The impact of bale vs. crop grazing over winter on the welfare of dairy cattle farmed in Southland, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Manawatū, New Zealand
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2024
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Massey University
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Intensive winter grazing of pregnant non-lactating dairy cattle in Southland New Zealand often leaves cows in wet, muddy and rainy conditions with minimal shelter. Management on winter crops, such as kale, involves using high stocking rates to maximise utilisation and encourage cows to eat down to the ground, leaving bare soil that easily turns into mud. This has led to welfare concerns, as these conditions leave cows unwilling to lay down and may impair thermoregulation. Lack of rest can result in frustration and stress, and prolonged thermoregulatory challenge can result in cold stress, which are negative experiences that can impair welfare. While it is less efficient due to lower yields of dry matter/hectare compared to crops, it is thought that bale grazing (management on pasture with access to hay bales) may alleviate some of these issues and improve the welfare status of cows over winter. Therefore, this study aimed to assess the impact on lying behaviours and thermoregulation when dairy cows are managed on a kale crop compared to bale grazing over winter. Eighty pregnant non-lactating dairy cows were managed on either a kale crop or using bale grazing (n = 40/group) for winter 2022. Data collection was divided into two stages. In stage one, lying behaviours were monitored for the first month of winter (27 days) in relation to weather conditions. After this, during stage two, 60 out of the 80 cows (20 bale grazing cows, 40 kale crop cows, n = 10 groups per treatment) went onto replicated experimental plots of either kale/bale grazing for in-depth, behavioural analysis of lying and thermoregulatory behaviours/parameters for two days. Hygiene scores (measure of coat cleanliness on a 3-point scale) were obtained before and after each stage. Live weight and body condition scores were obtained before and after stage one and again just before calving. Inferential statistics were only calculated during stage two due to the lack of treatment replication in stage one. During stage one, lying times were similar for both treatments (kale crop = 8.7 hours/day, bale grazing = 8.9 hours/day), whereas kale crop cows transitioned between lying and standing more often (15 vs. 19/day) and took more steps than bale grazing cows (2,327 vs. 2,045/cow/day) on average. Rain and/or cold temperatures reduced lying times, transitions and steps for both treatments, resulting in rebound lying behaviour when conditions improved. This was more pronounced in the kale crop cows. During stage two, conditions were cold and dry. Kale crop cows lay down less than bale grazing cows (P = 0.013) and transitioned significantly more often between lying and standing (P = 0.019) on day one. However, this was likely attributed to a very low space allowance on day one. Bale grazing cows spent more time in comfortable lying postures (P = 0.022), were observed ruminating more (P = <0.001), remained cleaner (P = 0.004), had higher rump and thigh skin temperatures (P = 0.007) and higher infrared nose temperatures when lying (P = 0.048) than the kale crop cows. The surface for the kale crop cows became more compacted (P = 0.008) and got muddier (higher mud/boot score; P = 0.051). Overall, bale grazing cows appeared more comfortable than kale crop cows, which may be attributed to the greater thermal comfort and the provision of drier lying surfaces at a lower stocking rate.