility were greater (P < 0.01) for 30 d than for 15 d. Additionally, greater (P ≤ 0.01) DE, ME, and TDN intake was observed for 30 d compared with 15 d. In conclusion, ZH supplementation of wether lambs consuming feedlot diets resulted in improved feedlot performance and reduced the intake and digestibility of some nutrients.

Effects of zilpaterol hydrochloride on growth performance, carcass characteristics, and wholesale cut yield of hair-breed ewe lambs consuming feedlot diets under moderate environmental conditions.

Twenty-four Dorper × Pelibuey ewe lambs initially weighing 25.1 ± 0.6 kg were used in a 34-d feeding experiment and after slaughter to evaluate the effect of zilpaterol hydrochloride (ZH) on feedlot performance, carcass characteristics, and wholesale cut yield. Ewe lambs were individually housed in pens, blocked by initial BW, and assigned randomly within BW blocks to 1 of 2 treatments: 1) control (no ZH) and 2) supplemented with ZH (10 mg/ewe lamb daily) during 32-d and a 2-d withdrawal preslaughter period. Feeding ZH increased (P < 0.01) final BW, ADG, and G:F of ewe lambs, whereas feed intake was unaffected (P = 0.80). Hot and cold carcass weights, dressing percentage, and conformation score were improved (P < 0.001) when ZH was fed. Likewise, LM area was 3.7 ± 0.41 cm(2) larger (P < 0.001) for ZH than control ewe lambs. Feeding ZH did not affect (P ≥ 0.29) cooling loss, carcass length, fat thickness, or KPH. With exception of peritoneum (P < 0.001), head (P = 0.021), and neck (P < 0.001), ZH did not increase (P ≥ 0.12) noncarcass components or wholesale cut yield percentage. A trend to increase (P = 0.060) loin percentage from HCW was observed in lambs supplemented with ZH. In conclusion, feeding ZH to Dorper × Pelibuey ewe lambs improved feedlot performance and also some carcass traits (HCW, cool carcass weight, dressing percentage, and LM area) of economic importance; however, fat deposition was not affected by ZH.