Artificial cooling as an alternative to increase productivity and welfare of steers under heat stress

Strategies to alleviate heat stress on performance and physiological parameters in feedlot-finished cattle under heat stress conditions. A systematic review-meta-analysis

Strategies to alleviate heat stress on live performance - dry matter intake (DMI), average daily gain (ADG), and feed conversion efficiency (FCE) - and on physiological parameters - respiratory rate (RR) and panting score (PS) - of feedlot-finished cattle were evaluated by systematic review-meta-analysis. Using the PICO framework were identified 3813 records, with 31 publications and 6729 cattle being considered in the meta-analysis (MA). The comparison most reported was sun vs. shade (n = 24 publications), followed by shade vs. shade (area per animal and effectivity in reduce solar load) (n = 7 publications) and sun vs. sprinkling (n = 4 publications). Cattle with access to shade with total reduction in solar load improved ADG (p = 0.008) and FCE (p = 0.024), and reduced RR (p < 0.001) compared to unshaded animals. Cattle with access to shade with a height between 3 and 4 m increased ADG (p < 0.001), tended to improve FCE (p = 0.054), and reduced RR (p < 0.001) compared to unshaded animals. An area of shade from 2 to 4 m2/animal increased ADG (p = 0.002), and higher than 4 m2/animal reduced RR (p < 0.001) compared to unshaded animals. Animals that received sprinkling volume below 1 L/animal/min improved ADG (p = 0.008) compared to unshaded animals. Cattle with access to shade with a high area per animal improved DMI (p = 0.023) and ADG (p < 0.001) compared to animals with a low area. In univariate meta-regression, it was observed that the variables significantly (P < 0.05) influencing DMI were THI category; influencing ADG were cattle gender, THI category, and coat color; influencing FCE were cattle age and hemisphere; and influencing RR were country, THI category and climate. Performance and physiological parameters of feedlot-finished cattle under heat stress depend on animal and environmental characteristics.

The influence of shade allocation or total shade plus overhead fan on growth performance, efficiency of dietary energy utilization, and carcass characteristics of feedlot cattle under tropical ambient conditions

Objective

The objective of this experiment was to evaluate the effect of shade allocation and shade plus fan on growth performance, dietary energy utilization and carcass characteristics of feedlot cattle under tropical ambient conditions

Methods

Two trials were conducted, involving a total of 1,560 young bulls (289±22 kg BW) assigned to 24 pens (65 bulls/pen and 6 pens/treatment). Pens were 585 m² with 15 m fence line feed bunks. Shade treatments (m² shade/animal) were: i) limited shade (LS) to 1.2 m² shade/animal (LS_1.2); ii) limited shade to 2.4 m² shade/animal (LS_2.4); iii) total shade (TS) which correspond to 9 m²/animal, and iv) total shade equipped with fans (TS+F). Trials lasted 158 and 183 days. In both studies, the average weekly maximum temperature exceeded 34°C.

Results

Increasing shade allocation tended (p = 0.08) to linearly increases average daily gain (ADG), and dry matter intake (DMI, quadratic effect, p = 0.03). This effect was most apparent between LS_1.2 and LS_2.4. Shade allocation, per se, did not affect gain efficiency or estimated dietary net energy (NE). Compared with TS, TS+F increased (p<0.05) ADG, gain efficiency, and tended (p = 0.06) to increase dietary NE. There was a quadratic effect of shade on longissimus area and marbling score, with values being lower (p<0.01) for LS_2.4 than for LS_1.2 or TS. Likewise, marbling score was lower for TS+F than for TS. Percentage kidney, pelvic, and heart (KPH) linearly decreased with increasing shade. In contrast, KPH was greater for TS than for TS+F.

Conclusion

Providing more than 2.4 m² shade/animal will not further enhance feedlot performance. The use of fans in combination with shade increases ADG and gain efficiency beyond that of shade, alone. These enhancements were not associated with increased DMI, but rather, to an amelioration of ambient temperature humidity index on maintenance energy requirement.

Up-regulation of milk secretion with modified microclimate through manipulating plasminogen-plasmin system in Murrah buffaloes during hot dry season

The present study was aimed at determining changes in milk yield and composition along with the plasminogen-plasmin system of milk, plasma hormones, and metabolites of buffaloes during hot dry season (air temperature range 39.7 to 44.8 °C) under two different management systems. Buffaloes were divided in two groups of six animals each: control and treatment, where treatment group animals accessed benefit of mist and fan cooling from 9:30 a.m. to 5:00 p.m., while control group animals were devoid of it. Duration of experiment was 6 weeks. Under mist and fan cooling system, buffaloes experienced better comfort by alleviating environmental stress as their physiological responses such as rectal temperature, respiration rate, pulse rate, and forehead and middorsal temperatures were significantly (P < 0.05) reduced compared to control, which subsequently resulted higher milk yield by 4.44 % (P < 0.001). Analysis of milk samples revealed higher concentration of plasminogen (7.99 vs 6.27 μg/ml; P < 0.01) and β-casein (1.09 vs 0.92 g/dl; P < 0.001) and lower plasmin level (0.178 vs 0.194 μg/ml; P < 0.05) in buffaloes under the treatment group compared to that under the control. Plasma glucose level was higher (P < 0.001) by 21.08 %, whereas cortisol, norepinephrine, and NEFA levels were lower (P < 0.001) by 19.19, 15.38, and 11.41 %, respectively, in treatment animals. However, exposure of buffaloes to cooling system did not alter composition and calcium content of milk, GH, and epinephrine level in plasma. Hence, it may be concluded that provision of cooling system during summer was effective to minimize environmental stress and improve milk production by manipulation of the PG-PL system in buffaloes.