Heat Load in Feedlot Cattle

John Gaughan, Ian Loxton, Allan Lisle and Stephen Bonner - The University of Queensland - Beef Support Services Pty Ltd - Meat and Livestock Australia

Type: Research Paper
Knowledge level: Advanced

Farm Table says:

This research article looks at an assessment of betaine and glycerol as ameliorants of heat load in feedlot cattle. The study reports on these findings and the treatment impacts on animal productivity and animal welfare with associated economic production benefits.


Assessment of Betaine and Glycerol as Ameliorants

What is the problem?

The Australian feedlot industry continues to review heat stress reduction methodologies to maintain animal production and enhance animal welfare through minimizing heat load event related morbidities and mortalities.
The main goal of this research was to investigate the effect of betaine included at 0, 10, 20 and 40 g/head/day and to investigate the effect of glycerol fed at an inclusion rate of 5% of dry matter intake on core body temperature and respiratory dynamics of feedlot steers over the summer.

What did the research involve?

2.2 Animal ethics approval
-This project was approved (SA 2007/06/2002) by the Queensland Department of Primary Industries and Fisheries, Staff Animal Experimentation Ethics Committee.

2.3 Methodology

2.3.1 Study design and treatments.
-A feedlot study was conducted between the 10 September 2007 and the 13 March 2008 using 164 Angus steers (396 kg non fasted live weight at induction).

2.3.2 Study period time sequence terminology.
-The study period commenced on 12 November 2007 when steers were inducted into their treatment pens and fed their first ration in the PM of that day.

2.3.3 Animals and feedlot description Animals -One hundred and seventy-seven Black Angus steers aged 12 – 15 months of age and of mean non fasted liveweight 378 kg were purchased from a single source in Goulburn, NSW. Feedlot description-The BRS feedlot has 22 pens consisting of 6 pens of 168 m2 (pens 1 – 6) and 16 pens of 144 m2 (pens 7 – 22) (see Appendix 1), and has a north south alignment.

2.3.4 Live animal phase measurement schedule of events A description of the date and measurement schedule for the study during the live animal phase is shown in Appendix Allocation of cattle to surgery and to treatment pens- On 7 October 2007 the rectal temperature, non fasted live weight, visual hip height and temperament scores were obtained for the 177 steers.

2.3.6 Description of body temperature transmitters and surgery
-Within each pen, 3 steers were implanted with an intraabdominal digital temperature transmitter (Sirtrack Ltd, Havelock North, New Zealand.

2.3.7 Induction of animals to treatment pens
-The steers were walked to the yards on 11 November 2007, for measurements of non fasted live weight, visually assessed USBCS and hip height, a collection of blood samples via the coccygeal vein of the tail and a check of the operation of the temperature transmitters.

2.3.8 Diets and feeding
-The diets (including mineral supplement composition) were formulated by Integrated Animal Production.

2.3.9 Feeding management program
-The feeding management used in the study was a modified ‘Clean Bunk at Midday’ program (Lawrence 1998). The procedures followed are outlined in Appendix Feed Analysis -Diet grab samples and refusals were air-dried, ground to 1 mm and dry matter (DM) of both was determined by drying a sample at 100 o C for 24 hours.

2.3.11 Daily acquisition of body temperature data
-Temperature pulses were acquired daily from a total of 62 transmitters, during livestock transport to the abattoir at Oakey and during abattoir lairage.

2.3.12 Panting score data collection
– Panting scores were visually assessed using the 0 – 4.5 scale, with panting score 0 being an animal under no heat load, and 4.5 being a severe heat stressed to the animal.

2.3.13 Exit procedures -Feedlot exit (Day 120) was on 11 March 2008.

2.3.14 Transport to abattoir
-On 11 March 2008, at feedlot exit, following measurements, drafting, installation of temperature humidity loggers (Hobo, Onset Computer Corporation, USA) and the installation of the receiver and aerial to one of the livestock transports,

2.3.15 Lairage and abattoir data collection procedures-Upon arrival at 1700 h at Oakey Abattoir on 11 March 2008, the steers were unloaded into lairage pens as described in Appendix 9.

2.3.16 Meat sample collection- Striploin meat samples were collected from each left-hand carcass side following chilling and chiller assessment on the morning of 13 March 2008.

2.3.17 Laboratory assay of meat samples
-The meat samples were received at the FSA on 25 March 2008 in a frozen state and placed in a -25°C freezer until required for the assay.

2.3.18 Laboratory assay of blood parameters- Blood samples were taken from all steers with temperature transmitters (n=62) at the start and near the completion of the study (days 1 and 110).

2.3.19 HSP assay -All diluents and buffers were brought to room temperature before use.

2.3.20 Fatty acid analysis- the Adipose fat was used for analysis of fatty acid composition, derived from a sub-sample of M. Longissimus dorsi from which other meat quality parameters were assessed.

2.3.21 Gas chromatography analysis of fatty acids.-A astandard curve was calculated using the peak areas obtained for the C:17 internal standards between C:17 concentration in µg/ml and peak area.

2.5 Animal heat stress management -The protocol for the management of the steers during a high heat load event is described in Appendix 13.

2.6 Statistical analysis 2.6.1 General -The study was designed with pens as the experimental unit, with some observations made on individual animals, and others on the whole of a pen.

2.6.2 Weather data Coding -Data were logged by the weather station every 30 minutes.

2.6.3 Pen level measurements Coding -Data recorded at the pen level on a daily basis combined the information on the dry matter and water intake, and on water temperature. Analysis -Pen measurement data were analyzed using the GLM procedure, with terms for diet, shade and their interaction.

2.6.4 Live weight and growth data. Coding -These data consisting of weights, condition scores, and hip heights, all originated from the ‘Master file’ data set, and limited modification was necessary prior to analysis. Analysis- Analysis of variance models were fitted with the MIXED procedure, using REML estimation.

2.6.5 Body temperature data Coding -All valid observations were combined into a single dataset with more than 250,000 records. Analysis -For the data summarised by month, analysis of variance models were fitted with the MIXED procedure, using REML estimation.

2.6.6 Panting score data. Coding-Panting score was recorded on a 0 to 4.5 scale. AnalysisFor the data summarised by month, analysis of variance models were fitted with the MIXED procedure, using REML estimation.

2.6.7 Blood assay data.Limitations within the full dataset prevented the fitting of a three-way interaction for diet x shade x month, however, the three-way interaction was able to be included using a subset of the full data where January and glycerol data was omitted.

2.6.8 Slaughter data CodingThis dataset combines information from ‘Abattoir Carcase Data’, ‘MSA Grade data’, ‘FSA data’ and ‘RW color data. Analysis Analysis of variance models were fitted with the MIXED procedure, using REML estimation. Adipose tissue fatty acid profile data Fatty acid composition data were analyzed using repeated measures in PROC GLM.

What were the key findings?

3.1 Weather conditions -Overall, the study period was cooler on average, with some intermittent hot days over 35 °C and average rainfall recorded.

3.2 Animal health -There were minimal health issues associated with the steers for the period they were on Brigalow Research Station, despite their relocation from Central NSW to Central Queensland. The steers adapted well to the climatic conditions in Central Queensland.

3.3 Feed analysis.-The the crude protein level of each treatment diet was higher than the theoretical levels of 13.2 to 13.3%).

3.4 Supplement analysis.-There was an inherent background concentration of betaine in the Control betaine placebo, Control glycerol placebo, Control/betaine base and glycerol-based supplements as a consequence of the grain cereal carrier that comprised a significant proportion of the composition of the supplements.

3.5 Analytical composition of glycerol -The chemical composition of the glycerol fed in the Glycerol treatment is shown in Table 9. Batches 1, 2 and 3 were fed sequentially over the study period.

3.6 Feed intakesAccess to shade had a positive response on DMI.

3.7 Water consumption -Water temperature Daily water temperatures were higher over days 30 to 60 in the Glycerol pens compared to the control or betaine treatment pens.

3.8 Change in liveweight.- The Glycerol treatment Exit liveweights were numerically similar to the Control and lower than the Betaine treatments.

3.9 Feed conversion efficiency-Over the entire study period (I – E), the Glycerol treatment recorded a numerically higher feed conversion ratio than the other dietary treatments.

3.10 Visual hip height and change in visual hip height -Dietary treatment had no effect on visual hip height throughout the study period.

3.11 US body condition score -Dietary treatment influenced US Body Condition Score (USBCS) with the Control treatment having a lower USBCS.

3.12 Body temperature
-The glycerol fed steers had a higher body temperature than the other dietary treatments between days 1 and 30.

3.15 Animal response during defined ‘hot’ periods of the study
-The climatic data were analyzed to identify a number of hot periods during the study.

3.16 Steer body temperature during livestock transport to abattoir- he microclimate on the respective compartments
of both the top and bottom decks of the livestock transport (Truck 3) recorded with Hobo climate sensors.

3.17 Steer body temperature during abattoir lairage period -The steers were in lairage at 1800 h on 11 March to 0900 h on 12 March 2008 (Refer to Appendix 10).

3.18 Carcase characteristics -The analysis of the abattoir data was complicated by the slaughter floor chain breakdown that occurred.3.18.1 Slaughter data -The steers were considered young based on their dentition with 98% of the steers having zero permanent incisors at slaughter. Dentition is considered an indicator of chronological age.

3.18.2 Chiller assessment data- Dietary treatment had no influence on cold carcass side weights, carcass shrinkage, eye muscle area or the subjective hard meat score.

3.19 Meat quality
-The loin temperature-pH decline measured over a three hour period post slaughter indicated that all carcasses regardless of treatment or position on the slaughter floor chain at the breakdown were heat shortened i.e. they reached a pH of 6.0 at a greater temperature than the preferred 20 °C (Anon 2003).

3.20 Effect of surgical implantation of temperature transmitter on subsequent animal performance.
– Because of the importance of the procedure for surgical implantation of temperature transmitters (surgery) to the objective of the study.

Final Comment

This study confirms that shade is the primary method for alleviation of heat load in black Bos taurus cattle.

2009 - Australia - John Gaughan, Ian Loxton, Allan Lisle and Stephen Bonner - The University of Queensland - Beef Support Services Pty Ltd - Meat and Livestock Australia
Read ArticleSave For Later

Related Resources