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Domestic cattle (Bos taurus taurus) are adapted to digest high-roughage diets, but in confinement they are commonly fed low-roughage, high-energy diets. This practice may leave cattle with an unfulfilled need to consume forage. A way to quantify motivation is to require animals to work to access a resource. Using this method, we evaluated cattle motivation to obtain forage when fed high- or low-roughage diets during and 30 d before the study. Individual heifers were fed Sudan grass (Sorghum × drummondii) hay (high roughage, n = 6) or a diet with 12% forage (as fed, low roughage, n = 6) in an open feed trough. In a second trough, 200 g/d of Sudan grass hay were fed behind a push gate, to which additional weight was added daily until heifers no longer pushed. We predicted heifers would push heavier weights, show a shorter latency, and spend more time pushing the gate when fed a low- vs. high-roughage diet. Indeed, heifers fed a low-roughage diet pushed the gate immediately after hay delivery (1.7 min) and much sooner than those fed a high-roughage diet (75.7 min). On the day before they no longer pushed the gate, latency for heifers in the low-roughage treatment remained only 3.2 min after hay delivery. The suddenness with which they ceased pushing the next day suggests they were unable to move heavier weights to express their motivation. This may explain why maximum weight pushed and time spent pushing the gate did not differ between treatments. The gate pushing by heifers with unrestricted hay access is the first demonstration by cattle of contrafreeloading: performing work to obtain a resource that is simultaneously available for free. In conclusion, consuming forage is important to cattle and is affected by both their primary diet and an internal motivation to work to obtain feed.

Chemically defined diets are commonly used in amino acid (AA) requirement studies to allow for tight control of AA delivery. However, those diets are not representative of commercial diets in the market and are unpalatable. Methionine (Met) is usually the first limiting AA in cat diets, but little is known about its requirement for adult cats. Thus, the objectives of this study were: 1) to develop a semisynthetic diet limiting in Met and evaluate its effect on acceptance and feeding behavior in cats; and 2) to evaluate the effect of different sources and inclusions of Met on preference in cats fed the semisynthetic diet. A semisynthetic diet deficient in Met and total sulfur AA (TSAA) was developed. Healthy adult male cats (n = 9) were fed (0800 and 1600 h) the semisynthetic diet top dressed with DL-Met solution (T-DLM), to meet 120% of the TSAA requirement, for 8 d. Feed intake was measured and a 30-min video recording was taken at the 0800 h feeding to evaluate feeding behavior of the cats. Following the acceptability trial, two bowl tests were performed where first choice was recorded and intake ratio was calculated as consumed food (A/A + B). Three combinations were tested: semisynthetic diet deficient in Met (T-BASAL) vs. T-DLM; T-BASAL vs. diet sufficient in Met provided 2-hydroxy-4-(methylthio)-butanoic acid (T-MHA); and T-DLM vs. T-MHA. Average feed intake remained high throughout the acceptability period (94.5% intake of total offered), but some cats decreased intake, resulting in a decrease in BW (≤2.5% of initial BW) over time (P < 0.05). Behaviors were similar among days (P > 0.05) with the exception of grooming the chest and body (P < 0.05). No preferences were observed towards a specific treatment (Met source and level) during the two-bowl tests (P > 0.05) and agreed with the cats expressing similar feeding behaviors during the preference tests (P > 0.05). In conclusion, a semisynthetic diet deficient in Met was successfully developed and can be used in studies to evaluate the effects of low protein and AA supplemented diets. Cats seem to show no preference for Met source and/or inclusion level in a semisynthetic diet application, which is of benefit for future studies aiming to determine the Met requirement in this species. [ABSTRACT FROM AUTHOR]

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