Sigrid Agenäs

Effects of Turnout to Pasture and Dietary Fat Supplementation on Milk Fat Composition and Conjugated Linoleic Acid in Dairy Cows

Turnout to pasture involves considerable changes in the feed intake and metabolism of dairy cows. The aim of this study was to investigate how these changes affect milk production and milk fat composition, in cows selected for high (HFI) or low (LFI) milk fat content producing the same yield of 4% fat-corrected milk. Furthermore, two different concentrates, with high or low inclusion of soya oil, were studied. The experiment was conducted with 44 multiparous mid-lactating cows over a 4 week period. Samples of milk and blood were obtained before turnout to pasture, during transition to pasture and when cows were adapted to pasture. Milk yield decreased with 3.6 kg energy-corrected milk (ECM) on average during the first 5 days after turnout to pasture. This decrease, together with a drop in plasma insulin and increased plasma non-esterified fatty acids (NEFA), indicated nutritional insufficiency at turnout to pasture. Milk fat composition changed towards more long-chain fatty acids (LCFA) and fewer de novo synthesized fatty acids. This was probably caused by an increased supply of LCFA of feed and body origin to the udder. LFI cows showed higher levels of conjugated linoleic acid at pasture than HFI cows.

Changes in metabolism and milk production during and after feed deprivation in primiparous cows selected for different milk fat content

Abstract The objectives of this experiment were to study changes in metabolism and milk production due to feed deprivation in peak-lactating primiparous cows and also to investigate whether cows selected for different milk fat content show differences in the response to feed deprivation. A total of 12 primiparous cows averaging 69±9 (S.D.) days in milk were subjected to a 48-h period of total feed deprivation and were monitored for 9 days after feed deprivation. The cows were chosen from a selection program in which high yielding dairy cows of the Swedish Red and White breed are selected for either high (HFI) or low (LFI) milk fat percentage, but with the same amount of energy in the milk. HFI cows showed a more pronounced insulin-response when plasma glucose increased after refeeding. Furthermore, β-hydroxybutyrate in plasma was higher in HFI cows. Plasma non-esterified fatty acid concentration increased more than 20 times in both HFI and LFI cows when feed was removed, plasma glucose and insulin decreased and plasma urea increased. Milk yield had decreased 24 h after feed removal and was at most decreased to 51% of the initial yield. Milk content of fat, protein and lactose was similar between the selection lines but sodium and potassium in milk was higher in LFI cows. It was shown that high-yielding primiparous cows have the ability to regain milk yield and composition after a short period of feed deprivation in peak lactation.

Relative impact of α-tocopherol, copper and fatty acid composition on the occurrence of oxidized milk flavour

The oxidative process in milk fat, resulting in spontaneous oxidized off-flavour (SOF), is commonly assumed to depend on contents of pro- and antioxidants in milk and availability of fatty acids acting as their substrate. An important antioxidant in milk is alpha-tocopherol whereas the most potent prooxidant is the metal ion copper. The separate effects of alpha-tocopherol, copper, and milk fatty acid profile, and their combined effect on SOF development were examined in milk from 44 multiparous cows fed different roughage types and different amounts of dietary, unsaturated fat. A clear association between concentrations of copper and poly-unsaturated fatty acids in milk and the risk for developing SOF was found. Heritability estimates suggest that occurrence of SOF is partly under genetic control which indicates that milk quality may be compromised if breeding bulls are selected that carry genotypes predisposing for milk prone to develop SOF.

Effect of different hand-milking techniques on milk production and teat treatment in Zebu dairy cattle

The aim of the study was to test three different hand-milking techniques (“pull down”, “thumb in”, and “full hand grip”) and their effects on milk production and teat treatment. This is important since milk production in many tropical areas still rely on hand-milking. The study was carried out at a peri-urban farm in the Bobo-Dioulasso area in Burkina Faso. Twelve indigenous Zebu cows in early lactation were used in the study. The sequences of the treatments (hand-milking techniques) and the milkers were balanced for carry-over effects between successive periods and days, respectively. The sequences were constructed by using special Latin squares. Yield and composition of saleable milk was not affected by milking technique but there were differences between the milkers in milk yield. There was also a significant interaction for saleable milk yield between milker and milking technique. Hemoglobin in milk was measured as an indicator of teat damage. The hemoglobin content was numerically higher in post-milking strip milk samples than in saleable milk. It was concluded that the amount of milk removed depends mainly on the milker and how well the milking technique works for the individual milker. No effect of milking technique was observed on teat treatment.

Editorial: We need to bring the calves back to the dairy cows

As a member of the Editorial Board of JDR I have the opportunity to write an Editorial. I want to use this opportunity to raise the possibility of bringing the calves back to the cows in modern dairy production. It would be great if we could review literature on this matter, but there are almost no publications available that deal with effects of keeping cow and calf together instead of the common separation at birth. There has been, and still are, very good reasons for separating calves at birth but there are also good reasons to study alternatives to this practice. There is a growing concern among both farmers and consumers over possible adverse effects on cows and calves from separation. Most of the attention historically, among consumers as well as research, has focused on effects on the orphan calf, but losing the calf may also add to the challenges for the transition cow. However, we do not know anything about the effects on the cow since all cows that are used in dairy research are separated from their calf within the first day or two after parturition. When consumers become more educated their resistance to early separation gets stronger, as was recently highlighted in transatlantic research (Busch et al. 2017). Organic production has a particular challenge since the ideology of organic production and the expectations from consumers include that the food is produced in a natural way and it is very difficult to argue that it is natural for a new-born mammal to be separated from its mother at birth. However, the discussion goes beyond organic production. From my horizon in Sweden, production of animal derived foods is full of contradictions. Sweden has very extensive animal welfare regulations and our farmers work hard within this framework. At the same time they face very strong opposition from parts of the Swedish society with large groups moving to vegetarian and vegan diets, often because they do not agree with management of production animals. In social media, posts that relate to dairy cows or dairy products quickly get comments on perceived problems with modern dairy production and separating mother and young is one of the most common concerns. In many parts of the world, particularly in arid areas, the dominating dairy management is to share the milk between humans and the animal offspring by allowing the offspring access to its mother during parts of the day. We now see a number of farms around Europe adopting similar management practices but they do it without the support of science and extension. The growing interest from farmers is one argument for doing research on how to integrate the calves into modern dairy production. The possibility of positive effects on sustainability of the dairy sector (in a broad sense) is another. My curiosity as a scientist also finds the idea attractive because research models where cows and calves are kept together will provide a better overall understanding of the biology of lactation. Current research is lacking the positive control of natural lactation and calf rearing and that has probably tainted our conclusions on how things work. Needless to say, there are also potential benefits in terms of consumer trust and the political climate. I look forward to seeing submissions reporting data on cows and calves that are kept together, and hope to see a comprehensive literature review when the time is right. If we keep the calves away from their mothers there is a real risk that dairy production will go out of business in markets where animal welfare is a priority for the consumers. Sigrid Agenäs is Professor in management of ruminants with a focus on lactation biology. She has been a member of the Editorial Board since 2015.

Farmer awareness of cow longevity and implications for decision-making at farm level

ABSTRACT The aim of this study was to investigate if farmer awareness of longevity can explain why the longevity of dairy cows does not increase in Sweden, despite the fact that the genetic trend for longevity in Swedish dairy cattle is positive. In this study, farmers’ decisions were put in the forefront through a qualitative study with semi-structured interviews. The results showed that farmers seemed well aware of biological factors related to cow longevity, that they think the demands on dairy cows have increased over time and that they correlate the higher demands to shorter longevity. However, the farmers had not worked explicitly with longevity of their own herd. There are subjective management decisions behind a culling of a dairy cow, and the reporting of culling reasons does not mirror the farmer’s reasoning behind the decisions, which is a key factor determining longevity.

Effect of low light intensity at night on cow traffic in automatic milking systems

Several studies have shown benefits of long-day (16 h) photoperiod in lactating dairy cows, but have not identified a suitable light intensity for the dark hours. It is known that the locomotion pattern of dairy cows is altered at low light intensities and this may translate to reduced cow traffic and milking frequency, which would have a negative impact on system productivity. However, it is also recognised that a significant disturbance of rest may have a negative impact on the health and productivity of high-yielding dairy cows. This study examined the effect of three different night-time light intensities (LOW: 11 ± 3, MED: 33 ± 1 and HIGH: 74 ± 6 lx) on number of gate passages, milking frequency and milk yield in dairy cows in automatic milking systems. The study was conducted in Sweden during the winter of 2012–13 and the treatments were applied in a crossover design to three herds with an automatic milking system. Minimum day time light intensity was 158 lx. Data on gate passages, milking frequency and milk yield for 172 ± 49 (mean ± s.d.) cows during the last 22 days of each 34-day study period were analysed for treatment differences and differences in daily distribution over 24 h, during day time and night time. Light intensity did not affect total number of gate passages per 24-h period and cow, but number of gate passages per hour and cow was in all treatments lower during night time than during day time. Milking frequency was increased in MED compared with both HIGH and LOW (P < 0.05). Milk yield decreased with reduced light intensity, and differed significantly between HIGH and LOW treatments, 45 ± 1 kg and 44 ± 1 kg, respectively (P < 0.001). Our conclusion is that reducing light intensity to 11 lx at night time does not affect cows’ general activity as gate passages remained the same for all treatments. However, milk yield decreased with reduced light intensity, which might be related to a lower feed intake. We argue that providing night light for dairy cows, as required by many welfare acts, might be related to production level rather than welfare aspects and that the recommendations should be revised.

First-night effect on sleep time in dairy cows

In human sleep studies, the probability of discomfort from the electrodes and the change in environment usually results in first-night recordings being discarded. Sleep recordings from the first night in human subjects often differ in amount of REM (rapid eye movement) sleep and the overall sleep architecture. This study investigated whether recordings of sleep states in dairy cows also show a first-night effect. Non-invasive electrophysiological recordings were carried out on nine cows of the Swedish Red breed during three consecutive 24-hour periods (recording days 1–3). Overall, cows spent 12.9 ± 1.4 hours awake, 8.2 ± 1 hours ruminating, 57.2 ± 20.3 min drowsing, 44.1 ± 20.2 min in REM sleep and 64.3 ± 38.1 min in NREM (non-rapid eye movement) sleep (mean ± SD) and there were no significant differences between recording days in total duration for any of the sleep and awake states. However, the bouts of REM sleep and rumination were longer, and the awake bouts were shorter, at night time compared to daytime, regardless of recording day. The awake bouts also showed an interaction effect with longer bouts at daytime during day 1 compared to daytime on day 3. Data on sleep and awake states recorded in adult dairy cows during three consecutive 24-h periods showed great variation in sleep time between cows, but total time for each state was not significantly affected by recording day. Further and more detailed studies of how sleep architecture is affected by recording day is necessary to fully comprehend the first-night effect in dairy cows.

Effect of increased milking frequency and residual milk removal on milk production and milk fatty acid composition in lactating cows

It has been well established that milk yield is affected both by milking frequency and due to the removal of residual milk, but the influence of a combination of these factors is unclear. In this study, four mid-lactation cows were used in a 4 × 4 Latin square design to test the hypothesis that the effects of more frequent milking and residual milk removal on milk yield and composition are additive and alter milk fatty acid composition. Treatments comprised two or four times daily milking in combination with (or without) residual milk removal over a 96 h interval preceded by a 2 d pretreatment period and followed by a 8 d washout in each 14 d experimental period. Milk was sampled at each milking for the analysis of gross composition and SCC. Samples of available and residual milk collected on the last milking during each treatment period were collected and submitted for fatty acid composition analysis. Increases in milking frequency and residual milk removal alone or in combination had no effect on milk yield or on the secretion of lactose and protein in milk. However, residual milk removal during more frequent milking increased milk fat yield. Milking treatments had no major influence on the fatty acid composition of available milk, but resulted in rather small changes in the relative abundance of specific fatty acids, with no evidence that the additive effects of treatments were due to higher utilisation of preformed fatty acids relative to fatty acid synthesis de novo. For all treatments, fat composition of available and residual milk was rather similar indicating a highly uniform fatty acid composition of milk fat within the mammary gland.

Milk Yield and Milk Fat Production in Feed-Deprived Dairy Cows

In this study we investigated cows from an ongoing selection program were high yielding dairy cows of Swedish Red and White breed are bred for either high or low milk fat percentage. The two selection lines are sired with bulls indexed for high (HFI) or low (LFI) milk fat percentage at the same amount of energy produced in milk (Akerlind et al., 1999). Six cows from each selection line, producing on average 23,9 kg milk (HFI) and 26,7 kg milk (LFI) at the onset of the experiment were used. The objective of this experiment was to study if there were differences in the response to feed deprivation between the selection lines regarding milk yield and milk fat production. Twelve primiparous cows in early lactation (wk 7-11) were subjected to a 48 hours period of total feed deprivation, and were then followed for seven days after refeeding. The cows were milked twice a day at 6 a.m. and 4.30 p.m. and milk samples were obtained at each milking. Milk yield was only recorded from three teats during the experiment, due to udder tissue sampling from one teat. Biopsy data are not reported here. Blood was sampled from the tail vein at 8 a.m. and at 5 p.m. When feed was removed the plasma NEFA concentration increased sevenfold. The plasma concentration had decreased markedly 12 hrs after refeeding and had returned to the initial level one week after refeeding. Milk yield decreased within 24 hrs after feed removal and showed the lowest values at the first milking after refeeding, when it was less than 50% of the production level before feed deprivation. Milk fat content increased reciprocally to milk yield and thereby the effect on total milk fat production was limited. The milk fat composition was strongly affected by the feed deprivation. The content of de novo synthesised fatty acids in milk fat decreased from the initial proportion of 30% down to 12% and C 18:1 fatty acids increased from 20% to 37% of the milk fat. There were no significant differences between the selection lines in any of these parameters during the feed deprivation but LFI cows showed significantly (P>0,0038) lower milk fat yield than HFI cows immediately after refeeding. These results show that cows in early lactation have a remarkable ability to adjust milk production when feed intake is limited and also to resume milk production quickly when they are fed again. It is also shown here that fat production is quite well maintained during feed deprivation, by mobilisation of body tissues. It may be speculated that the evolutionary purpose of this ability is to secure energy production for the offspring.