Field study of the drought’s impact on feeding strategy and biological parameters in early lactation dairy cattle
Sammanfattning: The summer of 2018 was unusually warm and dry. For animal production, this resulted in poor pastures, reduced harvests of crops, such as roughage and grains, and increased risk for heat stress in the animals. The drought led to problems as in shortage of animal feed, which made the feeding of dairy cattle difficult. This field study was performed to research how Swedish dairy farmers handled the drought and feed situation. Eleven farms were visited, and the farmers were asked questions from a questionnaire, regarding whether they experienced that they were affected by the drought and feed situation or not, questions about the feeding strategy on the farm, if alternative feedstuffs were used and if the farmers had been required to sell or slaughter animals because of the feed situation. The farmers had different experiences of the drought where some of them tried feeding alternative feedstuffs as bean straw, peas, whole crop silage, silage from fallow land or a complementing compound feed. Some farmers needed to slaughter or sell animals due to the lack of feed. In total, 59 primiparous cows in their early lactation were included. The examined cows were of the breeds Swedish Holstein (SH), Swedish Red (SRB) and Jersey cattle. In addition to the questionnaire, feed samples were collected from the roughage used, to see if relations could be found between the result of feed samples and other studied parameters. Milk- and blood samples were collected from 3-10 cows from each farm. These cows were also body condition scored. It was studied if a relation could be found between any experienced problems caused by the feed situation, and the studied biological parameters. These parameters were levels of myristic acid (C14:0), palmitic acid (C16:0), stearic acid (C18:0) and oleic acid (C18:1 cis-9) in milk, and levels of b-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), glucose, insulin and insulin-like growth factor 1 (IGF-1) in blood plasma, body conditions and feed samples. The feed samples were analysed for contents of dry matter (DM), metabolizable energy (ME), ash, crude protein (CP) and neutral detergent fibre (NDF). The majority of the examined cows (93%) had body conditions between 3.0 and 4.0 of a scale of 1-5, where 1 is emaciated and 5 is obese. Approximate energy balances on herd level were estimated via the software IndividRAM which showed that the herds were between 92 and 109%. Relations were found between some of the studied parameters, with different parameters identified on the different farms. Statistical analyses showed significant correlations between C14:0 and C18:1 cis-9; NEFA and C18:1 cis-9; BHB and C18:1 cis-9; BHB and C14:0; BHB and glucose; BHB and NEFA. An analysis of variance (ANOVA) showed significant differences between the farms regarding the levels of the milk fatty acids C14:0, C16:0, C18:0, plasma components BHB, NEFA, glucose, IGF-1 and body conditions.
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