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Research review: From the Journal of Dairy Science: Longevity definitions and feeding bakery byproducts

Pedro Nogueira for Progressive Dairy Published on 31 December 2020

“Invited review: Academic and applied approach to evaluating longevity in dairy cows.” Journal of Dairy Science Vol. 103 No. 12, 2020.

This review, written by researchers from the universities of Alberta, Florida and Guelph, aims to clarify the notion of longevity in the dairy industry and provide insight into influences affecting dairy cow herd life, such as farm- and cow-level factors associated with it.

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The authors indicate the decreasing average time a cow stays in the herd has been a growing concern in the dairy industry. They mention the Council on Dairy Cattle Breeding saying that extensive research focusing on genetic, environmental and management factors affecting time in the herd has been conducted in attempts to increase understanding and guide farm profitability.

The term longevity is not easy to define since life in cows is complex, and many factors contribute to determining a cow’s true length of productive life (LPL), making it difficult to develop herd-specific long-term goals for LPL. It is difficult to suggest a single definition for longevity for the purpose of academic discussions, as the outcome of interest varies among studies. Still, it is feasible to standardize the terminology used, and the authors recommend the following definitions:

  • LPL. Length of productive life should be used only in reference to the length of time in the lactating herd, calculated as the number of days between first calving and culling or death.

  • HL. Herd life should be used when referring to the entire time an animal spends in the herd, rather than time in the lactating herd, and should be measured as the number of days between birth and culling or death.

  • Stayability. When referring to a cow’s ability to avoid culling, the term “stayability” should be used. However, when referring to the ability to remain in the herd to a specific point in time, the term “survivability” should be used instead.

  • Survivability. The term “survivability” should be used to describe the proportion of cows surviving to a specific point in time and should be calculated as the number of cows that have survived to a given point in time divided by the number of cows included in the opportunity group. Additionally, the point of time of interest should be included in the definition (e.g., survivability to 48 months old or survivability to 12 months of productive life).

The authors stress it is important to acknowledge some cows are less efficient milk producers than others and that production efficiency is better served when the LPL of these less efficient cows is shorter. Better cows should be kept in the herd while less valuable cows are replaced. Hence, a more realistic goal for the dairy industry is to optimize rather than increase longevity or LPL.

This can partly be achieved through the use of genomic testing to rear only the heifers with the better genetic makeup as a selective youngstock goal. That is, producers should aim to get each cow to reach her phenotypic maximum performance capacity by providing a favourable environment via optimal management (which also reduces involuntary culling and shifts culling from forced to economic culling) so she can achieve her full genetic potential. Therefore, aiming to optimize longevity rather than striving to maximize life span will maximize the overall production efficiency of the dairy industry.

“Feeding of bakery byproducts in the replacement of grains enhanced milk performance, modulated blood metabolic profile and lowered the risk of rumen acidosis in dairy cows.” Journal of Dairy Science Vol. 103 No. 11, 2020. This article, written by researchers from Austria, investigated the use of bakery byproducts (BP) in ruminant diets. It is common to use starchy grains (cereals) as part of dairy cow diets.

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However, cereal grains are human-edible ingredients, and their reduction in ruminant feeding has recently become more important to increase net food production, which might improve sustainability in livestock production. Another critical aspect of using grains in cattle feeding is that starchy grains are associated with several health risks, especially rumen fermentation disorders such as subacute rumen acidosis (SARA). Bakeries and supermarkets generate large amounts of wasted BP, consisting mainly of unsold products (i.e., unsold sliced bread, croissants, biscuits, cakes, dough), which are not consumed largely due to consumer preferences for fresh products.

The authors refer that nutritionally, the BP supply slightly higher energy content, and the profile of energy precursors is different from starchy grains. For example, although the BP contain less starch, they contain more fat and sugars and less fibre than the native cereal grains. One concern when using BP is: There are extensive chemical changes that occur during baking, which may be a concern from a ruminant nutrition perspective because extensive treatments (grinding, heating) might increase ruminal starch degradation in a way that could affect feed intake as well as rumen and metabolic health.

For this study, the authors used 24 lactating Simmental cows (149 plus or minus 22.3 days in milk, lactation number 2.63 plus or minus 1.38, 756 plus or minus 89.6 kilograms of initial bodyweight), which were fed a total mixed ration (TMR) containing a 50-50 ratio of forage-to-concentrate throughout the experiment. They continually measured dry matter intake (DMI) and reticuloruminal pH.

Blood and milk samples were collected every week as well. Diet analyses showed that BP inclusion increased the ether extract (fat) and sugar contents of the diet, whereby starch and neutral detergent fibre decreased. Experimental data showed that feeding BP in the diet increased DMI. Furthermore, the cows fed 30% BP produced roughly 4 kilograms per day more milk (30.6 litres versus 35.1 litres) and energy-corrected milk (29.4 litres versus 34.3 litres) than the control cows. (The diets were not isocaloric, meaning that the BP diet had more energy than the one with cereals.)

An interesting result was that cows fed 15% BP had the shortest period of time in which ruminal pH was below 5.8. Taken together, the results suggest the inclusion of up to 30% BP in the diets of mid-lactation dairy cows shifted the nutrient profile from a glucogenic diet to a lipogenic diet, holding the potential to enhance performance and lower the risk of subacute ruminal acidosis in dairy cows.  end mark

This column brings you information regarding some of the research being done around the world and published in the Journal of Dairy Science. The objective is to bring to light areas of research that may have an immediate practical application on a dairy farm, as well as research that, even though may not have a practical impact now, could be interesting for its future potential application. The idea is to give a brief overview of select research studies but not go into detail on each topic. Those interested in further in-depth reading can use the citations to find each study.

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Pedro Nogueira
  • Pedro Nogueira

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