The objective of this dissertation was to determine the feeding motivation of dairy heifers and to determine management factors that contribute to satiety in limit-fed dairy heifers. The first study of this dissertation determined the difference in behavioural patterns between limit-fed and ad libitum-fed dairy heifers so that we may understand how limit feeding diverges from normal behaviour. Limit-fed heifers were found to decrease time spent feeding, consume less DM, and increase their feeding rate across the day in comparison to ad libitum-fed heifers. Additionally, the diurnal patterns of ad libitum-fed heifers were much closer to normal behaviour as they consisted of several short, small meals distributed throughout the day. The next three studies examined the management factors of frequency of feed provision and feed bunk space and how these may impact the behaviour of heifers. Increased frequency of feed provision did result in more distribution of feeding activity throughout the day but also imposed feeding amounts that were likely insufficient to achieve satiety. Heifers fed once daily likely experienced satiety in the short term and did spend the most time feeding throughout the day but the diurnal patterns of these heifers did not allow for expression of normal foraging behaviour. Providing increased feed bunk space did not allow limit-fed heifers to spend more time feeding or impact competition within a pen whereas providing straw alongside of a nutrient-dense TMR did result in more normal diurnal patterns, albeit with an increase in competitive behaviour. There was no interaction found between feed bunk space and frequency of feed provision, indicating that limit-fed heifers must be provided with sufficient bunk space to feed simultaneously. Heifers provided with un-restricted bunk space did gain more and were more feed efficient and less variable in feeding time than heifers given restricted bunk space. Feeding once daily resulted in an increase in competition but also enabled heifers to gain well and to spend more time feeding each day. The remaining studies sought to quantify whether a preference for supplementary feed exists in limit-fed heifers and whether heifers will work, and to what extent, for this extra feed. The results indicated that heifers will consume similar amounts of supplementary long or short straw if provided to them alongside of a limit-fed TMR. The limit-fed heifers do, however, show a clear preference for long straw when offered the choice, suggesting that they find long straw to be more satisfactory for achieving rumen fill and/or meeting their behavioural foraging needs. Heifers were also found to work harder (push more weight), spend less time feeding and ruminating, and consume feed faster when provided a high-concentrate, limit-fed ration than when provided a high-forage, ad libitum-fed ration, suggesting that these animals are experiencing feelings of hunger and may not be physically or behaviourally satisfied. These findings indicate that there are clear behavioural differences between limit-fed and ad libitum-fed dairy heifers. Management factors, such as frequency of feed provision and feed bunk space, may be altered in such a way as to provide some benefit to the animals but are limited in their ability to normalize feeding behaviour and diurnal patterns. Provision of supplemental, long particle low-nutritive roughage (i.e. straw) aids much more in allowing limit-fed heifers to achieve satiety and is considered a desirable resource by the animals, as evidenced through their willingness to work for this supplemental feed. / Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)/University of Guelph Production Systems research grant and a Campbell Centre for the Study of Animal Welfare research grant. This project was also supported through contributions from the Canadian Foundation for Innovation (CFI) and the Ontario Research Fund. Angela Greter was supported through NSERC Alexander Graham Bell Canadian Graduate Student scholarship

Master of Science / Department of Animal Sciences and Industry / Dale A. Blasi / Four pen studies and one digestibility trial were conducted to evaluate the effects of energy level and intake of corn by-product based diets on newly received growing cattle. In Exp.1 there were four diets where one was offered for ad libitum intake and formulated to supply 0.99 Mcal NEg/kg DM (0.99/100) and the other three treatments were fed at 95, 90, and 85% of the ad libitum treatment and to supply 1.10 (1.10/95), 1.21 (1.21/90), and 1.32 Mcal NEg/kg DM (1.32/85), respectively. ADG was unaffected by treatment (P = 0.32). However, G:F increased linearly with increasing energy and decreasing intake level (P < 0.01). In Exp. 2, a digestibility trial was conducted to study diets from Exp. 1. Ruminal propionate linearly increased with increasing dietary energy and decreasing intake (P < 0.01). Total tract DM digestibility increased linearly with increasing energy and decreasing intake (P < 0.01), whereas passage rate decreased (P < 0.01). Experiment 3 validated results from Exp. 1 feeding the 1.10/95 treatment at 2.40% of BW daily and the 1.32/85 treatment at 2.2% of BW daily and studied a DNA-immunostimulant (Zelnate, Bayer Animal Health, Shawnee Mission, KS). Zelnate had no effect on parameters measured. ADG was not different between energy treatments (P = 0.75), but efficiency was greater for the 1.32/85 treatment (P = 0.03). Experiment 4 was designed to observe effects of the 1.32 Mcal NEg/kg DM diet fed at four intake levels of 1.9, 2.2, 2.5, and 2.8 % of BW daily. ADG increased linearly with increasing intake (P < 0.01), however G:F was not affected (P = 0.98). In Exp. 5 a factorial design was employed to evaluate the effects of two by-products; wet corn gluten feed and wet distiller’s grains plus solubles, and two levels of corn processing; whole corn or dry-rolled corn. Final ADG and G:F were not affected by by-product, corn processing, or their interaction (P > 0.30). Additionally, animals and diets from Exp. 1 were used to study effects on antibody production, acute phase protein response, stress, and immunocompetency of healthy and morbid cattle. Diet had no effect on the parameters measured (P > 0.10). A quadratic response to time (P < 0.01) was detected for haptoglobin, titers for bovine viral diarrhea type 1 (BVD-1), and infectious bovine rhinotracheitis (IBR). Haptoglobin was highest on d 14, and close to baseline levels by d 27. Titer levels for BVD-1 and IBR were higher on d 14, and significantly higher on d 27. Titers for bovine viral diarrhea type 2 (BVD- II) responded linearly (P < 0.05) to time with the highest levels on d 27. Haptoglobin was elevated in morbid animals compared to healthy pen mates (P < 0.05). Titer levels for BVD-I and IBR were higher in healthy animals (P < 0.01). Fecal cortisol was higher on arrival than on d 14 (P < 0.05). In summary, high-energy limit-fed diets based on corn by-products do not affect health and are more efficient than when roughage-based growing diets are fed.

Master of Science / Department of Animal Sciences and Industry / Dale A. Blasi / An experiment was conducted to evaluate the effects of dry matter intake (DMI) restriction on early receiving performance by steers in a drylot and subsequent grazing performance, feedlot performance, and carcass characteristics. During the backgrounding period, crossbred, weanling steers (n = 329; initial BW = 191± 5.52 kg ) were randomly assigned to 1 of 4 DMI levels corresponding to ad libitum, 2.50% of BW (2.50%), 2.25% of BW (2.25%), and 2.00% of BW (2.00%) for 62 d. During the subsequent grazing period, the same steers were randomly assigned to 13 paddocks to graze for 90 d. Paddocks were stocked at 281 kg live weight per hectare. Initial steer BW were similar on each pasture and each backgrounding treatment was equally represented within a paddock. During the feedlot period, steers were finished at a commercial feedlot and were assigned to 1 of 4 pens according to their rank in BW. Entire pens were harvested when average steer BW reached 545 kg. During the backgrounding period, ad libitum-fed steers had greater (P < 0.001) ADG and final BW than other treatments; steers fed at 2.50 and 2.25% of BW had similar ADG and final BW and were greater (P < 0.001) than steers fed 2.00% of BW. During the grazing period, compensatory gain was observed in restricted DMI treatments. Steers fed at 2.00% of BW had greater (P = 0.006) ADG than ad libitum-fed steers but an ADG similar to that of the other restricted DMI treatments. Steers fed ad libitum, 2.50% of BW, and 2.25% of BW had similar final BW and steers fed 2.00% of BW had lesser (P < 0.001) final BW than other treatments. During the feedlot phase, steers fed 2.00% of BW were on feed longer (P < 0.05) than other treatments. Growth compensation during grazing illustrated that restricted feeding immediately prior to pasture grazing can reduce backgrounding costs.

Master of Science / Department of Animal Sciences and Industry / Christopher D. Reinhardt / Three experiments were conducted to examine nutritional and management strategies for different segments of the beef industry. The first experiment examined the effects of feeding traditional step-up diets (STEP) vs. limit-feeding (LIMIT) the finishing diet to adapt cattle to high-concentrate diets. When all cattle reached ad libitum intake of the finishing diet there was a trend (P = 0.09) for DMI to be different between treatments. During week 1, STEP cattle had higher total VFA concentrations (P = 0.02), while LIMIT cattle had higher valerate absorption (P = 0.02) and disappearance (P = 0.08). During week 4, LIMIT cattle had higher total VFA concentrations (P = 0.03) and lower valerate disappearance and absorption (P = 0.05) than STEP cattle. These results indicate that limit-feeding the finishing diet may inhibit nutrient absorption from the rumen or this method may cause increased production of valerate by lactate utilizing bacteria due to a more acidotic rumen environment. The second experiment examined the effects of feeding 5% (DM basis) dried, full-fat corn germ (GERM) on feedlot performance and carcass characteristics of naturally raised yearling steers and heifers. Carcass-adjusted ADG was higher for GERM cattle (P = 0.04). There were no other differences in performance or carcass characteristics. Total incidence of liver abscesses and the incidence of severe liver abscesses were decreased by 12 and 8.2% (P = 0.01 and 0.02, respectively) when GERM was added to the diet. Corn germ can be added to finishing diets at 5% without affecting performance and carcass characteristics. Producers raising natural cattle may also be able to benefit from the reduced incidence of liver abscesses. The third experiment examined concurrent metaphylactic treatment of high-risk calves with tulathromycin and chlortetracycline. Calves were placed on 1 of 3 treatments: 1) no top-dress pellets; 2) diet top-dressed with pellets containing chlortetracycline; or 3) diet top-dressed with pellets containing no chlortetracycline. There were no differences in the performance or health of these calves (P > 0.25). There are no additive benefits of concurrent metaphylaxis using both tulathromycin and chlortetracycline. This information could assist producers when designing receiving health protocols for high-risk calves.

Feedlot performance, carcass merit and chemical composition were compared using Waguli , Brangus, Hereford x Tuli and Wagyu x Crossbred Gene Combination (CGC) breeds. Steers were penned in the following manner: 6 Waguli steers, 6 Hereford x Tuli, 6 Wagyu x CGC and 8 Brangus. There was a significant difference (P<0.05) between Brangus and Waguli for ADGs. F:G was lower (P<0.05) for Hereford x Tuli compared to the other crossbreeds. A heavier final weight was observed (P<0.05) for the Wagyu x CGC than all other crossbreds. There was a significant difference (P<0.05) for REA between Wagyu x CGC and Hereford x Tuli and Waguli. Wagyu x CGC had higher shear force values (SFV) (P<0.05) than all other crossbreeds. Cost of gain was lower (P<0.05) for Hereford x Tuli compared the other breeds. Hereford x Tuli also had less protein (P<0.05) than to the other breeds.A second study was conducted comparing limit feeding (LF) vs. full feeding (FF) strategies. 23 steers and 27 heifers were penned by sex and were randomly assigned a treatment; 4 pens received the LF treatment and 4 were FF. ADG was lower (P<0.05) for LF and FF heifers compared to both LF and FF steers. Dressing percentage was lower (P<0.05) for LF steers compared to LF and FF Heifers. LF heifers YG was higher (P<0.05) compared to FF steers. Quality grades were higher (P<0.05) for LF and FF heifers compared to LF and FF steers. REA /cwt was significantly higher (P<0.05) for FF heifers compared to LF and FF steers. SFV were11lower (P<0.05) for FF heifers compared to LF and FF steers. A significant difference (P<0.05) in cost of gain was noted between LF steers and the rest, also between LF heifers and FF steers. Primal cut price/cwt was significantly lower (P<0.05) for LF heifers compared to FF steers. Lipid percentage was higher (P<0.05) LF heifers compared to FF steers. Moisture percentage was lower (P<0.05) for LF heifer compared to the other groups.